chapter 26 the atmosphere, energy in earth’s processes, insolation, greenhouse effect, specific...

Chapter 26Chapter 26The Atmosphere, The Atmosphere, Energy in Earth’s Energy in Earth’s

Processes, Processes, Insolation, Insolation,

Greenhouse Effect, Greenhouse Effect, Specific Heat, & Specific Heat, &

IsothermsIsothermsBFRB 228 – 236, 193 – 197, 170 – BFRB 228 – 236, 193 – 197, 170 –

174 174

MeteorologyMeteorology • The study of weatherThe study of weather• Weather is the Weather is the condition of the condition of the

atmosphere at any given time or placeatmosphere at any given time or place• Much of weather forecasting and Much of weather forecasting and

prediction can be accomplished by direct prediction can be accomplished by direct observation – observation – LOOK OUT THE WINDOW!!LOOK OUT THE WINDOW!!

• To predict weather, you must make To predict weather, you must make observations of the clouds, wind, observations of the clouds, wind, temperature, humidity, air pressure and temperature, humidity, air pressure and precipitationprecipitation

Atmospheric Atmospheric CompositionComposition

• The Earth’s atmosphere is made up of The Earth’s atmosphere is made up of many gases, but it is mostly (99%) many gases, but it is mostly (99%) nitrogen (78%) and oxygennitrogen (78%) and oxygen (21%) (ESRT’s (21%) (ESRT’s Page 1 bottom) Page 1 bottom)

• It also contains (the other 1%) H2O (water It also contains (the other 1%) H2O (water vapor), Ar (Argon) dust, COvapor), Ar (Argon) dust, CO22 (Carbon (Carbon Dioxide), CHDioxide), CH44 (Methane) and (Methane) and ozoneozone – O – O33 (a (a triple atom form of oxygen which triple atom form of oxygen which absorbs absorbs UVC raysUVC rays from the sun) from the sun)

• As you go higher in the atmosphere, the As you go higher in the atmosphere, the amount of air above you decreases and amount of air above you decreases and thus air pressure (weight of air) decreases!thus air pressure (weight of air) decreases!

ESRT Page 1

Structure of the AtmosphereStructure of the Atmosphere • Made up of five layers, each with different Made up of five layers, each with different

characteristics (ESRT’s Page 14 top only shows FOUR characteristics (ESRT’s Page 14 top only shows FOUR layers)layers)

• Troposphere-Troposphere- lowest layer (we live in this layer). All of lowest layer (we live in this layer). All of Earth’s weather occurs in the troposphere because this Earth’s weather occurs in the troposphere because this is where all of the water vapor Is located. is where all of the water vapor Is located. Temperature decreasesTemperature decreases as you go higher. as you go higher.

• Stratosphere-Stratosphere- above the troposphere, has strong above the troposphere, has strong winds. winds. Temperature increasesTemperature increases as you go higher as you go higher because of the absorption of UV rays by ozone.because of the absorption of UV rays by ozone.

• Mesosphere-Mesosphere- above the stratosphere. above the stratosphere. Temperature Temperature decreasesdecreases as you go higher. as you go higher.

• Thermosphere-Thermosphere- above the mesosphere. above the mesosphere. Temperature Temperature increasesincreases as you go higher due to oxygen and nitrogen as you go higher due to oxygen and nitrogen absorbing solar energyabsorbing solar energy

• FYI - Ionosphere-FYI - Ionosphere- above the thermosphere. This is above the thermosphere. This is where the sun’s solar winds get refracted off of the where the sun’s solar winds get refracted off of the ions to create the Aurora Borealis (NH) and the Aurora ions to create the Aurora Borealis (NH) and the Aurora Australis (SH)Australis (SH)

ESRT’s Page 14 top

Ionosphere is up here….Ionosphere is up here….

Movement of Heat – 3 Movement of Heat – 3 WaysWays

This is review from Plate Tectonics • 1) Conduction-1) Conduction- the movement of heat the movement of heat

from molecule to molecule through from molecule to molecule through contactcontact with each other or other objects with each other or other objects– Ex. Touching a hot pot on the stove Ex. Touching a hot pot on the stove

• 2) Radiation-2) Radiation- the movement of the movement of Electromagnetic Energy (heat waves) across a Electromagnetic Energy (heat waves) across a distance through ANY media (including empty distance through ANY media (including empty space!)space!)– Ex. Warming your hands in front of a fireplaceEx. Warming your hands in front of a fireplace

• Earth Earth receivesreceives EM energy radiated from the EM energy radiated from the sun sun at relatively short wavelengths (visible and UV)at relatively short wavelengths (visible and UV), , and Earth and Earth reradiatesreradiates this heat energy this heat energy at longer at longer wavelengthswavelengths known as Infrared waves (heat) known as Infrared waves (heat)

• Energy received on Earth from the sun is called Energy received on Earth from the sun is called InInsolsolationation ( (incomingincoming solarsolar radiationradiation))

Movement of HeatMovement of Heat – 3 Ways

• 3) Convection-3) Convection- the movement of heat in the movement of heat in currents due to differences in densitycurrents due to differences in density

• The most effective form of heat transfer The most effective form of heat transfer in in liquids and gases (fluids)liquids and gases (fluids)– Air gets heated and expands – the Air gets heated and expands – the

molecules move apart - makes it less molecules move apart - makes it less dense and lighter…it rises! dense and lighter…it rises!

– Colder air – molecules come together - Colder air – molecules come together - is more dense and heavier so it sinksis more dense and heavier so it sinks

– It gets heated it rises, it cools it sinksIt gets heated it rises, it cools it sinks– Just like in the putty-like Just like in the putty-like

asthenosphere!!!!!asthenosphere!!!!!

Movement of Heat – 3 WaysMovement of Heat – 3 Ways

CONVECTION CURRENT IN THE ATMOSPHERE CONVECTION CURRENT IN THE ATMOSPHERE DUE TO DENSITY DIFFERENCES!!!!!!!!!DUE TO DENSITY DIFFERENCES!!!!!!!!!

• Insolation is a one word expression for Insolation is a one word expression for INcoming SOLar radiATIONINcoming SOLar radiATION

• It is the energy that the Earth receives It is the energy that the Earth receives from the Sun.from the Sun.

• The amount of insolation varies with The amount of insolation varies with changes in latitude and the angle that changes in latitude and the angle that the insolation hits the surface of the the insolation hits the surface of the Earth.Earth.

• This is due to the variation of Earth’s tilt This is due to the variation of Earth’s tilt on its axis in relation to the sun’s rays on its axis in relation to the sun’s rays as it revolves.as it revolves.

What is What is InInSolSolAtionAtion??

In this example, the insolation is concentrated in a small area. More energy per unit area is hitting the

surface. This would be the Equatorial part of Earth.

In this example, the same amount of insolation is spread out over a larger area.

Less energy per unit area is hitting the surface. This would be 45° North or South

of the Equator.

Figure 1. A schematic of the electromagnetic spectrum, showing the Sun's energy output in relation to wavelength. Most of the Sun’s radiation is in what part(s) of the EM spectrum?

Greenhouse EffectGreenhouse Effect • Certain gases in the atmosphere (Certain gases in the atmosphere (water vapor (natural), water vapor (natural),

carbon dioxide (burning of Fossil Fuels, methane carbon dioxide (burning of Fossil Fuels, methane (emissions from livestock - lol!), decomposition of (emissions from livestock - lol!), decomposition of sewage),sewage), etc etc.) allow .) allow short wavelengths of energy from short wavelengths of energy from the sunthe sun to enter the atmosphere. The Sun’s shorter to enter the atmosphere. The Sun’s shorter wavelengths pass right thru…wavelengths pass right thru…

• Earth’s surface absorbs the shorter wavelengths, heats Earth’s surface absorbs the shorter wavelengths, heats up and reradiates the heat as up and reradiates the heat as infrared (heat) wavesinfrared (heat) waves, , which have longer wavelengthswhich have longer wavelengths

• Most of these longer wavelengths escape back into Most of these longer wavelengths escape back into space, but some of the infrared waves are space, but some of the infrared waves are trapped bytrapped by these gases and don’t escape, so they become these gases and don’t escape, so they become trappedtrapped in the atmosphere as heat.in the atmosphere as heat.

• This causesThis causes the temperature on Earth to increase.the temperature on Earth to increase.• This is a positive and necessary process that has made This is a positive and necessary process that has made

our atmosphere warm enough for evolution to occur and our atmosphere warm enough for evolution to occur and humans to be able to live on Earth!humans to be able to live on Earth!

Why we call it the “Greenhouse Effect”

This HUMAN ENHANCED (aka Anthropomorphic or This HUMAN ENHANCED (aka Anthropomorphic or Anthropogenic) Greenhouse Effect is the Anthropogenic) Greenhouse Effect is the cause of cause of

CLIMATE CHANGE – otherwise known as Global WarmingCLIMATE CHANGE – otherwise known as Global Warming..

1. IntroductionThe greenhouse effect is responsible for the Earth’s warm, livable atmosphere. Gases like methane and carbon dioxide trap heat near the surface, keeping the Earth about 33° C (60° F) warmer than it would be without its natural blanket of protective gas. The greenhouse effect is a natural phenomenon, but human activity can enhance its effect and destabilize the climate.2. GasesWater vapor, methane, carbon dioxide, CFCs, ozone and nitrous oxide are all greenhouse gases (GHGs). Carbon dioxide (CO2) is the most important, followed in descending order by methane, CFCs, ozone and nitrous oxide.Climate scientists say human activities that pour enormous volumes of these gases into the atmosphere are raising the planet’s temperature. Some of these activities are the burning of fossil fuels and the deforestation of the Earth.3. SunThe sun sends energy toward Earth in the form of light and radiation. We experience solar radiation as light and warmth on a sunny day4. AtmosphereWhen the sun’s rays strike the atmosphere, some of the radiation is immediately reflected into space.The radiation that gets through the atmosphere heads toward the Earth’s surface.5. EarthSolar radiation that passes through the Earth’s clear atmosphere is absorbed by the ground, water, plants and other objects. As the sun warms objects, they emit infrared radiation. This is the energy we know as heat.A portion of the solar radiation that reaches the Earth’s surface — particularly areas covered by ice, snow or the ocean — also bounces back into space, where its heat energy dissipates.6. Heat and gasesMolecules of greenhouse gases in the atmosphere absorb infrared radiation and release heat, which raises the temperature of the ground and air and warms the Earth’s surface.Infrared radiation has a longer wavelength than visible light, so it is easier for molecules like carbon dioxide and water vapor to absorb energy and trap the sun’s energy beneath Earth’s atmosphere.7. Into spaceSome infrared radiation continues on its path out of the atmosphere and into space.

Temperature Changes on Temperature Changes on EarthEarth

• Temperature changes with seasonal change Temperature changes with seasonal change occur because the occur because the sun’s insolation strikes sun’s insolation strikes Earth at different angles (and therefore Earth at different angles (and therefore different intensities)different intensities)

• Where the sun’s rays strike Earth at 90°, the Where the sun’s rays strike Earth at 90°, the insolation is concentrated in a smaller area. insolation is concentrated in a smaller area. This causes temperatures to be the greatest. This causes temperatures to be the greatest.

• Where the sun’s rays hit Earth at very low Where the sun’s rays hit Earth at very low angles, the insolation is spread out over a angles, the insolation is spread out over a large area. This causes temperatures to be large area. This causes temperatures to be low.low.

Warmest and Coldest Warmest and Coldest MonthsMonths

• Northern Hemisphere- Northern Hemisphere- – Maximum sunlight is June 21st, but Maximum sunlight is June 21st, but

maximum temperature is in July – maximum temperature is in July – there is there is a lag!!!a lag!!!

– Minimum sunlight is December 21st, but Minimum sunlight is December 21st, but minimum temperatures are experienced minimum temperatures are experienced in January – in January – there is a lag!!!there is a lag!!!

• It takes time for the heat to build up, and for It takes time for the heat to build up, and for maximum temperatures to be reachedmaximum temperatures to be reached

• Also, it takes time for heat to dissipate (go Also, it takes time for heat to dissipate (go away), and for minimum temperatures to be away), and for minimum temperatures to be reachedreached

in NYS

Warmest and Coldest Time of Warmest and Coldest Time of DayDay

• The The coldest hour is usually just coldest hour is usually just before sunrisebefore sunrise, since the Earth has , since the Earth has been cooling off all night – been cooling off all night – there is there is a lag!!!!a lag!!!!

• The The warmest time is later in the warmest time is later in the afternoon (after solar noon)afternoon (after solar noon), since , since the Earth is still receiving more the Earth is still receiving more heat than it is losing – heat than it is losing – there is a there is a lag!!!lag!!!

As the insolation is absorbed by the Earth, the temperature will continue to increase if absorption exceeds radiation.The earth absorbs more heat than it radiates into the afternoon, therefore the highest temps are not at Solar noon, but later on!

Why is there a Daily and Seasonal Lag between the Why is there a Daily and Seasonal Lag between the time of maximum intensity of insolation and time of maximum intensity of insolation and

highest temperatures? highest temperatures? Heating of Water and LandHeating of Water and Land

• Water and land heat up and cool off at Water and land heat up and cool off at different rates because they have different different rates because they have different properties.properties.

• This is due to their different This is due to their different heat capacitiesheat capacities AKA SPECIFIC HEAT (P. 1 of ESRT’s)AKA SPECIFIC HEAT (P. 1 of ESRT’s)

• LandLand needs very little energy to heat up needs very little energy to heat up (low heat capacity)(low heat capacity)– This allows land to heat up quickly, and also to This allows land to heat up quickly, and also to

cool down quicklycool down quickly• WaterWater needs more energy to heat up needs more energy to heat up (high (high

heat capacity)heat capacity)– This allows water to heat up slowly and to cool This allows water to heat up slowly and to cool

off slowly - off slowly - – WATER IS STUBBORN!!! It takes a long time to WATER IS STUBBORN!!! It takes a long time to

heat up and a long time to cool down…heat up and a long time to cool down…

ESRT Page 1ESRT Page 1

What is specific heat?What is a Joule/gram ●⁰C ?

Liquid water has the highest specific heat value

The amount of heat required to raise the temperature of one gram of substance by 1 degree Celsius or Kelvin

How do the specific heats of land and water affect the rate at which they heat up and cool down?

• Air temperature and other weather conditions of Air temperature and other weather conditions of different locations are affected by how near or far different locations are affected by how near or far they are from water (oceans) due to heat they are from water (oceans) due to heat capacitycapacity

• VIF - Water has a mitigating effect to extremes of VIF - Water has a mitigating effect to extremes of temperature and climatetemperature and climate

• For example, a coastal city may have a average For example, a coastal city may have a average annual high of 75annual high of 75°° and an average annual low of and an average annual low of 4040°°. (35. (35°° range) range)

• An inland city may have an average annual high An inland city may have an average annual high of 82of 82°° and an average annual low of 33 and an average annual low of 33°°. (49. (49°° range)range)

• The coastal city is near the water, so the water’s The coastal city is near the water, so the water’s temperature doesn’t change as quickly as the temperature doesn’t change as quickly as the land’s temperature due to water’s high specific land’s temperature due to water’s high specific heat.heat.

How Does Water’s High How Does Water’s High Specific Heat Affect Weather & Specific Heat Affect Weather &

Climate?Climate?

Case study of an inland vs. Case study of an inland vs. a coastal city’s climatea coastal city’s climate

• Dark colors absorb energy well, and Dark colors absorb energy well, and light colors reflect energy well light colors reflect energy well (think...dark color clothes in winter, (think...dark color clothes in winter, light colors clothes in summer)light colors clothes in summer)

• Rough surfaces absorb energy well, Rough surfaces absorb energy well, while smooth surfaces reflect energy while smooth surfaces reflect energy well well (think…a mirror is smooth and (think…a mirror is smooth and reflects your image really well.)reflects your image really well.)

• VIF – The best ABSORBERS make the VIF – The best ABSORBERS make the best EMITTERS of energy.best EMITTERS of energy.

• This is why radiators (heaters) are often This is why radiators (heaters) are often black in color!!!black in color!!!

The Rules of Absorber and The Rules of Absorber and ReflectorsReflectors

Smooth Surfaces reflect Better than rough surfaces, therefore rough surfaces will absorb more insolation than smooth surfaces and will become hotter.

Chapter 28Chapter 28Atmospheric Pressure Atmospheric Pressure

and Windsand WindsLows & Highs Lows & Highs

BFRB PagesBFRB Pages Pressure & Winds P. 172-180Pressure & Winds P. 172-180

Lows & Highs P. 180-182Lows & Highs P. 180-182

Relative Humidity Relative Humidity is is determined by using a determined by using a hygrometer or a sling hygrometer or a sling psychrometer psychrometer measured as a %measured as a %

Wind speedWind speed is is measured using an measured using an anemometeranemometer (units (units are are knotsknots; ; 1 knot = 1.15 mph) 1 knot = 1.15 mph) 

Meteorology Meteorology InstrumentsInstruments

Wind directionWind direction is is determined by determined by using a using a wind vane wind vane or aor a wind sockwind sock (like (like you see at the you see at the airport) measured airport) measured as a compass as a compass direction N, S, NE, direction N, S, NE, SW, etc.SW, etc.

Temperature Temperature is is determined by using a determined by using a thermometerthermometer measured in °C,°F, or measured in °C,°F, or KK

Pressure Pressure is determined is determined by using a by using a barometer barometer measured in millibars measured in millibars (mb) or inches of Hg (in) (mb) or inches of Hg (in)

wind vane wind vane Amount of Amount of precip precip is is measured by measured by using a using a rain rain gauge gauge measured in measured in inches or cminches or cm

Air PressureAir Pressure

• the weight of the air in a certain areathe weight of the air in a certain area• Air pressure is measured using an Air pressure is measured using an

instrument called a instrument called a barometerbarometer (aneroid or mercury)(aneroid or mercury)

• It is measured in It is measured in inchesinches (height of (height of the mercury column in the the mercury column in the barometer), or with the metric units barometer), or with the metric units called called millibarsmillibars

• Use your reference tables for Use your reference tables for “converting” inches to millibars “converting” inches to millibars

• (ESRT’s Page 13 Right Top)(ESRT’s Page 13 Right Top)

• Right Right here here tells you tells you which which side is side is millibars millibars and and which which side is side is inchesinches

• FYI – the FYI – the increments increments are not the are not the same on same on both sides. both sides. Figure out Figure out each sides’ each sides’ increments increments and write and write them in them in right now…right now…

Inches:Inches:Increment = Increment =

____________________

Millibars:Millibars:Increment = Increment =

____________________

• Air pressure decreases with increasing Air pressure decreases with increasing altitudealtitude (less air above you means less (less air above you means less pressure pushing down on you) pressure pushing down on you)

• This is an This is an inverse (indirect) relationshipinverse (indirect) relationship• Weather maps show Weather maps show sea levelsea level air pressure. air pressure.

It ranges from 960mb – 1050mbIt ranges from 960mb – 1050mb• IsoIsobarsbars are lines on the weather maps are lines on the weather maps

which connect areas of equal air pressurewhich connect areas of equal air pressure• VIF!!!!VIF!!!! - The same rules apply for isobars as - The same rules apply for isobars as

isotherms and contour lines. If the isotherms and contour lines. If the isobars isobars are spaced close together, the pressure are spaced close together, the pressure gradient is steep and winds are fastgradient is steep and winds are fast..

Changes in Air PressureChanges in Air Pressure

Changes in Air PressureChanges in Air Pressure • How does temperature affect air How does temperature affect air

pressure?pressure?• Warm air’s molecules are further apart Warm air’s molecules are further apart

than cold air’s molecules! than cold air’s molecules! • It is less dense and not as many It is less dense and not as many

molecules are on top of an area to add molecules are on top of an area to add pressure.pressure.

• Therefore, as temperature increases , Therefore, as temperature increases , air pressure _________________. air pressure _________________.

• This is a(n) ______________ relationship.This is a(n) ______________ relationship.

Changes in Air PressureChanges in Air Pressure

• How does humidity (the amount of How does humidity (the amount of water vapor held in a parcel of air) water vapor held in a parcel of air) affect air pressure?affect air pressure?

• Humid (moist) air contains more water Humid (moist) air contains more water vapor molecules (Hvapor molecules (H22O) O)

• These HThese H22O molecules have less atomic O molecules have less atomic mass than Nmass than N22 and O and O22 molecules that molecules that they take the place of!!!they take the place of!!!

• Let’s PROVE it!!!!!Let’s PROVE it!!!!!

Changes in Air PressureChanges in Air Pressure

• How does humidity (the amount of How does humidity (the amount of water vapor held in a parcel of air) water vapor held in a parcel of air) affect air pressure?affect air pressure?

• OK so we just proved that humid air OK so we just proved that humid air actually weighs less than dry air.actually weighs less than dry air.

• So, as humidity increases, air pressure So, as humidity increases, air pressure ____________________.____________________.

• This is a(n)_________________ This is a(n)_________________ relationship.relationship.

Winds and Air PressureWinds and Air Pressure • Winds are caused by the unequal Winds are caused by the unequal

heating of the atmosphere heating of the atmosphere (remember that temperature (remember that temperature causes changes in air pressure)causes changes in air pressure)

• Warm air is lighter (lower Warm air is lighter (lower pressure) and colder air is heavier pressure) and colder air is heavier (higher pressure)(higher pressure)

• Remember…warm stuff rises and Remember…warm stuff rises and cold stuff sinks…cold stuff sinks…– Ex: Sea breezes and land breezesEx: Sea breezes and land breezes

Sea Breeze – the surface wind is blowing in FROM the sea.

Land Breeze – the surface wind is blowing out FROM the land.

Another view of sea breezes and land breezes…

• Winds blow Winds blow out of highout of high pressure pressure and and into lowinto low pressure pressure

• The greater the difference The greater the difference between the high pressure and between the high pressure and low pressure, the faster the wind low pressure, the faster the wind speed (this is called the speed (this is called the pressure pressure gradientgradient))

• This is shown on a weather map This is shown on a weather map by by closely spaced isobarsclosely spaced isobars (think of (think of closely space contour lines on a closely space contour lines on a topographic map – steeper slope)topographic map – steeper slope)

Air Pressure’s Effect on Winds Air Pressure’s Effect on Winds on a Larger Scaleon a Larger Scale

Isobars are ___________ spaced resulting in a ___________ pressure gradient and ___________ winds.

Isobars are ___________ spaced resulting in a ___________ pressure gradient and ___________ winds.

What parts of the US and Canada have the fastest winds?

the slowest?

ISOTHERMSISOTHERMS• TemperaturesTemperatures are shown on maps by are shown on maps by

using using IsothermsIsotherms• These are lines which connect areas of These are lines which connect areas of

equal temperatureequal temperature• These are very similar to contour lines, These are very similar to contour lines,

and the same rules apply!!and the same rules apply!! • Example – closely spaced isotherms mean Example – closely spaced isotherms mean

a fast change in temperature (steep temp a fast change in temperature (steep temp gradient) the same way closely spaced gradient) the same way closely spaced contour lines mean a fast change in contour lines mean a fast change in elevation (steep land gradient).elevation (steep land gradient).

Where in the US is the steepest temperature Where in the US is the steepest temperature gradient?gradient?

Where is the gentlest temperature gradient?Where is the gentlest temperature gradient?

Coriolis Revisited!Coriolis Revisited!

• The The Coriolis EffectCoriolis Effect (caused by the spin of (caused by the spin of the Earth) the Earth) causes winds to bend to the causes winds to bend to the rightright in the northern hemisphere in the northern hemisphere

• Winds blow out of the High and in to the Winds blow out of the High and in to the Low and bend to the rightLow and bend to the right, causing a High , causing a High Pressure System to spin Pressure System to spin clockwiseclockwise

• Winds blow into the Low from the High Winds blow into the Low from the High and bend to the right, causing the Low and bend to the right, causing the Low Pressure System to spin Pressure System to spin counter-clockwisecounter-clockwise

• FYI - FYI - HurricanesHurricanes are areas of extreme low are areas of extreme low pressure and always pressure and always flow counter-flow counter-clockwise in the Northern Hemisphereclockwise in the Northern Hemisphere

In a High, the air wants to move directly out from High to Low Pressure but is deflected to its right by the Coriolis Effect, creating a Clockwise flow out from the High.

VIF!!!!!!

H

In a Low, the air wants to move directly in from High to Low Pressure but is deflected to its right by the Coriolis Effect creating a Counterclockwise flow into the Low.

VIF!!!!!!

L

MEASURING WINDMEASURING WIND• Wind directionWind direction is is

determined by determined by using a using a wind vane wind vane or aor a wind sockwind sock (like you see at (like you see at the airport)the airport)

• Wind speedWind speed is is measured using measured using an an anemometeranemometer (units are (units are knotsknots; 1 ; 1 knot = 1.15 mph) knot = 1.15 mph) 

Global Wind CirculationGlobal Wind CirculationPressure Belts and WindsPressure Belts and Winds

• The The jet streamjet stream is a narrow zone of high is a narrow zone of high speed air found in the upper troposphere speed air found in the upper troposphere (about 30,000 feet)(about 30,000 feet)– Wind speeds here may be over 300 Wind speeds here may be over 300

knots!knots!• Large convection currents of air occur on Large convection currents of air occur on

the Earth’s surface due to the unequal the Earth’s surface due to the unequal heating of the atmosphereheating of the atmosphere

ESRT’s Page 14 BottomESRT’s Page 14 Bottom

Global Wind CirculationGlobal Wind Circulation

ESRT’s Page 14 BottomESRT’s Page 14 Bottom

These planetary winds shift with the These planetary winds shift with the seasons due to the changing insolation seasons due to the changing insolation

because of Earth’s tilt! Astronomy because of Earth’s tilt! Astronomy connection!!! connection!!!

3-D Version of the ESRT’s3-D Version of the ESRT’sPlease note the deflection of the wind to Please note the deflection of the wind to ITS right in the N.H. due to Coriolis EffectITS right in the N.H. due to Coriolis Effect

This is what the air circulation would look like if This is what the air circulation would look like if the Earth DID NOT ROTATE – NO Coriolis the Earth DID NOT ROTATE – NO Coriolis

Effect!!!!!!Effect!!!!!!

ChapterChapter 2727

The Water Cycle, Relative Humidity, Dew The Water Cycle, Relative Humidity, Dew Point, Clouds, Specific Heat, Orographic Point, Clouds, Specific Heat, Orographic

EffectEffect

BFRB Pages BFRB Pages

Atmospheric Moisture 174-179Atmospheric Moisture 174-179Specific Heat P. 197-200 Specific Heat P. 197-200

Orographic Effect P. 237Orographic Effect P. 237

WaterWater• exists as a solid, liquid, and gasexists as a solid, liquid, and gas• can change from one state to another by can change from one state to another by

adding or removing energy (heat)adding or removing energy (heat)• FusionFusion - the changing of state of matter of - the changing of state of matter of

water between a solid and a liquidwater between a solid and a liquid• From a solid to a liquid is called From a solid to a liquid is called meltingmelting, ,

liquid to a solid is called liquid to a solid is called freezingfreezing• Properties of water on P. 1 of ESRT’sProperties of water on P. 1 of ESRT’s

• Heat of Heat of FusionFusion = +/- 334 = +/- 334 J/g/°CJ/g/°C• Add (+) 334Add (+) 334 J/g/°C of heat to melt ice to J/g/°C of heat to melt ice to

waterwater• Take away (-) 334Take away (-) 334 J/g/°C of heat to J/g/°C of heat to

freeze water to icefreeze water to ice

WaterWater

Solid to Solid to liquidliquid

Liquid to Liquid to solidsolid

Liquid to Liquid to vaporvapor

Vapor to Vapor to liquidliquid

Think of 3.98° C as 4° C!!! Round it…Think of 3.98° C as 4° C!!! Round it…

Water is most dense as a liquid at 4° C Water is most dense as a liquid at 4° C (solid ice which has a temp of < 0(solid ice which has a temp of < 0° C° C has a density < 1.0 g/cmdensity < 1.0 g/cm33 so it floats!!!) so it floats!!!)

WaterWater

How many Joules of energy would it take to melt 3 g of ice into liquid How many Joules of energy would it take to melt 3 g of ice into liquid water?water?

How many Joules of energy would be released if 3.2 g of water vapor How many Joules of energy would be released if 3.2 g of water vapor condensed into liquid water?condensed into liquid water?

GASGAS LIQUID LIQUID SOLID SOLID

• Energy is absorbed by the water Energy is absorbed by the water molecules as they change from solid to molecules as they change from solid to liquid to gasliquid to gas

• This gives them more energy and This gives them more energy and allows them to move faster and move allows them to move faster and move further apart! Do the molecule further apart! Do the molecule dance!!! dance!!!

EvaporationEvaporation • the process of water changing from a liquid the process of water changing from a liquid

to a gasto a gas• occurs when occurs when water absorbs energy water absorbs energy from its from its

surroundings and becomes warmer.surroundings and becomes warmer.• because water sucks the heat energy from because water sucks the heat energy from

its surroundings, its surroundings, evaporation results in the evaporation results in the surroundings becoming coolersurroundings becoming cooler (think of (think of sweating)sweating)

• Liquid water absorbs heat energy to Liquid water absorbs heat energy to become a vapor so….become a vapor so….

Heat of Vaporization = + 2260 Heat of Vaporization = + 2260 Joules/gram/°CJoules/gram/°C

Each gram of water is absorbing 2,260 Joules of energy to change its temperature by 1º Celsius and change from a liquid to gas (vapor).

The surroundings (air) are cooling because the water needs to ABSORB the heat from somewhere!!! The heat is being absorbed from the air surrounding the water!!!

EVAPORATION IS A EVAPORATION IS A

COOLINGCOOLING PROCESSPROCESS

CondensationCondensation

• the process of water changing from a gas to a the process of water changing from a gas to a liquidliquid

• occurs when occurs when water vapor loses energy water vapor loses energy (releases heat into its surroundings)(releases heat into its surroundings)

• Because of this, Because of this, condensation results in the condensation results in the surroundings getting warmer (the air surroundings getting warmer (the air surrounding the condensing water droplets surrounding the condensing water droplets heats up) heats up)

• Water vapor Water vapor loses heat energy to become a loses heat energy to become a liquid so….liquid so….

Heat of Vaporization = - 2260 Heat of Vaporization = - 2260 Joules/gram/°CJoules/gram/°C

WARM TEMPS = EVAPORATIONWARM TEMPS = EVAPORATION

• COOL TEMPS = CONDENSATIONCOOL TEMPS = CONDENSATION(but the surrounding air actually heats up a little as (but the surrounding air actually heats up a little as the air condenses and releases the stored energy)the air condenses and releases the stored energy)

Each gram of water is releasing 2,260 Joules of energy into its surroundings to change its temperature by 1º Celsius and change from a gas (vapor) to a liquid.

CONDENSATION IS CONDENSATION IS

A A WARMINGWARMING PROCESSPROCESS

Back to Evaporation…Back to Evaporation… • What 3 factors affect how What 3 factors affect how

quickly water evaporates?quickly water evaporates?• 1)1)• 2) 2) • 3) 3)

Rate of Evaporation…Rate of Evaporation… • Temperature – The higher the Temperature – The higher the

temperature, the ______________ temperature, the ______________ water will evaporate.water will evaporate.

• This is a _________ relationship.This is a _________ relationship.• Think about it. Do you put Think about it. Do you put

clothes into a hot dryer or a clothes into a hot dryer or a cold dryer to dry them quickly?cold dryer to dry them quickly?

Rate of Evaporation…Rate of Evaporation… • Humidity – The higher the Humidity – The higher the

humidity, the ______________ humidity, the ______________ water will evaporate.water will evaporate.

• This is a _________ relationship.This is a _________ relationship.• Think about it… Do you dry off Think about it… Do you dry off

faster in the steamy bathroom faster in the steamy bathroom after you shower, or in your after you shower, or in your dry bedroom?dry bedroom?

Rate of Evaporation…Rate of Evaporation… • Wind – The higher the wind Wind – The higher the wind

speed, the ______________ speed, the ______________ water will evaporate.water will evaporate.

• This is a _________ relationship.This is a _________ relationship.• Think about it… does your Think about it… does your

hairdryer just get hot, or does hairdryer just get hot, or does it blow the hot air at you in it blow the hot air at you in order to dry your hair quickly?order to dry your hair quickly?

Water Vapor in the AirWater Vapor in the Air • The amount of water vapor in the air The amount of water vapor in the air

depends on the air depends on the air temperaturetemperature• The warmer the air, the more water The warmer the air, the more water

vapor it can contain (think of those vapor it can contain (think of those hot, humid summer days)hot, humid summer days)

• The actual amount of water vapor in The actual amount of water vapor in the air is called the air is called absolute humidityabsolute humidity

• This is measured in grams per liter.This is measured in grams per liter.

Relative Humidity Relative Humidity • This is the amount of water vapor in This is the amount of water vapor in

the air, the air, comparedcompared to the maximum to the maximum amount of water vapor amount of water vapor the air could the air could containcontain at that temperature at that temperature

• Relative humidity is a Relative humidity is a percentpercent measurementmeasurement

• Air with 100% humidity is said to be Air with 100% humidity is said to be saturated (that temp air can’t contain saturated (that temp air can’t contain any more water vapor)any more water vapor)– Precipitation (rain/snow/sleet) or Precipitation (rain/snow/sleet) or

condensation (dew/frost) will occurcondensation (dew/frost) will occur

Finding Relative HumidityFinding Relative Humidity • Use an instrument called a Use an instrument called a hygrometerhygrometer• One particular type of hygrometer is called a One particular type of hygrometer is called a sling sling

psychrometerpsychrometer– This instrument is made of two thermometers attached to a This instrument is made of two thermometers attached to a

handlehandle– One thermometer has a piece of gauze (called a sock) which is One thermometer has a piece of gauze (called a sock) which is

the soaked with water.the soaked with water.• This is called the This is called the WET BULBWET BULB• The other thermometer is called the The other thermometer is called the DRY BULBDRY BULB

– These thermometers are swung in the air for a few minutes, and These thermometers are swung in the air for a few minutes, and then the temperatures are recorded (take the wet bulb then the temperatures are recorded (take the wet bulb temperature first)temperature first)

• The wet bulb thermometer should have a lower The wet bulb thermometer should have a lower temperature, since it temperature, since it removes heat from the removes heat from the thermometer as water evaporatesthermometer as water evaporates from it. Remember, from it. Remember, evaporation is a cooling process!!!evaporation is a cooling process!!!

• The two temperatures are then used to look up the The two temperatures are then used to look up the relative humidity on a chart (ESRT’s Page 12 relative humidity on a chart (ESRT’s Page 12 BOTTOMBOTTOM))

Why do you think the SE part of the US has a higher relative humidity?Why do you think the Pacific NW coast has a high relative humidity?Why do the Rockies and Midwest parts of the US have low relative humidities?

Condensation and DewCondensation and Dew • VIF - remember that VIF - remember that air’s ability to contain air’s ability to contain

moisture decreases as the temperature decreasesmoisture decreases as the temperature decreases• As the air cools, its relative humidity increases As the air cools, its relative humidity increases

EVEN THOUGH IT CONTAINS THE SAME AMOUNT EVEN THOUGH IT CONTAINS THE SAME AMOUNT OF WATER VAPOR, THE OF WATER VAPOR, THE RELATIVERELATIVE HUMIDITY HUMIDITY INCREASES, BECAUSE ITS ABILITY TO HOLD THE INCREASES, BECAUSE ITS ABILITY TO HOLD THE WATER VAPOR DECREASES.WATER VAPOR DECREASES.

• When the relative humidity reaches 100% When the relative humidity reaches 100% (saturated), the water condenses out of the air as (saturated), the water condenses out of the air as liquid droplets or ice crystalsliquid droplets or ice crystals

• The temperature at which this will occur is called The temperature at which this will occur is called thethe dew pointdew point

• **The dew point can be found using the same **The dew point can be found using the same method for relative humidity, except use the dew method for relative humidity, except use the dew point chart (ESRT’s Page 12 point chart (ESRT’s Page 12 TOPTOP))

VIF – MAKE SURE THAT VIF – MAKE SURE THAT YOU USE THE CORRECT YOU USE THE CORRECT TABLE. BECAUSE I CAN TABLE. BECAUSE I CAN GUARANTEE YOU THAT GUARANTEE YOU THAT

THE # FROM THE OTHER THE # FROM THE OTHER TABLE WILL BE ONE OF TABLE WILL BE ONE OF THE CHOICES THAT THE THE CHOICES THAT THE “EVIL ONES” PROVIDE!!!!“EVIL ONES” PROVIDE!!!!

• Condensation can only occur if the water has Condensation can only occur if the water has something to condense onsomething to condense on

• VIFVIF - Tiny particles in the air on which water - Tiny particles in the air on which water molecules condense are called molecules condense are called condensation condensation nucleinuclei

• This can be dust, salts, volcanic ash, soot from This can be dust, salts, volcanic ash, soot from forest fires, chemicals from burning fuel, etc.forest fires, chemicals from burning fuel, etc.

• * Water vapor that condenses on the ground is * Water vapor that condenses on the ground is called called dewdew (think of walking across wet grass in (think of walking across wet grass in the morning)the morning)

• If the dew freezes on the ground, it is called If the dew freezes on the ground, it is called frostfrost• Water vapor condensing in the air forms Water vapor condensing in the air forms cloudsclouds• If the cloud forms close to the ground, it is called If the cloud forms close to the ground, it is called

fogfog

Condensation and DewCondensation and Dew

DewDew

FrostFrost

Fog in San Francisco – Cloud formed on the Fog in San Francisco – Cloud formed on the ground…ground…

CloudsClouds - - (This is FYI – you DO NOT need to (This is FYI – you DO NOT need to

memorize the types of clouds, but you should know that they memorize the types of clouds, but you should know that they exist at different altitudes and are associated with different air exist at different altitudes and are associated with different air

masses…)masses…)

• formed by the formed by the condensation of water vapor condensation of water vapor • There are three main types of clouds: There are three main types of clouds: cumulus, cumulus,

stratus, and cirrusstratus, and cirrus– Cumulus Cumulus clouds are thick, puffy clouds. They tend to be clouds are thick, puffy clouds. They tend to be

lower in the skylower in the sky– StratusStratus clouds appear as low to middle sheets or layers clouds appear as low to middle sheets or layers

of cloudsof clouds– CirrusCirrus clouds appear as high, thin or “feathery” clouds. clouds appear as high, thin or “feathery” clouds.

These clouds are made of ice crystalsThese clouds are made of ice crystals

• There are many forms of these types of cloudsThere are many forms of these types of clouds– Ex. Cumulonimbus clouds often produce strong Ex. Cumulonimbus clouds often produce strong

thunderstorms and can form tornadoes!!thunderstorms and can form tornadoes!!– NimbusNimbus – rain/storm in Latin – if you combine the above – rain/storm in Latin – if you combine the above

3 type names with nimbus or nimbo, it means that the 3 type names with nimbus or nimbo, it means that the cloud produces precipitation.cloud produces precipitation.

CLOUDS have CLOUDS have FLAT FLAT BOTTOMSBOTTOMS which which show where the show where the dew point dew point temperature has temperature has been reached been reached and the cloud and the cloud starts to form!starts to form!

This is called the This is called the CLOUD BASECLOUD BASE

•CumulusCumulus clouds that are white clouds that are white and puffy like cotton balls are and puffy like cotton balls are "fair weather" clouds and are "fair weather" clouds and are unlikely to produce precipitationunlikely to produce precipitation

•They form in warm air on sunny They form in warm air on sunny daysdays

•Cumulus clouds can form at Cumulus clouds can form at almost any altitude, with bases almost any altitude, with bases sometimes as high as 14,000 sometimes as high as 14,000 feet feet

• Cumulus clouds are clouds of Cumulus clouds are clouds of vertical vertical developmentdevelopment and may grow upwards and may grow upwards dramatically under certain dramatically under certain circumstancescircumstances

• The updrafts may be caused by The updrafts may be caused by intense heating of the air by the intense heating of the air by the ground surface, the action of a cold ground surface, the action of a cold front, or by extreme temperature front, or by extreme temperature differences between land and waterdifferences between land and water

• The vertical air currents results in The vertical air currents results in towering clouds with an towering clouds with an anvil headanvil head on on top called top called cumulonimbuscumulonimbus clouds clouds

•StratusStratus clouds are low clouds, clouds are low clouds, ranging in height from near the ranging in height from near the earth's surface up to 6,500 feetearth's surface up to 6,500 feet

•Stratus clouds form flat Stratus clouds form flat layerslayers or uniform or uniform sheetssheets– Only a fine Only a fine drizzledrizzle can form from can form from

stratusstratus clouds because there is no clouds because there is no vertical developmentvertical development

– NimbostratusNimbostratus (nimbo = rain) (nimbo = rain) clouds produce long periods of clouds produce long periods of steady rainsteady rain

• CirrusCirrus clouds are clouds are wispywispy in in appearance, and resemble appearance, and resemble horsetails of a running horse (they horsetails of a running horse (they are sometimes called are sometimes called mares' tailsmares' tails))

• They are among the They are among the highesthighest clouds, forming at elevations of clouds, forming at elevations of 25,000 feet and above, where the 25,000 feet and above, where the temperatures are far below temperatures are far below freezing freezing

• Cirrus clouds are formed almost Cirrus clouds are formed almost entirely of tiny entirely of tiny ice crystalsice crystals

These are called cirrocumulus clouds These are called cirrocumulus clouds because they are very high (cirrus), but because they are very high (cirrus), but

have the cumulus (puffy) appearance, not have the cumulus (puffy) appearance, not the wispy appearance of regular cirrus the wispy appearance of regular cirrus

clouds…clouds…

These are called cirrocumulus clouds These are called cirrocumulus clouds because they are very high (cirrus), but because they are very high (cirrus), but

have the cumulus (puffy) appearance, not have the cumulus (puffy) appearance, not the wispy appearance of regular cirrus the wispy appearance of regular cirrus

clouds…clouds…

Precipitation Precipitation • any form of water that falls from the clouds when they any form of water that falls from the clouds when they

become become too massive be supported by the rising airtoo massive be supported by the rising air• Forms of precipitation include:Forms of precipitation include:

– RainRain– SnowSnow– Sleet – rain that falls through Sleet – rain that falls through air that is below air that is below

freezingfreezing– Freezing rain – rain that Freezing rain – rain that freezes on contactfreezes on contact with a with a

surface that is below freezing (the ground)surface that is below freezing (the ground)– Hail – formed in Hail – formed in cumulonimbuscumulonimbus clouds clouds

(thunderstorms). These are ice balls which can be (thunderstorms). These are ice balls which can be as large as a softball!! as large as a softball!! HAIL ONLY HAPPENS IN THE HAIL ONLY HAPPENS IN THE SUMMERTIME!!!!SUMMERTIME!!!!

• **When water condenses on nitrate and sulfate **When water condenses on nitrate and sulfate particles (from burning fossil fuels), particles (from burning fossil fuels), acid rainacid rain is formed is formed

Rain LevelRain Level

SupercooleSupercooled Rain d Rain LevelLevel

Ice LevelIce Level

Snow LevelSnow Level

BRRRR…I’m BRRRR…I’m CHILLY!CHILLY!

Orographic Effect -Orographic Effect -VIF!!!!!VIF!!!!!

• Precipitation does not occur via the same processes Precipitation does not occur via the same processes everywhere. Another way that precipitation forms is everywhere. Another way that precipitation forms is OROGRAPHIC LIFTOROGRAPHIC LIFT– Wind hits the Wind hits the windwardwindward side of the mountain, side of the mountain, RRises, ises,

EExpands, xpands, CCools, and ools, and CCondensation occurs to form ondensation occurs to form CClouds and louds and PPrecipitation often occursrecipitation often occurs

– The air becomes saturated and the dense clouds result in The air becomes saturated and the dense clouds result in precipitation on the precipitation on the windward and top side windward and top side of the of the mountain.mountain.

– As the air goes over the top, is sinks on the As the air goes over the top, is sinks on the leewardleeward side side– As the air sinks, it compresses together and gets warmed As the air sinks, it compresses together and gets warmed

by the friction of the molecules compressing together by the friction of the molecules compressing together – Since the warmer air can hold more moisture, and since Since the warmer air can hold more moisture, and since

the air lost most of its moisture on the windward and top the air lost most of its moisture on the windward and top sides, condensation sides, condensation does notdoes not occur (therefore no occur (therefore no precipitation)! This area is sometimes called a “Rain precipitation)! This area is sometimes called a “Rain Shadow Desert”Shadow Desert”

• This effect occurs along the Sierra Nevada Mts. The This effect occurs along the Sierra Nevada Mts. The California side is wet, the Nevada side is dry. Also, the California side is wet, the Nevada side is dry. Also, the Cascade Mountains – Seattle is wet, the rest of Washington Cascade Mountains – Seattle is wet, the rest of Washington is dry.is dry.

Orographic Effect Animation

VIF - LAKE EFFECT VIF - LAKE EFFECT SNOWSNOW• Great Lakes Region – NYSGreat Lakes Region – NYS

• cP air mass passes over the cP air mass passes over the warmer & more humid lake air warmer & more humid lake air causing it to rise rapidly and form causing it to rise rapidly and form into cumulonimbus cloudsinto cumulonimbus clouds

• HEAVY snowfall occurs rapidlyHEAVY snowfall occurs rapidly• Western NYS is known as the Western NYS is known as the

SNOW CAPITAL of the USA!SNOW CAPITAL of the USA!• Lake effect snows diminish as the Lake effect snows diminish as the

lakes freeze over.lakes freeze over.

Chapter 29

Air Masses and Air Masses and FrontsFronts

Air MassesAir Masses • Large areas (blobs) of the

troposphere that have approximately the same weather, temperatures and humidity

• Air Mass Types - Named for where they develop over and come FROM

• Weather changes occur with changes in air masses

TYPES of Air MassesTYPES of Air Masses• maritime Tropical (maritime Tropical (mTmT)- warm & humid )- warm & humid

airair• continental Tropical (continental Tropical (cTcT)- hot (warm) & )- hot (warm) &

dry airdry air• maritime Polar (maritime Polar (mPmP)- cold & humid air)- cold & humid air• continental Polar (continental Polar (cPcP)- cold & dry air)- cold & dry air• continental Arctic (continental Arctic (cAcA)- very cold & dry air )- very cold & dry air • THESE ARE ALL LISTED IN THE ESRT’s ON THESE ARE ALL LISTED IN THE ESRT’s ON

PAGE 13 ON THE BOTTOM!PAGE 13 ON THE BOTTOM!

• There are no mA air masses – WHY???There are no mA air masses – WHY???

TYPES of Air Masses – TYPES of Air Masses – ESRT’s Page 13 BottomESRT’s Page 13 Bottom

Please note – NY Please note – NY DOES NOTDOES NOT receive cT air masses!!!!receive cT air masses!!!!

Please note – NY Please note – NY DOES NOTDOES NOT receive cT air masses!!!!receive cT air masses!!!!

FrontsFronts • boundaryboundary between two air masses between two air masses• bring changes in the weather bring changes in the weather

(from west to east)(from west to east)• VIF!!!!VIF!!!! - Fronts are named for the - Fronts are named for the

air that is air that is behindbehind them them• The 4 types of fronts and their The 4 types of fronts and their

symbols are listed in the ESRT’s symbols are listed in the ESRT’s on Page 13 on the bottomon Page 13 on the bottom

TYPES of Fronts – TYPES of Fronts – ESRT’s Page 13 BottomESRT’s Page 13 Bottom

Air Mass Army AnalogyAir Mass Army Analogy

• Think of air masses as an army Think of air masses as an army regiment (the bulk of the army is regiment (the bulk of the army is BEHINDBEHIND the frontline) the frontline)

• AT the Front there is FIGHTING and AT the Front there is FIGHTING and lots of VIOLENCE (lots of VIOLENCE (stormy weatherstormy weather))

• Behind the front (Behind the front (inside the air massinside the air mass) ) the general sits on his duff and the general sits on his duff and watches the goings-on while enjoying watches the goings-on while enjoying the the nice weathernice weather!!

FIGHTING/BATTLE FIGHTING/BATTLE FRONT - STORMSFRONT - STORMS

Back here…An Back here…An air mass with air mass with

NICE WEATHERNICE WEATHER

Cold FrontCold Front • Cold Cold densedense air pushes warm air pushes warm less denseless dense

airair up and out of the way up and out of the way• Cold fronts usually move very quickly Cold fronts usually move very quickly

and bring and bring short periods of short periods of showers/thunderstormsshowers/thunderstorms

• Lower temperatures are behind the front Lower temperatures are behind the front • SYMBOL – the direction of the “arrows” SYMBOL – the direction of the “arrows”

points towards the direction the front is points towards the direction the front is MOVINGMOVING

Cross Sectional View

Overhead View on Map

Cross Section View – Why does the cold air mass stay near the ground and lift the warm air

mass up?

Warm FrontWarm Front • Warm air moves up and over the cold Warm air moves up and over the cold

front as it front as it slowly displacesslowly displaces the cold air the cold air• Warm fronts move slowly, and may bring Warm fronts move slowly, and may bring

many days of steady precipitationmany days of steady precipitation• Higher temperatures are behind the frontHigher temperatures are behind the front• SYMBOL – direction of “semi-circles” is SYMBOL – direction of “semi-circles” is

the direction the front is movingthe direction the front is moving

Cross Sectional View

Overhead View on Map

Cross Section View – Why does the warm air mass slowly override the cold

mass causing long periods of rain?

Stationary FrontStationary Front • The air from the warm front and The air from the warm front and

cold front meet, but cold front meet, but do not movedo not move• These fronts have similar weather These fronts have similar weather

conditions as warm fronts conditions as warm fronts • SYMBOL – warm and cold fronts SYMBOL – warm and cold fronts

are moving in opposite directions, are moving in opposite directions, thus making a stationary conditionthus making a stationary condition

Cross Section View – look at the spread out, horizontal stratus clouds

Occluded FrontOccluded Front • Cold air catches up to and Cold air catches up to and overtakesovertakes a a

warm front (often warm front (often squeezing it between squeezing it between another cold frontanother cold front))

• May produce precipitation for many days May produce precipitation for many days • SYMBOL – cold and warm fronts “mix” SYMBOL – cold and warm fronts “mix”

hence the purple color - the “bumps” hence the purple color - the “bumps” are also on the SAME SIDE OF THE LINE are also on the SAME SIDE OF THE LINE (sometimes just a mix of red & blue (sometimes just a mix of red & blue symbols)symbols)

Overhead View On Map

Cross Sectional View

As seen here, occluded fronts (purple) are often seen in these Low Pressure Systems (mid-latitude cyclones) that move either E or NE across the US. The cold front catches up to the warm front as they circulate in a CCW rotating low pressure system, and the

occluded front is formed…

This is the jet stream. It moves from West to East in the US and dictates what our weather will be. What kind of air mass is being brought to NY right now?

Chapter 30Chapter 30WEATHER WEATHER

FORECASTING & FORECASTING & SEVERE SEVERE

WEATHERWEATHERSevere Wx BFRB Pages 125-Severe Wx BFRB Pages 125-

129129Wx Forecasting Pages 130-132Wx Forecasting Pages 130-132

FORECASTINGFORECASTING

Station ModelsStation Models • Used on weather maps to show Used on weather maps to show

the current weather conditions the current weather conditions for a particular locationfor a particular location

• They are easy to read and They are easy to read and understand understand

• ESRT’S Page 13 BottomESRT’S Page 13 Bottom

ESRT’s Page 13 Bottom

ESRT’s Page 13 Bottom

• The circle at the center shows the The circle at the center shows the amount of cloud coveramount of cloud cover

• The “flag pole” coming out of the The “flag pole” coming out of the circle shows the direction that the circle shows the direction that the wind is coming wind is coming fromfrom

• VIF - WINDS ARE NAMED FOR WHERE VIF - WINDS ARE NAMED FOR WHERE THEY COME FROM!!! Just like people, THEY COME FROM!!! Just like people, we’re from New York so we’re New we’re from New York so we’re New Yorkers!!!!Yorkers!!!!

• Each “flag” shows approximate wind Each “flag” shows approximate wind speed. A half flag shows an approx. 5 speed. A half flag shows an approx. 5 knot wind, and a whole flag shows an knot wind, and a whole flag shows an approx. 10 knot windapprox. 10 knot wind

• *Add up the amount for all of the *Add up the amount for all of the flags to get the total wind speedflags to get the total wind speed

• Air pressure is shown by using only Air pressure is shown by using only the the last 3 digitslast 3 digits of the pressure in of the pressure in millibars (coded)millibars (coded)– Ex. 1018.6 mb = 186 on the station Ex. 1018.6 mb = 186 on the station

modelmodel• To determine the air pressure from To determine the air pressure from

the numbers on the station model, the numbers on the station model, use the following rule: (aka to use the following rule: (aka to decode)decode)– If the first number is 4 or less, put a 10 If the first number is 4 or less, put a 10

in front of itin front of it– If the first number is 5 or higher, put a If the first number is 5 or higher, put a

9 in front of it9 in front of it– Put the decimal point between the last Put the decimal point between the last

two numberstwo numbers

• Ex. 892 for air pressure on the station Ex. 892 for air pressure on the station modelmodel

• The first number (8) is greater than 5, The first number (8) is greater than 5, so I will put a 9 in front of it (becomes so I will put a 9 in front of it (becomes 9892)9892)

• Then I put the decimal between the Then I put the decimal between the last two numbers (becomes 989.2 mb)last two numbers (becomes 989.2 mb)

• The correct air pressure is 989.2 mb The correct air pressure is 989.2 mb from the number 892 on the station from the number 892 on the station modelmodel

• **Remember, per the barometer in the **Remember, per the barometer in the ESRT’s, surface air pressure is usually ESRT’s, surface air pressure is usually between between 950 mb – 1040 mb950 mb – 1040 mb

• If your answer is not in this range, If your answer is not in this range, then it is wrong. Check your work then it is wrong. Check your work using the barometer in the ESRT’s!using the barometer in the ESRT’s!

Encode this weather data:Encode this weather data:

Cross River – Cloudy, wind is from the SW at a Cross River – Cloudy, wind is from the SW at a speed of 9 mph, temp is 61°F, 58° DP, 8.0 mile speed of 9 mph, temp is 61°F, 58° DP, 8.0 mile visibility, pressure is 30.35 inches and falling.visibility, pressure is 30.35 inches and falling.

61

58

8

280

\

0

88

¼

86

862

-11\

.35

Decode this Station Model!!!

SEVERE SEVERE WEATHERWEATHERESRT Page 13ESRT Page 13

I: ThunderstormsI: Thunderstorms

• small area storms formed by the small area storms formed by the strong strong upwardupward movementmovement of warm, of warm, moist airmoist air

• usually occurs usually occurs ahead of a cold frontahead of a cold front as the colder, denser air shoves the as the colder, denser air shoves the warmer air upwardwarmer air upward

• This forms the cumulonimbus This forms the cumulonimbus clouds that produce thunderstormsclouds that produce thunderstorms

• These storms are accompanied by These storms are accompanied by heavy rain, thunder, lightning, heavy rain, thunder, lightning, sometimes hail, and can also sometimes hail, and can also produce tornadoesproduce tornadoes

• All thunderstorms produce lightningAll thunderstorms produce lightning• Lightning is the discharge of huge Lightning is the discharge of huge

amounts of amounts of static electricitystatic electricity (think (think of walking across a carpet in your of walking across a carpet in your socks and then touching something-socks and then touching something-ZAP)ZAP)

• Lightning can travel from the cloud Lightning can travel from the cloud to the ground, cloud to cloud, or to the ground, cloud to cloud, or even from the ground to a cloud! even from the ground to a cloud!

• Thunder is the result of the Thunder is the result of the air air quickly expanding from the heat quickly expanding from the heat of of the lightning bolt (causes a sound the lightning bolt (causes a sound wave)wave)

• You cannot have lightning without You cannot have lightning without thunder and vise versa!!thunder and vise versa!!

Supercell Supercell Thunderstorm Thunderstorm

formations – will form formations – will form SEVERE storms and SEVERE storms and tornadoes! THIS IS tornadoes! THIS IS ONE BIG STORM ONE BIG STORM

SYSTEM!SYSTEM!

II: TornadoesII: Tornadoes

• Form from Form from very powerful very powerful thunderstormsthunderstorms (cumulonimbus (cumulonimbus clouds)clouds)

• These are These are funnelfunnel shaped columns of shaped columns of spiraling winds that extend down to spiraling winds that extend down to the ground from the base of a cloudthe ground from the base of a cloud

• The winds move into a tornado (low The winds move into a tornado (low pressure), and can reach a pressure), and can reach a maximum of 318 mph! maximum of 318 mph!

• The actual funnel is made by water The actual funnel is made by water droplets (clouds) and dustdroplets (clouds) and dust

• Tornadoes are especially Tornadoes are especially dangerous because it is so difficult dangerous because it is so difficult to predict where they will formto predict where they will form

• Damage is usually along a Damage is usually along a narrow narrow path path where the tornado traveledwhere the tornado traveled

• They usually last less than one They usually last less than one hourhour

• Most fatalities are caused by Most fatalities are caused by flying debrisflying debris

• Tornadoes are rated on the Fujita Tornadoes are rated on the Fujita scale (F0 – F6)scale (F0 – F6)

• An F6 is very rare, and can have An F6 is very rare, and can have wind speeds up to 318 mphwind speeds up to 318 mph

This area of the US is known as “tornado alley”

Why do most tornadoes in the US happen here in “tornado alley”?

This is a maritime tropical air mass “mT”

Cool, dry, dense air comes down from Canada

This is a continental polar air mass “cP”

Warm, moist, less dense air comes up from the Gulf of Mexico

The 2 air masses meet at a front and the cool dense air pushes the warm less dense air up very quickly creating a horizontal tube of swirling air – think of a roll of toilet paper.

Then, this horizontal tube of swirling air may be tilted toward the vertical by some sudden updrafts of air.

This turns the spinning tube of air into a vertical funnel cloud which eventually builds strength and speed and turns into a tornado

Here is an animation….

How does the tornado funnel form?

http://www.msnbc.msn.com/id/9007188/ns/weather-weather_news/

And now, some very And now, some very cool pictures of cool pictures of

tornadoes…tornadoes…

• Tornadoes are especially Tornadoes are especially dangerous because it is so dangerous because it is so difficult difficult toto predict predict where and when they where and when they will formwill form

• Damage is usually along a Damage is usually along a narrow narrow path path where the tornado traveledwhere the tornado traveled

• Most fatalities (deaths) are caused Most fatalities (deaths) are caused by by flying debrisflying debris

• High winds cause High winds cause severe property severe property damagedamage

TornadoesTornadoes – How they cause damage…

NEW YORK TORNADOES!NEW YORK TORNADOES!

Tornadoes will Tornadoes will pick up dust and pick up dust and debris from the debris from the ground when ground when they “touch they “touch down” – this down” – this creates a wider creates a wider swirl at the swirl at the bottom of the bottom of the tornadotornado

Yes, tornadoes are very Yes, tornadoes are very cool and interesting…cool and interesting…

But, they can also be very But, they can also be very deadly to people and deadly to people and

costly to the economy. costly to the economy. What should people do to What should people do to

prevent loss of life and prevent loss of life and damage to structures? damage to structures?

A Government or Public A Government or Public emergency emergency preparednesspreparedness

(before) plan for tornadoes (before) plan for tornadoes should consist of… should consist of…

•Warning system – TV/Radio/Internet/Sirens

•Emergency shelters designated before hand for people made homeless by the storm

•Building/Construction codes that minimize damage – ex – no mobile homes or weakly built structures

A Family/Personal emergency A Family/Personal emergency preparednesspreparedness (before) plan (before) plan for tornadoes should consist for tornadoes should consist

of… of… •Where to go? Basement/storm cellar or an interior room with no windows like a bathroom or closet

•What to have? Bottled water/canned food/battery powered radio/flashlight

•What to do? Stay put until they announce that the danger has passed

III: Hurricanes – How they III: Hurricanes – How they formform

• Huge Huge tropical low pressure systemstropical low pressure systems that get their energy from the that get their energy from the tremendous amount of tremendous amount of warm ocean warm ocean waterwater that is evaporated and that is evaporated and condensed inside the stormcondensed inside the storm

• Hurricanes MUST form over open Hurricanes MUST form over open warm ocean water (warm ocean water (WARM WATER = WARM WATER = FUEL FOR HURRICANE)FUEL FOR HURRICANE)

• Atlantic Ocean Hurricanes form over Atlantic Ocean Hurricanes form over the warm water off of the West Coast the warm water off of the West Coast of of AfricaAfrica and travel and travel WestWest across the across the Atlantic via the Atlantic via the trade windstrade winds. .

VIF - Since this is where it gets its VIF - Since this is where it gets its energy from, hurricanes weaken as energy from, hurricanes weaken as they pass over land or colder waterthey pass over land or colder water

Hurricanes form over the warm ocean water near the Equator on the West Coast of Africa

Hurricanes – How they Hurricanes – How they formform

• Hurricanes form off of the West coast of Africa and travel WEST across the Atlantic.

• Once they hit about 30 North latitude, they start to turn East!

• WHY??????

• Since hurricanes are extreme Since hurricanes are extreme low pressurelow pressure storms, the winds blow storms, the winds blow in towards the in towards the centercenter of the storm, and it spins of the storm, and it spins counter- counter-clockwiseclockwise (in the Northern Hemisphere) (in the Northern Hemisphere)

• Hurricanes are associated with very high Hurricanes are associated with very high winds and heavy rainswinds and heavy rains

• On average, hurricanes are On average, hurricanes are 400 miles400 miles wide wide• The The eyeeye of the hurricane is the center of the hurricane is the center

where there are no clouds or precipitation where there are no clouds or precipitation and the weather is generally calmand the weather is generally calm

• The The lowest air pressureslowest air pressures on Earth have on Earth have been recorded been recorded insideinside the eye of hurricanes the eye of hurricanes

• All hurricanes are named in each ocean in All hurricanes are named in each ocean in alphabetical order, with alternating male alphabetical order, with alternating male and female namesand female names

Hurricanes – Some factsHurricanes – Some facts

• A “tropical storm” is designated a A “tropical storm” is designated a “hurricane” when its winds reach “hurricane” when its winds reach 74 mph74 mph (and vice versa). (and vice versa).

• Hurricanes are classified by the Hurricanes are classified by the Saffir-Simpson Scale as Category Saffir-Simpson Scale as Category 1 (1 (weakestweakest) – Category 5 ) – Category 5 ((strongeststrongest))

• Hurricanes, Typhoons and Cyclones are all Hurricanes, Typhoons and Cyclones are all the SAME THING!!!the SAME THING!!!

• Different Ocean = Different NameDifferent Ocean = Different Name– Atlantic & East Pacific = HurricaneAtlantic & East Pacific = Hurricane– Indian & South Pacific = CycloneIndian & South Pacific = Cyclone– West Pacific = TyphoonWest Pacific = Typhoon

• The three parts of a hurricane that cause The three parts of a hurricane that cause the most damage are the most damage are storm surgestorm surge, , high high windswinds and and intense precipitationintense precipitation

• Storm surgeStorm surge is the term used for the water is the term used for the water that a hurricane blows onto the shore, that a hurricane blows onto the shore, causing causing severe floodingsevere flooding and and extreme extreme property damageproperty damage– Spring Tides = more severe floodingSpring Tides = more severe flooding– Neap Tides = less severe floodingNeap Tides = less severe flooding

• Most fatalities (deaths) are caused by Most fatalities (deaths) are caused by people drowning in the storm surge (many people drowning in the storm surge (many foolish people do not foolish people do not evacuateevacuate areas when areas when told to do so)!!told to do so)!!

• Storm surge is what caused the flooding in Storm surge is what caused the flooding in New Orleans and the Gulf Coast during New Orleans and the Gulf Coast during Katrina Katrina

Hurricanes – How they Hurricanes – How they cause damage…cause damage…

And now, some very And now, some very cool pictures of cool pictures of

hurricanes…hurricanes…

The “eye” of the hurricane is the center portion where there are no clouds

The Eyewall of a Hurricane

Air Force Meteo planes fly through Eyewalls of Hurricanes to collect data to help meteorologists determine where a

Hurricane will travel toward

Hurricane Irene – August 2011 – Note extremely powerful but extremely LARGE and able to drop a tremendous amount of precipitiation due to size and slow speed.

Hurricane Katrina – August 2005

Hurricane Katrina – August 29th, 2005

Hurricane damage can Hurricane damage can range from broken windows range from broken windows to complete demolition of to complete demolition of buildings. Until Katrina, buildings. Until Katrina, Andrew was the costliest Andrew was the costliest hurricane to date for the hurricane to date for the USA with a price tag of over USA with a price tag of over $20 BILLION! Katrina is $20 BILLION! Katrina is now estimated to have a now estimated to have a $200 BILLION price tag!!!$200 BILLION price tag!!!

Yes, hurricanes are very cool Yes, hurricanes are very cool and interesting…and interesting…

But, they can also be very But, they can also be very deadly to people and costly deadly to people and costly

to the economy. What to the economy. What should people do to prevent should people do to prevent loss of life and damage to loss of life and damage to

structures? structures?

A Public emergency preparedness A Public emergency preparedness plan for hurricanes should haveplan for hurricanes should have

Warning system – TV/Radio/Internet

Evacuation routes and signs so people can get out before the storm surge.

Emergency shelters designated for people to go to if they can’t evacuate or they are made homeless by the storm

Building/construction codes that minimize damage – ex – no mobile homes/weakly built structures

Emergency equipment/ supplies ready to come in as soon as the storm is over.

A Family/Personal emergency A Family/Personal emergency preparedness plan for preparedness plan for

hurricanes should consist hurricanes should consist of… of… Where to go?

Evacuate the area if you are in the storm surge warning area

What to have? Bottled water/canned food/battery

powered radio/flashlight/cash/ emergency contact numbers/extra clothes

What to do? Board up the windows of your home to

minimize damageStay evacuated until given the OK by the

authorities to return

A Family/Personal emergency A Family/Personal emergency preparedness plan for preparedness plan for

hurricanes should consist hurricanes should consist of… of… Where to go?

Evacuate the area if you are in the storm surge warning area

What to have? Bottled water/canned food/battery

powered radio/flashlight/cash/ emergency contact numbers/extra clothes

What to do? Board up the windows of your home to

minimize damageStay evacuated until given the OK by the

authorities to return

Climate• Def: Typical weather patterns observed over a

number of years in a given location/area.

• Weather = short term• Climate = long term

The MAJOR Factors that Affect an Area’s Climate

• Latitude – low (equatorial) – very hot, high (polar) – very cold, mid (temperate) – 4 seasons

• Elevation/altitude – low - warmer, high - cooler• Mountains – on windward (wet/cool) or leeward

(dry/warmer) side of mountain range – this is due to the orographic effect of air lifting over the mountain

• Proximity to ocean – near – moderate temp range both daily and seasonally, far – great temp range both daily and seasonally. More humid conditions.

• Ocean currents – what current flows by the area? A cold current (California is cooler than average for its low latitude) or a warm current Great Britain is warm for its high latitude

• Global air currents/circulation – weather moves west or east across that area? Brings continental (dry) air or maritime (moist) air as the winds move across the continent.