LACEMOPLACEMOP

Factors that shape Weather

Some DefinitionsSome Definitions

Weather: a condition of the atmosphere in one place during a short period of time

Climate: weather patterns typical for an area over a long period of time

LatitudeLatitudeEarth-Sun Relationships — seasons and atmospheric scattering and energy spreading.

Air MassesAir MassesAir masses take on the “weather” of the place from which they came.

The meeting of two air masses is a front.

Air MassesAir Masses

Convectional Precipitation:Typical of hot climates; convection occurs after morning sunshine heats warm moist air. Clouds form in the afternoon and the rain falls.

Near Equator

Convectional PrecipitationConvectional Precipitation

Frontal Precipitation — when 2 fronts of different temperatures meet.

Warm air forced upward by heavier, cool air.

Rising warm air cools = precipitation--Most common type

CContinentalityontinentalityLarge bodies of water have moderating effect on land temperatures.

In Plain English: Temperatures along the coastline are always milder (cooler in summer, warmer in winter) due to the effect of breezes coming from the water.

CContinentalityontinentality

Why? Land and water absorb and store energy at different rates. Land changes quickly — water more slowly. Opposite air blows off the water and moderates land temperature.

Mid-Latitudes

a) summer—warm masses of air from the Tropics

b) winter– cold masses of air from the high latitudes

ElevationElevation

a)Height above sea level

b) Temperature decreases as elevation increases

MMountain Barriersountain Barriers•Blocks air masses and causes precipitation.

• Orographic Precipitation: warm moist air forced upward when passing over a mountain. Warm winds cool as they rise over the mountains and clouds form

• Air is warm and dry on the other side

• Windward: mountain side which faces the ocean

• Leeward: mountain side which is in a “rain shadow” (no precipitation received)

OOcean Currentscean Currents• Help to distribute heat

• Carry warm water from tropics to poles and return cold water to the Equator

• Winds affect current movement

• Air masses take on water temperature

PPressure & Windressure & Wind•Rising warm air = low pressure

•Falling cool air = high pressure

•Wind moves high to low

•Movement from equator to poles and back

•Coriolis Effect: rotation of the earth bends the patterns of the wind

Winds blow in constant patterns and are called prevailing winds.

Historical Fact:Historical Fact: Many were named for the direction they blew…some were even given names because they were used by trading ships through the region…

Trade winds -- blow from the northeast toward the Equator and from the southeast toward the equator

Westerlies – prevailing winds in the mid-latitudes blow diagonally west to east

Polar Easterlies – blow diagonally in the high latitudes east to west—pushing the cold air toward the mid latitudes

Doldrums: windless area near the equator

Horse Latitudes: Historically, ships would lighten their loads in order to take advantage of the slightest wind such as cargo, excess supplies and livestock…this also included horses.

Greenhouse EffectGreenhouse Effect

Earth’s atmosphere acts a a greenhouse trapping 50% of the sun’s heat radiation.

Clouds, water vapor and carbon dioxide absorbs the heat reflected by the earth and radiates it back again to keep the balance.

Greenhouse EffectGreenhouse Effect

Global WarmingGlobal Warming

Burning of coal, oil and natural gas has caused the CO2 levels to rise—increased burning will trap more heat in the atmosphere.

Global WarmingGlobal Warming

Global Warming: Scientists claim that there has been a rise in CO2 levels and that has caused a rise in global temperatures.

• Some scientists predict it will cause more extreme global weather patterns such as rapid water evaporation causing drier soils between rain and humidity might increase due to rapid evaporation in the oceans

•Not all scientists agree on the nature of global warming-hmmmmm!