atmospheric temperature, pressure and density
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Atmospheric Temperature, Pressure and Density. What is Weather?. Weather is the condition of the variables of the atmosphere for any given location for a specific period of time. - PowerPoint PPT PresentationTRANSCRIPT
Atmospheric Temperature, Pressure and Density
What is Weather?Weather is the
condition of the variables
of the atmosphere for
any given location for a
specific period of time.
Weather Variables include: temperature, air pressure, wind, moisture conditions, cloud cover,
precipitation and storms.
Atmospheric Temperature Atmospheric Temperature is measured in degrees Celsius, Fahrenheit or
Kelvin scales. Air temperature is measured
with a thermometer.
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Heating of the AtmosphereThe sun is the source of almost all heat in the atmosphere. If the intensity and duration of insolation is high, then the heat
energy within the atmosphere and at earth’s surface will increase. Ways by which the atmosphere can be heated include
the following:
Conduction
Heat energy from the sand moves into the atmosphere at the interface between atmosphere and
lithosphere
Conduction of heat from sand to air above sand.
Direct Absorption of Insolation
Heating of the Atmosphere
Absorption of Long-wave Terrestrial Radiation
Insolation absorbed by aerosols (ie: dust, volcanic ash, etc…) in the atmosphere lead to atmospheric heating.
Radiation from the Earth’s surface (ie: infrared radiation) is absorbed in the atmosphere with water vapor, CO2 and other gases. This will lead to atmospheric heating.
Heating of the Atmosphere
Condensation Coriolis Effect
The condensation of water (phase change
from gas to liquid) releases stored heat into
the atmosphere.
The rotation of the Earth creates friction with the atmosphere – producing a small amount of heat
in the atmosphere.
Transfer of Heat in the Atmosphere
Heat Energy within the atmosphere is
transferred by convection.
Air that is heated becomes less dense, will rise and lead to
a drop in air pressure.
Once in the upper atmosphere, air will cool, descend back to Earth and lead to
an increase in air pressure
Changes in Air Density and Air Pressure lead to the creation of
convection cells – circular patterns of heat transfer within the
atmosphere.
Transfer of Heat in the Atmosphere
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What happens to air
temperature and air
pressure as a parcel of air rises in the
troposphere?
As a parcel of air rises in the
troposphere, its temperature and pressure
decrease.
Atmospheric Pressure and Density
Atmospheric Pressure – or Barometric Pressure and Air pressure – is the pressure
exerted on a parcel of air due to weight of the overlying atmosphere pushing down
upon it.
Atmospheric Pressure is measured in millibars and/or inches of
mercury using an instrument known as a barometer.
Standard atmospheric Pressure at sea level is known as 1 atmosphere.
1 Atmosphere = 1013.2 millibars or 29.92 inches of mercury
Atmospheric Pressure and
Density
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999.0 millibars
Luis noticed a drop in air pressure for a parcel of
air moving over binghamton, ny. The barometer he is using
measured the air pressure of the parcel of
air as 29.5 inches of mercury.
What is this measurement in
millibars?
Comparison of Atmospheric Pressure with other variables
As air temperature increases, air
pressure decreases.
As the amount of water vapor
in the atmosphere
increases, the air pressure decreases.
Tem
pera
ture
Pressure Pressure
Water molecules have a smaller mass
than oxygen and nitrogen
As you increase in altitude, the
air pressure decreases.
Wat
er v
apor
Altit
ude
Pressure
Weather Station Model
A weather station model is a series of symbols referencing weather data collected for a particular
location at a specific time of day.
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TEMPERATURE
The air temperature is recorded in (˚F)
The location has an air temperature of 28˚F.
Weather Station Model
Barometric (Air) Pressure
The Barometric Pressure is recorded in millibars.
**If the number is above 500, place a “9” in front of the first number and place a decimal
before the last number.**
**If the number below 500, place a “10” in front of the first
number and place a decimal before he last number.**
The location has a barometric pressure of
1019.6 millibars.
Weather Station Model
Barometric Trend
The barometric trend is recorded in millibars. Place a
decimal between the two numbers to determine the
barometric trend
+ = pressure higher than 3 hrs. ago.
- = pressure lower than 3 hrs. ago.
/ = pressure that is steadily rising
\ = pressure that is steadilyfalling
The barometric trend for the location is as follows: There has been a steady rise in barometric pressure over the last three hours by 1.9 millibars.