Weather

Word	Definition
Weather	describes the condition of the atmosphere during the near terms (over the next few days).
Air Temperature	is a measure of how fast the air molecules move. It gives a number to how hot or how cold the air is.
Thermometer	is an instrument for measuring air temperature.
Humidity	the amount of moisture (water vapor) in the air.
Relative Humidity	is the amount of moisture in the air divided by the maximum amount of moisture that can be in the air.
Dew Point Temperature	is the temperature at which water comes out of the air when the air temperature drops to this temperature threshold.
Psychrometer	an instrument for measuring dry-bulb temperature and wet-bulb temperature, which are used to determine the relative humidity and the dewpoint temperature .
Air Pressure	the force of air pressing on a surface divided by the surface's area.
Barometer	an instrument for measuring air pressure.
insolation	sunlight or incoming solar radiation.
Precipitation	the water falling down from the air in the form of rain or snow or ice.

Word

Definition

Weather

describes the condition of the atmosphere during the near terms (over the next few days).

Air Temperature

is a measure of how fast the air molecules move. It gives a number to how hot or how cold the air is.

Thermometer

is an instrument for measuring air temperature.

Humidity

the amount of moisture (water vapor) in the air.

Relative Humidity

is the amount of moisture in the air divided by the maximum amount of moisture that can be in the air.

Dew Point Temperature

is the temperature at which water comes out of the air when the air temperature drops to this temperature threshold.

Psychrometer

an instrument for measuring dry-bulb temperature and wet-bulb temperature, which are used to determine the relative humidity and the dewpoint temperature .

Air Pressure

the force of air pressing on a surface divided by the surface's area.

Barometer

an instrument for measuring air pressure.

insolation

sunlight or incoming solar radiation.

Precipitation

the water falling down from the air in the form of rain or snow or ice.

Key Things to Know in Weather

Black and rough surfaces are the best absorbers and radiators.
Black absorbs / white reflects.
Good absorbers of radiation are good radiators.
The closer the air temperature is to the dew point temperature, the greater the chance of precipitation.
As temperature increases, air pressure decreases.
As moisture content increases, air pressure decreases.
Air pressure decreases with altitude.
Highs are cool and dry; Lows are warm and wet.
Wind is due to air pressure differences.
Wind blows from high to low pressure.
Wind is named for the direction it is coming from.
Highs are regions of divergence (clockwise).
Lows are regions of convergence (counterclockwise).
The closer the air temperature is to the dew point temperature, the greater the chance of precipitation.
Weather moves from west to east.
As temperature increases, air pressure decreases.
As moisture increases, pressure decreases.
Air pressure decreases with altitude.
High pressure areas are cool and dry; low pressure areas are warm and wet.
Wind is due to air pressure differences.
Weather moves from west to east in the United States.
Infrared has long wavelength.
Carbon dioxide and water vapor absorb infrared radiation.
LOW PRESSURE: WET WEATHER (WARM).
HIGH PRESSURE: DRY WEATHER (COOL).
WEATHER MOVES WEST TO EAST.

Example 1

On a cold winter day, the air temperature is 2° C and the wet-bulb temperature is –1° C. What is the relative humidity at this location?
(1) 6% (3) 51%
(2) 37% (4) 83%

On p.12, on the bottom table, go down from a difference of 3° C = 2° C - (–1° C) = (2 + 1)° C . stop at the dry-bulb of 2° C. The relative humidity = 51%. (3)

Weather

Key Words in Weather

Key Things to Know in Weather

Example 1

Exercises