Atmospheric Atmospheric VariablesVariables

04/19/2304/19/23

Air TemperatureAir Temperature

Instrument used to Instrument used to measure:measure: ThermometerThermometer

Units:Units: °C, °F, °K°C, °F, °K

How it is shown on How it is shown on a weather map:a weather map: IsothermsIsotherms

Important Information:Important Information: Solar radiation is the Solar radiation is the

main source of heat main source of heat energy for the energy for the atmosphere.atmosphere.

The amount of solar The amount of solar radiation is affected radiation is affected by:by: Hours of sunlight/dayHours of sunlight/day Reflection, refraction, Reflection, refraction,

and absorbtionand absorbtion

Isotherms Isotherms

Air PressureAir Pressure Instrument used to Instrument used to

measure:measure: BarometerBarometer

UnitsUnits cm, inches, millibarscm, inches, millibars

How it is shown on a How it is shown on a weather map:weather map: Isobars, H and L Isobars, H and L

pressurepressure

Important Information:Important Information: Affected by altitude, Affected by altitude,

temperature, and temperature, and moisture content.moisture content.

Warm air = less dense = Warm air = less dense = low pressurelow pressure

Cold air = more dense = Cold air = more dense = high pressurehigh pressure

Dry air = high pressureDry air = high pressure Moist air = low pressureMoist air = low pressure High altitude = low High altitude = low

pressurepressure Pressure differences Pressure differences

affects wind speedaffects wind speed

Moisture in the AirMoisture in the Air Instrument used to Instrument used to

measure:measure: Hygrometer, Hygrometer,

psychrometerpsychrometer UnitsUnits

% relative humidity% relative humidity °C, °F Dew point °C, °F Dew point

temperaturetemperature How it is shown on a How it is shown on a

weather map:weather map: Dew point temperature Dew point temperature

is shown on a station is shown on a station modelmodel

Important Information:Important Information: Dew point temperature is Dew point temperature is

the temperature at which the temperature at which air is saturated. air is saturated.

Relative Humidity is the Relative Humidity is the ratio of the amount of ratio of the amount of water vapor in the air to water vapor in the air to the maximum amount that the maximum amount that it can hold at that it can hold at that temperature.temperature.

Absolute humidity is the Absolute humidity is the number of grams of water number of grams of water vapor in one cubic meter of vapor in one cubic meter of air. air.

Air MovementAir Movement Instrument used to Instrument used to

measure:measure: Anemometer (speed)Anemometer (speed) Wind Vane (direction)Wind Vane (direction)

UnitsUnits Km/h, mi/h, knotsKm/h, mi/h, knots N, E, S, WN, E, S, W

How it is shown on a How it is shown on a weather map:weather map: Isotachs or on a station Isotachs or on a station

modelmodel

Important Information:Important Information: Wind ALWAYS blows from Wind ALWAYS blows from

high pressure to low high pressure to low pressure and is influenced pressure and is influenced by the Coriolis Effect.by the Coriolis Effect.

In High pressure In High pressure (anticyclone) winds blow out (anticyclone) winds blow out from the center and from the center and clockwise.clockwise.

In Low pressure (cyclone) In Low pressure (cyclone) winds blow toward the winds blow toward the center and center and counterclockwise.counterclockwise.

Air TransparencyAir Transparency

How it is shown on How it is shown on a weather map:a weather map: a station modela station model

Visibility:Visibility: Horizontal distance Horizontal distance

the eye can see (mi)the eye can see (mi) Cloud Cover:Cloud Cover:

Fraction/percentage Fraction/percentage of the sky that is of the sky that is obscured (covered) obscured (covered) by cloudsby clouds

Cloud Ceiling:Cloud Ceiling: The base height The base height

(bottom) of the (bottom) of the cloud layers.cloud layers.

Measure with a Measure with a ceilometer which ceilometer which uses light pulses uses light pulses and photoelectric and photoelectric telescope.telescope.

Base height