Atmospheric VariablesAtmospheric Variables

08/22/1308/22/13

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 a How it is shown on a weather map: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 by:radiation is affected by: Hours of sunlight/dayHours of sunlight/day Reflection, refraction, and Reflection, refraction, and

absorbtionabsorbtion

Isotherms Isotherms

Air PressureAir Pressure Instrument used to measure:Instrument used to 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 pressureIsobars, H and L pressure

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

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

Warm air = less dense = low Warm air = less dense = low pressurepressure

Cold air = more dense = high Cold air = more dense = high pressurepressure

Dry air = high pressureDry air = high pressure Moist air = low pressureMoist air = low pressure High altitude = low pressureHigh altitude = low pressure Pressure differences affects wind Pressure differences affects wind

speedspeed

Moisture in the AirMoisture in the Air

Instrument used to measure:Instrument used to measure: Hygrometer, psychrometerHygrometer, psychrometer

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

How it is shown on a How it is shown on a weather map:weather map: Dew point temperature is Dew point temperature is

shown on a station modelshown on a station model

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

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

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

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

Air MovementAir Movement

Instrument used to measure:Instrument used to 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 modelIsotachs or on a station model

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

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

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

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

Air TransparencyAir Transparency

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

Visibility:Visibility: Horizontal distance the Horizontal distance the

eye can see (mi)eye can see (mi)

Cloud Cover:Cloud Cover: Fraction/percentage of Fraction/percentage of

the sky that is obscured the sky that is obscured (covered) by clouds(covered) by clouds

Cloud Ceiling:Cloud Ceiling: The base height (bottom) The base height (bottom)

of the cloud layers.of the cloud layers. Measure with a ceilometer Measure with a ceilometer

which uses light pulses which uses light pulses and photoelectric and photoelectric telescope.telescope.

Base height