1. Atmospheric Variables 9/3/2015

2. Air Temperature Instrument used to measure: Instrument used to measure: Thermometer Thermometer Units: Units: °C, °F, °K °C, °F, °K How it is shown on a weather map: How it is shown on a weather map: Isotherms Isotherms Important Information: Solar radiation is the main source of heat energy for the atmosphere. The amount of solar radiation is affected by: Hours of sunlight/day Reflection, refraction, and absorbtion

4. Isotherms

5. Air Pressure Instrument used to measure: Instrument used to measure: Barometer Barometer Units Units cm, inches, millibars cm, inches, millibars How it is shown on a weather map: How it is shown on a weather map: Isobars, H and L pressure Isobars, H and L pressure Important Information: Affected by altitude, temperature, and moisture content. Warm air = less dense = low pressure Cold air = more dense = high pressure Dry air = high pressure Moist air = low pressure High altitude = low pressure Pressure differences affects wind speed

9. Moisture in the Air Instrument used to measure: Instrument used to measure: Hygrometer, psychrometer Hygrometer, psychrometer Units Units % relative humidity % relative humidity °C, °F Dew point temperature °C, °F Dew point temperature How it is shown on a weather map: How it is shown on a weather map: Dew point temperature is shown on a station model Dew point temperature is shown on a station model Important Information: Dew point temperature is the temperature at which air is saturated. Relative Humidity is the ratio of the amount of water vapor in the air to the maximum amount that it can hold at that temperature. Absolute humidity is the number of grams of water vapor in one cubic meter of air.

10. Air Movement Instrument used to measure: Instrument used to measure: Anemometer (speed) Anemometer (speed) Wind Vane (direction) Wind Vane (direction) Units Units Km/h, mi/h, knots Km/h, mi/h, knots N, E, S, W N, E, S, W How it is shown on a weather map: How it is shown on a weather map: Isotachs or on a station model Isotachs or on a station model Important Information: Wind ALWAYS blows from high pressure to low pressure and is influenced by the Coriolis Effect. In High pressure (anticyclone) winds blow out from the center and clockwise. In Low pressure (cyclone) winds blow toward the center and counterclockwise.

11. Air Transparency How it is shown on a weather map: How it is shown on a weather map: a station model a station model Visibility: Visibility: Horizontal distance the eye can see (mi) Horizontal distance the eye can see (mi) Cloud Cover: Cloud Cover: Fraction/percentage of the sky that is obscured (covered) by clouds Fraction/percentage of the sky that is obscured (covered) by clouds Cloud Ceiling: The base height (bottom) of the cloud layers. Measure with a ceilometer which uses light pulses and photoelectric telescope. Base height