Ch 23 - Water in the Atmosphere

Atmospheric Moisture Changing forms of Water Water exists in three states on Earth Solid - ice Liquid - water Gas - water vapor

2. Latent Heat Heat is absorbed or released when water changes phases Water Releases Heat Ice Water Water Vapor Water Absorbs Heat

4. Sublimation- process by which water changes phases from solid directly to gas 3. Most water enters the atmosphere through evaporation

B. Humidity- water vapor in the atmosphere When water vapor is condensing at the same rate it is evaporating, the air is saturated Dew point - the temperature at which water begins to condense faster than it evaporates

3. Absolute humidity - the amount of water in the air 4. Relative humidity - the ratio of water vapor in air to amount needed to reach saturation a. Cold air holds less humidity b. warm air holds more humidity 5. When air is saturated, water will condense with just a small drop in temperature- air has then reached the dew point

C. Measuring Humidity Thin polymer film- measured with conductivity Psychrometers Two thermometers which are spun Dry bulb records temperature Wet bulb records rate of evaporation Table is used to calculate humidity

Clouds are identified by for altitude and shape! Clouds and Fog Cloud formation Temperatures below dew point Condensation nuclei Cloud Types-3 Basic Types: Clouds are identified by for altitude and shape! Cirrus Cumulus Stratus

Precipitation Rain - Liquid precipitation Drizzle - small rain drops

Solid Precipitation Snow Most common form of frozen precipitation Consists of ice particles Sleet - rain that freezes near ground Hail - lumps of ice that form in thunderstorms by circulating in cumulonimbus clouds Ice storms- rain that freezes when it hits the ground

5. Formation Coalescence- smaller drops clumping together Supercooling - droplets that are chilled to below freezing without turning to ice

C. Measuring Precipitation Rain gauge - funnel that collects rain Measuring stick for snow Doppler Radar

D. Weather Modification - limited success Cloud seeding - providing condensation nuclei with silver iodide