CH 18 Moisture, Clouds, and Precipitation

The States of Water  Evaporation And Humidity States of water States of water solid- ice, hail, snowsolid- ice, hail, snow liquid- rainliquid- rain gas- water vapor, steamgas- water vapor, steam

Lake Lure and the Water Cycle Water evaporates from the Lake into the air. In the air, the water vapor condenses into clouds. As more evaporation occurs, more clouds form. The clouds become saturated with water. When the clouds can hold no more water, they release it as precipitation.

Evaporation  Evaporation water molecules with enough energy escape the water's surface water molecules with enough energy escape the water's surface a cooling process a cooling process When you sweat, water evaporates from your body and you are cooled.

Humidity  a measure of the amount of moisture in the air  specific humidity-the amount of water vapor actually present in the air when specific humidity = air's capacity for holding water vapor  air is saturated when specific humidity = air's capacity for holding water vapor  air is saturated

Humidity  Relative humidity expressed as a % expressed as a % amount of water moisture the air presently holds amount of water moisture the air presently holds compared to the amount of water moisture it could hold at same temperature compared to the amount of water moisture it could hold at same temperature 100% = almost raining! Tropical Rainforest = 80% or more Desert = 25% or less Rutherfordton Avg = 45% - 89%

How Does Condensation Happen?  Air Temperature Reaches the Dew Point Dew Point - temperature at which saturation occurs Dew Point - temperature at which saturation occurs 4 Ways that air loses heat 4 Ways that air loses heat contacting a colder surfacecontacting a colder surface radiating heatradiating heat mixing with colder airmixing with colder air expanding when risesexpanding when rises

Water needs to condense on something  condensation nucleicondensation nuclei Salt Salt sulfate or nitrate particles (pollution) sulfate or nitrate particles (pollution) puff of smoke contains millions of particlespuff of smoke contains millions of particles

F/A 18 forces condensation out of the air approaching the speed of sound

Clouds  Clouds high fogs, mist, or haze that form when air above the surface cools below its dew point high fogs, mist, or haze that form when air above the surface cools below its dew point  Three main cloud types Cirrus Cirrus thin feathery or tufted high ice-crystal cloudsthin feathery or tufted high ice-crystal clouds Stratus Stratus low sheets or layers, form in stable air (moving upward slowly)low sheets or layers, form in stable air (moving upward slowly) Cumulus Cumulus thick fleecy masses formed by vertically rising air currentsthick fleecy masses formed by vertically rising air currents

Cloud Types  Clouds are classified into a system that uses Latin words to describe the appearance of clouds as seen by an observer on the ground.  Latin RootTranslationExample cumulus heap cumulus Stratuslayer altostratus cirruscurl of hair cirrus nimbus raincumulonimbus

Types of Clouds

Cumulonimbus

Cumulonimbus w/wall cloud

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Forms of Precipitation  Rain – liquid from stratus / cumulus clouds  Hail – frozen clumps of ice crystals from cumulonimbus  Sleet – raindrops that freeze on their way down  Snow – solid particles from stratus / cumulus clouds

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Snow Thunder Snow ayer.html?from= &bcpid= & bclid= &bctid= Snowbound ayer.html?from= &bcpid= & bclid= &bctid= Snowflake man ayer.html?from= &bcpid= & bclid= &bctid=

Sleet and Ice Black Ice vs. Sleet ayer.html?from= &bcpid= & bclid= &bctid= MSN Ice Storm in Midwest US&brand=msnbc&vid=1a768a27-b151- 4d11-93e9-8af0158dd0e5&wa=wsignin1.0

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Where it Rains…

Pacific Northwest

Precipitation Areas  Where it Rains windward side of mountain ranges windward side of mountain ranges storm areas, places where air rises and cools storm areas, places where air rises and cools areas favored by global wind belts areas favored by global wind belts where air converges and has to go up…. around the Equatorwhere air converges and has to go up…. around the Equator  Where it Doesn’t leeward side of mountain ranges areas of sinking (warming) air high pressure areas where global wind belts diverge

Acid Rain  Sulfate (SO 2 ) and Nitrate (NO 2 )particles from pollution act as condensation nuclei from burning of fossil fuels, volcanoes, and automobiles from burning of fossil fuels, volcanoes, and automobiles

Effects of Acid Rain  Avalanche Lake in Adirondack Park, New York State. Watersheds are especially vulnerable to acid rain  Vermont's maple trees are particularly susceptible to the effects of acid rain