If outside temperatures stay the same or decrease, what happens to relative humidity?
RH increases (greater chance of precipitation) with decreasing temperatures
2. Specific Humidity The actual amount of moisture in the air. The actual amount of moisture in the air. High Low
B. Dew Point The temperature to which air must be cooled to reach saturation The temperature to which air must be cooled to reach saturation At any temperature lower than the dew point, water vapor begins to condense At any temperature lower than the dew point, water vapor begins to condense
Dew: air contacts a cool surface and loses heat until it reaches saturation
Frost: if dew point falls below freezing, water vapor changes directly to solid ice crystals, or frost
II. Clouds Clouds are visible masses of liquid water droplets suspended in the atmosphere
A. Cloud Formation Clouds form when water vapor condenses into liquid water droplets in the air In order for condensation to occur: 1. air must be saturated (cooled to dew point) 2. must have a solid surface to condense on (condensation nuclei )
Condensation Nuclei: small particles in the air created by: – dust – volcanoes – factory smoke – forest fires – ocean salt
How does precipitation form? Clouds produce precipitation when its droplets or ice crystals become large enough to fall as rain or snow
Coalescence: Droplets are carried by the updrafts and downdrafts in a cloud They collide and coalesce to form larger droplets. When the droplets become too large to be sustained on the air currents… they begin to fall as rain or snow.