Atmosphere Ch – 17 & 18
troposphere (0 - 13 km) most weather is here most water is here 80% of mass of atmosphere is here density decreases with height temperature decreases with height 6.5 C / Km lowest levels warmest due to heating of the ground Tropopause boundary between the troposphere and the Stratosphere stratosphere (13-47 km) clear and dry temp rises due to ozone layer stratopause boundary between the stratosphere and the mesosphere Layers of the Atmosphere
mesosphere (47-90 km) temperature drops again Mesopause Boundary between the mesosphere and the thermosphere thermosphere extremely thin atmosphere temp rises up to 1000 C intense solar radiation Ionosphere a portion of the thermosphere 90 – 500 km above earth air highly ionized ions form when UV rays knock electrons off N & O charged air is moved towards the poles and form auroras. Layers Cont.
The energy received from the sun Incoming must equal outgoing for a balanced heat budget The speed we get rid of the heat is very important we need a small amount of greenhouse effect to keep us warm without it we would be about 33 C colder too much greenhouse effect and we get too warm Insolation
depends on the angle the closer you get to 90 degrees the stronger the intensity what determines the angle time of day less angle in morning and evening coldest temps just before dawn more in mid day hottest temps afternoon Latitude the closer your are to poles the less the angle time of year when the planet’s poles are pointing toward the sun then the angle is the highest towards summer away winter cloud cover the more clouds you have the less intense the insolation Intensity of insolation
different objects heat at different rates land warms up quicker than water water transfers the heat to the depths while only the top layer of land gets the heat water has a higher specific heat than land water uses the heat to evaporate land cools down quicker than water Anomalies temperature inversions when cool air is trapped under warm air happens at night and early morning ground gets cold cools lower air more than the upper air smog gets trapped here Heating.
Relative humidity how close to full it is given in a % what the weather person tells us Specific humidity how much water is actually in the air expressed in grams per kilogram air can only hold so much Saturated evapo = cond the temp determines how much colder less warmer more doubles for every 11 C Types of Humidity
how to measure humidity Psychrometer 2 thermometers wet & dry evap causes cooling diff in temp correlates to humidity Humidity Cont.
Condenses Things needed 1. temp cools to the dewpoint air saturated so condenses how it cools A. contact something cold B. radiate the heat C. mix with cold air D. expansion as it rises (pressure) 2. condensation nuclei water must have something to condense on dust, salt What happens to the humidity
dew and frost air cools due to contact with cold ground and condenses the liquid if above freezing – dew, below – frost Fog two types 1. radiation fog ground cools air above ground to the dewpoint 2. advection fog warm moist air is moved over cold ground Clouds What Water Forms
Terms alto = high nimbo or nimbus = dark rain clouds Types Stratus low level Layered Nimbostratus long rains Cumulus fluffy tall clouds flat bases cumulonimbus = t-storm clouds Cirrus high feathery ice crystals due to elevation Clouds
air rises to the dewpoint Either on its own or forced up by 1. moved up a mountain 2. moved over denser air mass (front) 3. low pressure system cools at two rates moist adiabatic lapse rate 5 C – 9 C / km not a set rate due to changes in moisture content lower than dry due to condensation as a warming process dry-adiabatic lapse rate 10 C / km cloud bottoms represent condensation level Cloud Formation
Raindrops grow by bumping into each other Types of precipitation Rain Sleet condenses as rain, falls through cold layer and freezes snow sublimates from vapor to a crystal Hail condenses into rain, pushed up and freezes grows until too heavy then falls Thunderstorms freezing rain condenses into a cold rain that hits a surface that is below freezing and freezes on it Precipitation
Global Hadley cells rise = wet/sink = dry Locally Mountains Windward side side facing the wind air cools (Moist ALR) as it goes up slope wet Leeward side side opposite wind air warms (Dry ALR) as it goes down Chinook winds Eastern rockies Warm 20 C in hour Santa Ana Southern california dry and hot Where does it rain