Unit 2 Notes Moisture in the Atmosphere Where is the water on the surface of the planet The oceans Oceans contain 92 22 of Earth s water freshwater contributes about 2 28 Surface water Ice and glaciers make up the bulk of this water 99 357 of the surface water Lakes 0 61 Atmosphere 0 03 Rivers and streams 0 003 Water can be solid liquid or gas in the atmosphere Each phase of water is associated with an amount of energy solid having the lowest energy Must add energy to a system to get it to change into a solid Solid liquid takes about 80 cal per gram of liquid water Liquid solid 80 cal Liquid Gas 540 cal Water can exist at 100 degrees Celsius as both liquid and gas To move from gas to liquid you have to take gas out of the environment 540 cal Latent Heat the amount of energy that gas contains more than liquid 540 cal Humidity the measure of how much moisture is in the air Relative humidity Water vapor content of air over the maximum h2o vapor In order for evaporation to occur you much add energy to the system constant of the air times 100 The cooler the air the less hotter it can hold At any temperature there is a point at which that air may become saturated full Saturation o Due point the temperature at which air becomes saturated Specific Humidity based on the mass of the water So calculate the mass of the water molecules that are in a volume of air and divide it by the mass of the air This humidity does not depend on temperature because the mass is always the same as long as you don t reach the due point Air in the atmosphere moves Air that is relatively warm rises up into cooler air There is a relationship between temperature and pressure Moving air o Temperature P T P T the ratio remains constant so if you change the pressure of air you also change its temperature o As you increase air s elevation the pressure goes down o Volume PV P V PV T P V T o This means that air cools as it rises so relatively increases as it goes up because cool air can hold more water Adiabatic Processes A change in temperature to due pressure Clearly involves a movement in a parcel of air o Dry Adiabatic Lapse Rate 10oC 1000 meters also known as DALR First you need to know whether or not a parcel of air is dry As long as the temperature of air is above the dew point it is considered to be dry KNOW THESE o Say you have a location on the beach and the air temp is 30 oC First you want to know if its saturated T 30 Dew point 22 Not saturated so dry We are going to carry these up a thousand meters Take temp of air at 0 meters minus lapse rate equals temperature of air at 1000 meters o Dew Point Lapse Rate 2oC The air decreases 2 degrees We have to calculate what the dew point is at 1000 Dew Point at height temperature at dew point minus DPLR This is wet because it s at 100 humidity o The lifting condensation level The elevation at which air becomes saturated As air rises above this you end up with a cloud o If you continue to raise the elevation of a parcel of air the temperature goes down as well as its ability to condense water o Temperature at 2000 m Temp at 1000 MALR o Once you get above the condensation level you don t need the dew point o As the air starts to go down in the atmosphere the temperature of the air goes up Its ability to form water goes up Anytime you re dealing with air decreasing in elevation you use dry lapse rate opposite T o Dry Lapse Rate T 1 T2 But the air when you get back down is warmer This is because all of the energy that was in the water vapor has been added to the temperature of the air It is also much dryer that it was when it started This transfer of energy has warmed the air o Ex At the surface T 24 T Dew point 20 It s dry because the dew point temp is less that the air temp The temperature at 1000 m would be 16 which the temp at the dew point is 18 This gives you a temp less that the dew point so the condensation level is somewhere between the two At 500 m T drops by 5 half of a thousand T 24 5 19oC SO 500 is LCL Temperature at 1000 is above LCL so use moist rate 19 3 16oC o Trick LCL T Tdewpoint 8 x 1000 base elevation o When base elevation is saturated fog How do we actually get air up into the atmosphere Convective lifting when hot air rises Clouds have flat bottomed clouds because that is where the cloud hits the LCL Also get late afternoon showers which are typically short and sporadic and don t cover a large area Orographic lifting requires a mountain We re looking at air that are pushing towards the mountain and cools when it cools over the mountain where it can run into the LCL As it goes down the other side of the mountain it is warming and dry We get very different conditions on each side of the mountains There is a lot more water on the west side of the Rockies than the east Rain shadow occurs on the windward side of the mountain Receives all the rain This is caused by the previous process Happens on the big island in Hawaii in the saddle between two mountains Frontal lifting Has to do with when air masses of different types coming into contact with each other o Air Mass conditions of temperature and humidity and stability a regional homogenous mass of air having specific o All of the air masses are classified by moisture and temperature characteristics of the source region o Moisture classified as m or c m means maritime which means they form over water C means continental so they form over land o Temperature dependent on where that continent or where the ocean is A P T E AA A Artic AA Antarctic coldest P Polar T Tropical E equatorial o Polar front o mP mT cP cT These are the ones we come into contact the most o mid latitude cyclones migrating low pressure centers that are associated with different air mass types any front is the boundary between two air masses A Polar front specifically is a boundary between maritime tropical air coming from the pacific and cP air from Canada Low pressure develops creating a cyclone large movement of air around a low pressure area in northern hemisphere it moves in counter clockwise motion A low pressure area can develop two fronts both a cold front and a warm front So …