AOSC 200 Atmos umd edu hudson Website username aosc200 password aosc200fo9 Videos about Montreal ice storm and Hurricane Irene WEATHER vs CLIMATE Weather instantaneous description of what atmosphere is doing at a particular time and place Climate Description of what weather is usually like in region not just average weather description of extremes too Why do different hemispheres have different weather Different ratios of land to oceans Oceans tend to heat up and cool down more slowly than land does Mountains cause instabilities in airflow southern hemisphere is calmer That and the ocean stuff is why S hemisphere is generally better weather Warm front warm air mass flows over cold air mass produces light rain Cold front cold air mass flows under warm air mass produces heavy rain warm air is forced up very rapidly Discussion Section 1 30 Weather shorter timescales What s happening today Climate time region averaged weather Understanding Extremes DIFFERENCES BETWEEN NORTHERN AND SOUTHERN HEMISPHERES 70 of land is in North Mostly water in the Southern 82 water and 18 land Ocean acts as a thermostat and keeps seasonal difference in summer and winter less extreme in Southern hemisphere Presence of tall and wide mountain ranges in the North affect the flow of air and cause great stipulations in temperature and climate patterns Can sail all the way around globe on Southern Ocean without hitting land this means there s less friction for the air to come in contact with and weather is rougher over that area Southern Ocean right above South Pole PRESSURE Low pressure on weather map indicated with L When there s low pressure Clouds storms winds move counterclockwise Coldfront Blue on map moving downwards and Southeast Warmfront Red on map moving from Northeast So basically when a low pressure system comes through a warm front will hit followed by a Coldfront and heavy winds Behind the warmfront and ahead of the Coldfront is heavy rain whereas behind the Coldfront and in front of the warmfront is light rain see first page of notebook for image ATMOSPHERIC COMPOSITION Molecular oxygen and nitrogen compose more than 99 Of remaining 1 97 is Argon Of the remaining 93 of it is carbon dioxide All remaining gasses are known as trace species these control chemistry of atmosphere ATMOSPHERIC EVOLUTION Early atmosphere consisted of Hydrogen H Helium He Methane CH4 and Ammonia NH3 As earth cooled volcanic eruptions emitted water vapor H2O CO2 and nitrogen N2 Graph shows levels of CO2 in relation to time and is an increase over time as well as a fluctuation during each year The reason for this a maximum amount of CO2 in the atmosphere during Spring and a minimum in Fall is that since during the winter beginning of spring there are no plants to take in CO2 there is more floating around in the atmosphere However as the plants grow and take it in by the beginning of fall there is less CO2 floating around out there Example of Atmospheric CO2 Figure from lecture slides 2 Volcano releases it into atmosphere Dissolves in ocean Plants photosynthesize When we cut down forests we re releasing CO2 into atmosphere HYDROLIC CYCLE Rain falls into ocean and stuff which evaporate back up into clouds Rain falls on land mountain flows via river back into ocean and evaporate back to clouds Also water on trees transpire back into clouds All driven by energy from the sun OTHER IMPORTANT GASES Methane CH4 produced when plant material decays below water Is greenhouse gas long lifetime in Troposphere but breaks down in Stratosphere to form water Chlorofluorocarbons greenhouse gases break down in Stratosphere responsible For Ozone Hole CFCs Banned emitting CFC s into the atmosphere in US 1987 banned them in Montreal Montreal Protocol After the US banned but before protocol the amount of CFC s emitted leveled off however after the Montreal Protocol the amount emitted dropped significantly Aerosols particles suspended in atmosphere very small Deflect radiation back out to space LECTURE 3 Torricello Filled glass tube with mercury sealed at one end Inverted tube in bowl of mercury Found it didn t flow out of the tube height of bottle remained constant Concluded that pressure was holding the mercury at the bottom of the Bowl and not allowing the remaining mercury still in the tube to flow out Originally recorded results at various altitudes seeing how much mercury Remained in the tube at different air pressures Average sea level conditions caused 29 92 inches to remain Measured in mb mini Bar Pressure at a point is the weight of air above that point Column of air at surface weighs slightly more than 1 Kg per square cm Pressure Density X Temperature X Constant See chart at end of lecture 2 slides of airplane and temperature in atmosphere Can see increase in temperature from Tropopause to Stratosphere because that s where the atmosphere is being heated through the Ozone s filtering of the sun s heat Then from Stratopause through Mesosphere the temperature drops again no heating source as pressure Finally from Mesopause through Thermosphere the temp rises back up b c there s little density and pressure 1 Troposphere where air turns over Temp decreases 2 Stratosphere 3 Mesosphere region where temp again decreases with height 4 Thermosphere little mass High energy radiation received by thermosphere high temp experienced When atmosphere moves moves along constant pressure lines isobars and not along altitude lines In meteorology it s helpful to refer to geopotential height height of particular pressure value rather than altitude 850 mb 1500 m 300 mb 9000 m TEMPERATURE SCALES Dr Fahrenheit was physician defined upper fixed point 100 degrees F as the average temp of his patients In Centigrade scale 0 is defined as melting point of ice and upper fixed point 100 is defined as boiling point of water lowest possible point was 273 Kelvin scale lower fixed point 0 is theoretically lowest temperature possible melting point of ice is 273 degrees Celsius starts at 273 Kelvin starts at 0 but degrees are the same intervals SPECIFIC HEAT Specific heat amount of heat required to increase the temperature of 1 gram of the substance 1 degree C measured in cal Takes less to raise temperature of land which is why oceans stay more constant HOW IS ENERGY TRANSFERRED IN ATMOSPHERE Tornados hurricanes severe storms all require large energy source All comes from sun but how s it transferred Conduction Convection Advection Transfer of radiation Latent heat of