Presentation on theme: "The Atmosphere Earth radius 6,370 km (3,981 miles) The atmosphere extends upward to 500 km (321 miles), HOWEVER, 99% of all atmosphere gasses are below."— Presentation transcript:
The Atmosphere Earth radius 6,370 km (3,981 miles) The atmosphere extends upward to 500 km (321 miles), HOWEVER, 99% of all atmosphere gasses are below 32 km (20 miles) Therefore Although the entire atmosphere = 8% of earth’s solid radius 99% of gasses 0.005 = 0.5% (one half of one percent) of earth’s radius The atmosphere is very thin Troposphere Tropopause barrier! Cloud charts, radiosonde. instruments
Dry Air Two common gasses, N 2 (78%) and O 2 (21%), make up 99% of dry air. Other gasses, e.g. CO 2 CH 4 NO 2 and water vapor H 2 O also play an important role by keeping the atmosphere warm, the “greenhouse effect”. For Wet Air add water vapor (up to 7% in moist hot tropics) 4% is more typical around here.
Solar Heating The equator receives 2.5 times more sunlight (insolation [photons / m 2 ]), incoming solar radiation, than the poles. Highest average annual ocean surface temperatures (~27 o C) at equator Lowest 0 o C at high latitudes Diff. drives density/pressure Differences => wind DEMO flashlight and globe 23.5
Density falls off with altitude; pressure is caused by impacts, dense air has more impacts P = RT
Pressure differences cause WIND Winds flowing into low pressure = low density areas are said to Flow in response to the Pressure Gradient Force.
Heat vs. Temperature Atoms in air are in constant motion, the energy of their motion is known as kinetic energy. Kinetic energy increases as the speed of atomic motion increases. E k = 1/2mv 2 (identify symbols) Heat energy is the total kinetic energy of all the atoms in a substance. The more atoms present, the greater the heat. Temperature represents the average kinetic energy of the atoms in a substance. A few atoms with rapid motion will have a higher temperature than many atoms with slow motion.
1. Atmosphere Layers w/ Pauses 2. Pressure the weight of air above 4. 75% of gasses In Troposphere 6.5 o C/km equator poles Ozone layer 6. Note change of sign of lapse rate at Tropopause (next slide) 5. lapse rate 3. Tropopause higher at equator
Coriolis Effect Air masses at rest above the equator are moving much faster than air masses at rest over us in NJ. Both must rotate once per day, but the equatorial air goes much further.
Coriolis Effect Air in Northern Hemisphere deflects to the right, reverse in Southern H. Equatorial Air has faster spin As it moves toward poles it still has it, so it is faster than land below DEMO: Coriolis Clip Coriolis Effect: Flowing winds appear to turn due to earth’s rotation
Winds blowing parallel to isobars are called geostrophic winds This occurs well above the surface where there is no friction Notice pressure gradient force always from high to low pressure, but Coriolis perpendicular to actual flow direction Earth’s rotation appears to turn winds flowing along a pressure gradient
The major wind cells Coriolis “turns” them If Earth did not rotate, there would be one cell in each hemisphere. Note the formation of Ocean Current Gyres LOW HIGH LOW Hadley Cell Ferrel Cell Polar Cell
Horizontal temperature differences Temperature effects density and pressure: 500 mb 700 mb 850 mb WarmCold P surface If you heat something it expands and gets less dense A 500 millibar pressure level is much higher in hot air. Hotter air has lower density and greater volume 1000 mb P = R’ T so T = P / R’
Polar Jet Formation Steep gradients of Pressure cause higher velocity geostrophic winds. This is the trigger for jet stream flow.
For the Polar Jet, the eddy is in the Ferrel cell on the upper polar side, and so air flows from the west to the east, the “Westerlies” Since the pressure difference is great at the boundary, the jet is a very fast wind More polar air is denser, so it wedges under the low density warm air. Rotation causes an eddy to form
Subtropical Deserts +/- 30 o latitude Highs where Hadley/Ferrel Cells descend
Water only compound in three states (liquid, gas, solid) on Earth’s surface. Heat energy is transferred through the atmosphere as water changes from one state to another. The atmosphere’s heat is absorbed by water in processes such as melting, sublimation, and evaporation. ““These two transfer the most energy, are less common, don’t cause storms Evaporation puts moisture (water vapor gas) into the atmosphere and cools the air Condensation releases heat to air & forms cloud droplets “water vapor”
Figure 1-4b Lifting a moist air mass results in condensation, liquid droplets are clouds, coalescence yields precipitation
Orographic Lifting Windward Rain Forest Leeward Rain-Shadow Desert Rain also on the high Leeward drainage sometimes Flash floods on dry plateau
Frontal lifting occurs when two large air masses of contrasting density (temperature, moisture content) meet. The boundary between the air masses is termed a front and may be 10 to 150 km (6-94 miles) across and hundreds of kilometers in length. Frontal Lifting
Friction turns surface winds back toward the pressure gradient. Near the surface, winds almost move from High to Low pressure They spiral counterclockwise into a Low in Northern Hemisphere AT THE SURFACE
Buoyancy Lifting Start Local Heat Hot Air Expands Dense air falls into low density area hot molecules bounce off the high density floor bounce up (heated atoms speed up paddle board analogy) Atoms close together (dense, high pressure) “fall into” the nearly empty (low pressure) area
Hurricanes &Typhoons (Tropical Cyclones) When extremely hot ocean surface temperatures (>26 o C) cause hot, moist surface air, huge clusters of thunderstorms develop at sea. If uplift gets extreme, these can organize into a gigantic Low with spiral storm lines, and winds exceeding 74 mph, a Tropical Cyclone, aka Hurricane
Hurricanes are fueled by Latent Heat of Condensation release. One day equals the energy production of US for a year