1. Problem 8 EQ: What is air?

2. METEOROLOGY What are the cookbook ingredients of weather? What is air? What is the atmosphere? What is atmospheric pressure? What is wind?

3. What are the four main “cooking ingredients” to cook up some weather? Air Water Land Heat (Solar) WEATHER Let’s talk about air first.

4. Air A mixture of gases: N 2, O 2, CO 2, H 2 0 Air Pressure demos toilet plunger on board note card supporting water in upside down jar can with boiling water crushes when placed upside down in cold water water stays elevated in test tube when placed upside down in beaker of water Kinetic theory of matter: fast moving air molecules collide with surfaces creating a force P = F / A Last demo a type of barometer mercury aneroid ~30 in.

5. The Atmosphere Structure Atmosphere like “swimming pool” of air, P ~ 1 / alt 75% gases in troposphere Stratosphere temp. increases due to O 3 energy absorption Tropopause “lid” on weather

6. Atmospheric Pressure P = F / A (1 kg/cm 2 or 14.7 lb/in 2 at Earth surface = 10 meter column of water) SI: 1 Pa = 1 N/m 2 A standard atmosphere ( 1 atm), avg. at mid latitude location = 101,325 Pa at sea level. National Weather Service unit is the millibar (mb). 1 mb = 100 Pa. Standard sea level pressure = 1013.25 mb.

7. Surface Atmospheric Pressure Surface pressure map = contour map of isobars Isobars = lines of equal pressure Pressure gradient = rate of pressure change Pressure gradient force = force acting on air to accelerate it 1000 mb 950 mb If the Earth did not rotate, which direction does the wind blow and what is its relative speed?

8. But the Earth does rotate and low and high pressure areas make isobars curve around them. As a result, winds tend to move parallel to isobars due to a balance between pressure gradient force and Coriolis effect + inertia.

9. How does the temperature change in the troposphere? Adiabatic lapse rate = ΔT / ∆Alt. Adiabatic means TE insulated air parcel (imaginary box of air) Air Parcel P Vol TE stays the same T DALR = Dry adiabatic lapse rate = cooling rate for air parcel <dew pt. Moist ALR = cooling rate for a.p. > dew pt. (latent heat release) ELR = Environmental lapse rate = surrounding atm. lapse rate ΔDew pt. = change due to P change Lifting Condensation Level = (DALR-Δdew pt) -1 x (T G -dew pt) If ELR<DALR, then air is stable If ELR>DALR, then air is unstable, rising air will gain buoyancy Altitude (m) T( 0 C) DALR ~3 -10 0 C/km USE 10 0 /km ELR ~ 6.5 0 /km ΔDew Pt. ~ 2 0 /km

10. Problem: Cumulus clouds are observed on a sunny afternoon. The temperature is 25 0 C and the dew point is 7 0 C. How high are the flat bottoms of the cumulus clouds? Answer: 2.25 km or 7380 ft.

11. Wind A convective response to temp/pressure difference. Direct solar rays (concentrated energy) at Equator, and low angle rays (less concentrated light) at Poles makes temp differential. Coriolis Effect (Earth rotation) on wind direction. Model of global wind patterns. Coriolis Effect, Hadley cell, ITCZ (doldrums), 0 0 latitude, Easterly trade wind, Horse latitudes, 30 0 latitude, Westerly trade winds, Subtropical jet stream, Polar front jet stream, 60 0 latitude. Polar Easterly trade winds