CHEM-5151_S05_L3_Transport1

CHEM-5151_S05_L3_Transport1 - Lecture 3: General...

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1 Suggested Reading: Brasseur 1999, Ch. 2 Atmospheric Chemistry CHEM-5151 / ATOC-5151 Spring 2005 Prof. Brian Toon (PAOS) Lecture 3: General Circulation of the Atmosphere TRAN SPORT AND TRAN SFORMAT ION GENERAL GOA L: TO UN DERSTAND THE INTERPLAY BETWEE N ATMO SPHERIC MO TION S AND ATMO SPHERIC CHEMISTRY EXAMPLE: FOR A RELATIVELY INERT MATERIAL THE DISTRIBUTION OF THE GAS IS CONT ROLLED BY TRANSPORT. GIVEN ENOUGH TIME THE MATERIAL WILL BE UNIFORMLY MIXED THROUGH THE ATMO SPHERE Midlatitude Chlorine release Antarctic Ozone Hole
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2 EXAMPLE: FOR A SHORT LIVED MATERIAL THE DISTRIBUTION IS CONT ROLLED BY CHEMISTRY 10 -17 10 -16 10 -15 10 -14 10 -13 10 -12 10 -11 10 -10 10 -9 0 20 40 60 80 100 Volume mixing ratio Altitude, km CFCl 3 (F11) CH 3 Cl CCl 4 NaCl SPECIFIC GOA LS: 1 . DETERMINE THE TRAN SPORT TIMES IN VARIOUS PORTION S OF THE ATMO SPHERE FOR COM PARISON WITH CHEMICAL LIFETIMES A. OB SERVED WINDS B. BOX MO DELS 2 . UND ERSTAN D HOW TO LINK CHEMISTRY AND DYNAM ICS A. CONT INU ITY EQUATIONS B. METEOROLOG ICAL “T RACERS” 3. FIND WAYS TO SIMPLIFY THE DYNAM ICS SO WE CAN CON CENT RATE ON THE CHEMISTRY TRANSPORT TIME SCALES -SOME COMMON TRANSPORT TERMS 1. ZONAL MEAN CIRCULATION - TIME AVERAGED WIND PARALLEL TO LATITUDE CIRCLES A. FASTEST TRANSPORT SINCE ANGULAR MOMENTUM “ACCELERATES WINDS” WHAT DRIVES THE ZONAL WINDS? -ANGULAR MOMENTUM CONSERVATION zero km per day 40,000 km per day zonal
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3 WE CAN EASILY WORK OUT THE VELOCITY OF THE AIR PARCEL IF THE PARCEL IS INITIALLY AT REST AT A PARTICULAR PLACE WHERE THE DISTANCE TO THE EARTH’S AXIS IS R THEN, IT HAS ANGULAR MOMENTUM PER UNIT MASS J= R 2 =ANGULAR ROTATION RATE OF EARTH 7.3X10 -5 RADIANS/SEC IF WE MOVE TO ANOTHER PLACE WHERE THE DISTANCE TO THE CENTER OF THE EARTH IS R+dR, THE ANGULAR MOMENTUM IS (Ω +dU/(R+dR)) (R+dR) 2 = Ω R 2 HERE dU IS THE VELOCITY THE AIR PARCEL HAS OBTAINED. EXPAND OUT AND DROP THE SMALL TERMS dRdU AND dRdR LEAVES dU=-2 dR EXAMPLE: MOVE AN AIR PARCEL FROM THE EQUATOR TO 30N. dR=-Rearth (1-cos(30)) dU=2*7.3x10 -5 *.134*6.4*x10 6 m/s=125 m/s
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4 www.weizmann.ac.il/ESER/People/Yinon-Rudich/ courses/Lecture5- Circulation.pdf B. TYPICAL ZONAL WINDS TRADE WINDS- LIGHT WINDS THAT BLOW FROM THE EAST (EASTERLIES) IN THE TROPICS WESTERLIES-NEAR SURFACE WINDS THAT BLOW FROM THE WEST (WESTE RLIES) IN MIDLATITUDES SUBTROPICAL JET-A HIGH SPEED NARROW REGION OF WE STERLY WIND WELL ABOV E THE SURFACE THAT MARKS THE POLEWARD EXTENSION OF THE HADLEY CIRCULATION POLAR NIGHT JET-A HIGH SPEED NARROW REGION OF WE STERLY WIND WELL ABOV E THE SURFACE THAT MARKS THE BEGINNING OF THE POLAR REGION S
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5 www.weizmann.ac.il/ESER/People/Y inon-Rudich/ courses/Lecture5- Circulation.pdf www.weizmann.ac.il/ESER/People/Yinon-Rudich/ courses/Lecture5-Circulation.pdf
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This note was uploaded on 03/03/2012 for the course CHEM 5151 taught by Professor Staff during the Spring '08 term at Colorado.

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CHEM-5151_S05_L3_Transport1 - Lecture 3: General...

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