Influence ofvarious physical factors upon the radiative equilibrium...
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l ,id ifln J. . Url. Owp11 !JH. (1971). 22. 101·168 651·52 1'3 Influence of various physical factors upon the radiative equilibrium of the atmosphere R. V. GODBOLE and R. R. KELKAR I l1stitute of Tropical M eJe qrology , Poona (Receival 12 A ugust WIO) ABSTRACT. The effflCt8 of given vari. ' ioUlJ in water 7&pour. carbon dioxide, and oaone upon the radiative equilibrium of the atmosphere have boon in n,tigal8d. The equilibrium tempera tu re haa been computed aa an 8.,s mptol !(l eteedy "ta te by ma rchi ng p l'OCX"8lt . The study has shown that water vapour can alone aooo un l for 96· 7 per cent of the tempera ture distribution of the troposphere. whereee ozone toget her wit h carbon dioxide can practically aooount for the temperature d btelbu ticu of the etretosphere . Ozone theont y gal reepoueible Cor maintaining wcrm etretoephere. The surf ace Albedo and benoe tho ground temperatu re plays a vory impor t ant role in fixing the tem peratu re di stributi on of th e vertical column. r. IntrodueUoQ Und er the influence or radia tive alone, the vertical distribution of temper ature in the ut mospherc tenus to .\llju.t itself in such n way that the heating caused by solar radiation and the cooling clue to terrestrial radietion balance each other at every level. Absorption of solnr radi ation is a funotion of the amount of absorbing material, tho solar altitud e, and tho albedo of th o eart h'. surfuce and of clouds. The terrestr ial radiation is det ermined by considering the radi ati ve ex- chang e processes between th e various level s in the atmosphere a IHI it is essentially t\ function of th e distribution of th e absorbing mater ial in the vertical. In an earlier work (Godbole ef al . 19;0) , hereafter referred to a. poper A, the authors computed the radiative equihbrium tem- perature (RET ) of the atmosphere using a model which incorporated the effects of t he absorption of solar and terrestrial radiation by water v.lpour, carbon dioxide, and ozone, as well as the effects of convection. In the present work, the internetion between the heating and cooling components due to given chsnges in the amount of water vapour, carbondioxide, and ozoneand in the values of surface albedo has been investigated. Such a study would help understand the relative im- portance of each of these factors at different heights under differ ent conditions anti the sensi- tivity of the equilibrium temperat ure toward . changes in each individual factors. M anabe and Wetherald (1967) have reported similar work 161 but for given conditions which nrc widely different from those considered in t he present study. 2. Metbod or computation The method of app roach to the problem consists or computing tho RET for a given set of mean atmospheric conditions and recomputing it for arbitrary changes introduced in the mean atmos- pheric condition s. Changes considered are intro- duced only in one parameter at i\ time; other parameters remain unchanged from tho mean values. The mean atmospheric conditions consi- dered are those for the month of July at the locat ion 22·5°N and 80 0E which corresponds to one or th e eighteen grid points at which RETs were computed Ul paper A. The heights and pre- ssures of the sigma-levels used in the pre sent stud)' arc shown in Tabel 1. Paper A describes in detail the method of computat ion with convect ive ad j ustme nt of temperature. The same method is being adopted in the present study. The nET is computed by marching process with sta ndard a tmospheric temperature distribution (U. S. St and ard Atmo- sphere, 1962) a. initial condition. The iterations a ," continued in time steps of 6 hour. until the difference between the daily mean temperatures on two consecutive <lays becomes 1 083 th an 0·01 _ decree. Equilibrium is normally found to have r",; ehed after 800 time steps which corresponds to 200 days, and ouly in a few cases, the itera tio ns had to be extended to 300 and even 400 day s.
Transcript of Influence ofvarious physical factors upon the radiative equilibrium...
l ,id ifln J . .U rl . Owp11!JH. (1971). 22 . 101·168
651·521'3
Influence of various physical factors upon theradiative equilibrium of the atmosphere
R. V. GODBOLE and R.R. KELKAR
I l1stitute of Tropical MeJeqrology, Poona
(Receival 12 August WIO)
ABSTRACT. Th e effflCt8 of given vari.' ioUlJ in water 7&pour. carbon dioxide, and oaone upon the radiativeequilibrium of the atmosphere have boon inn,tigal8d. The equilibrium tempera tu re haa been computed aa a n8.,s mptol !(l eteedy "tate by marchi ng pl'OCX"8lt.
Th e study has shown tha t water vapour can alone aoooun l for 96· 7 per cent of th e temperature dist ributionof the t roposph ere. whereee ozone toget her wit h carbon dioxide can practically aooount for the temperatured btelbuticu of the etretosphere . Ozone ~ theonty gal reepoueible Cor maintaining wcrm et re toephere. Th e surfaceAlbedo and benoe th o ground temperature plays a vory impor tant role in fixing the tem perature distribution of th evertical column .
r. IntrodueUoQ
Under the influence or radia tive proccs~s alone,the vertical distribution of temperature in theut mospherc tenus to .\llju. t itself in such n waythat th e heat ing caused by solar radiation and thecooling clue to terrestrial radi etion balance eachother at every level. Absorption of solnr radiationis a funotion of the amount of absorbing material,tho solar altitude, and tho albedo of th o earth'.surfuce and of clouds. The terrestrial radiationis det ermined by considering the radi ati ve exchange processes between th e various levels inthe atmosphere a IHI it is essentially t\ function ofth e distribution of th e absorbing mater ial inthe vert ical. In an earlier work (Godbole ef al.19;0) , hereafter referred to a. poper A, theauthors computed the radiat ive equihbrium temperature (RET) of the atmosphere using a modelwhich incorporated the effects of t he absorptionof solar and terrestrial radiation by water v.lpour,carbon dioxide, and ozone, as well as the effectsof convection. In the present work, the internet ionbetween the heating and cooling componentsdue to given chsnges in th e amount of watervapour, carbon dioxide, and ozone and in th e valuesof surface albedo has been invest igated. Sucha study would help understand th e relative importance of each of these factors at differentheights under different conditions anti the sensitivity of the equilibr ium temperature toward .changes in each ind ividual factors. Manabe andWethera ld (1967) have reported similar work
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but for given conditions which nrc widely differentfrom those considered in t he present study.
2. Metbod or computation
The method of approach to the problem consistsor computing tho RET for a given set of meanatmospheric conditions and recomputing it forarbitra ry changes introduced in the mean atmospheric conditions. Changes considered are introduced only in one parameter at i\ time; otherparameters remain unchanged from tho meanvalues. The mean atmospheric conditions considered are those for th e month of July at thelocation 22·5°N and 800E which corresponds toone or th e eighteen grid points at which RETswere computed Ul paper A. The heights and pressures of the sigma-levels used in the presentstud)' arc shown in Tabel 1.
Paper A describes in detail the method ofcomputation with convect ive ad justment oftemperature. The same method is being adoptedin the present study. The nET is computed bymarching process with sta ndard atmospherictemperature distribution (U. S. Standard Atmosphere, 1962) a. initial condition. The iterationsa," continued in time steps of 6 hour. until thedifference between the daily mean temperatureson two consecutive <lays becomes 1083 than 0·01 _decree. Equilibrium is normally found to haver",; ehed after 800 t ime steps which correspondsto 200 days, and ouly in a few cases, the itera tionshad to be exte nded to 300 and even 400 days.
