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Maw<vn. (1996). 47. l 115-124 551.52 : 551.588.1 Energy balance at the land-surface interface SANGEETA SAXENA, 1,' S. PILLA!. B. S. MURTH Y an d K. G. VERNEKAR Indian In.titute oj Tropical Mtlta rolagy, Pun. (Rtcti ••d /0 November /994, Modiji.d /7 April /995) _ -"a lIIlt a I(IIa , """"'. l\' 1ilt II{ 'II' m h "'" <it "'M,I\. 'l'" II{ '""'" ... ivt1e • 'I ........ ""'" """ mil I t,,""' <kII, 'l'I oR ... 'I" """'"' ..m m '" ""'" """ • "" Oft __ aflmI . "'" __ a!lmI . 'l'" PIT aflmIlI!t oR 8 mil .... ""'" .. ..... ,. mil I .... wt tT-! • """' .... II{ fn1t h "'" IIItil 0l!'A IIT1ll mil I ""'" • 'II' "'" • '"" it .ro-. • aa"'" II{ 1ll .... lI!l .,. i I ABST1lACT . A lIDa111C1le field upniment ... conducted a . the Indian Institu te of Tropical Meteoro- 101)' (lTTM). Path_n. Pune and the enel"lY bud, n at the land surface interface ...... studied (or clear and d oudy daY' eve r bare IOil usi na in .. rumented • nd radiometer and 'Oil temperature probe. all the componenu of the cnc l'JD' budad. t.e .. the seru ib1e beat Ilux, latent heal nux. soil hUI nux and net radiltion wen meuured directly and the t neflYbalance was computed. It is observed that when considered over Ihe ..mole day, the enefl)' budaet is (airly balanced. As • part of ettersy the Bowen's ratio b abo dbcuued. Kl')' words - Sensible heat Oux. Latent heat flux. Soil heat flux.. Nrt radi ation. Enel'lY budeet· I. Introduction It bas been increasingly realised that land surface processes si inifican lly influence wea ther and climate. Charney et 01. (1977). Shukla an d Mintz (19821, Sud and Sm ith (1985) have s hown the need far Inclusion of land s urface exc hange processes in the meteo rological models. To paramete rize land surface processes many field experiments on medium scale an dl arge scale have been conducled. AmoniSt the se. HAP EX-MOBILHY (Andre et aL 1986), FIFE (Sellers et 01. 1988) and La Cra u experiments are major ones . In these experiments. emphasis was given to observa tiona l techniques , and the variou s fluxes were determined precisely and validated with the help of satellite observations. In some of the bi"er programmes like World Climate Research Programme (WC R P) and Global Energy and Water Cycle Experiment (GEWEXl. th e measurement programmes arc planne d 10 resolve 'scaling-up ' prob lem s of smaller i rid point observations to mesoscale grid point obs ervations. That is to begin with. observations reiard ini p artition of so lar energy over a plain land and over a vegetated land. soil moisture (II ' and roughness. arc taken on a small scale of 10 X 10m or 100 X 100 m. The present study is a small scale expe riment which may be the beginning of an experiment in the underst an d ing of larie grid mesh. A small scale field programme was conducted at the Indian Institute of Tropi cal Meteorology (llTM). Pashan, Pune , (18' 32'N. 73' 5I'E ). 10 study the part ition of energy at the land surface interface. Earlier studies on land surface energy balan ce have been reported by Mitsuta tt 01. ( 1973) and ' Smith et 01. (1991). Mitsuta studied the partition of incoming energy over a period of 24 hour s a nd tried to find out- lhe imba la nce . Smith's elaborate experiment co nsis ted of the installation of net radiometer. sonic anemometer. soil thermometer. Bowen's ratio measuring instrument. nux plates etc. Usini thes e inf rastructures. Smith tried 10 verify the evapo transpiration eq uations given by Penman. The aim of the present experiment is 10 study the partition of the incoming energy al the land surface interface using tower instrumentat ion , 'oil temperature probe and a net radiome ter.

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Page 1: t,,'metnet.imd.gov.in/mausamdocs/14721_F.pdf · Energy balance at the land-surfaceinterface SANGEETA SAXENA, 1,'S. PILLA!. B. S. MURTHY and K. G. VERNEKAR Indian In.titute ojTropical

Maw<vn. (1996). 47. l 115-124

551.52 : 551.588.1

Energy balance at the land-surface interface

SANGEETA SAXENA, 1,' S. PILLA!. B. S. MURTHYand

K. G. VERNEKARIndian In.titute ojTropical Mtlta rolagy, Pun.

(Rtcti••d / 0 November /994, Modiji.d /7 April /995)

_ -"a lIIlta ~a I(IIa , """"'.~ l\'1ilt~ II{ 'II' m h "'" <it "'M,I\. 'l'" II{ '""'" ...

ivt1e~ • ~ 'I........~ ""'" """ ~ mil I t,,""' <kII, 'l'I oR~ ... 'I" """'"'~ .. m m '" ""'" """ • "" ~. Oft __ aflmI. "'" __ a!lmI . 'l'" PIT aflmIlI!t oR~ 8 ~ mil .... ""'"~ .. .....,.~ mil I .... wt tT-! • """' .... II{ fn1t h "'" IIItil 0l!'A~IIT1ll mil I ""'" • 'II' "'" • '"" it .ro-. • aa"'" II{ 1ll .... lI!l .,. i I

ABST1lACT . A lIDa111C1le field upniment ... conducted a.the Indian Institu te of Tropical Meteoro101)' (lTTM). Path_n. Pune and the enel"lY bud, n at the land surface interface ...... studied (or clear andd oudy daY' eve r bare IOil usina in ..rumented IO~n. • nd radiometer and 'Oiltemperature probe. all thecomponenu of the cncl'JD' budad. t.e.. the seru ib1e beat Ilux, latent heal nux. soil hUI nux and net radiltionwen meuured directly and the t neflYbalance was computed. It is observed that when considered over Ihe..mole day, the enefl)' budaet is (airly balanced. As • part of ettersy bu~et. the Bowen's ratio b abodbcuued.

Kl')' words - Sensible heat Oux. Latent heat flux. Soil heat flux.. Nrt radiation. Enel'lY budeet·

I . Introduction

It bas been increasingly rea lised that land surface processes si inificanlly in fluence wea ther andclimate. C harney et 01. (1977). Shukla and Mintz(19821, Sud and Smith (1985) have shown the needfar Inclusi on of land surface exc hange processesin the meteo rological models. To paramete rizeland surface processes many field experiments onmedium scale and large sca le have been conducled. AmoniSt the se. HAP EX-MOBILHY (Andreet aL 1986), FIFE (Sellers et 01. 1988) and La Crauexperiments are major ones. In these experiments.emphasis was given to observational techniques ,and the variou s flux es were determ ined preciselyand validated with the help of satelli teobservations.

In some of the bi"er programmes like WorldClimate Research Pro gramme (WC R P) andGlobal Energy and Water Cycle Experiment(GEWEXl. th e measu rement programmes arcplanned 10 resolve 'scaling-up' problem s ofsmaller i rid point observations to mesoscale gridpoint observations. That is to begin with. observations reiardini partit ion of so lar energy over aplain land a nd over a vegeta ted land. soil moisture

(II '

and roughness. arc taken on a small scale of10 X 10m or 100 X 100 m. The present study is asmall scale expe riment which may be the beginning of an experiment in the understand ing o flarie grid mesh .

A small scale field programme was co nductedat the Indian Institute o f Tropical Meteo rology(llTM). Pashan, Pune, (18' 32'N. 73' 5I'E). 10

study the partitio n of energy at the land surfacein terface. Earlier studies on land surface energybalance have been reported by Mitsuta tt 01. ( 1973)and' Smith et 01. (1991). Mitsuta studied the partition of incoming energy over a period of 24 hoursa nd tried to find out - lhe imbalance . Smith 'selaborate experiment co nsis ted of the installationof net radiometer. sonic anemometer. soil thermometer. Bowen's ratio measuring instrument.nux plates etc. Usini thes e infrastructures. Smithtried 10 verify the evapotranspiration eq uationsgiven by Penman.

The aim of the present experiment is 10 studythe partition of the incoming energy al the la ndsurface in terface usin g tower instrumentat ion , 'oiltemperature probe an d a net radiometer.