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5:' 1. :'()Il . .13~ : 55 1. 55.1 . ~I

Predict io n of A sian summ er mo nsoon onset usingthe new JMA global model

M ASATO S G I

Japan ,\!('Ienrolog;ral Aj(t'my. Tokyo. Japan

ffi't - JJI"1Pr ~-'ilf;r ;~ ~I f 'f :r. ~T 'i;~ 1fr.:rf'l'if f~r.R 1JiB fT winr ,;'t9" &"": 1'1i~ 3ft7 p IS ~~ !;j"fn'tf 'r.~T.-e; ~A't ':Ilirrr h;r." lfT ~ I 1 'I ~s Of. ~n:<l :r. f'1'; 1f~"r1.:r Iffl l' rr lT, l1r-r%7 'TfTl2JTllr::r.J 1fr rr7T~f!Jf f'f."llT 'flIT trT I t"'1~lfr.,l if ,~_':I17~~ 'if'r*·orT.~~t iT:.rTn:1l f.r~ ~:r:" r<r.r. rl'~tvfr- 'TflJ;fqt lfH -1;~f. fq:f,TJf"f ir~ ~ I ~fU"'r."fT fn.f f~·tq tlFf1f~i:" "rmrloi'n1 7;:rOfI y.)d;~"if,"lf ii::r f:r. SIT r,"~ ~ flJ9'" 1Ii"1: IIT¥f,::nf~ r;:;"T <l'~/ ~llf:Fnfr PT lif~ it f.t lTt~ I h :'=r!';ff~~iNT l~HlT,!f-f=r ~~r fq~~ '1r ::r;'lf. l1:JT'l' if h;Nf~Fir i. , ' ~

AHST RACT. Lb illg rh nc.... HoI,\ o p..ra tiona l gluhal model . som e prc Ji ct ion ex periments were carriedou t rl1f 1979 end 19Ht'l m msoon o. iscts. T he results o f the op erat iona l model forecasts for 19HXnusct \\l.' I'C <Ilso examined. In tilC' .'': forecast s. realist ic so uthwesterly mon soon Ilows develop ed sta rting fro m thepre-onset init tal coudiuons. In mo I CUSI.'S 1'( lrm:l li ,, 1l and \.k vclopmcru o f synop tic disturbances such . IS u nsetvonc .... andIl101hn tlili.!'pr ~ssi\~ns \\i l,:r .: ;.'I"o predicted h) the mod el. Th e accuracv ( ~ r the predictio n of thesedi-a urf- nncc v. h l l \ -c cr. ~':l l' i ~ ~ ;1I11'l 1l1' Ih l'I"I~L"

1.\1A Glohal wccsrut model

lcvcl-. A lo ng with th e inc rease of t h ; re sol u tion . all th ephyxical process pararnete r izat ion s wen: rene wed , Byt he -e changes. th e new model, compa red with th e o ldmodel, ha s much ... tronger radia tive cooling more preci ­pitation and more intense tropica l circulat ions, The:out line o f the new J \ -1 A opera tiona l globa l model i"show n in T able I.

LOlli... 's :...chclIlc for surface:l1 uxe: ~ a nd level 2 c1o~ltn:

1110de:1for ,"ertka l dim,.., jtln

Oni ly anal Y/cd va luc

Integ ration do ma in: Globe

Hor izont al re...olution : Triangular truncation ut wa ve-number 63

9(, Gau...s ia n latitude, a nd 192longitude"!

16Semi-implici t scheme

7~ hr for 00 G M T initia l.192 hr for 12 G M T initia l

Incl ud ed . Small sca le smoothedNonlinear no rmal mode iniriah za­

t ion with phy~ics

M o nt hly a vera ged a lbedo. soil1l10i,turc. icc co ver ,pl'ci fk-dgcographica lly

Earth , urfa cc

Sea surface te m pera t ure

Phr Jical {Jaram" tcrf:aliolJf

( 11 Surface cXl'hangc'

Orogra phy

Initializa tio n

Grid

Vertical level ",

Time integra tion

Forecast ti me

In Ma rch 19S~ . JMA ·... op~ra t i onl l predi ct io n modelswerc rencwed. rile nevI" glo bul modc l is :t ~pcct ra l

model with T tH hori: ontal resol ut io n and Ifl vcrlka l

2. :\l odrl and d lltn

There have been ma ny n:.lll1.:tical pred iction - t ud ic....o f t he As ian sum mer mon-oon on-,...:L \VG N E selectedthe 1979 o nset a ... o ne o fth r C:bC'; fo r th e forccact inte r­comparison exper iments t Tcrnpcr to n a nd K rish na mu rti('/ 01. 1983 ). A mo ng t he seven mod els pa r ticipa ted th eexperiments , on ly the FS U model rca ..o nahly well re­produced th e on ...ct vo r tex , showi ng t he di fficulty orth e fo reca st of monsoon o rr-ct . Ker sha w (19H4) co n­ducted :)Ol11e cxper imcnt-, on the same case and showedth e impor tance of in it ia l ana lysis . Kcrshuw (19M5)further showed th c ..en... it ivih of the pred iction ofonsetvo rte x to t he sea surface temperatu re of the A ra bianSC;l. At J~1A . Ka numitvu ( 19S11.t1..o took the same c..l..,eand ca rr ied o ut pred ictio n experiment. In hi.:; cxper i­rnc.u, global aspects of the monsoon o n -,et were pred i­cted well . wh ile th e local a ..pcct-, such as [11;: format ionof onset vortex were not \\ 1.'11 predicted. M o re rece nt ly.Kuma (19 88) st udied the 1986 onset, a nd rev ea led theimportant rol e of th e co nvective hea tinc over thewestern Pa cific reg io n on the development and we-awardsh ift or th e T ibeta n high .

Using the new J~1A opera tiona l g lo ba l mode l. ..o rnemllrc prediction c\p.:rimcll1s we re carried out fo r the1979 a nd 1986 o'''el. In th i, paper. t he re,ults o r th e,ee.'tper imen t a rc pre ,cn teu an d d i' ctl"i ';t,' d . The rC"iulr... o fth c o pcra tiona l gloh' !1 IlHld'."l fPi lhe 19~X on'ct rerindarc a l,o di "cu""l'd

I . ln trod uct lon

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