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VAP DUNG PHNNG PHAP DII BAO TtfH0P
BE DU BAO OUY DAO DAO HAN 5 NGAYTBtN KHU VUC DIEN BONG
TRAN TAN TIEN, CONG THANH, HOANG THj MAI, HOANG THU THUY, BUI MINH TUAN
Tn/iJng B^ hQC Khoa Fv?c Tl/ rUtn, B^ hpc Qu^c gia Ha N^i
Bai bao gifii thl|u cac phiTdng phap dU bao bao sieu \6 hop: nu6i nhiiu (BGM), loc Kalman (LETKF) va sHr dung cac thanh phin cQa i\! ban to h^p loan cS'u. Cac tac gii da ap dung phUdng phap lpc nhan iC Itg't h9p vdi siSu t^ hdp d^ xSy d^ng phddng trinh sigu t6 hfip d^ra trgn ciic dir bao cua cac cdn bao trong giai doan tir 2009 dSn 2011, Da sir dung cac phiTong trinh tim dirglc di dd bao cho cac cdn bao inh hudng dg'n Vi§t Nam trong nam 2012 va 2013.
Sai $6'khoing each cho cac ban dd bao 24, 48, 72, 96 va 120 gid bing phddng phap BGM tren me hinh RAMS (The Regional Atmospheric Modeling System) la khoing 125, 197, 265, 275 va 354 km; bing phUdng phap LETKF tren m6 hinb WRF (Weather Research and Forecasting) la 145, 182, 290, 263 va 376 km; bing phUdng phip tfch phan md hinh WRF vdi cac IrUdng ban diu la cic thanh phin dU bio td bdp toan clu cia NCEP (Trung tam Du bio mfii trudng Hoa Ky) la 107, 117, 272, 339 va 365 km. Kg't qui nay dap dng dUdc ygu clu hign nay ciia vlh d l du bao quy d^o bao b^n 5 ngay trgn khu vuc Biln Dgng.
Tir khda: phuang phap nudi nhieu, lgc Kalman, Uif bao to hgp, itf bao bao.
I To htfp kA qui dtf bao I quy dao bao
Di; bdo quy d^o bao ludn 1^
I v^n d^ du<3c cac nudc quan t§m I vi mye dfch khoa hpc, kinh t^ vd Iphfing chSng thiSn tai. KS qu4 l d u bao quy dao bao thay ddi ftheo thdi gian. Nhin Chung, xu I the sai s6 dtf bao quy dgo bao S Icdc hgn dl,/ bdo gidm theo thdi
• gian, song sai s6 ndy hdng ndm Ivan dao dong r^t idn, phu thud'' I ddc diem cua cdc cdr^ *""
Indm.Odnha' ^ oinh Icua di,r b' ay BSC Thdi [Binh ' i ^^<>c bi4u di^n ,nh i . Sai s6 di; bdo han J ngay trong cdc ndm g^n ddy 'Khodng 300-350 km.
In this paper, the authors introduce superensemble methods including Breeding of growing mode (BGM), Kalman filter (LETKF) and WRF with input data which are components of the global ensemble forecast. To construct an operational procedure for ensemble typhoon track forecast with a forecast period up to 5 days, the authors have used the filtering method from 2D09 to 2011 and its application from 2012 to 2013. Forecasting error of distance for 24, 48, 72, 96 and 120 hours based on the BGM method on RAMS model is about 125, 197, 265, 275 and 354 km; 145, 182, 290, 263 and 376 km for LETKF on WRF model; and 107, 117, 272, 339 and 365 km for WRF with input data which are components of Ihe global ensemble forecast respectively. This result can meet the current requirements ot typhoon track forecast for the 5-day period on the East sea.
KeywordiBGIVI. LETKF. ensemble forecast, typtioon forecast
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^fWCON so vdi NCON. So trUdng tidp sCf dung di tinh la 613,486 va 299 tifdng dng vdi dd bao 24,48 va 72 gid.
Ket qua tfnh dddc bieu di§n tren hinh 3. Tir k^t quk cho thay SCON khong lam tang dp chinh xac cua dd bao quy dao bao so vdi f*iCON d tat ca cac han dd bao, WCON lam tang dang ke ket quk dU bao d 24 va 48 gid, con 6 72 gid thi phddng phap NCON cho ket qua tot nhat (hinh 3). Phddng phap NCON cho ket quk tot hdn cac dd bao thanh phan khoang 10-15%.
Hinh 1: sai s6 trung binh cSU bao quy dao bao tren khu vUc Tay Bac Thai Binh DUang [5}
Sai so dd bao quy dao bao la tong cac sai so do xac djnh trddng ban dau khong chinh xac, sai so do cac mo hinh du bao chua hoan thien, sai so do to hop ket qua du bao cua cac md hinh... Trong so do, sai so to hop k§'t quk du bao ddng vai tro quan trpng trong tdng sai so du bao to hop quy dao bao. Tren the gidi sii dung 3 phuong phap to hop la to hdp khdng chpn Ipc NCON (non - selective consensus), to hdp cd chpn Ipc SCON (Selective consensus) va to hpp co trpng so WCON (Weightet consensus). Hinh 2 bieu diln each to hdp cua cac phuong phap khdng tuyen chpn va sai so khoang each cua cac md hinh thanh phan va cua NCON.
Hinh 2: phuang phap t6 hQp khdng lUa chon NCON [4]
Phuong phap WCON dua tren s6' lieu lich sii de tim trpng so cho cac mo hinh bSng phUdng phap binh phuong td'i thieu. Theo ket qu^ cua Kuo-Chen Lu [4] vdi chudi so li^u phy thupc dU bao quy d?o bao bang phuong phap V^' ""ON tdt hdn NCON khoang 4%, 3% va 1% cho cac du bao 1, 2 va 3 ngay tUdng Ung. Doi vdi so lieu dpc lap thi WCON t.., --n NCON d 2 ngay dau, con ngay thd 3 thi khdng De t -^ ohUdng phap SCON va WCON vdi NCON. chuiii, '-i,. hanh tinh toan mdc dp gi§im sai ao ciu bao (phan -ua phUdng phap SCON va
Hinh 3: hidu qua cCia phUdng phip SCON va WCON so vdi phuang phap NCON
6 Viet Nam, chda cd chUdng trinh nao nghidn cdu phddng phap sieu to hop de dd bao quy d^o bao ngoai Chuong trinh KC08. Cac nghien cufu dU bao va danh gia ket qua du bao chi dua tren trung binh to hdp [1,2].
PhtfiAig phap sieu to htfp
Sau khi chpn dddc cac thanh phan tham gia td hdp, sd dyng cac phddng phap thong ke de dUa ra k^t quk dd bao to hdp. MgX trong cac phddng phap thong ke dddc Krishnamurti de xuat de dU bao quy dao bao la phUdng phap sieu td hpp [3].
PhUdng phap "sieu tS h0p" xkc djnh cho mdi thanh phan {thanh phan tham gia to hdp) mot trpng so dUa tren tap so lieu ve quy dao bao thuc va dd bao cua c^c mo hinh. Trpng so cua cac md hinh xac djnh bang phUOng phap binh phddng toi thidu. Qua dd lam gikm vai trd ciia ckc md hinh du bao khong tdt, dong thdi lam tang vai trd cac md hinh cd cac dU bao tdt trong qu^ khd.
Phuong phap "sieu tS hpp" dddc thdc hi$n qua hai giai doan:
- Giai doan chuan bj: sd dyng chuSi s6 li$u ctia c^c du bao quy dao bao da qua tU cac th^nh ph^n \ik guy dao quan trac thUc te cua nhdng cdn bao dd (c6 the ia tu mua bao trddc hoac tU hai mua bao trddc) xay di/ng phUdng trinh hoi quy dU bao vi trf Xkm bao (kinh dO, vT
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dd). 6 day, phUdng phap hoi quy tuyen tinh nhieu bien duoc sijf dyng de tim cac trpng so cho mdi thanh phan 6 thdi dilm (00 h, 6 h..., 120 h) vdi tdng bidn dd bao (kinh dd, vTdd). Ngoai ra, can luu y den dp dn djnh cua cac dd bao thanh phan giOa cac mua bao khac nhau. Dp on djnh cCia cac dy bao thanh phan cang giam, tUc la sU bien ddng cua cac dy bao thanh phan Idn, din den ket qua dy bao td hpp khong tdt, Sau khi tinh dupc cac he sd hdi quy (trpng sd), cac he sd nay dUdc sd dyng trong giai do^n du bao.
- Giai dogn dd bao: trong giai doan nay, cac dU bao dupc thuc hien nhd ket quk dy bao cua mo hinh thanh phan va nhOng hieu chinh thdng ke dupc xky dyng trong giai do^n chuln bj.
Phddng trinh sieu td hdp co dang:
Trong dd: O \k gik tri trung binh da quan trac d giai dogn chuln bj, N la sd cac md hinh thanh phin, a, la trpng sd hd[quy cua mo hinh i, F,(t) la gia trj dU bdo cua mo hinh I, F, la gia trj trung binh cua cac du bao cCia md hinh I trong giai dogn chuln bj.
Kat q u i dtf bao siau to htfp S6II4U
Bd sd lieu nghien cUu la ckc cdn bao trong 5 mda bao nam 2009,2010, 2011, 2012 va 2013. Tdng sd trUdng hpp thd nghiem la 199 cda 30 cdn bao knh hudng ddn khu vyc Vipt Nam. S6 lieu toan cau l^y tU NCEP vdi dd phan giai 1x1 dp kinh vTdp.
Di/bdo sieu t6h0p cho cdc con bao nam 2012 va 2013
Dl/ bko si§u t6 hpp til cac thanh phan dUpc tao ra biing nudi nhlSu:
PhUdng phdp nudi nhilu (BGM) la phUdng phap tao ra cac trUdng ban diu khac nhau td mdt trUdng ban dau chda cac dao dpng phat trien. Da tgo dupc 25 trudng ban diu td mdt trddng ban diu cda NCEP. Cac trudng ban diu nay dupc dda vao md hinh de tich phan 5 ngay cho 25 dy bio. Sd dyng sd lieu dy bao td nam 2009 den 2011 dung iam sd lidu phy thupc de xay dung phUPng trinh sl§u td hpp nhd da trinh bdy trong phin chuan bj cda mye thU 2 (phUdng phap sieu td hpp). Ket quk la tim ddpc ckc phUdng trinh du bao sidu to hpp vdi 25 thanh phin. Giai dogn du bao, Ip dyng cac phUdng trinh tim dupc trdn bd sd li$u doc l^p la cac cdn bao nam 2012 va 2013. Kdt qua nhan dupc t h i hien trfen hinh 4.
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tren bo s6 lidu nam 2012 vi 2013 So sanh kdt qua si§u td hdp vdi phUdng an lay trung binh don giSn 25 thanh phan do nuoi nhieu tgo ra cho thay, phUPng an sieu td hpp cai thien sai sd vj trf tam bao so vdi tam bao thyc te gikm khoang 50-70 km d cac hgn 24,48, 96 va 120 gid. Tai hgn dU bao 72 gid sai sd vi tri cua phuong an td hpp gikm khoSng 10 km so vdi trung binh don g\kn.
Dif bao sieu to hpp ti/ cac thdnh phSn dupc t^o ra tii phUPng phip Ipc Kalman (LETKF):
PhUdng phap LETKF la phUdng phap tgo ra cac trudng ban diu tU bd Ipc Kalman cd ddng hda sd lidu vd tinh vd sd lieu cao khdng. Da tgo 15 trudng ban diu blng phUdng phap ndy. Tich phan md hinh WRF vdi cac trudng ban diu ddpc tgo ra cho ky quan trie 00 gid cac ngay cd bao tren khu vpc Bien Ddng trong cac nam tU 2009 ddn 2013. Sd lieu dy bao td nam 2009 den 2011 dung de xay dyng phUdng trinh sidutd hpp vdi 15 thanh phin. Cac phuong trinh tim ddpc da kilm nghiem trdn bp sd lieu ddc lap nam 2012 va 2013. Kdt quk nhSn dupc the hien tren hinh 5.
!uUShcipl5t*i4nhphSn - Ihtdhi/p 15 thinh phin H\nh 5: sai s6 v/ tri trung binh ciia d(/ bio siiu t6 h0p vi trung binh t6 h0p 15 thinh phin LETKF tr&n bi) s6 ll^u
d0c lip nSm 2012 vi 2013
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So sanh ket qua sieu td hpp 15 thanh phin LETKF vdi phUdng an lay trung binh ddn gian cho thay, tai cac hgn dd bao 24 va 120 gid ket qua sai sd la tUdng ddong.
PhUdng an sieu td hpp cai thidn sai sd vj trf giam khoang 50, 80 va 100 km d cac han 48, 72 va 96 gid.
Dl/ bio sieu td hpp tCf cac thanh phan dUdc t^o ra ti/
kSt qui tfch phan mo hinh WRF vdi cac tn/dng ban dau la cic thinh phin dt/ bao tS hdp tokn ciu cOa NCEP:
Sii dung 5 trudng khi tddng todn clu cua NCEP (cac dp bao thanh phan cua du bao td hpp toan clu) de ldm trudng ban diu cho mo hinh WRF. frong mo hinh WRF lln lUdt SLf dyng so dd ddi IUu Kain-Fritsch, Betts-l\/liller- Janjic vaGrelLDevenyide dubao. Nhu vay ta tgo ra 15 du bao khac nhau. 15 dd bao nay se chda du thdng tin ve trudng khi tUdng thyc can tim. Sd lieu du bao td nam 2009 ddn 2011 dung de xay dUng phuong trinh sieu td hpp vdi 15 thanh phin. Cac phUPng trinh tim dUdc da kiem nghiem tren bp sd lieu phy thudc (2009-2011) va ddc lap (2012-2013). Ket qua nhgn dUpc the hien tren hinh 6 va 7.
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so lidu phu thupc, sai sd du bao quy dgo bao tang theo han du bdo. Sai sd quy dgo bao tren bp sd lieu ddc lap SLf dung phUdng phap sieu td hpp cho sai sd dd bio tddng dUdng vdi cdc nudc trong khu vUc (hinh 1). Sai sd dy bdo han 72 gid khodng 270 km, va sai sd dd bdo hgn 120 gid khoang 360 km. VdisaiaddUbdonhUtren, viec Ung dyng phUdng phap nay vao dU bdo nghiep vy la hoan toan kha quan va de dang thyc hien tgi cac trung tam du bao cija Viet Nam.
Ket luan
Qua ket qua nghien cdu cho thay cd t h i dy bdo quy dgo bao dnh hddng ddn Viet Nam hgn 5 ngay bang phUdng phdp sieu td hdp. Ket qua thD nghiem trdn bp sd lieu dpc lap cda 2 mua bao (2012 va 2013) cho ket qui dp bao d cac han dd bao tuong dddng vdi cdc nudc tien tien trong khu vUc . Cy the sai sd khodng cdch cho cac hgn du bao 24,48, 72, 96 va 120 gid bang phUPng phdp nuoi nhilu tren md hinh RAIvlS la khodng 125,197,265, 275 vd 354 km; bang phUPng phap LETKF tren md hinh WRF la 145, 182, 290, 263 va 376 km; bang phUdng phap tich phan md hinh WRF vdi cac trudng ban diu la cac thdnh phan dp bao td hpp todn clu cua NCEP 11 107, 117, 272, 339 va 365 km. Cac ket qua nay hoan toan dap dng yeu cau cua dp bao nghiep vy cf Vidt Nam ndn cac phddng phdp trdn co t h i sd dyng cho cdc trung tam khf tupng ^f
Tai li$u tham khao
[1] Hoang DiJc dicing (2011), NghiSn cilu u'ng dyng mfl hinh WRF phyc vu 6ii bao thcii ti^t va bao fl Viet Nam. Bao cao tdnq kgt tSi tdi NCKH cap bo.
[2] Vo Van Hoa, U Ode. D 6 Le Thuy, Dtl Diic Ti^n, Nguygn Mgnh Linh, Nguyin Thanh Tung, Nghign cu'u x§y di/ng he th5ng di/ bdo to h(fp thdi Iiet ngan cho khu vi,ic Viet Nam dya tren cdch tiSm can da m6 hinh, da phan tich Phdn 2 - K^t qui danh gid dil bdo trung binh t6 hflp. T^p chlKhitydnglhuyvan s6 616, thdng 4.2012, tr.23-31.
[3] Kiishnamurti T.N., Kishtawal CM., Zhang Z., LaRow T E., Bachiochi D R„ Williford C.E., Gadgil S and Surendran S. (2000), Improving tropical precipitation forecasts from a mult! analysis superensBmble. J. Climate, 13. pp. 4217- 4227.
[4] Kuo-Chen Lu (2007), Typhoon Forecast and Warning System in Taiwan, 2nd International Conference on Urban Disaster Reduction.
November 27-29, 2007.
[5] Yamaguchi M. (2012), Outline of the Typhoon Ensemble Prediction System at the Japan Meteorological Agency, Report.
TL/ hinh P v? 7 cho thay, sai sd dp bdo quy dao bao I so heu ddc la|. '--no dUPng vdi sai sd khi sd dyng
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