THAM DINH DlT BAO ML^A KHU VT/C BAG BO BANG PHU^ONG PHAP CRA
Pham Hai An M O DAU
Ngiy nay md hinh sd tri dugc su dung rgng rai trong ITnh vyc dy bao khi tirgng. So vdi cac phuong phap tmyen thdng, san phim mo hinh so phong phu v i chi tiet hon rat nhieu.
Tuy nhien, ket qui dy bao tu mo hinh khong phai li hoan hao. Bdi vay, de sd dung tdt ban cac sin pham dy bio tii md binh, ngudi ta phii thyc hien qua trinh danh gii. Day dugc xem la dieu kien hing dau v i khdng the thieu cho bat ky md hinh so nao dugc su dung frong cdng tic dy bao. Qua trinh danh gia niy khong chi giup su dung sin pham mo hinh hieu qui ban ma cdn hiiu ich doi vdi cac nhi phit trien mo hinh trong viec cii tien md hinh. De lam dugc dieu niy, mdt ITnh vyc ly thuyet vdi cac phuang phap danh gia hay tham dinh da ra ddi. Cd rat nhieu phuang phap danh gia san pham cua md hinh so.
Phuang phap truyen thdng su dung cic diem sd thdng ke danh gia chat lugng dy bao mua, thudng dac tnmg bdi cac diem phan tich rieng le. Bii viet niy gidi thieu chi tiet phuang phip mdi dang dugc phat trien v i ap dyng trong nhung nam gan diy: tham dinh dy bao mua bang phuang phip CRA (Contiguous Rain Area) [6], nham bo sung mgt cich cd he thong frong viec danh gia chung cho toin khu •vyc, the hien manh tinh dac thii ve phan bd mua khdng gian. Ket qui thu dugc cua viec ip dung phuong phip CRA khdng nhirng giup ich cho cdng tac tham dinh mua dy bio hien dai, ma con cung cap nhiing thong tin ly thu ddi vdi cac nhi khoa hgc trong cac ITnh vyc khic co dugc nhan biet chung khi su dyng cac ket qui dy bao mua, nham ap dung cho nhimg muc dich rieng.
I. TAI LIEU VA PHLTOfNG PHAP 1. Tai Ueu
Tai hdi nghi WGNE (Working Group on Numerical Experimentation), nhom cdng tic thu nghiem so cua WMO (World Meterological Organization) da khuyen nghi viec danh gii QPF (quantitative precipitation forecast) dy bao mua dinh lugng cho mdt so
•vimg tren toin ciu. Ket qui la nam 1995 da bat dau thyc hien tham dinh QPF ddi vdi mo hinh toin ciu. Dgc theo qua trinh dd E. Ebert, U. Damrath cimg vdi cac cdng sy (2003) da tdng kit nhung kit qui nghien cim v l tham dinh QPF cua WGNE trong thdi gian 1997-2000, trong dd cac tic gii dac biet chu y den ket qua danh gii dy bio mua tich luy 24 gid cua cac md hinh sd nghiep •vy, ke c i mgt sd md hinh khu •vyc. Tuy nhien cac tic gii nay tap trung chu ylu vio danh gia dy bio mua cua cic mo hinli toan cau, chua dl cap din md hinh khu vyc phan giii cao, du cho loai nid hinh niy co xu hudng dy bio mua chi tilt va chinh xac ban tren cac lanh thd ban che. PGS. TSKH Kieu Thi Xin da nghien cuu ap dyng cdng nghe thim dinh CRA thim dinh QPF cua md hinh dy bao khu vyc ban cbl phan giai cao phat triin tii md hinh HRM (High resolution Regional Model) [2]. Md hinh khu vyc ban che mdi phat trien niy dugc ggi la VNU- HRM vdi nhieu nhirng phien ban khic nhau.
Tren ca sd phan bd tram do mua v i nguon so lieu mua thyc te du de dap img dugc thim dinh mua dy bao, tie gii da lya chgn mien khio sat li kbu •vyc Bae Bg nam trong pham vi phan tich 19.500-22.OOON, 105.000-107.750E. Sd heu mua dua vao su dung li cac dgt mua ldn dien hinh trong cac thing 7, thing 8, thing 9 td nam 2003 den nam
Pham H^i An
2005 dugc thu thap tir hon 150 fram quan trac khi tugng thuy van fren mang ludi thude pham vi phan tich. Tat ca cic sd lieu mua nay deu dugc kilm nghiem thdng qua cic chuang trinh kiem tra chat lugng, nham giam bdt cic sai si ngau nhien. Nhin chung khu vyc Bic Bd cd mat do sd fram do mua la tdt fren ci nude vi dam bio han khi chiing ta lya chgn cac dgt mua ldn dien hinh tai khu vyc niy (hinh 1).
10G kinh-do
Hinh 1. Tram phan bo do mua tren khu vuc Bae B9
Bai viet nay dya fren nhiing ket qui tac gia tham gia thyc hien DTDL-2002/02 do PGS. TSKH Kieu Thi Xin lam chu nhiem. Ca sd ly thuyet chinh vi cac ket qua thyc hien tham dinh CRA dy bao mua dinh lugng dya theo tai lieu gdc cua hai tac gia E.E.
Ebert va J.L Mcbride, 2000 [6].
2. Phirong phap
2,1. Gi&i thi^u phuomg phdp tham dinh CRA
Khic vdi eae trudng khi tugng khac, mua cd ca hai thanh phan la pha mua va lugng mua. Vi vay ta can nghien cuu danh gia kha nang cua md hinh frong viec dy bao mua co hay khdng va lugng mua la bao nhieu. Hien nay da cd nhieu phuang phap tham dinh khach quan va dinh lugng hon so vdi cac phuang phap tmyen thdng. Trong nhieu md hinh dy bao thdi tiet sd gan day ky nang dy bao mua ciing da dugc cai tien nhieu. Nhiing nhan td chinh ddng gdp vao sai sd QPF bao gdm: sai sd phan tieh (sai so dilu kien ban diu), sai sd ddng lye (sai sd frong dy bao ddng khi quyen), sai sd vat ly (sy chua thich hgp eua cae sa do tham sd hda ddi luu) va sai sd do lam fran dia hinh be mat frong md hinh. Ket qua sai sd QPF cd nhieu dang: sai sd frong vi tri he thdng mua, sai sd do nhgn va kich tiiudc kieu mua (pattern), sai so gia tri va cudng do mua. Neu sai sd la he thing thi cd kha nang xac dinh nguyen nhan gay sai sd vi tim ra bien phap cai tien vat ly md hinh tuong iing hoac hieu chinh thing ke san phim md hinh de dua ra QPF tdt ban.
182
Tuyen tap Tai nguyen va Moi trudng bien. Tap XIV
De tach v i tham dinh dugc mua trong mgt he thong thdi tiet cu the thi phii phan biet dugc mua xay ra d dau trong khu vyc mo hinh. E.E. Ebert va cac cong sy da de xuat khai niem CRA - vung mua lien tuc, l i •vung cua mua tham sat lien tyc hay mua dy bao lien tuc dugc khep kin bdi mgt dudng dang tri quy dinh. Neu cic vung mua dy bao v i tham sit tudng nhu li nhirng thyc the tach rdi thi CRA la don vi cua nhirng thuc the mua dy bao hay mua tham sit, trong gidi ban moi thyc the muaduge coi li lien tuc.
Phuang phip CRA quan niem rang, mdt QPF tdt phii dy bio dung: cudng do mua, vi tri he thdng mua va -vung mua.
Trong dd •vi tri cua he thdng mua (location) ndi len sai sd •vi tri. The hien khoang each giua hai tam mua cua hai •vimg mua dy bio va tham sat, tu do giup ta xic dinh dugc doan dudng can dich chuyen khi hieu chinh (can phai dich chuyen de dua vimg mua dy bio den gan nhat vdi vimg mua thim sat). Cudng do mua (volume) noi len sai so the tich. Vimg mua (area) the hien sai sd tuang ung ve hinh dang •vimg mua (sai sd kieu ding). Bang phuong phip thdng ke tham dinh tmyen thdng thi ta khd co the xac dinh dugc nguon goc sai so xay ra frong tat ci cac dai lugng fren ca mien md hinh. Phuang phap tham dinh tmyen thong thudng chi tap trung vao ddi chung giua dy bao va tham sit fren timg fram rieng le hay timg diem m i khong xem xet den quan he khong gian giua cac diem, it quan tam den bieu dien sai sd khong gian giua hai •vimg mua, dieu niy se dugc khac phuc v i bo sung qua phuong phap tham dinh CRA dy bao mua dinh lugng. Muc dich ciia phuong phip CRA li tham dinh xem thyc the mua dy bio khic vdi mua tham sat ve vi tri, hinh dang v i cudng do den muc nio. Vi the nhiing thong ke tham dinh m i ta quan tam la do dich chuyen ngang ciia dy bao, sai so ve lugng mua giua hai •vimg mua dy bio v i tham sit, toe do mua tmng binh va cyc dai, dien tich mua va tuong quan kieu mua tham sat tmdc v i sau hieu chinh.
2.2. Xdc dinh sai sd dfch chuyen vd sai sd cu&ng do
Trong phin ldn trudng hgp thi thyc the mua dy bao v i thyc the mua thim sat co phin chdng len nhau, nhit l i ddi vdi nhung he thong mua ldn. Tuy nhien ca trong tmdng hgp thyc thi mua dy bao hoin toan khdng trung vdi mua thim sit van c6 the do dugc sai sd dich chuyin va sai sd cudng do neu nhu tmdng dy bio d gin. Ben canh do cung cd tmdng hgp khac la c6 mua tham sat nhung khong c6 mua dy bio hay ngugc lai thi gin dung CRA van cd gia tri.
Categorical statistics
Predicted
yes no a> yes
(U
•S no O
hits false alarms
misses correct negatives
Forecast Observed
Hinh 2: Minh h9a thong ke cac viing H, F, M, C
Pham Hii An
Trong do: H la si dy bao dung sy xuat hien cua mua, F la so dy bao mua xuat hien nhung thyc tl khong xiy ra, M so quan trac mua ldn hon ngudng mua dugc chgn ma mo hinh khong dy bao dugc [5].
a) Phuong phdp xdc dinh sai so
Sai si dich chuyin dugc xac dinh bdi sy chuyen ddng tmdng dy bao din tmdng tham sat cho din khi tieu chi dung nhat li tdi uu. Do dich chuyen la vecta hieu giua vi tri cuoi cimg vi vi tri glc eua dy bao. Gia tri duong cua dich chuyen x vi y chi rang tmdng dy bio nim d phia dong va bic cua kieu mua tham sat. Hof&nan (1995) da thd nghiem hai tieu chi dung nhit va tim dugc ket qua tuong ty vdi su dung cyc tieu hda sai sd RMS va cyc dai hda he si tuong quan fren •vung tham dinh vudng gdc. Trong tmdng hgp cua CRA vimg thim dinh la mgt tap hgp nhiing diem chua frong CRA xuit phat cung nhu frong CRA sau khi trdi •vimg dy bio din •vimg dugc hieu chinh, tuc li hgp cua cac thyc the tham sat goc va dy bio vdi thyc thi dy bao da dugc frdi. Tic gia chu dinh loai tru nhiing diem ngoii CRA dl chi tap trung vao he tiidng mua dang quan tam. Vi sd nhung diem frong
•vimg thim dinh N phy thugc vio vi tri cua dy bao da dugc frdi nen tic gia da chgn de toi thilu hda sai si binh phuang tong (Total mean squared error- RMS) chu khdng chgn sai so tmng bmh binh phuang (RMSE) dl xac dinh sy dung nhat cua dy bao vdi tham sat.
b) Tdch cdc sai so thdnh phdn
Vdi phuong phip xac dinh sai sd nhu tren, gin dung cua cyc tieu hda sai sd binh phuang tdng se cho ta sai si QPF dy bao mua dinh lugng dugc tach thanh cac sai so thinh phin: sai si dich chuyen, sai sd lugng mua (volume) va sai sd kieu dang mua (pattern). Tuy nhien ciing can luu y ddi vdi sy minh hga cua mgt he thdng dii. Khi do mgt dich chuyen dgc theo dudng true cua mua cyc dai se dugc coi la sai sd nhd hon so vdi dich chuyin •vudng gdc vdi dudng true. Nhung nhiing nhan kieu nhu vay lai kh6 dua vio trong tham dinh ty ddng. Dd la ly do mi frong mdt tham dinh thich hgp eua QPF dy bio mua dinh lugng tren diem ludi, thudng ngudi ta lap bang ngau nhien chi ra tin suit cua hits (dy bio dung mua), misses (dy bio khdng mua d noi tham sat ed mua) vi false arlarms (dy bao mua nod khong xay ra mua). Nhu vay chung ta cd the dung gan dung niy d day de tham dinh mua. Tham dinh hien tugng cua mgt sd ldn CRA se eho ta thong tin hiiu ich ve bin chat cua sai sd dy bao.
II. MU'A LU, Dir BAO MU'A GAY LU d TRONG VA NGOAI Nu'dc
1. Tinh hinh mua Id, du bao mua gay Iii
Nhin chung lugng mua ldn, ddng deu cua Viet Nam cap du nude eho hau bet mgi nhu cau. Tuy nhien, nhiing thien tai lien quan den nude lai nghiem frgng nhat va gay ra nhimg ton that vat chat, tinh mang con ngudi va nghiem trgng ve kinh te. Thiet hai ldn nhat li do lu lut, dac biet khi kem theo bao ldn. Dudi day li hinh minh hga cac •vung thudng xay ra thien tai gan lien vdi mua ldn vi cic •vung ngap lu tuong ung (hinh 3).
Mua do bao ldn co thi gay ra lu quet khdng bao tmdc, pha buy •vimg ha luu. Trung binh hing nam cd 4 din 6 eon bao ldn do bd vao Viet Nam. Mua ldn la nguyen nhan gay nen 4 loai lu chinh: lu tren sdng sinh ra do mua keo dii, hoac mua ldn do ap thip nhiet ddi vi bao, giii hdi tu nhiet ddi. Lu quet xay ra khi cd mua ldn tren •vung nui cao vdi do doc ldn vi do rgng dong chay nho. Lu do thi d cic thinh pho ldn do mua ldn gay nen vi ngap lut ven biin chu ylu do bao, nude dang, song vi trieu cudng.
184
Tuyen tap Tai nguyen va Moi trudng bien. Tap XIV
Van de dy bao lu lyt cing sdm, cing chinh xac de kip phong tranh, ban che toi da nhimg thiet bai do chung gay ra la bai toan vo cimg phuc tap va cip thiet hien nay. Viec giai quyet tot bii toin nay vdi ban dy bao dii phy thugc trudc bet vio chat lugng dy bao lugng mua ldn, •vung mua ldn v i phan bo lugng mua tren dien rgng. Bien phap hieu qui nhat tren the gidi hien nay de nang cao chat lugng dy bao thdi tiet va khi hau, trong do dy bao mua ldn cd tam quan trgng dac biet, li ap dyng phuang phap dy bao bang md hinh thuy ddng hien dai.
Hinh 3: Vung thudng xay ra thien tai gan lien chat che vdi mua Idn (ben trai) va viing ngap lu ldn (ben phai) nam 1999, DMU
Tu nhirng nam 50, Chau Au l i mgt trong ba noi diu tien tren the gidi phat trien dy bao thdi tilt bing md hinh s i trong nghien cuu cung nhu ap dung thyc te. Phan ldn nhung mo hinh tdt nhit tren thi gidi hien nay deu co nguon gdc tii Chau Au. Tai cic nude My, Anh, Due, Nhat dy bao mua ldn bing phuang phip s i fri so vdi cac phuang phap khic chilm vai trd chu dao. Cic trung tam dy bio toin cau deu dugc phit trien manh d cac nude nhu: NOAA, NCEP, NCAR (My), ECMWF (Anh - Chiu Au), Vien MIM v i DWD (Due), JMA (Nhat). Trong vii thap ky gin day, vdi nguon sd lieu thim sit hien dai va su dung nhung miy tinh sieu tie, khong gian cda nhimg mo hinh dy bio thdi tilt khi hau hien dai nhit d cac nude niy khong dimg lai d khi quyen m i Idng ghep c i dai duang. Vi du dien hinh cua loai mo hinh Idng nay la md hinh COLA cua My.
COLA ed kha nang ddng thdi dy bio ca khi tugng va thuy van nhu bao, mua bao va lu lut do mua bao mang lai. Trong chuong trinh thdi tilt cua My hien nay vin de dy bio mua dinh lugng (QPF) dugc xep vio dien uu tien.
2. Tham dinh d u bao mua
Mua vua la ylu td khi tugng, -vua li hien tugng thdi tiet dugc liet vio loai hien tugng thdi tilt khd dy bao nhit. Khdng nhiing chi kho dy bio m i viec danh gia dy bao mua ciing hit sue phuc tap. Trudc het vi tmdng yeu td mua la tmdng bat lien tuc ca theo thdi
Pham Hii An
gian lan khong gian. Nhieu dac tnmg thdng ke co tinh quy luat d nhiing yeu td khi tugng khic, nhung lai khdng cd d mua lam cho viec xu ly sd lieu mua rat khd khan.
NIU khong CO si lieu kilm chung dang tin cay tiii du ta chgn chi tieu gi vi phuang phap dinh gia nao cung se khdng cd ket qui tin cay. Do dd tmdc tien ta se tiln hanh xu ly kilm tra si lieu mua thyc te cung nhu ci san pham mua md hinh, sau dd se chgn cac chi tieu danh gii dy bio, tinh toin vi bieu dien cae ket qui, va cudi cimg phan tich danh gia cac kit qua. Quy trinh vi muc dich tiiam dinh dugc minh hga bing sa dd cho dudi hinh 4.
So d6 thim dinh (verification)
I l%kh nimnO.Hiw(lJ»WMbglW4 _
Hinh 4. So* do bieu dien quy trinh tham djnh (Damrath, DWD)
Tham dinh dy bio bao gdm giai thich rd va tdm tat quan he giua hai tap sd lieu: dy bao va thim sit sau do so sanh giiia ket qua thyc hien cic he thdng dy bao vdi ket qua cua he thdng cua dy bio miu. Day li mgt bai toan thdng ke, nghTa li phai su dung cac phuong phap thdng ke frong khoa hgc khi quyen. Bai •viet khdi xudng viec can phai tham dinh du bao thdi tiet diu tien li cua Finley (1884). Tham dinh dy bao chua frd thinh mdt chuyen de nghien cuu frong nua diu the ky XX. Sau nay mdi cd anh hudng quan frgng den ly thuyet ciing nhu thyc hanh frong van de tham dinh dy bio. Nam 1991, Murphey da ban ve tinh phuc tap, tinh khdng thu nguyen cua •viec tham dinh dy bao. Cdng viec tham dinh QPF fren the gidi thyc sy mdi bit diu d cac nude phat trien td diu the ky nay, dy bao sd d Viet Nam mdi chi frong giai doan khdi diu va chat lugng dy bao mua nhiet ddi cdn la van de phuc tap fren tam qudc te, nhung DTDL/02 van tien hanh thim dinh dy bao mua cua VNU-HRM, tmdc het •vi ky nang kha cao frong dy bao eua HRM. 14-31 da dugc khang dinh doi vdi dy bao chuyen ddng bao fren Bien Dong, sau do •vi nhimg cai tien dugc thyc hien frong de tai ve tham sd hda vat ly ciing nhu dong hda sd lieu dia phuang thyc sy da gdp phin nang cao ky nang dy bao thdi tilt, kl ci mua tren lanh tho Viet Nam. Tuy nhien, do tinh rat bat lien tuc cua mua, nen ddi hdi phii co so Ueu tham sit mua cd chat lugng cao thyc sy. De dugc nhu vay viec xu ly sd lieu mua la van de quan frgng vi rat phuc tap. Han the niia mang ludi tram do mua qua thua that d Viet Nam cing gay khd khan them cho •viec xu ly sd Ueu tham dinh mua.
III. KET QUA THAM DINH CRA DlT BAO MU'A DINH LU'QnVG 1. Tham dinh CRA du bao mua djnh lugng
Tham dinh dy bao mua dinh lugng cho ta bilu biet sau ban ve bin chat frong sai sd cua du bao. Dudi day la mdt frong cac kit qua diln hinh vl tiiam dinh tuyen chgn sa do tiiam sd hda
186
Tuyen tap Tai nguyen v^ Moi trudng bien. Tap XIV
ddi luu nhd phuang phap CRA, bieu dien ket qua tham dinh dy bao mua ban 24h ngiy 26/08/2003 bing md hinh H14-31/BMJ (Betts-Miller-Janijc) cho vung Ddng Bic vdi ludi tham dinh 0.125 xet cho ngudng mua 5.0 mm/ngay. De thay ro hen chung ta c6 the theo ddi cic diem sd tham dinh CRA cho frong bang tuong img, ciing nhu ket qui tham dinh (hinh 5).
RMS (mm/ngay)
H? so tuong quan
So diem nut co R > 5 (mm/ngay)
Toe do mua trung binh (mm/ngay)
Sai so khoang each Sai so djch chuyen Sai so the tich Sai so kieu mua
Mua cyc dai (mm/ngay)
The tich mua (km^)
Ban dau Sau troi Ban dau Sau troi Phan tich Du bao Phan tich Du bao km
%
%
% Phan tich Dubao Phan tich Du bao
30.61 20.86 0.205 0.605 201 279 35.26 20.59 92.4 53.6 2.3 44.1 97.29 73.08 1.28 1.03
Bang 1. Diem so tham djnh 24h ngay 26/08/03 bing H14 -31/BMJ
Gia tri tren bang nay cho ta thay, sau khi trdi vimg mua mo hinh len tay bae tren , doan dudng 92.4 km thi sai s i RMS giam td 30.61 mm/ngiy xudng 20.86 mm/ngay, he so tuang quan giua tmdng mua tham sat va tmdng mua dy bao tang tu 0.205 len 0.605.
' Sai sd tdng cua dy bao mua ldn Bic Bd, ngiy 26/08/03, ban 24h bang phien ban HI4 - 31/BMJ dugc tich lim ba phin theo ti len phin tram, trong dd sai so di chuyen chiem 53.6%, sai sd thi tich chilm 2.3% va sai sd kilu dang vung mua chiem 44.1%). S l dilm nut cd mua phan tich (tham sat) > 5mniyngay li 201 v i mua dy bio >5nim/ngiy li 279.
Tdc do mua trung binh cua mua phan tich l i 35.26mm/ngiy, trong khi cua md hinh l i 20.59mm/ngay. Mua cyc dai thim sit dugc l i 97.29nim/ngiy trong khi md hinh xac dinh dugc mua cyc dai thip ban l i 73.08nini/ngay. Thi tieh mua tham sat l i 1.28km trong khi thi tich mua md hinh xac dinh dugc la 1.03km^
Trong dd: tmdng mua phan tich td ludi do mua •vimg Dong Bae the hien tren anh dudi ben frai (hinh 5). Vecta fren tmdng mua md hinh eho thiy vimg mua md hinh can phii trdi v l hudng tay bic fren quang dudng xac dinh bdi do dai vecta. Ket qui tham dinh cho tren bang (hinh 5 dudi, ben phai) chi s l displacement (E,Ni = [0.50,-0.63] cd nghTa la so vdi thim sat •vimg mua mo hinh da frdi vl phia ddng 0.50 kinh do va trdi ve phia nam 0.63° vT do. Do vay cin diy •vimg mua mo hinh frdi ngugc lai ve phia vung mua tham sat theo vec ta cimg hudng tay bae vdi do dii xac dinh bdi khoing cich sau
7 ( 0 . 5 ' +0.63^)x\\0km = 92.4km .
Pham HSi An
Ba=3o fcst 2003082B
^s»
106
w
1\
107
\^
Anolysis 2 D 0 3 0 8 2 6
luu BO
60
40
20 0
CRA 2003082B
A* / :
+ \ / +
'M^^XA A •
0 20 40 60 80 100 Analyzed rainfall
BOCBD 00-24 fcst 20030B2B n-286 (19.63",105.00-) to (22.00-,107.7S") Vcrif. grid-0.125' CRA threshold-5.0 m m / d
jl gridpointa i5 m m / d Avorogo rainrote (mm/d) Maximum rain (mm/d) Rain volumfl (km') Displocemenl (E,N) - [0.50"
RMS cmjr (mm/d) Correlation coefficient DiBplacement moy be wrong Error Decomposition:
Displocement error Volume error Pattern error
Analysed 201 35.26 97.29 1.2B - 0 . 6 3 " ]
Original 30.61 0.205 - correlation
53.6%
2.3X +4.1 X
Forea3st 279 20.59 73.0B 1,03
Shifted 20.86 0.605 not signlf
Hinh 5. Mo phong H14-31/BMJ ngay 20/08/03
Ddi vdi tham dinh CRA dy bao mua dinh lugng tai ngudng mua 5mm/ngiy cho dy bao mua tich luy 24h bang H14-31/BMJ frong 22/07/04, gia tri cho tren hinh 6 li phan tich vi dy bao tuong ung (phan tren), sai sd RMS, he sd tuong quan tmdc vi sau khi frdi trudng dy bao mdt khoang each bang do dii vecta tren anh (phan d giiia). Vecta tren hinh fren gdc trai bieu dien gia tri doan dudng vi hudng can day trdi vung mua dy bio tien tdi •vung mua tham sat. Trong phan d gdc dudi ben phii (hinh 6) sai sd phan fram dugc tach thanh ba thanh phan: sai sd do dich chuyen, sai sd the tich va sai so kieu dang tuong ung. Trong ca hai tmdng hgp nay mua md hinh ludn thap ban mua tham sat trung binh ca ve gia tri tnmg binh vi gia tri cyc dai. RMS v i he sd tuong quan deu dugc cai tien rd ret sau khi trdi tmdng dy bao ve hudng tmdng tham sat fren doan dudng bang do dai vecta fren hinh. Tiep theo li gia tri he sd tuang quan giua tmdng tham sat va tmdng dy bao ban dau (original), da dugc tang len sau khi trdi (giua tmdng tham sat va trudng dy bio da dugc frdi - shifted).
Tmdng hgp thim dinh cho dy bio 24h cua mua ngiy 22/08/05 bing H14-31/BMJ (hinh 7) cho mua phan bd xung quanh dudng ly tudng - dudng cheo, mua md hinh d day gin vdi mua tham sat ban. Cd the thay mua trung binh gan vdi tham sat ban (34.25 so vdi 46.47) nhung lai cho mua cyc dai thip ban nhiiu so vdi tiiam sat (89.95 so vdi 164.70). Khi xac dinh dugc khoing each (bang vecta) froi tmdng mua dy bio hudng tdi tmdng tiiam sat, sai sd RMS giam (27.11 so vdi 38.78). Dac biet he sl tuang quan tang (0.199 len 0.558). Hiu hit cac dilm sl nay deu the hien tinh uu •viet cua HRM 14-31 /BMJ tiidng qua tiiim dinh mua dinh lugng.
Tuyen tap Tai nguyen va Moi tivdng bien. Tap XIV
BacSo fcst 20 22
iffi^-' msi^w^^"'^
MKL-Jvi •*.» vK^Bsra
l ^ f ^ £ i r "^^
0 4 0 7 2 2
^^^s
107
^
, 2 2
f ^ ^ Wm
• j f f l ^ '
Analysis 20040722
mSh^ljfy^
S * ^ 106
1 ^ ^^
167
JOO
| 2 5 0
S. 200 3 .•c ISO
1 'W'
l i 50 0
CRA 2 0 0 4 0 7 2 2
7 / ;
•J^4^^*^^^ ^ ^
/ • , , , •
0 50 100 150 200 250 300 Anotyzed roinfall
BocBo 0 0 - 2 + fc3t 2 0 0 M 7 2 2 n - 3 D l ( 1 9 . 5 0 M 0 5 , 0 0 - ) lo (22.00-, 107.75') Vcnf. 9 n c l - 0 . I 2 5 " CRA l h r t s h o l d - 5 . 0 m m / d
^ gridpointa i 5 m m / d AyBrogo rainrotB ( m m / d ) Maximum rain ( m m / d ) Roin volumfl (km') Dlsplacomenl (E,N) - [ - 0 . 7 5 "
RMS error ( m m / d ) Correlation coefficient Dieplocemonl may bo wrong - Error Decomposition:
Displocflment error Volume error Pattern en-or
fina\yse<i 295 52.03 255.12 2.76 -O.S3°l
Original 50.19 0.003
Forecast 3 0 1 46 12 13a 17 2 50
Shfted 43,30 0.490
>255C of fcGt remov 25.6X
0.9X 73.5X
Hinh 6. H14-31/BMJ ngay 22/07/04
B e t t m i l l e r f c s t 2 O 0 5 O S 2 2
P9i»ti«*
i6s
^ ^
IC
rai*^
>7 A n a l y s i s 2 0 0 5 0 B 2 2
2CX3
1 150
=
.c ICM
"1 M
0 CRA
I f t - i . , .
2 0 0 5 0 8 2 2
1
0 50 100 150 200 Analyzad rainfall
Bettmiller 00-24 fcsi 2D050822 n-301 [19.50MD5.DO-) to (Z2.00M07.75') VenF. grk)-0.125" CRA thr^shcld-5.0 m m / d
)(( gndpoinlH fcS m m / d Avorngo rninroto ( m m / d ) Woximum rain ( m m / d ) Rain voluma (I'm*) Diaplocament (E.N) - [0.68"
RMS error ( m m / d ) Carrclotian coefficient Displgcrmenl may bo wrong Error Docompoaillon:
Diaplacflment error Volume error
Anolj-eed 2aQ 46 47 164.70 1.75 0,00°]
Oriqinol 38.78 0.199
— corrolotion 5Q.9X
Q.3X 4a. 8%
forscasl 301 3 * 2 5 89 95 1 86
Shiaed 27.17 0,558 not signif
Pham HSi An
2. Ket luan
Qua mot s6 nhung kit qua nghien cuu ung dung va phat triin dy bao mua dinh lugng bing thim dinh Cra, cho chiing ta thay tham dinh Cra co thi xac dinh true giac va dinh lugng nhung tinh chit ma ta nhin thay dugc, tinh dugc sai so vi tri trong du bao, sai so t6ng CO thi tach thanh sai so vi tri (location) sai so the tich (volume) va sai so kieu dang (pattem). Hien tugng du bao co the phan loai thanh hits, misses. Nhiing mo ta nay co thi cho ta cong cu hiiai ich de quan ly qu^ trinh du bao. Song phuong phap nay phu thuoc vao su doi chiing kilu dang nen phai lien ket dugc cac thuc the du bao voi cac thuc thi tham sat, nghia la du bao phai diing mgt nua. Ket qua tham dinh doi vai so Cra Ion se CO xu huong vl du bao diing, tiic la nhiing du bao co sai so vi tri va sai so the tich CO thi dugc xac dinh voi do tin cay. Nguai su dung phai chgn phuang phap d6i chiing kilu ciing nhu duong ding tri dung de xac dinh thuc the. Tuy nhien de ap dung dugc phuang phap thim dinh Cra thi luoi tram tham sat mua phai dat den do day nhat dinh de CO thi coi vimg tham sat thoa man tinh lien tuc.
TAI LIEU THAM KHAO
1. Pham Hai An, 2005. Thim dinh du bao mua cua mo hinh HRM bing phuang phap CRA. Ha Noi 2005.
2. PGS. TSHK Kieu Thi Xin, 2005. DTDL-2002/02 Nghien ciiu du bao mua Ion dien rgng bing cong nghe hien dai phuc vu phong chong Iii lut a Viet Nam. Ha Noi, 12-2005.
3. Ebert E.E, J.L McBride, 1997. Methods for verifying quantitative precipitation forecasts: application of the Bmrc Laps model 24-hour precipitation forecasts.
BMRC Techniques Development Report No. 2.
4. Verification of quantitative prtecipitation forecasts firom Operational Numerical Weather Prediction Models over Australia.
5. Jollife I.T and D.B. Stephenson, 2003: Forecast verification, A practitioner's Guide in Atmospheric Science.
6. McBride J.L. and E.E. Ebert, 2000: Verification of quantitative precipitation forecasts from operational numerical weather prediction models over Australia. Wea.
.Forecasting 15, 103-121.
7. Murphy A.H, 1996. The Finley affair: a signal event in the history of forecast verification. Werather forecasting, 11,3-20.
8. Ebert E.E, J.L McBride, 2000. Verifiction of precipitation in weather systems:
determination of systematic errors.
Summary
QUANTITATIVE PRECIPITATION FORECAST IN NORTH VIET NAM BY CRA METHOD
Pham Hai An
The CRA verification method is described above using rain forecasts as an example.
The method is described in detail by Ebert and McBride (2000). From the results of research and development quantitative precipitation forecast (QPF) with CRA verification (CRA - a Contiguous Rain Area is defmed as acontiguous area of rain in the analysis 190
Tuyen tap Tai nguyen vS Moi ta/dng bien. Tap XIV
and/or forecast), for we see CRA venfication the advantage and weak points. Besides the traditional methods in the use of score statistics assess prediction of rain, typical points by analyzing individual. New methods are being developed and applied in recent years:
assessment methods Cra predicts additional rainfall will be a systematic assessment of rainfall for the area, show strong characteristics of rainfall distribution in space.
Cardinal points to apply this approach are the network stations in rainfall detectives must reach certain thickness to be considered in areas detectives satisfy continuity is recognized in the method. This is a useful property for model developers who need such information to improve the numerical weather prediction models. Such results are not only helpfiil for the forecasted rainfall modem, but also provide interesting information for scientists in other areas can identify them and trust using results predicted rain had CRA verification to apply for the purposes most relevant individual.
