Ngtiien ciiu - Trao doi
^ DU BAO KHI HAU B A N G PHL/ONG P H A P
DOWNSCALING T H 6 N G KE T C / S A N P H A M CFSV2
Thur nghiem dU bao nhiet do va luong mua thang 6
O VU THj SIM
Trffdng Dai hpc Tai nguyen va Mdi trffdng Ha Npi N G U Y I N D A N G MAU, LUU NHAT LINH Vi$n Khoa hpc Khi tffdng Thdy van va Biin doi khi hau
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et qua nghiSn cffu cho thiy, san pham dff bao CFSv2 d mdt sd tram nghiSn cffu cdn nhiiu han ehi, sai sd dff bao Idn va khong cd quan hS tdt vdf sdliSu quan trac (Ob). Tuy nhien, khi ap dung phitang phap downscaling thdng kS (SD), kit qua dff bio da difdc cai thien ding ke so vdS CFSv2. He sd tucmg quan giffa dff bio bing SD vdi Ob: Khoang tff 0,76 din 0,89 ddi vdi nhiet dp;vi khoang tff 0,76 din 0,88 ddi vdi IffOng mffa. Dinh gla ddi vol trudng hpp bii toin dff bao hai pha (vffdt vi hut) eho thay, xic suit dff bio dting eie pha cua nhiet dp trong khoang tff 79,3 din 93,lYovi vdi lifgng mua vio khoang 68,9 din 82,7%. Kit qua niy eho thiy, kha nang phit triin htfdng nghien cffu dff bao thdng ke tff san phim md hinh CFSv2 cho khu vue Viet Nam li CO triin vpng eao.
Gidi thieu
PhQdng phap thdng ke trong dy bao khf hau d Viet Nam da dope phat trien IQ rd't sdm, mdt trong
nhQng edng trinh ddu lien dope thoe hien bdi Pham OQcThi (1987).
Hien nay, nhieu ket qua nghien cQu do bdo khf hau bang phoong phap thdng ke vdn cd y nghTa khoa hpc va thyc lien cao. Ddi vdi dieu kien khf hdu node ta ed md'i quan hd rd rang vdi dien bien ENSO (Nguyen DQe NgQ, Nguyen Trpng Hieu, 2004), thi hudng liep can nay cung hoan loan hpp ly. Ngoai ra, eae san phdm do bdo khf hdu loan eau tmdc dd van cdn nhieu han che va chim dope cung cap phd bien nho ngay nay.
Trong nhQng ndm gan day, nhd ed so phdt Iriln vopt bac eiia he Ihdng may tfnh cung nhO sO hilu biet cCia con ngt/di ve cae qua trinh vat ly khf quyen, kha ndng do bao cQa cae md hinh so da dope ldng len rat nhieu. 6 eac node Chau A trong do cd Viet Nam - ndi thdng trj bdi khi hau gid mtia, sd lidu GFS vd CFS da va dang trd thanh hai ngudn sd lieu dy bao chfnh de cung cap thdng tin vd lam dau vao eho ede md hinh ddng loc khu vye va SD. Ndm 2014, Mai Vdn Khiem va nnk (2014) da xay dyng md hinh dy
bao han khi topng cho khu vyc Viet Nam doa Iren each tiep can SD IQ cac md hinh toan eau. Theo danh gia ciia cae tac gia, md hinh thd hien kha tdt dien bien han han, ddc biel la mdt sd dpi han nSng cung da the hien dope. Trong sd cae md hinh do bao toan cau eho khu voc Viet Nam, Suranana Saha va nnk (2013) eho rang, CFSv2 cho ket qua do bao phu hpp ve hoat ddng cQa gid Chau A va eac dde trong khf hau.
Nho vdy ed t h i thay, vdi viec san phdm dy bao loan eau eCia CFSy2 6ddc eung cap mien phf, ddy dii va edp nhat tren mang internet da md ra hirdng khai thde san pham nay la ed Ifnh thye te eao. Trong nghien cQu nay, ehting tdi sQ dung each tidp can SD IQ san pham eiia md hinh CFSv2 eho khu vyc Vidt Nam. BQdc dau nghien eiiu, chung tdi thQ nghi&m Qng dung phOdng phOdng SD d l Ihyc hien dy bao nhiet dp va lopng moa thang 6 cho 7 tram tieu bleu cho 7 vung khf hdu Viel Nam (Lai Chau, Lang Son, Ha Ndi, Vinh, Nha Trang, PIdy Cu va Can Thd).
2 6 Tdl nguydn vg Mdt trudng | Ky2-Thing6fi015
Hinh 1. So sinh nhiet dd CFSv2 vdi quan trie
(Ob)
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Hinh 2. So sanh nhiet dd SD vdi quan trie
(Ob)
H^v^^l
Hinh 3. So sanh luang mua CFSv2 vdi quan
trie (Ob)
Hinh 4. So sanh luang mua SD vdi quan trSc
(Ob)
.R.i.
J:::Hinh 5. H$ si tffdng quan giffa dff bao nhiet dd SD vdi Ob (miu cam) vi CFSv2 vdi Ob (mau xanh)
So' lidu va phQOng phdp
Sd lieu dope sQ dijng trong nghien cQu bao gdm:
(1) Sd lieu quan trie vd (2) Sd lieu dy bdo thang 6 (vdi ttidi dilm ehay dy bdo la vdo ttidng 3) cQa md hinh CFSv2 thdi ky 1982-2010. Trong dd, sd lieu quan trae Id chuoi sd lidu chuan sai nhiel dp vd lopng mOa ttidi ky 1982-2010 lai edc tram dupe lya chpn. Ket qua dy bao khf hdu thang 6 thdi ky 1982-2010 bang md hinh CFSv2 vdi thdi diem ehay dy bao Id ttiang 3 (dy bao frudc 3 tiiang) dope sQ dung d l lim chpn nhdn td dy bao. Cu ttil, cae san phdm dy bdo IQ CFSv2 dupc lya chpn bao gdm: Nhiet dp, lupng moa (tai cdc tt^m nghien cQu); cae thanh phin gid (kmh hodng va vT hodng) d myc 850 mb vd 200 mb (U850, U200, V850, V200); dp eao dm the vj myc 50 Omb (HGT500); bOc xa sdng ddi (OLR); khf dp muc node biln (PRMSL). Todn bd ket qua dy bdo nay dupc cung cap tai dia chi ttang web:http ://nomads .ncep .noaa.gov/pub/data/nccf/com/
cfs/prod/efs/.
Phuong phdp nghien cQu dupc lien hdnh nho sau:
Oau tien, tien hdnh khao sdt vd ddnh gia kha ndng sQ
Hinh 6. H§ so tmng quan giffa dff bao lupng mua SD vdi Ob (miu cam) va CFSv2 vdi Ob (miu xanh) dung ket qua do bao eiia CFSv2 tai cac diem tram. Sau dd, tien hanh khao sat loa chpn nhan td dy bao tQ eae tmdng do bao khac cQa CFSv2 (PRMSL, HGT500, OLR, U (850 mb, 20 Omb), V (850 mb, 200 mb) dya fren mdi quan he tiid'ng ke vdi sd lieu quan frac (nhiet dp va lopng mOa) tai eac diem fram nghien ctiu. Tren so sd IOa ehpn dupc nhan Id dy bdo, sQ dung phoong phap hdi quy da bidn d l xay dimg cdc phoong ttinh dy bao.
Ket qua va thao luan
Kdt qua tinh loan cho thay, sai sd giQa nhiet dp vd lopng moa thang 6 (dope dy bao tQ thang 3) bang md hinh CFSv2 cd sai sd kha rd rang vdi sd lieu quan trac lai (Ob) cac diem tram (Hinh 1 vd Hinh 3). Dd'i vdi lopng moa, md hinh CFSv2 do bao eac ngodng moa ldn (IQ 400 den 800 mm) la rat kem, thap hdn khoang 200 den 600 mm so vdi thyc le. Ngopc lai, vdi ngodng moa tQ 200 de'n 400mm, md hinh dy bao lopng moa cao hon thoctdtQ 100 ddn 300 mm (Hinh 3). Tuy nhien, khi sQ dung phoong phap SD, sai sd dy bao nhiet dp va lopng mim da dope cai thien dang ke (Hinh 2 va Hinh 4). Trong do, sai sd nhiet dp Irong dy Tdi nguyen vd Mdi trudng | Ky 2-Thing6/2015 27
Hinh 7. Xac suit dubao dung nhiit dp va Iffdng mua thing 6 thdl ky 1982-2010 do'i vdi bii toin dff
bao hai pha bang phffdng phap SD bao bang phoong phap SD chii ydu tap trung Irong khoang dodi 1 "C. Ngodi ra, sai sd dy bao lopng mOa, dodng hdi quy Iren Hinh 8 khdng cdn nghidng vd phfa sd lieu quan trac nhO trong Hinh 4. Dieu nay cho thd'y, chenh lech giQa do bdo vdi quan trae da dope eai lien ddng ke bang phoong phdp SD so vdi CFSv2. 6 day, sai sd dy bao bang SD vdi quan trie pho bien lap Imng trong khoang tQ 0 den khoang 200 mm.
Chat lopng dy bao bang phuong phdp SD dope cai thien ro rang nhat so vdi CFSv2 khi so sdnh he sd toong quan giQa dy bdo vdi quan trac (Hinh 5 va Hinh 6). Cy Ihl, he sd toong quan giQa dy bao nhiet dp cQa CFSv2 vdi sd lieu quan trac tai eae diem tram nghien la rat thap, cao nhat la dd'i vdi trodng hpp do bao nhiet dp lai tram Play Cu (0,49). Thdm chf, mdt sdtram phfa Ble (Lai Chdu, Lang Son, Ha Ndi) cdn cd he sd toong quan dm (Hinh 5). Tuy nhien, khi sQ dung phoong phap SD, he so toong quan giQa dy bao vd quan ti^c ddu cao hon 0,7 den gan 0,9. Ddi vdi lopng moa, he sd toong quan giQa dy bao CFSv2 vdi quan trie cung rat thap, deu nhd hdn 0,18, chdm chf ldn tai - 0,22 lai tram Lai Chau. Tuy nhien, khi sQ dung phuong phap SD, he sd toong quan glQa dy bao va quan trac da dope cai thien rat rd rang. Trong dd, hd sd toong quan glQa dy bao mOa bang phoong phap SD vdi quan trac phdn bd trong khoang IQ0,76 den 0,88.
Kdt qua ddnh gia xac suat dy bdo dting ddi vdi ttudng hdp dy bao hai pha (vopt vd hut) cung cho thay, phi/dng phap SD ed xde suat dy bao diing cao ddi vdi ea nhiet dp va lupng moa. Trong dd, xae sud'l dy bao dting ddi vdi nhiet 66 phan bd IQ 79,3% (Lang Son) den 93.1% (Play Cu va Can Tho). Odi vdi lopng mOa, xae suat dy bao dung dd'i vdi bai loan dy bao hai pha phan bd trong khoang IQ 68,9 (Play Cu) den 82,76%
(Lang Son, Ha Ndi, Nha Trang, Cin Thd) (Hinh 7).
2 8 Tdi nguyen yg Mdi trudng | Ky 2-Thing 6/2015
Ket luan vd kien nghj
Nhin ehung, CFSv2 eho dy bao lai eac dilm tram nghien cQu cd ket qua khdng tin cay (sai sd ldn va he sd loong quan thd'p) ddi vdi ca nhiet dp v^
lopng moa thang 6 thdi ky 1982-2010 tai cae dilm tram nghien cliu. Ngodi ra, nhidu trodng hpp do bdo cdn cho ket qua ngopc xu the so vdi thQc Id (loong quan am). Vdi cdch tidp can bai loan dy bdo theo phQdng phap SD cd the Ihay rang, chat lopng dy bao lai edc dilm tram nghien cQu da dope cai Ihien ro rang so vdi CFSv2. Doi vdi nhiel dp, sai sd dy bao phd bien Ihap hPn I^C, he so loong quan giQa nhiet dp do bdo vdi quan trac trong khoang iQ 0,76 ddn 0,89 va xde suat dy bao dung ddi vdi bdi lodn dy bdo hai pha trong khoang 79,3 den 93,1%. Odi vdi lopng moa, sal so do bao eung dope eai Ihien dang k l , he sd toong quan giQa lopng moa dy bao vdi quan trong phd bien trong khoang IQ 0,76 den 0,88 va xae suat dy bao dung ddi vdi bai loan dy bao hai pha la trong khoang IQ 68,9 de'n 82,7%.
Mde du, nghien cQu mdi ehi dQng lai d mQe dp thQ nghidm ddi vdi trodng hpp do bdo nhiet do va lopng mua thang 6 tai 7 tram nghien cQu. Tuy nhiSn, kel qua nghien cQu da md ra hodng nghien cQu kha quan trong viee Qng dung phoong phdp SD trong dy bao khf hdu d Vidt Nam vdi nhan Id dau vao Id san pham eQa md hinh CFSy2.
Ldi cam on: Bai bao hoan thinh nhd sff trd gidp tu di tii eip Bp "Nghien cffu dff bao hoat dpng ctia gid mua mOa he tr§n khu vffc Viet Nam bing mo hinh ddng Iffc", mi so TNMT.36 thupe Chffdng trinh TNMT.05/10-15.
Tai lieu tham khao
1. Nguyen DQc NgQ, Nguyen Trpng Hieu, 2004:
Khi hiu vi tii nguyan khi hau Viet Nam. Nhd xual ban Ndng nghiep Ha Ndi.
2. Mai Vdn Khiem va nnk (2014). Nghiin cdu thff nghiem dff bio han han tai Viet Nam bkng san phim dubao cOa mpt so md hinh toin eiu. Tap chf KTTV, lr. 21-25.
3. Nguyen Duy Chinh va nnk, 2002: Nghien cffu thff nghiem Dff bao khi hau Vidt Nam. Di an nghien cQu cap Tdng cue KTTV, 2002.
4. Pham DQc Thi, 1987: Xay dtmg mpt so phUdng phap dff bao han vffa, han dii nhiet dp mOa ddng vi mffa mua he khu vffc phia Bic Viet Nam. Tdng cue KTTV De tai Choong trinh 42.B
