^J^^Jian Khi ludng. Thuy vein vd Dcing lire hgc Bien
DAC TRUMG NU'6C DANG TRONG M O T SO CON BAO KHU VXJC VEN BO BIEN HAI PHONG
Nguyen Minh Hai"', Tran Anh Tii'"
"Vien Tai nguyen va Mdi trudng biin. Sd 246, Da Ning, Hai Phdng Email: [email protected]
Tdm t a t :
Trong giai doan 47 ndm (1960-2007) co 13 can bdo dd bg true tiip vdo khu virc ven biin Hdt Phong. Khi bdo dd bg vdo khu vuc ndy Ihudng kem theo mua Idn, gid manh, nuac eidng. Tie do gia cue dgi cd thi dgt duac trong bdo la 46 m/s (1996, 2003). Hdu hit cdc can bag diu bit nguin tir phia Tdy Thdi Binh Duang hade Biin Dong, sau khi di be) vdo khu vuc Hdi Phong diu suy gidm Ihdnh dp Ihdp nhiet dai. Qua cdc kit qud nghien cieu nude ddng Igi thai gian bdo do bg vdo khu vuc Hdi Phong nhdn thdy cdc can bdo khi di vdo vimg biin ciia khu vuc thuang gdy ra nuac ddng tren 60 cm. cd 5 can bdo gdy ra nuac ddng lir 100 cm Ira len.
SPECIFICILITIES OF RISING WATER IN SOME STORMS IN COASTAL ZONE OF HAI PHONG Abstract:
In period of 47 years (1960-2007), there were 13 storms that landed directly in coastal zone of Hai Phong. When they landed, heavy rain, strong wind, rising water often happened. Maximum wind speed in the storms could reach about 46m/s (1996, 2003). Most storms originate from -western Pacific Ocean or East Vietnam Sea. After landing, they were reduced to tropical depression.
Research of rising water at that time when storms landed coastal zone of Hai Phong showed that water rose over 60cm, and there were 5 storms that made water rise from 100cm or over.
I. M 6 DAU
Hai Phdng la thanh phd cang nim ven bd bien phia tay cua vinh Bic Bg, mgt trong nhimg noi chiu anh hudng manh cua nude dang trong bao. Nuae dang do bao la su chenh lech tam thai cua muc nude biin d ven bd so vdi muc nude trieu thien van gay ra do ap thip va gid manh trong can bao. Nd la mgt loai sdng trgng lire dai voi chu ky cd Ihl tir vai gio din vai ngay phu thugc vao thdi gian cua con bao [5]. Nude bien dang cao se tao dilu
Hgi nghj Khoa hgc vci Cong nghe biin todn quoc Idn thu V
kien cho nude man xam nhap sau vao dat lien, gay anh huong ldn din san lugng luong thuc va da dang sinh hgc. Trong nhiing nam gan day hien tucmg nude dang da cd nhitng tac ddng tieu circ tdi cae khu du lich (Dd Son, Cat Ba) d Hai Phdng nhu lam hdng nha cita, he thing dien, gay ngap lut dudng phd, d nbilm mdi trudng. Dac biet mgt sd khu vuc nhu khu vuc ciu Lac Long, dudng Cii (ihinh Lan va mgt sd khu vuc thugc phudng Ddng Khe, Quan Ngd Quyln... thudng hi ngap vao nhitng ky triiu cudng. Dira tren chudi so lieu muc nuac (1960-2007) dugc quan trie tai tram Hdn Diu va sd lieu cac con bao dd bd vao viing bd bien Hai Phdng, nhdm tac gia da nghien ctru mdi quan he giira miic do ctia nude dang va van tde gid cue dai trong bao.
II. TAI LIEU VA PHU'ONG PHAP 1. Tai lieu
So lieu dao ddng muc nude quan trac lien tuc tirng gio tii nam 1960 - 2007 tai tram Hdn Dau (20''40'N - 106*'49'E) dugc lay tir trung tam Khi tugng Thuy van Quoc gia.
Ngudn sd lieu bao dugc sti dung la sd lieu "best track" tren khu vuc Tay Bac Thai Binh Duong thdi ki 1960-2007 tir trang web www.weather.uniys.com (Co quan du bao bao, ap thip nhiet ddi cua My) [6]. Dua vao vi hi dja ly Viet Nam (6,21-230 N - 102-111,150 E) va khu vuc Hai Phdng (20° 51' 59" N - 106° 40' 57" E), so lieu "thd" tren dugc xii ly va tinh toan dl tir dd xac djnh dugc sd lugng (s6 con bao) boat ddng d khu vuc Hai Phong.
2. Phuong phap
Cong trinh ndy da sir dung cdc phuang phdp sau:
+ Phuang phap loai trieu [2]:
Phuang phap loai trieu de tach rieng thanh phan dao dgng khdng tuin hoan theo eong thiic:
hi,ii,=hi - hit, (,j
Trong dd h, la muc nude quan trie; hui, dao dgng muc nude khdng htin hoan; hu, la dao dgng muc nude tuan hoan.
Dl giai quylt bai toan nay cd rit nhilu each khac nhau dugc ap dung. 6 day, tac gia sti diing phin inim Wgrld Tide [7] dl tach thanh phin khdng tuan hoan va thanh phin man hoan (thtiy trieu). Worid Tide la chuong trinh tinh va dii bao muc nuoc miln phi, vilt bang ngdn ngii Matlab chay tren Windows.
Ci day, chuang trinh cd thi tinh dugc 35 sdng ttilu khac nhau nhu M2, N2, S2, 0|, Ki> Qi, Pl theg ly thuylt phan tich dilu hoa. Theo 1^ thuylt nay thi dg cao thuy triiu thuc tai tram quan trac tren sd khong dg sau vao thdi diem t dugc bieu diin bing tdng cac phan hieu theo cong hie tdng quat [3]
h{t) = h, + Y.f,H.cos(cOjt + Uj-k'j) (2)
Ticubcm Khi I
Trong dd / - thoi gian; Ao - dp cao cua muc nude hung binh tren so khdng tram tai thdi gian ;; f . he sd phu thugc cac yeu td thien van (he so suy biin); Hj -nhirng gia trj trang binh cua bien do phan trieu; eo^ - tan sd eua thanh phan thii j ; u - phin pha thien van cda cac phan triiu bieu dien cac gdc gid ctia nhirng tinh tit gia djnh tai thdi dilm I, k' - nhiing gdc vi dac trung cho hieu giira pha phan trieu va pha ctia lire tao trieu. Phuong phap de phan tich hing sd dilu hda thuy trieu la phucmg phap binh phuong nhd nhit.
+ Phuang phap tinh he sd tuong quan [4]:
De danh gia mdi quan he glQa mdt bien doe lap x (van tdc gid) va mgt biin phu thugc la y (dao dgng mue nude) vdi n cap tri sd quan sat {(x, y„ 1=1..n} ta di tim mdi lien he giira chung thdng qua viec tinh toan he sd tuong quan R.
He so tuong quan R giira x va y dugc xac djnh bdi eong thirc sau:
p_ zov(x,y) _!:ov(x,y) ,Jvar(.x).vaT(y) S,S..
Bien doi
t^x. -x){y, -y) t(''i-y,)--tx±y,
(4)
He sd R dugc biet den nhu la he sd Pearson. Gia tri tuyet ddi cua he sd tuang quan - Rxv cang ldn thi mdi quan he tuyen tinh giua hai bien cang chat che. He sd tuang quan dac trung cho mue do tuang quan tuyen tinh giua 2 bien. Khi he sd tuong quan duong phan anh mdi quan he cung chieu (ddng bien), he sd tuang quan am phan anh mdi quan he ngugc chieu (nghjch bien).
De danh gia do tin cay cua he sd tuang quan R ta tinh thdng ke t theo cdng thiic sau:
Trong dd R la hg so tuong quan Pearson va n la sd lugng mau
Gia tri t sau khi tinh dugc dung de tim ra mtic do tin cay P ctia he so hrang quan R bang each tra bang
tigi nglu Khoa hoc va Cong nghj bien lodn quae lan mu v
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1 5356 1.5550 1,3333 13577 13571 1 3566 1,3560 133Ee 1,53E1 1 5 5 : :
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31 32 53 S:
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6635 6636 663:
6632 6630 662S 6626 6623 ,6622
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15357 15S33 13833 13336 13333 13373 13576 1357!
1,3370 1 SWT
III. KET QUA VA THAO LU^N 1. Bao khu vuc Hai Phong giai doan 1960-2007
So vdi cac vimg ven bien khac, Hai Phdng la khu vuc phai hung chju bao va ap thap nhiet ddi nhieu, trung binh hang nam cd ed 1-2 can dd bg vao khu vuc nay. Tu nam 1960 den nam 2007 Hai Phdng cd khoang 44 can bao anh hudng true tiep va gian tiep. Khi bao dd bd vao khu vuc Hai Phdng thudng kem theo mua Idn, gid manh, nude dang cao.
Tdc do gid cue dai ed the dat dugc trong bao la 46 m/s (1996, 2003) (Hinh 2). Sd lugng bao anh hudng den khu vuc cd su dao dgng giua cac nam, cd nhiing nam khdng cd bao nhu I960, 1961, 1965, 1970...., ed nhijng nam xudt hien 3 can bao nhu 1973, 1996 (Hinh 1).
1970 1975
Hinh 1. So can bdo do bd true tiep vd gidn tiip tai Hdi Phdng
2J£ultiin Klii tieonv. Thiiy viin vci Diing liec hgc Bien
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> 10
0 1960
,
1965 1970 1975
• • « •
9B0 198S Nam
,
• •
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1990 1995
*
2000
•
•
2005 2010
Hinh 2. Toe do gid cue dai trong bdo 2. Nuoc dang khi bao do bg true tiep vao Hal Phong giai doan 1960-2007
Tir nam 1960 den nam 2007 Hai Phdng cd 13 eon bao dd bg true hip gay ra nude dang lai khu vuc nay. Hau hit cac con bao diu bit ngudn tir phia Tay Thai Binh Duong hoac bien Ddng, sau khi dd bg vao khu vuc Hai Phdng deu suy giam thanh ap thip nhiet ddt. Cae con bao khi di vao viing bien Hai Phdng deu gay ra nude dang tren 60cm trir can bao xay ra vao thang 8/1962 gay nude dang 33,55c,i i vi can bao 9/1968 gay nude dang la 49,4cm, cd 5 can bao gay ra nude dang hr lOOcm trd li. i (Bang 2, Hinh 3, Hinh 4). Nude dang do bao rit nguy hiem, dac biet neu roi vao dung thdi ki trieu cudng. Tuy nhien hau bet cac con bao gay ra nude dang ldn dd bg vao Hai Phdng thudng vao thdi ki triiu kem [I ].
TT
1 2 3 4 5 6 7 8 9 10 11 12 13
B a n g 2. Muc Nam
1962 1964 1968 1973 1973 1991 1992 1992 1994 1994 1996 1996 2005
Ngay
11/8 3/7 9/9 26/8
2/9 14/7 29/6 14/7 29/8 7/9 24/7 23/8 31/7
nir&c cu-c
Giu 20h l l h 14h 5h 12h 8h 19h
Ih 8h 18h 3h Oh U h
dai trong thcri gian co bdo Nuorc dang
(cm) 33,55 104,29
49,4 91,63 50,16 100,0 78,98 68,92 61,08 64,12 151,36 158,75 123,49
Thiiy trieu (cm) 223,16 107,71 180,58 62,37 195,84 26,0 279,04
82,08 246,92 238,88 176,64 278,41 124,25
Muc nuffc quan trac (cm)
254 212 230 154 246 126 358 151 308 303 328 304 283
ngi ngni i\nou ngc va '~ong ngne oien loan t/M
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Hinh 3. Mrtre ddng do ean bdo Ihdng 7/1964
3.5
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2.5
^ 2 ^ E -i 1-5
a
^ 0 . 5
^ . 5 | -1
1 1 g i
Thai gian L ^ f W
M X
%
M v c n u D c quan tr^i:
X Thiiy tneu 1 N u a c dang
1
Hinh 4. Wird-c ddng do can bdo thdng S/I 996
De danh gia moi quan he cita nude dang cue dai va van tdc gid trong bao tuong irng tai thdi diem dd, ta di thiet lap moi quan he giira 2 yeu to nay:
Mdi quan he giira muc nude cue dai va van toe gio tuong irng trong bao duong, chung td van tie gid hong bao cang ldn gay ra nude dang cang Idm (Hinh 5). Mdi tuong quan gitta 2 ylu td kha chat che ling vdi he so tuong quan R = 0,846. Dl danh gia mitc dg tin cay cua he sd hrong quan ta di tim thdng ke t theo cdng thiic (5) sau dd tra Bang 1 tim mirc do tin eay cila R ta dugc t = 5,27, P = 100%. Mtic do tin cay ctia he sd tuang quan R ldn.
Tieu bjm Khi tugng, Thiiy van vd Ddng lire hgc Bien
Khi tinh trung binh muc nude trong khoang thdi gian nude dang, va van tdc gid trung binh trong khoang thdi gian tuang ung, sau do xet mdi quan he giua gia tri nude dang va van tdc gid tir nam 1960 den nam 2007. Neu tinh day du tat ca eac nam cd bao thi he sd tuang quan giira nude dang va van tdc gid trung binh R = 0,65 va muc tin cay cua he sd R la 97,8%. Tuy nhien khi ta ve bieu dd nude dang va van tdc gid trung binh trong thdi gian cd bao thi thay ed mdt sd nam van tde nhd nhung gay ra nude dang ldn. De lam rd mdi quan he giua nude dang va van tde gid ta thu xet trudng hgp la loai bd di mdt sd nam bat thudng nay. Ket qua eho Ih^y khi loai bd di mdt sd nam thi he sd tuang quan giiia 2 bien tren tang Ien dang ke R = 0,79 va muc do tin cay ciia he so R la 99,4%. Dieu nay chung td ed mdi lien he giua nude dang va van tde gid trong bao.
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y =0.134x +7 8267 R^ = 0.7164
2 0 0
Hinh 5. Moi tuang quan giira muc nuac cue dgi vd van toe gio trong bdo
IV. KET LUAN
Nude dang do bao d khu vuc Hai Phdng hau het la ldn ban 50cm. Mgt so can b"ag gay ra nude dang tren 150cm (24/07/1996 va 23/08/1996). Nuoc dang cue dai Ion nhit trong bao khdng hoan toan roi vao cac con bag rat manh hoac manh ma dg ldn ctia nude dang trong bao phu thugc vao nhieu yeu to nhu: tdc do va hudng di chuyen ciia con bao, do giam ap va siic gid trong can bao. Ngoai ra do sau va hinh thai dudng bd cung vdi che do thuy triiu ciing anh hudng tdi trj sd nuac dang do bao.
TAI LIEU THAM KHAO
1. Nguyin Minh Hai, 2010. Nghien cuu hien tuang nu&c ddng & viing ven bien Hdi Phong. Bao cao tap su. Luu trii tai Vien Tai nguyen va Moi truong biin.
2. Nguyen Tai Hoi. 1995. Report on tidal characteristics (Sub. A5). Design water levels (Sub. A13). Marine Hydrological center. Vietnam VA project, Hanoi
l-igt ngm Khua hgc va Cong nghe bien todn quoc lan mu r
3. Pham Van Huan, 2002. Ddng luc hgc bien phdn III. Thiiy triiu. Nha xuSt ban Dai hgc Qudc gia Ha Ngi.
4. Phan Van Tan, 2005. Phirang phdp thong ke trong khi hdu. Nha xu5t ban Dai hgc Qudc gia Ha Ngi.
5. Vii Thi Thu Thuy, Nghiem Tien Lam, 2003. Thiet lap md hinh linh todn mrdc ddng do bdo cho bd bien Viet Nam.
6. www, weather, uniys.com
1. http://www.worldtidesandciirrents.com 8. http://amchan2.net/SlatT00ls/1ndex.php
