NGHIgNCCfU-TRR0ID6l
NGHIEN Ciru KHA NANG XUAT HIEN SUONG MUOI 6 KHU VUC TAY BAC
TS Di/dNG V A N K H A M , CN N G U Y I N H 6 N G SON V\$n Khoa hgc K.hi ti/^ng Thuy vin vi M6\ trudnq
DCSEADCH INTO THE P0(S&151L1TY o r HOADFDOST
INNODTHWESTDEGION
The Northwest region has been rated as an advantaged region to develop the area of perennial crops, particularly long-term Industrial crops (rubber, coffee) and other fruit trees. Hoarfrost Is very dangerous meteological phenomenon for crop. Its serious effects for long-term industrial crops, especially rubber and coffee in the Northwest region in recent years have been demonstrated. The results of this report help managers, and producers capture the necessary information about the frost, establish the reasonable plan and useful precautions to reduce the damage caused by severe weather phenomenon.
l.Mo'dau
Viing T4y Bjc 6ii!>c dSnh giS l i viing c6 nhiSu Icji thi 64 phil Iriln dien tfch tr6ng c4c cSy ISu nSm, nhft li cSy c6ng nghidp dii ngiy (cao su, ci ph&) v i cSy an quS. Tuy nhiSn, hgn chi ldn nh^t cCia khu VI/C niy l i 81,1 xulit hien cua cic di^u ki^n thdi ti^t Cilc doan nhu sUdng mu6i, SUdng gii, nhigt dd thSp, D l cd nhOng cd sd khoa hpc giup cic nhi quSn iy, ngUdi sin xui't nSm bSt dupc nhuing thdng tin cdn thilt v l SUdng mud'i, tif dp cc nhQng quy hcgch hdp ly va bi?n phap phdng tranh kjp thdi, giSm bdt nhQng thigt hai do hj$n tUdng thdi till nguy hiim niy gay ra, chiing 161 da tiln hinh: "Nghidn cQu khi ning xuit hidn sQdng mudi 6 khu vQc Tiy Bic" vdi cic ndi dung:
- Nghien cQu die trung v i mQc dd inh hudng cua sddng muoi.
- Dinh gii cic yiu td hinh thinh sQPng muoi d khu vuc Tiy Bac.
2. Cac dac trang va muc do anh hvimg cna suong muoi
2.1. T6ng quan ve suong mudi
SUdng mud'i l i hidn tdpng hdi nudc dong bing thanh cic hat nhd, rSn, xdp va tring nhu mud'i ngay trdn mit dit hay be mit ciy c6 ho$c cac vit thi khic khi khdng khi tren dd Im v i Ignh [2], [3]. Khi nhidt dd b l mat thilc vit h? thip xuSng dUdi O'C, nudc trong thin ciy se ddng bing Igi v i gian nd t h i tich, phi vd cic t l bao, cac dng din nhi/a cung ngQng hogt ddng, khdng vin chuyin dUdc cac chat dinh dudng nudi ciy. VI viy, sau khi cd sUdng muSi ciy trong bit diu xuit hi§n nhOng vit "chiy tip" trdn mat l i . Ngpn ciy khd dSn, idp v6 trdc ra, ciy heo ua rdi chit [2].
Thdng thudng, suong mull hinh thinh v l dem ho^c sang sdm, trdi lang^gid, quang miy, nhiet dO khdng khi xuing thip trong dilu kidn dd am khdng kh( thich hpp lam cho nhi$t dd b l mat cic vit thi hay ciy c6 dat tdi diem sUdng dO cho hoi nudc ngung kit. Theo kit qui nghidn ciju [2], sJOng mudi d Tiy Bic chia thanh 3 ioai: sUdng mu6i binh iuu, sUOng mudi bQc xg v i sUdng mudi hon hop.
2.2. Die trung suang muSi khu vtrc Tiy Bic
6 Tiy Bic, SUdng mudi xuit hi^n d nhilu dja diem khic nhau (trdn ddi, sudn doi, phieng bai), trong thdi gian td nCia ddm ve sing (td 0-7 gid), bit dSu til thing 11 din thing 3 nam sau, tip trung nhieu nhit vio cic thing chinh ddng (thing 12,1).
TQnam 1961 den nay, trong tong sd 21 trgm khi tupng d Tiy Bic
« KHoTHt"c^'**^"^"°'=
NGHieiM CCrU - TRflO BOI
va vimg lin can cd 16 trgm da IQng quan trie thiy sUOng muoi (chilm 76%), chl cd 5 trgm chua quan trie thiy siiang mudi (deu cd do cao dudi 600 m). NhOng khu vuc CO do cap tQ 600 din trdn 1.000 m deu cd tU 4 dint 4 nim xuit hien sUdng mud'i vdi tan suit nim tU 17% den 46%, va 6 do cao trdn 1.500 m (Sin Ho) thi hiu nhu nam nio cung xuit hien sUOng mudi (tin suat nim 100%).
- 6 viing nui cao trdn 1.500 m (Sin Hd): trung binh 1 nim cd 10,93 ngay v i cao nhit i i 22 ngiy cd sUdng muoi, trong dd 2 thing chinh ddng cd tU 3 (thing 1) din 5,64 ngiy (thing 12), die bidt cd nhQng thing cd tdi 16 ngay sUOng mudi, cdn cic tiling khac (11,2, 3) sUdng mud'i chf tu 0,14 din 1,43 ngiy.
- 6 vung nui tQ 800 din 1.500 m (Mdc Chiu, Tgm Dudng): trung binh 1 nim co IQ 0,39 de'n 1,64 ngay, cao nhat ii 11 ngay cd SUdng mud'i. Thing cd sUdng mud'i cao ii thing 12 (0,32-1,04 ngay).
- 6 vimg hQi IQ 600 din 800 m: sd ngiy co sUOng mud'i trong nim dao ddng tQ 0,39 den 1,57 ngiy, cao nhat la 10 ngiy (Cd Ndi). tip trung chii yiu trong thing 12 va thing 1.
- 6 vung cd dd cao dudi 600 m: sQdng muoi xua't hien chil yiu trong thing 12, trung binh 1 nam cd tU 0,18 den 0,21 ngay, cao nhit l i 6 ngiy cd sQdng mudi.
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B t e r e n C6N6i vanChSu SAngMB Qutnh Nhai MJcChSu PMlYir.
Son La TBuin Chiu Pha Dm
T0> cnua Mn Bttn U l C M u MtiengNM UMt^Ti SInHS Thm JySn T ™ DUdng Phong ThS einh Lu
BScao
B42,9 B70,B 314,0 359,5 802,0 972,0 169 0 675,3 652,0 1347 0 5718 10410
•75,1 243,2 641,0 329,4 1533,7 801,2 900,0 570,0 6B4 0
K h i ning . l i l t hi^n suong mudi
'.r
K X 1 x K X t
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X X X
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X K K X x X X
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r u i 9 e i a l n 2 D i » S6t\Sm
6 M a
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X 14 2 14 KHB
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KHP
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29 6
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KHD KHD
T i n sull nam (%|
21 43
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0 0 46
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46 0 0 0
4:
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100 18
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Thing xutfl
Xll-I X|.|
Xil-l XII X Xl-i XII
— ^ - i —
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_ „ _ 1
XI III XIM Xll-I
mudi TBNN 0,.
1,6 Q,23 0 0
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0,21
— -'—
'-^"-~
— — 0 — 10,9 0,5 0,4
2.3. Oinit gii mUc dg khic nghidt cua suang mudi Cic chi tidu dinh gii mQc dp khac nghidt cua SQdng muoi dUdc xem xet bao gom sd ngiy cd sUdng muoi trung binh nhilu nam - TBNN (ngay) v i tan suit sQOng muoi trung binh nim:
MUC et) I t h k nghiei
KhAng D|dnh hudng Anh hiJSng nfie Anh huing Irungblnh Anh hudng nftng Anh hufing rfllnSng
Chl tieu Stf (iflay cfi SUOng mu6l
TBNN IngAy) 0 0,01 • 0,20 0,21 -1,0 1,1-3,0
>3,0
T^n suSi sUong mutfl Irung binh nam (%)
0 1 - 5 5 - 2 0 2 1 - 6 0
> 6 0
Bing 1: thing k& v4 sUdng muH d Tdy B4c [1M2},[4},(5],[6}
(trong dd: X - Di tdng xuit hi$n sdOng muH; K - Khdng xuit hiin SUdng muii; KHD - Tram quan trie khdng cdn host ding)
Bing 2: ch! tidu dinh gii mdc dd khic nghidt cda sUdng muii
Tren ccJ sd b^ng 1 va 2 cho thay:
- Doi vdl cac khu vi;c niii cao tr§n 1.500 m: d§y la khu vi^c CO nhieu sUdng mud'i, hang nam trung binh cd tr§n 3 ngay suong muoi, trong 10 nam co tren 6 nam xuat hien saong mudi (tan suat tren 60%), Cu the, tai Sin Ho b dd cao 1.533,7 m. trong nam co 10,9 ngay suong mud'i, vdi 100% sd nam quan trac deu cd sUdng mud'i. d khu VLfc nay miic do anh htfdng cilia saong mudi la rat nang.
Ddi vdi khu vi/c cd dp cao tis 600 de'n 1.500 m:
mtfc dd knh hudng cua siiong muoi tis trung binh de'n nang.
- Bdi vdi khu vifc cd do cao dudi 600 m: kha nang xuat hien suong muoi la rat thap, rat nhieu khu vUc khdng x^y ra sUOng mudi (Tuan Giao, Sdng Ma, Mudng Te, Lai Chau) hoac hiem suong mudi (Dien Bidn), trung binh nam chi cd 0,2 ngay xuat hien suong mudi va tan suat sUOng mud'i n§m dUdi 5%. Mdt so khu vUc nhu Phu Yen, Yen Chau sUOng mudi it, trung binh nam chf dudi 0,3 ngay c6 sUOng mudi, tan su&'t xua't hidn sUOng mudi trung binh nam tU7 den 11%. d dd cao nay cd rS't nhidu khu vUc khdng bj anh hudng cua sUOng muoi hoac chf vai khu vuc bi knh hudng vdi cap do nhe.
3. Nghien cihi danh gia cac yeu to hinh thanh sutmg muoi
3.1. Khong khi l$nh (KKL)
Sau khi phan tich chudi sd lieu quan trie ve sUdng mudi d vung Tay Bac nhan tha'y:
- Khi KKL bdt dau anh hudng den Viet Nam thi thudng sau td 2 de'n 4 ngay sUdng mudi se xua't hien d Tay Bac (b^ng 3).
S6'thang 5.2012 ^ j j l j " ' * * * " "
NGHI€NCaU-Tfll^0D6l
Thdi gian Kui\ N$n suong mu6i sau khi KKL i n h hiidng dd'n Vigt Nam (ngdy)
1 2 3 4 5 e
>6
SC! Ifln x&y ra si/Ong mudi
0 10 19 16 1 4 2
NgUBng nhi^l i»
MlAngMK (=C) iO 0,1-2 0 2,1-5 0 5,1-7 0
>7,0 T ^ g ^
Stf IruSng hop ihBO nguane n h i ^ l d f
4B 196 1281 2 745 8.369 i2.ese
Stf trUdng nppc6 suong
4B S5 282 65 9 497
T^ 14 {%) stf tiUdng hQp cA suong mufll
So vdl sd IrUAng hgp Iheo ngudng nhl«t i K
68 46 22 2 0,1 1BB,1
SovdlnSngsB IrUdng hop oA suong mudi
B IS 57 13 2 100 Bing 4: tf' 1$ (%} khi ndng xuit hl^n sddng muii
theo cic ngudng nhidt dd til thip td 0 din 7 gid
3.3. Dg im khong khi
Trong didu kien nhidt dd thuSn Itji (< 5°C) thi yd'u td cd ^nh hudng de'n khli n§ng hinh thanh sUdng mud'i \k dd am khdng khf. Sau khi ph§n tich chuoi s6 lieu v^ dd
a'm khdng khi (bSng 5) nh$n thdy: trong tdng sd 479 trudng hdp cd sUdng mud'i thi cd ddn 458 trudng hop cd dd ^m khdng khf trung binh (tU 0 ddn 7 gid) trong khoSng 75-95%, chidm tj-1$ 92%; ngudng dd I m tU60 ddn 74% cd 25 trudng hop, chidm ty Id 6%; ngudng dd
^m S 59% vk S 96% chf cd 14 trUdng hdp cho c^ hai ngudng, chidm \^ Id r&X nhd (2%).
Sdng 3. inh hUdng cua KKL din khi ning xuit hidn sUdng mud'i 6 cic khu vdc cd dd cao ditdi 1.500 m - Mdt sd trudng hdp d vung nui cao, do ndn nhi^t trong cdc thSng mija ddng thdp ndn trong thdi ky khdng bj knh hudng cua KKL viin cd t h i xud't hidn SUdng mud'i.
3.2. Nhi^t 60 khdng khi
De ddnh gid md'i quan hd giUa nhiet dd khdng khf vdi khd nang xud't hidn sUdng mudi, chung tdi phfin tich dieu kien nhidt dd vdi sU hinh thanh sUOng mud'i cjja 16 tram quan trie trong khodng thdi gian tif 0 ddn 7 gid t\S n§m 1981 den 2009 (bdng 4): trong 48 trudng hop cd nhiet dd khdng khf th^p nhat nhd hon 0°C thi 46 trudng hqp cd xua't hien sUdng mudi (ty le 96%), ngudng nhiet dd tU 0,1°C den 2,0°C cd 95 trudng hdp xuat hien sUdng mudi trong tong so 196 trudng hdp (ty le 48%). 6 ngUdng nhiet do tU 2,1°C den 5°C quan trac dUdc 1.281 trUdng hop thi cd 282 trudng hdp xua't hien sUdng mudi (chiem 22%). Neu so sanh sd trudng hdp cd SUdng mud'i theo cac ngUdng nhidt dd vdi tdng sd trudng hdp cd suong mudi 6 16 dilm quan trdc vung Tdy Bic thi cd ddn 85% sUdng mudi xu^t hidn khi nhidt dd khdng khi < 5 °C.
NgifOnB dO ftm (%)
^S6 7 5 - 9 6 e o - 7 4 5 5 8 T d n g stf
S S IruOng t i 9 p c 6 a u o n g m u f i l 7 458 25 7 497
T J 1$ (%) 1 92 6 1 100 Bing 5: ty 1$ (%} khi nang xuit hi$n sUOng muii theo cic ngUdng dd im khing khi trung binh td 0 din 7 g,
3.4. GI6 vd mdy
Cung nhuydu td nhidt dd, dd im, chung tdi da phdn tfch toan bd chuSi sd lieu trong nhQng ngay cd sUdng mud'i, kd't quk phdn tfch cho thSy:
- d bdng 6: trong 497 trudng h0p cd sUdng mudi, thi cd den 356 trudng hdp lang gid (tdc dd bing 0 m/s), chid'm ty Id 72%; khi tdc do gid trong khoSng tiS 1 ddn 2 m/s (gid nh?) cd 121 trUdng hqp cd sUdng mudi, chidm ty 1$ 24%; khi td'c dd gid Idn hdn 2 m/s chl cd 20 trUdng hdp cd SUdng mudi, chidm ty Id 4%.
Nhu vay, dgi bd phan khk ndng xudt hi^n sUdng mudi chf xdy ra trong trudng hdp Idng gid va gid nh?, tdc do gid trong khoSng td 0 dd'n 2 m/s.
Ngi/dng tfic dQ gi(i (m/s) 0 1 - 2
> 2 TJng s6
Sti trtJdng hQp xSy ra siJdng mu6i
356 121 20 497
T} 1$ {%) 1 72 24 4 100 BSng 6:1} i$ (%} Iihi nang xuSt hi$n suang mu6i theo cSc
ngt/dng tdc d^ gid iuc 1 gid
- d bJng 7: trong 497 trirdng hop co suong muSi thi CO 282 truOng hop co sUOng mu6'l trong 6iiu kiSn il mSy, chid'm ty 1$ 57%; trong dieu ki$n may thay ddi co 135 trudng hop, chiSm ty li 27%; trong dieu ki§n trOI nhiSu may cung co den 80 trudng hop xiy ra sUdng mud'i, chiSm ty le 16%. Nhu vay, phSn nhilu k h i nang xuat hign suong muoi x^y ra trong trudng hop it mSy va may thay 66i, iuong mSy tong quan trong khoSng
< 3/10 \ii 3/10-6/10, tuy nhi§n trdi nhilu mSy vftn co 16% x^y ra SUOng mudi.
KHOAH^C^***"^^'^"'^
CE(P d$ mdy
11 may (£3/10) May Ihay d i l (3/10-6/10)
NhiSu may (>6/10) Tong stf
Stftradngli^pxayra sifdng mu6i
2S2 135 60 497
Tyi?(%)
57 27 16 100 Bing 7: tf Id (%) khi ning xuit hidn sddng muii theo cdc
ngUdng lUQng miy ting quan liic 1 gid vi 7 gid
3.5. Xdy dt/ng cdc kich bin xud't hi$n suang muii theo cdc yeu tokht tugng
Tren cd sd phdn tfch b tren, nhiet dp khdng khi Id mdt trong nhUng ydu td quan trong d^u tidn quydt djnh den khd ndng hinh thanh sUdng mudi, 6 mdi ngudng nhiet do khac nhau, khd ndng hinh thanh sUdng mudi khac nhau, Khi nhiet dp khdng khf nhd hon 7°C thi nhiet dp d Idp sat mat da't hoac be mdt vdt t h i (cdy cd) cd the dgt dilm sUdng, hdi nudc ngung kd't Igi thanh hat bdng, trong didu kidn dp am, gid thfch hdp thi sUdng mud'i dUdc hinh thanh.
To hop tdt ck cac yd'u td', trong dd ye'u td quyet djnh va quan trong da dUdc xem xdt trong qua trinh td hdp, Ke't qua kich bSn x6 hdp ve kha nang xuat hien sUdng mudi vung Tay Bac dUdc t h i hien trdn bang 8,
NGHieNCQU-TRnOOOl
- Khi gid miia ddng bic hoac KKL anh hudng den nudc ta thi sau 2-4 ngdy sUdng mudi xua't hien b Tay Bic. Dieu kien d l sUOng mudi hinh thanh la nhiet dd tdi tha'p < 5°C, dp am khdng khi trung binh dao ddng td 75% dd'n 95%, tdc dd gid nhd hdn 2 m/s.
- Cang len cao mdc dd ^nh hudng cija sUdng mudi cdng Idn. 6 dd cao dudi 600 m cd nhidu khu vuc khdng bj dnh hudng cua sUdng mud'i hodc ndu cd knh hudng cung chf b cdp dd nhg, 6 dd cao tren 800 m mUc dp dnh hudng cCia suong mud'i 6 c^p dd nang den rat ndng.
Kd't qu^ nghidn cdu nay gdp phdn giup cac nhd qudn ly, ngudi sdn xuat nam bit duOc nhSng thdng tin cdn thie't ve sUdng mudi, td dd cd nhdng quy hogch hop ly va cd bien phdp phdng tranh kjp thdi, giam bdt nhflng thidt hgi do hidn tUdng thdi tie't nguy hiim nay gay ra •
Nhieldo khAng khi toi thap (0-7
£G 0-2 2-5 5-7
>7
>7 Dglm khfing khi Injng binh (0-7 gid)
(%)
75-95
<75 hojc TiScdA gi6 iuc 1 gifl (m/s) 52
i.Z Khi n^ng xu j l hien muSi (%) 96 85 59 IB 2
Kha nSng sual hien si/dng mu6i
Kni nJng xu3l hi^r rSt cao K^anSngxiicIt hign cao K\\k n^rg x j j l hi$n tmng binh Khi nSng x j i l hi$n Ihilp Khcl nSng x j i l hi$n r£t IhSp Khong c6 khi nang x^y ra suong
Tai lieu tham khao
1. Nguyin Duy Chinh, Xay di/ng ccJ s6 dd lieu va danh gi^ tai nguySn khi h S j phyc vy phdt tri^n kinh te - xa hoi tinh Dign Bi6n, Bao cao t6ng ke't de tdi nghifin ciJu clip b$, Vi§n khoa hoc Khf tuqing Thuy van va Moi trircing, 2009.
2. Lai Van Chuyen, Vi/tJng HSi, Nguyen Trong Hifiu, Dieu tra khoanh vung sUdng muoi g i y h^i cdy ca phfi tinh Son La, Bao cao tong k€t d l tai nghien ci^u clip tinh, 1999
3. http //www.thoitietnguyhiem net
4. Nguyfin V3n Liem, DiSu tra khSo sdt va danh gia dieu kien khi h | u nSng nghifip phyc vy khu ISi dinh cU cOa DJ an Thuy difin Sdn La t^i hai VLing Si Pa Phin vS MUflng Nhe, tinh Dt#n Bifin, Bao cao tong ket diJ &n. Vien Khoa hpc Khi tyijng Thuy vSn vd M6i tryflng, 2006,
5. l<i van N l u vd nnk, Dgc di^m khi hSu tinh Lai Chdu (cu), Dai Khi lU(Jng Thuy vdn Lai Chdu, 1991,
6. Phan v a n Tdn. PhUOng phdp thfing ke trong khi hdu. Nha xuat bdn Dai hpc Quoc gia Hd N^i, 2005.
Bing 8: kich bin xuit hidn sUdng muii 6 khu vdc Tiy Bic
Ket luan
- SUdng mudi xudt hidn trong cac thang mua ddng [tis thang 11 dd'n thang 3 nam sau), tdp trung nhieu nhdt d cac thang 12,1, SUdng mud'i cdxu thd tdng ddn theo dp cao, cang len cao tan sua't vd sd ngay xuat hidn SUdng mud'i cang nhidu.
So'thang 5.2012 j ^ Q ^ j j Q C