NGHIEN CUU - THAU LUAN
Chiet tach tham so khi mong tu anh ve tinh phue vu giam sat qua trinh bien floi Uhi hau
O TSKH. Ll/ONG C H I N H KE, KS. NGUYEN VAN HUNG Trung tam ViSn tham quoc gia
DAT VAN DE
Cac nha khf tupng nhan thay rang, cd bdn bleu hien cua qua trinh bien ddi khf hau tren the gidi va khu vuc la: nhiet do tang; mi/c nwac bien dang; bao gid that thuong; mua 10.
Bdn bleu hien dd phu thupc vao 3 tham sd co ban cua khf hau: Nhiet dp khf quyen; Ap xuat khf quyen; Hoi nude va dp am khf quyen.
Theo phuong phap truyen thdng, nhung tham sd neu tren dupe xac dinh bang cae tram quan trac true tiep trai deu tren lanh thd. Vdi tien bd khoa hpc nhu hien nay, viec ap dung edng nghe tien tien vao ITnh vuc nghien euu bien ddi khi hau khong the khong ndi tdi vien tham ve tinh.
Bdi vi, tu lieu anh vien tham dupe cap nhat thudng xuyen (hang gid, hang ngay, vai ngay tdi trong vdng 1 thang) tren dien rong toan lanh thd, mang tinh khach quan. Tu tu lieu vidn tham, Chung ta cd the chiet taeh cae tham sd Cd ban cua khf hau. Do vay, chung ta cd the ndi: edng nghe vien tham la cdng cu huu hieu, ap dung trong giam sat qua trinh bien ddi khf hau. Dieu dd da duoc khang djnh tU nhieu nam nay tren the gidi. 6 nude ta, vdi cd sd vat chat va tiem nang ve dpi ngu can bp, chung ta hoan toan cd the dua cdng nghe vidn tham vao ap dung, giam sat qua trinh bien ddi khi hau.
MO HINH THAM SO KHl' HAU CHIET TACH TU" ANH VE TINH
De cd san pham sir dung trong ddi sdng tU cdng nghe cao, trude het ddi hoi phai cd san pham tri tue tren mat giay trang. Dd chfnh la co sd khoa hpc dupe ehdng minh ma san pham cua no la cac bleu thuc toan hpc md phdng cho mot hien tupng tu nhien. Dudi day la co sd khoa hpc ve dng dung edng nghe vidn tham de chiet tach mot sd tham sd co ban cua khf hau la tham sd hoi nude, dp am va nhiet dp khf quyen phue vu giam sat bien ddi khf hau
/. Dp am ti/aig doi cua l<hi quyen R {ReM\\e humidity) xac djnh bang bieu thde:
R„ =
(1)
Vdi e = K^QP (2)
^ v = ^ , i - e x p
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(7) / = 1,2,3... (8)
(6)
Cae ky hieu:
,- Kenh phd eija dau thu anh ve tinh tuong dng vdi bude sdng va ;
- He sd phan xa ddi tupng tai dinh khf quyen d cac kenh phd dac thu;
- He sd truyen anh sang qua tang khf quyen chda hoi nude vdi cac tham s d , dac trung eija khu vuc;
- Hoi nude ngung tu thanh phan de tfnh ty s d ;
- Hoi nude trung binh tinh tir vdi cae trpng sd(i = 1, 2, 3 );
- Op am dac thu;
- Ap xuat hdi nude bao hoa cua khf quyen vdi cae tham sd, va la ham sd cua nhiet dp khf quyen;
- Ap xuat hoi nude tuc thdi;
- Ap xuat khong khf;
- Nhiet dp khi quyen chiet tach tu anh ve tinh;
Nhu vay, de tfnh dupe dp am tudng ddi cua khf quyen bang tu lieu anh ve tinh theo bieu thire (1), chung ta can thiet hai dai Iuong co ban:
i s
Tdi nguyen vd Mdi traong I Ky 1 - Thang 1/2010
- He sd phan xa tai dinh khf quyen (8)
- Nhiet dp khf quyen T (3) He sd phan xa tai dinh khf quyen, chung ta hoan toan cd kha nang Xcic djnh dupe, thdng qua ham toan hpc cd lien quan tdi gia trj dp xam quang hpc (DN) cac pixel cua anh vi6n tham, gde phuong vi va gde cao mat trdi; Lay vf du tfnh gia tri tU anh Landsat:
Trong dd : - BLTC xa anh tai dau thu;
P n.L^.d
Eg.cosd (9)
- Khoang each thien van tU mat trdi tdi trai dat;
- Buc xa mat trdi ngoai khf quyen;
- Gde phuang vi mat trOi;
2. Nhiet dp l(hi quyen co the xac dinh tu" cac tram do mat dat, nhi/tig can phai hieu chinh theo dp cao H cua dja hinh (cong thifc 5) ap dung cong nghe viin tham ve tinh, CO the dupe xac djnh mang tfnh khach
quan hon, d tren dien rong. Lay vf du, nhiet dp khf quyen (°C) cua dau thu (sensor) ve tinh Landsat ETM d kenh nhiet duoc xae dinh:
T^ K,
In\^A J
(10)
nhiet;
Vdi , - He sd kiem djnh kenh BUc xa anh tai dau thu;
(Xem tiep trang 56)
Hinh 1: Ban do phan t)6hc^m/cic (trai), nhiet dp (giffa) va dp am l(hf quyen (phai) chiet tach tir tif lieu ve tinh MODIS (11a.m, 12-08-2004)
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Hinh 2: Ban do nhiet viing bien phia nam Viet Nam (trai) (anh MODIS, ngay 22-05-2007, 10h15'); Vung lu khu vi/c song Me Kong (giify) va sau khixCfly anh (phai)
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Tdi nguyen vd Mdi traong | Ky 1 • Thang 1/2010 ^"^
nhieu loai thudc bao ve thuc vat, dae biet la viec sir dung khdng diing chung loai, lieu lupng, thdi gian cd the gay anh hudng den mdi trudng dat, gay hien tUdng nhdn thudc va anh hudng tdi chat Iuong ndng san.
Ket luan
1, Dien Chau la mpt huyen Ddng bang vdi tdng dien tfeh dat la 30.492,36 ha, trong dd dien tfch dat canh tac la 14,636,12 ha, Toan huyen CO 38 kieu sir dung dat trdng eay hang nam chinh, dupe phan bd tren 3 vung sinh thai ciia huyen (viing dat cat ven bien, viing dat ddng bang va vung dat ddi niii),
2, Ket qua nghien eUu ve hieu qua sir dung dat canh tac cho thay:
- Nhin chung hieu qua kinh te sir dung dat canh tac eiia huyen tuong ddi Idn va khdng cd su chenh lech giua cae viing dat. Binh quan GTSX/ha va GTGT/ha trong toan huyen Ian lupt la 59,34 va 34,48 trieu ddng; binh quan GTGT/LD la 62,25 nghin ddng,
- Trong mdi viing dat, su chenh lech ve hieu qua sir dung dat eanh tac
tuong ddi khac nhau giUa cae chan dat va cac kieu sir dung dat, Cae kieu sir dung dat truyen thdng liia- mau cho hieu qua kinh te thap hon han so vdi cae kieu sir dung dat cd eay rau (ea chua, bf xanh, khoai tay,,.). Vi vay de nang cao hieu qua sir dung dat canh tac ddng thdi dam bao dupe van de an toan Iuong thuc cho viing huyen can cd giai phap tham canh tang vu, dac biet la eay rau vu ddng va vu xuan.
- TI le bdn phan N:P205:K20 binh quan cho cae eay trdng la tuong ddi hop ly. Tuy nhien can dieu chi'nh ti le bdn dam cho lua va tang ti le bdn phan huu co va phan lan cho mpt sd eay rau (bfxanh, khoai tay, su hao ...).
- Chua thay dau hieu eiia viec bdn nhieu thudc bao ve thuc vat. Tuy nhien can kiem seat chat che ehiing loai thudc, lieu lupng va thdi gian diing thudc de tranh hien tupng nhdn thudc, d nhiem mdi trudng dat, nude va anh hudng tdi chat Iuong ndng san.
- Cac giai phap ehu yeu de nang cao hieu qua sd dung dat eanh tac ciia huyen la phat trien thj trudng tieu thu ndng san, tang cudng dau tu
ngudn luc va khoa hpc cdng nghe;
thuc hien tdt va hoan thien he thdng chinh sach lien quan den ndng nghiep, ndng thdn va ndng dan.
TAI LIEU THAM KHAO 1. Dang Kim Son. 2006. Ndng nghiep ndng thdn Viet nam 20 nam doi mdi va phat then, NXB Chinh trj qude gia. Ha Npi.
2. Phdng tai nguyen va Mdi trudng huyen Didn Chau, So lieu thong ke dat dai nam 2007.
3. Do Thj Tam. 2001. Danh gi^
hieu qua sCr dung dat nong nghiep theo hwdng san xuat hang hoa huyen Van Giang - tinh Hang Yen, Luan van thac sT ndng nghiep, Dai hpc ndng nghiep I, Ha Npi.
4. Nguydn Ke Tuan. 2006. Nang cao kha nang canh tranh cue nong san Viet Nam trong qua trinh hoi nhap kinh te, nomy.vn/home.htm.
5. Nguydn Tif, Phf Van Ky. 2006.
Thanh tifu nong nghiep Viet Nam sau 20 nam doi mai, Tap chf NN & PTNT, sd 1/2006. •
CHIET TACH T H A M SO KHI T U O N G . (Tiep theo trang 51)
De minh hpa cho tiem nang to Idn cua cdng nghe vidn tham trong giam sat qua trinh bien ddi khf hau thdng qua viec chiet taeh eac thdng sd CO ban eiia khi hau la nhiet dp va dp am khi quyen, hinh 1 dudi day gidi thieu ban dd phan bd hai nwac, nhiet do va do am khf cfuyen eiia viing Penifnular, Malaysia ti; anh MODIS, do cac nha khoa hpc Trung Qude va Malaysia thuc hien.
Vi dudi day (hinh 2), gidi thieu ket qua xir ly anh ve tinh - lap ban dd
nhiet cho khu vuc bien phfa Nam Viet Nam (do Trung tam Viin tham Qude gia thuc hien) va bieu hien eiia bien ddi khf hau la lu lut cho khu vuc sdng Me Kong ,
KET LUAN VA KIEN NGHj Vdi CO sd vat chat va edng nghe vien tham eua Viet Nam hien nay, eiing vdi dpi ngu can bp, chiing ta cd kha nang lam chu cdng nghe viin tham dua vao ung dung trong ITnh vuc giam sat qua trinh bien ddi khf hau d
Viet Nam, Trung tam Vien tham Quoc gia vdi tinh than hop tac sau rong, sin sang tham gia dam nhan xCr ly anh ve tinh de chiet taeh mpt sd cac thdng sd can thiet nhu da neu d tren, phue vu cho "ChuWg trinh quoc gia uTigpho vdi bien doi khf hau"
San pham thu dupe qua chiet tach tu tu lieu anh ve tinh la: Ban dd phan bd hai nude khf quyen; Ban dd phan bd nhiet do khf quyen; Ban do phan bd do am tuang doi cua khi quyen, Nhurng san pham nay se la cd sd cho qua trinh giam sat bien ddi khi hau.B
5 5 Tdi nguyen vd Mdi trudng | Ky 1 - Thang 1/2010