Surface Temperatrue Rerieeval from Satellite Data Over South China sea
Sea Surface Temperature Model
Single Channel Method
This model describes a single infrared channel method to retrieve surface temperature from space ( Masor and Embi , 1996). The model follows a relationship as (2).
| Ts=[ |
Tib
------------
Îi ti |
- |
Tab kiW
----------
Îi ti cos q |
- |
2(1-Îi)
------------
Îi |
TabkiW]1/b (2) |
Where T
s sea surface temperature to be calculated ,
T
i brightness of i channel, T
a atmospheric temperature,
K
i absorption coefficient of the atmosphere,
Îi emissivity,
ti transmittance,
q zenith angle,
W total amount of water vapor,
b least squares fitting coefficient.
The unknown variables of the above modeling expression can be determined form radiosonde profiles or from historical data. For this model
10.5-12.5
mm spectral channel data of any satellite can be used to get surface temperature from space.
Split Window Method
This model uses two adjacent channels to retrieve the surface temperature. The model ( sorbrino et al ., 1991) is as follows .
To=T1+A( T1-T22)+B
Where, T
o is surface temperature, T
1 and T
2 are respectively the radiometric temperatures in tow adjacent channel of 11 an 13
mm, A and B are coefficients which depend on the surface emissivities, atmospheric absorption coefficients and total vapour amount as (4) & (5).
A = (a2b1
+b1b2 W)/Q (4)
B=((1-Î1) a1b1 (1-2k1 W)
L1/ Î1Q)-
((1-Î2) a2b1 ( 1-2k2 W)
L2/Î2Q) (5)
Where,
ai =
Îi
ti
cos
q,
bi =
k
i [1+2
ti
(1-
Îi) cos
Î], and
Q =
a1b2-
a2b1. the unknown variables are of same meaning like single channel method and the values are found as the same manner as in single channel method.
Study area and data used
The study area in south china sea from 1030E to 1100E longitude and 10N to 70N latitude approximately. The survey map at scale 1:760,000 including peninsular Malaysia and South China sea has been used for geocoding the images.
NOAA-14 AVHRR data of April 1996 and the corresponding radiosonde data has been used to estimate .
