ISHIKAWA Hirohiko

KOIKE Toshio

MA Yaoming

TSUKAMOTO Osamu

WANG Jiemin

Tsukuba Repository

Remote Sensing Parameterization of Regional
Net Radiation over the Heterogeneous Land
Surface of GAME-Tibet, HEIFE and AECMP'95
(Session 6: Large Scale Energy and Water
Balances studies)
著者 MA Yaoming, WANG Jiemin, ISHIKAWA Hirohiko,
TSUKAMOTO Osamu, KOIKE Toshio
journal or
publication title
Bulletin of the Terrestrial Environment
Research Center, the University of Tsukuba,
Proceedings of the International Workshop on
GAME-AAN/Radiation
volume 1
number 別冊
page range 98-101
year 2001-03
URL http://doi.org/10.15068/00147198
Remote Sensing Parameterization of Regional Net 
Radiation over the Heterogeneous Land Surface of 
GAME-Tibet, HEIFE and AECMP'95 
Yaoming Ma Jiemin Wang 
Cold and Arid Regions Environmental and Engineering Research Institute, The Chinese Academy of Science, 
Lanzhou 730000 China, E-mail: 畑叩@m,(zb, a<;.~
Hirohiko Ishikawa 
Disaster P柁ventionResearch Institute, Kyoto University. Uji, Kyoto 61, Japan 
Osamu Tsukamoto 
Faculty Sciences, Okayama University. Okayama 70, Japan 
Toshio Koike 
Department of Civil Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan 
1. Introduction 
The regional distribution of net radiation plays a very important role in the exchange processes of 
water and heat on the land surface. So the observational study on net radiation is an important 
component in many land surface processes experiments, such as GEWEX Asian Monsoon Experiment 
on Tibetan Plateau (GAMErribet), the HElhe basin Field Experiment (HEIFE) and Arid Envirorunent 
Comprehensive Monitor Plan, 95 (AECMP'95). There have already been some initial studies in some 
stations reported based on these data sets. However, the investigation of the regional distribution of 
surface net radiation is not enough for the heterogeneous landscape of GAME(fibet, HEIFE and 
AECMP'95 areas. The objectives of this study are estimating the regional distribution of surface albedo 
and surface temperature, appraising the regional distribution of net radiation over the areas of 
GAME/Tibet, HEIFE and AECMP'95 using the satellite remote sensing and field observations. 
2. Satellite data and field observational data 
Three NOAA-14 AVHRR scenes (15:43 BT, Jlle 12, 1998; 14:21BT 16 July, 1998 and 14:25h BT, 
August 21, 1998) of the GAMErribet area, one Landsat TM scene of the HEIFE area (11:00BT, July 9 
1991) and one Landsat TM scene of the AECMP'95 area (11:00BT, August 21 1995) were used in this 
study. All of the scenes were with clear day. The most relevant data, collected at the stations of 
GAME/Tibet, HEIFE and AECMP'95 to support the analysis of satellite images, consist of land surface 
albedo, surface temperature, surface radiation budget components, Tether-sonde data, radio-sonde data 
and the vegetation state, etc. 
3. Theory and scheme 
Using remote sensing data (eg. NOAA A VHRR data and Landsat TM data) and field observations 
can derive the surface net radiation flux densities over the heterogeneous landscape. The procedure is as 
NOAA A VHRR data 
Land sat TM data 
Field measurements 
Atmospheric correction s:;1 window techniqf (ro, T sfc・co 
a MODTRAN 
In other words, the regional net radiation can be derived from 
Rn (x,y) = (1-'i。 (x,y))•K↓(x,y) + L↓ (x,y)-e0(x,y)aTsfc4cx,y) , (1) 
Where ro(x,y) is surface albedo, &,。(x,y)is surface emissivity, T,1c(x,y) is surface temperature, K心y)is 
incoming short-wave radiation flux density and L↓ (x,y) is incoming long-wave radiation flux density. The 
surface emissivity of邸(x,y)is a function of the vegetation coverage, itcan be derived from the model of 
Valor and Caselles (1996). The incoming long-wave radiation flux density L↓ (x,y) can be derived from 
radiative transfer models such as MODTRAN directly. The incoming short-wave radiation flux density 
Ki(x,y) in Eq. (I) can be derived from MODTRAN. It means that atmospheric short-wave transmittance 
な，canbe derived from MODTRAN directly. Hence K↓ (x,y) can be obtained as 
ふ(x,y)= i-,wK↓ TOA (X, y), (2) 
Where the regional variation of radiation flux density perpendicular to the top of atmosphere K↓ roA(x,y) is 
a spectrally integrated form of in-band radiation flux density perpendicular to the top of atmosphere 
K TOA(B). And 
k↓ TOA(X,y)= 
K exo(b)cosB,un(x,y) 
d 2 , (3) 
Where r匹 (b)is the mean in-band solar exo-atmospheric irradiance undisturbed by the atmosphere 
如 =0°,d, isthe earth-sun distance, ~un sun zenith angle. 
Surface albedo and surface temperature in Eq.(1) can be derived in different ways depend on the 
different remote sensing data Using the NOAA AVHRR data, the surface albedo can be derived from the 
models of Paltridge and Mithchell(1990) and Valiebte et al (1995). Surface temperature Tsfc(x,y) can be 
derived from split window technique (SWT) (Becker and Li,1990; Becker and Li, 1995;Sobrino et 
al. ,2000). The split window technique gives the surface temperature as a simple linear combination of 
the brightness temperatures T1 and刀measuredin two adjacent thermal infrared channels i andj, namely 
Tifc =Ao +A1T; +A2Ti, (4) 
Where Ao, A1and A2 are local coefficients which depend mainly on spectral emissivities of surface. The 
accuracy of surface temperature T sfc retrieval is dependent on the correct choice of the coefficients Ao, 
A1and A2 (Becker and Li, 1995). Itmeans that the surface temperature derived from NOAA AVHRR can 
be determined as 
T,fc = F(T4,Ts, ら，&5,W,0), (5) 
Where T4 and T5 are the brightness temperatures of channel 4 and 5 of A VHRR, f:4 andぁthe
spectral emissivities of channel 4 and 5 respectively, W water vapor content,Othe view angle of satellite. 
Eq.(5) can be expressed by different algori出ms(Beckerand Li ,1995). Based on many case studies in 
Tibetan Plateau area, the surface temperature over this area can be detem血edas 
T sfc(x, y) = T4 (x, y) + l.56[T4 (x, y)-T5 (x, y)] + 0.28[T4 (x,y) -T5 (x, y)]2 + (48 -5W)(l-&) • (6) 
Using the Landsat 1M data, a four-stream radiative transfer assumption for atmospheric correction in 
solar spectral bands (Verhoef, 1997) is introduced to derived the surface albedo. Surface temperature 
Ts1Jx,y) in Eq.(l) can be derived from Landsat TM thermal infrared band-6 (10.2-12.5μm) spectral 
radiance. Because the 10.2-12.5μm 1M band is relatively transparent to radiation transfer in atmospheric 
layer under the cloud-free sky, the absorption in this band is smaller except under the turbid weather 
condition, the main substance of continuous absorption are water vapor and aerosol. The upward them叫
radiance at wavelength入passingthrough the local atmosphere layer is described by 
z~=L,. -B,. , do 
(7) 
Where 8 isatmosphere optical thickness, x=cosR, 0 is the angle between normal of the horizon and 
radiative stream, and B,. is black emitted radiance as given by Planck function 
B, (T) C [ c, , (8) 
訟 exp(号）ー 1]
Where Tis temperature, c1 and~are constants. There are following boundary condition for radiative 
transfer ｛ら(0:。,x)-B,(T*) 
LA,(O,z)=O 
8=~。
8=0 
Then the upward radiance can be derived after integrating equation (6) as 
(9) 
L;. (8,z) = L;.(T,1c)e予＋［叫T(8')]eデ⑱， (10)
Where L;. (I',1,J is upward radiance emitted from land surface, o atmospheric optical thickness at an 
arbitrary altitude, the satellite sensor detected radiance Ls(x,y) for each pixel will be considered as two 
parts: contribution from land surface and from atmosphere layer 
Ls(x,y) = r L。(x,y)+S(x,y), (11) 
WhereL。(x,y)is emitted band radiance from the land surface, S(x,y) band upward radiance at the top of 
atmosphere emitted from the atmospheric layer, andてbandaverage transmittance. S(x,y) and r can be 
derived from the simulation of MODTRAN model . Equation.(} 1) can be rewritten as 

Net Rad,at;on (12 June 1998) (W/m2) Net Radiation (16 July 1998) (W/m2 ) Nat Rad, ● tion (21如gu●t 1998) (W/m 2 l 
炉duo 『80 l r<"64-0 「 ―- ・・640 『一し .f,nduo ＋ Anduo 
600 11 700 I I 1100 
700 -' I 11800 
l紐 --I LJsoo~·,.. -I紐＇ NPAM r ＋ 
>-900 ＿』 ●>-9000 
Fig.2 The distribution maps of net radiation flux densities in the GAMEffibet area. 
10 
ヘ 8f HEIFE 
'i/1. 
. I: さ． 
r゜ 300 400 500 eo 700 800 
Net radiation R, (Wlm') 
ま 250[ GAME/Tlb●I 
~15 
C 
コ゜ ↑ 0 
er 
~5 
u. 
今 I 
500 600 700 800 900 1000 
Net radiation R n (Wlm 2 ） 
eo 
● Anc加 じ lA NPNd 550 -＂ 500 
i -知
20 
??（?）
? ? ? ? ? ?
300 350 400 450 500 550 600 
Net rsdletion R. (Wlm勺
Fig.3 The frequency distributions of 
net radiation flux density in the 
areas of GAME!fibet, HEIFE 
and AECMP'95 
? ? ? ?
? ?
?
? ?
?
?? ?
?
°' 
r GAME/Tibet 
喘如 600 紐 加 800
R 7f' ,__, (IM加） ? ??）?? ?、? ?? ??
? ?
?
? ?
?
??? ?
?
ー
AECMP'95 
?
． ． ?
? ?
?
? ? ? ? ? ?
（ ?
?
? HEIFE 
Fig.4 Validation of the derived results against the field measurements net radiation flux densities in the 
areas of GAME/Tibet, HEIFE and AECMP'95, together with 1:1 line. 
corresponds to the Gobi desert area; For AECMP'95 area, one around Rn =540 Wlm corresponds to 
oasis, another peak Rn =360 w; 屈 correspondsto the Gobi desert. The net radiation in HEIFE area over 
the oasis (wheat) is higher than it in AECMP'95 (com), the reason is that the surface albedo and surface 
temperature in AECMP'95 area is large than it in HEIFE area (3) The distributions of net radiation in 
GAME/Tibet area have different values in different month. (4)The derived net radiation flux densities 
over three cases study area are very closed to the field measurements withMAPD being less than 5%. 
5. Concl~ding remarks 
The regional net radiation flux densities over the areas of GAME/Tibet, HEIFE and AECMP'95 have 
been obtained with the aid of remote sensing and field observation, which are mostly acceptable. Itforms 
a sound basis to study the exchange processes of water and heat on the heterogeneous land surface. 
AcknowledJ印加nt:The authors wish to acknowledge Dr.Shin Miyazaki, Dr. Kenichi Ueno, Dr.Hu 
Zeyong, Dr. lchiro Tamagawa and other scientists in GAME/Tibet group, HEIFE group and AECMP'95 
group for their very kind help in the field work. 
References (Om比'ed)


Remote Sensing Parameterization of Regional Net Radiation over the Heterogeneous Land Surface of GAME-Tibet, HEIFE and AECMP\u2795 (Session 6: Large Scale Energy and Water Balances studies)

Remote Sensing Parameterization of Regional Net Radiation over the Heterogeneous Land Surface of GAME-Tibet, HEIFE and AECMP\u2795 (Session 6: Large Scale Energy and Water Balances studies)

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