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cover exceeding 0 cm divided by the number of days in 
any month 
G10 = -0.277 + 0.014 - Ta + 1.146 - Go ...(Seino and Uchijima, 1988) (5). 
The monthly average daily amount of diffuse radiation 
Sth was computed using the following equation; 
[SaH] = [SH] - [SbH]  ..... (6). 
We calculated both of these diurnal variations in the 
hourly amount of direct solar and diffuse radiation by 
applying Seino and Uchijima models in the following: 
SbH()=[SbH A0 + A1cos t + A2cos2 t } 
...(Seino and Uchijima, 1988) (7) 
SaH(t)=[SaH]{Bo + Bicos t + B2cos?t } 
ae (Seino and Uchijima, 1988) (7) 
where [StH], [SdH]: monthly average daily amount of direct solar and 
diffuse radiation, respectively, 
and t is deviation of the hour angle from that at 
southing. A and B are constants. 
The simultaneous downward  short-wave radiation 
coincident with NOAA daytime observation at each 
monitoring station was retrieved from the value 
indicated from restored energy variation curves. Then, 
the short-wave radiation at each station was interpolated 
to bring into registration with NOAA imagery(Fig. 9). 
As for interpolation, the values on the four sides of a 
square map obligatorily have values such as minimum, 
average or zero. In this study, we assigned the values 
from the nearest monitoring points to any points on the 
sides. This procedure was applied to parameters such as 
the diffusion coefficient to conform with NOAA pixel 
data. 
4.1.2 Parameters related to upward short- 
wave radiation: Albedo correction: Surface 
relative wetness is estimated from the absolute albedo 
derived from the correction of the percentage albedo 
multiplied by the sine of sun elevation, longitude and 
latitude parameters to first approximation. However, 
other components of heat balance analysis require the 
percentage albedo derived from the NOAA visible 
channel. 
Normalization of albedo and surface relative 
wetness: The relative wetness of the soil surface is an 
indispensable parameter for the thermal inertia model. 
Wetness estimation models for both loamy and sandy 
soils were developed upon relationships between soil 
wetness within 1 cm depth and the absolute albedo of 
the soil surface derived from experimental data for 
upland fields on the terraces and the Kujukuri coastal 
plain, Central Japan (Fig.10). The relative wetness of 
the soil surface was calculated using the normalized 
absolute albedo w' in each NOAA pixel in the 
following: 
w=1-_0-omin_ _ (Utsunomiya, 1988,92) (8) 
omax - oanin 
where wu ': relative wetness of soil surface, & ' : absolute 
albedo in each pixel of NOAA imagery, max, 
omin: maximum and minimum absolute albedo 
derived from observed data. 
  
Fig. 9 Distribution of shortwave radiation in 
and around Hokkaido Island, Japan (Oct. 
17,1990). 
  
  
  
  
: te get pb T A: 
  
Fig. 10 Model for estimation of soil surface 
wetness (wetness of loamy soil from 
absolute albedo). 
  
Fig. 11 Distribution of soil surface wetness 
(assuming that a model was applied 
to all pixels of NOAA imagery, 
Oct. 17,1990). 
Figure 11 shows soil surface wetness in the Hokkaido 
Island, Japan. We assumed that a model was applied to 
all pixels of NOAA imagery. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996