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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