Dear Dr. Hasegawa:
 
We have tested the soil temperature model in CROPGRO-Soybean, which I
believe is identical to the one
in CERES.  We found that the accuracy of the model decreases with depth.
The current soil temperature model works well in the surface layer if you
accurately estimate TAMP and TAV for each year in the weather file.
The current soil temperature model gives increasingly poor results as you
get deeper in the soil. We have incorporated a more complex soil
temperature model (an energy balance approach along with Fourier's law)
in a proptotype version of the model that gives better results in deeper
layers and slightly better
results in the top 15 cm.  However, we still use TAMP and TAV to estimate
the lower boundary soil
temperature, which is required to solve the one-dimensional heat flow
equation.  The inputs to the model
are the same as in the DSSAT models.  In my opinion the existing soil
temperature model in CERES is
adequate if you are just interested in the top 15 cm soil layer.  However,
you might have to use a
more complex soil temp. model if you want good estimates for deeper layers.
 Hope this helps.
 
Allan A. Andales
 
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Allan A. Andales                Office Phone: (515) 294-7350
Graduate Research Assistant     e-mail: [log in to unmask]
124 Davidson Hall (ABE)