Dear Hong,
Well, you should have mentioned that you "only" want to use the science
behind DSSAT but not DSSAT itself. (Are you a wheel-re-inventor? :-))
As you know, DSSAT's temperature module (as that of several other crop
models) is based on an equation that describes soil T as a sinoid/cosinoid
fluctuation around an annual mean, damped with depth and driven/influenced
by the soil surface temperature. This has been described for instances by
Carslaw and Jaeger already in 1959 and later-on by several other authors.
I have to say that I don't like this kind of approach very much. It is
probably 100% empirical and the very details of the widely ramified
equations are quite complicated to understand.
No wonder, the logical evolution in crop models seems to be to abandon the
old module and move to an energy balance approach.
Best regards,
Rolf
___________________________________________________________
-----Original Message-----
From: Hong Wang [mailto:[log in to unmask]]
Sent: Thursday, March 25, 2004 09:15
To: [log in to unmask]
Subject: Re: Soil temperature and moisture corrections
Dear Rolf,
Thank you. This is the first response I ever got from this group
including another question I asked a while ago.
Maybe I should not ask here as the model I am dealing with is not in
DSSAT.
Anyway, this model is writtten by c++ and I have to change the sourse
codes. I assume that the model's simulation on the relationships between
different layers in soil temperature and moisture is sound, so I can
adjust temperatures and moisture at other depths using the
relationships. For example, our measurement on temperature at depth 2
was 20C. The simulations were 19C at depth 1, 17C at depth 2, and 16C
at depth 3. So they can be replaced by 22C at depth 1, 20C at depth 2
and 19C at depth 3.
I am not sure if my approach is ok.
Thank you again.
Hong
>>> [log in to unmask] 03/25/04 08:29am >>>
Dear Hong,
Your approach to replace simulation results by measured soil
temperatures
sounds interesting. But, how do you do this?
If I understood you correctly, in a second step you want to use the
measured
soil temperature to model temperature at depths below (and above?) the
measurement point? And you want to use the DSSAT's regular procedure?
Again, all quite interesting, and I and probably others here would like
to
know how you do that - seems to be impossible without major changes in
the
code of the soil temperature module.
Best regards,
Rolf
___________________________________________________________
Rolf Sommer
CIMMYT (International Maize and Wheat Improvement Center)
Apdo. Postal 6-641, 06600 Mexico, D.F., Mexico
Tel. +52 (55) 5804 2004 Ext. 2128
Fax +52 (55) 5804 7558/59
www.cimmyt.org
___________________________________________________________
-----Original Message-----
From: Hong Wang [mailto:[log in to unmask]]
Sent: Thursday, March 18, 2004 08:42
To: [log in to unmask]
Subject: Soil temperature and moisture corrections
Dear colleagues,
I am testing a greenhouse gas emission model. Because this model
simulates soil temperature and moisture unsatisfactorily and we
actually
have those measurements at one depth, I am trying to replace simulated
numbers by measurements and then to see if we can improve the
simulation
of greenhouse gases.
My question is how we can correct soil temperature and moisture at
other depths? I assume that the model's simulation on the
relationships
between different layers in soil temperature and moisture is sound, so
I
can adjust temperatures and moisture at other depths using the
relationships. I am wondering if there is a better approach?
Thank you.
Hong
Hong Wang Ph.D.
Research Scientist
Semiarid Prairie Agricultural Research Centre
Agriculture & Agri-Food Canada
P.O. Box 1030
Swift Current, Saskatchewan
Canada S9H 3X2
Tel: (306)778-7288
Fax: (306)773-9123
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