Dear Anamika,

Netscape 6 is preventing me from opening your more recent message.
Detail about the problem from that message would have been useful to
DSSAT LISTSERV recipiants.

In the data set that you sent me, there seems to have been only one
March rainfall observation through the period of record.  I did not
implement the gamma distribution parameter estimation algorithm, and do
not understand it completely.  However, you can see the potential (and
so far quite rare) problem of fitting a 2-parameter rainfall
distribution to one observation. The resulting negative alpha parameter
value was incorrect.  I added a simple fix that sets alpha = 0.988
(i.e., just below the upper limit of one).  WM will calculate beta based
on alpha and the mean wet-day amount (i.e., alpha * beta = rwet), giving
you a distribution with the correct mean but an arbitrary shape and
variance. Since many DSSAT LISTSERV users may not be able to handle
large attachments, I will send the modified version (both the DSSAT and
Y2K-compliant versions) directly to you.


anamika arora wrote:

> Does anyone know that while generating ".cli" files from observed weather
> why the value of alpha comes out to be zero for some months,
> even when the data format is correct.
> _________________________________________________________________________
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--
Dr. James W. Hansen
Associate Research Scientist - Agricultural Systems
International Research Institute for Climate Prediction
P.O. Box 1000
Palisades, NY 10964-8000
USA

845-680-4410 (voice)
845-680-4864 (fax)