Dear Prakash,
I developed the early prototype that was incorporated into the
WeatherMan software, but have not used this feature within the current
WeatherMan version. The most common problems seem to result from (a)
using the wrong unit (mm per day or mm per month?) for the rainfall
targets (I'm not sure which the current WeatherMan implementation uses,
so check the documentation.), (b) rainfall targets that are either too
far from the long-term mean for the month or too close to zero, or (c)
format problems such as a missing column or tabs instead of spaces
separating columns. I don't know how robust this version is in the face
of missing values for any of the monthly parameters. My initial
prototype wasn't.
After developing the prototype for WeatherMan, I made some
modifications, and published the methodology:
* Hansen, J.W. and Ines, A.V.M., 2005. Stochastic disaggregation of
monthly rainfall data for crop simulation studies. Agric. For.
Meteorol. 131:233 246.
... and a couple of applications:
* Mishra, A., Hansen, J.W., Dingkuhn, M., Baron, C., Traoré, S.B.,
Ndiaye, O., Ward, M.N., Sorghum yield prediction from seasonal
rainfall forecasts in Burkina Faso. Agricultural and Forest
Meteorology.
* Hansen, J.W., Indeje, M., 2004. Linking dynamic seasonal climate
forecasts with crop simulation for maize yield prediction in
semi-arid Kenya. Agricultural and Forest Meteorology 125:143-157.
* (plus another currently in review)
I found it easier to refine and test the methodology in command-line
version of the tools. It still uses the same parameter file format and
estimation procedure as WeatherMan. My current version does not deal
with standard deviations for monthly targets, but does add rainfall
relative frequency and mean intensity targets as additional inputs to
the .MTH file. I haven't had time to make them user-friendly, but may
attempt to do so if there is sufficient interest. I recently made a few
minor modifications that should handle some of the more common
difficulties, including writing a file that lists any warning messages.
The tools are still rather picky about input file formats, so I suggest
you start with the sample files. The target file (*.MTH) must have all
of the required variables in the specified order. It does accept
missing targets ("-99"), in which case it generates in an unconstrained
mode. Tabs should not be used. Note that the unit of rainfall in the
monthly target file is mm/day, not mm/month. If monthly rainfall
targets are too far from the climatological distribution, the iterative
sample-reject method will never accept a realization for that given
month, and the software will hang, although I recently implemented a
partial fix.
You can download the stochastic disaggregation tool, a command-line
version of the same parameter estimation procedure (not needed if you
WeatherMan), instructions and sample files at:
http://iri.columbia.edu/~jhansen/Tools/StochasticDisaggregationTool/New/
Please let me know whether this is useful.
Regards,
Jim
Prakash Dixit wrote:
> Hi all,
> I am trying to use DSSAT Weatherman to generate daily data. I have created the Monthly Target File *.MTH in following format. When I try to open station which I created with .PRM I can't generate daily weather data from the monthly paramters I have in file *.MTH. How should I proceed? The manual is not very clear. It just tells that weather data can be generated from Monthly Target File. I would be thankful if someone can let me know step by step procedure.
>
> Thanks
> Prakash Dixit
>
> @ StYr StMn SpYr SpMn
> 1986 1 2002 4
> @ yr mo srmn srsd txmn txsd tnmn tnsd ramn rasd
> 1986 1 25.7 2.38 25.6 1.18 13.8 0.76 58.9 7.49
> 1986 2 28.0 4.34 28.8 2.68 12.7 1.04 0.0 3.76
>
>
>
>
--
James W. Hansen, Ph.D.
Research Scientist - Agricultural Systems
The International Research Institute for Climate and Society
The Earth Institute
Columbia University, Lamont Campus
61 Route 9W, Monell Building
Palisades, NY 10964-8000
USA
voice: +1-845-680-4410
fax: +1-845-680-4864
e-mail: [log in to unmask]
WWW: http://iri.columbia.edu/cgi-bin/staff?jhansen
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