There are several weather generators available.
They can be classified in parametric and non-parametric. Theoretically, the non parametric should give better results.
You could try both methods.
I would recommend LARS-WG that ca be freely downloaded from the Rothamstead Exp. Station web page, as well as with a manual.
LARS-WG is one of the most used weather generators and the only non-parametric I know!
You will need a daily series (you already have it). You can obtain realizations for the unknown period by "perturbating" LARS-WG with the changes in the monthly means. It is not hard to do.
Good luck!
Dr. A. Utset
ITACYL
Ctra. Burgos km 119, 47071 Valladolid
ESPAŅA - SPAIN
-----Mensaje original-----
De: DSSAT - Crop Models and Applications [mailto:[log in to unmask]] En nombre de Sommer, Rolf (ICARDA)
Enviado el: jueves, 17 de julio de 2008 9:43
Para: [log in to unmask]
Asunto: Re: disaggregate monthly rainfall data
Hi Arnold,
thanks for your fast reply.
Coincidence - I was just checking if ClimGen could do the job, but couldn't find out how.
Could you give me an advice here?
Regarding precipitation and monthly data - probably a misunderstanding - but I pretty much assume that data are the sum of precipitation in that respective month, and not daily data averaged over a month. (Anyway, one could be converted into the other easily.)
Best regards,
Rolf
________________________________
From: Arnold Salvacion [mailto:[log in to unmask]]
Sent: Thursday, July 17, 2008 10:34
To: Sommer, Rolf (ICARDA)
Subject: Re: disaggregate monthly rainfall data
Hi Rolf,
A weather generator (i.e. SIMMETEO, CLIMGEN, WGEN, etc.) can disaggregated your monthly data into daily values. However, I am not sure if they can handle monthly sums because the usual input to weather generators are monthly averages.
Hope this help.
Best regards,
Arnold
Arnold R. Salvacion
___________________
M.Sc. Environmental Science Student
School of Environmental Science and Management
University of the Philippines, Los Baņos
College 4031, Laguna, PHILIPPINES
Telefax: 049.536.2381
E-mail: [log in to unmask] <mailto:[log in to unmask]>
[log in to unmask]
--- On Thu, 7/17/08, Sommer, Rolf (ICARDA) <[log in to unmask]> wrote:
From: Sommer, Rolf (ICARDA) <[log in to unmask]>
Subject: disaggregate monthly rainfall data
To: [log in to unmask]
Date: Thursday, July 17, 2008, 2:24 PM
Dear all,
I have historic rainfall data (1940-1985) as monthly sums, which I would
like to disaggregate to obtain approximate daily data to use it for crop
modeling. I wonder if anybody of you ever has done this, if there is
standard procedure or (even better) software that could do
that for me.
Of course, I have more recent (approximately 30 years) daily records of
the same region. So I could do all kind of supporting statistical
analyses.
Best regards,
Rolf
==============================================
Dr. Rolf Sommer
Agro-Ecosystem Modeling
International Center for Agricultural Research
in the Dry Areas (ICARDA)
P.O. Box 5466, Aleppo, Syria
Tel 00963 21 2691 590
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