Dear Rolf,
if you relate the calculated radiation to the absolute daylength (86400
seconds) instead to the daylight length which is calculated in colunm I
in the Excel version and convert it then into MJ/m2/d you get a
reasonable result with a maximum of slightly over 30 MJ/m2/d for the
example data.
Greetings from Tanzania
Jans
Am 7/7/2010 8:37 AM, schrieb Sommer, Rolf (ICARDA):
> Dear Zoltan,
>
> thanks a lot for solving this mystery!
> You are absolutely right, the figures are for daytime only!
> Day length is also provided in the MS-Excel version.
>
> So, just for the records:
> Converting MT-Clim generated Downward Shortwave Radiation (W m-2;
> acronym in the table: Srad) into average (shortwave) solar radiation
> data (Rs; MJ m-2 d-1) the following equation applies:
>
> Rs = Srad * daylength / 1,000,000
>
>
> Thanks to Mr. Jolly for programming MT-Clim for Excel and sharing it
> with the community!
>
> Best regards,
> Rolf
>
>
>
>> -----Original Message-----
>> From: DSSAT - Crop Models and Applications
>>
> [mailto:[log in to unmask]]
>
>> On Behalf Of Zoltan BARCZA
>> Sent: Tuesday, July 06, 2010 20:23
>> To: [log in to unmask]
>> Subject: Re: solar radiation prediction with MT-CLIM
>>
>> Dear Rolf,
>>
>> MT-Clim provides daytime (i.e. from sunrise to sunset) average solar
>> radiation. Daylength (in seconds) is also provided by MTClim (at least
>> by the MS-DOS version, I am not familiar with the Excel version), so
>>
> you
>
>> may use that to estimate daily sums.
>>
>> Comparing with our measurements in Hungary the agreement between
>> measured and observed data was quite good (i.e. bias-free).
>>
>> I hope this helps.
>>
>> Kind regards,
>> Zoltan
>>
>> Sommer, Rolf (ICARDA) wrote:
>>
>>> Dear all,
>>>
>>>
>>>
>>> I am using MT-CLIM for Excel (0.4 beta;
>>>
>>>
> http://www.ntsg.umt.edu/models/bgc/index.php?option=com_weblinks&catid=1
>
>>> 8&Itemid=32) to estimate solar radiation and humidity from daily
>>>
> Tmax,
>
>>> Tmin and precipitation. (This is based on the improved
>>>
> Bristow-Campbell
>
>>> model invented by Thornton and Running in 1999.)
>>>
>>> However, I am getting somewhat confused by the magnitude of the
>>>
> results
>
>>> produced:
>>>
>>> MT-CLIM predicted solar radiation in summer often exceeds 500
>>>
> Watt/m2
>
>>> (daily average ...I assume...), i.e. 40 MJ/m2/day, whereas
>>>
> corresponding
>
>>> observed data never surpass 31 MJ/m2/day.
>>>
>>> Same problem (much too high predicted solar radiation) with the
>>>
> default
>
>>> data set that is included in the Excel version of the model, meaning
>>> that the problem does not lie in my data, but in my apparently
>>>
> limited
>
>>> ability to make sense out of the results.
>>>
>>> Anybody who could solve this mystery?
>>>
>>>
>>>
>>> Best regards,
>>>
>>> Rolf
>>>
>>> ==============================================
>>>
>>> Dr. Rolf Sommer
>>>
>>> Soil Fertility and Agro-Ecosystem Modeling
>>>
>>> International Center for Agricultural Research
>>>
>>> in the Dry Areas (ICARDA)
>>>
>>> www.ICARDA.org
>>>
>>> P.O. Box 5466, Aleppo, Syria
>>>
>>> Tel 00963 21 2691 2545
>>>
>>> P Help save paper - do you really need to print this email?
>>>
>>> ==============================================
>>>
>>>
>>>
>>>
>> --
>> ///////////////////////////////////////////////////////////////
>> dr. Zoltan BARCZA E-mail: [log in to unmask]
>> Department of Meteorology Web: http://bzoli.web.elte.hu
>> Eotvos Lorand University Phone: (+36 1) 372-2500/6603
>> Budapest, 1518 P.O.Box 32 Fax: (+36 1) 372-2904
>> H U N G A R Y
>> \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
>>
--
Jans Bobert
Stavangerstrasse 23
10439 Berlin
Germany
phone: ++49 (0)30 6923768
email: [log in to unmask]
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