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Solar radiation accumulated over different dates

Added by Theodoros Gkousarov over 10 years ago

Hi all,

Its a complex task i want to do but aint sure if its possible with CDO.

I have a wrf output file containing the number of days taken since 10th june 2012 until a threshold ( varying from 30to 60 days depending on the location). So basically it shows the lenght of the period over each lat and lon location.

Now, i want to calculate the amount of total solar radiation gained during these different periods over different locations.

any ideas?
Thanks


Replies (6)

RE: Solar radiation accumulated over different dates - Added by David Gobbett over 10 years ago

Hi Theodoros,

Have you come across this publication:

Allen RG, Pereira LS, Raes D, Smith M. 1998 Crop evapotranspiration-Guidelines for computing crop water requirements. FAO Irrigation and drainage paper 56.
(Note there are two versions online - one contains 15 pages only, and the other e.g. http://www.kimberly.uidaho.edu/ref-et/fao56.pdf contains 326 pages)

This document contains many useful equations relating to solar radiation. It is complex, but the calculations are broken down into separate sub-equations, so it is doable.

I have also posted a query about solar radiation calculations. Many of those equations require the Latitude of each grid cell as input, and also the julian day (day of year). I am not sure how to use the grid Y value (latitude) in CDO - although it would surprise me if it was not possible. Day of year can be accessed using the CDO muldoy operator.

regards
David

RE: Solar radiation accumulated over different dates - Added by Ralf Mueller over 10 years ago

Coordinates aren't data variables for CDO - so I don't think, it can be done with CDO out if the box. My suggestions are:

RE: Solar radiation accumulated over different dates - Added by Theodoros Gkousarov over 10 years ago

I have 2 files:
SIS5.nc --> daily mean solar radiation in W/m2/day --> June10th July 21st 2002 - 2012
TEMP1.nc WRF daily average temperature in Centigrades--> June10th July 21st 2003 -2012

I Want to :
Calculate the amount of days taken to accumulate the 660 degree days starting from 10th june for each year in each grid point using as input the fileTEMP1.nc and export a file or mask which shows the amount of days. ( varying between 30-55 I guess)

Start accumulating solar radiation from SIS5.nc for as many days in a row as defined by the file created in the previous step.

In the end I want to have a file which shows how much solar radiation was accumulated over the whole domain, based on the days taken to accumulate 660 degree days.

Any help is very valuable.
Theo

RE: Solar radiation accumulated over different dates - Added by David Gobbett over 10 years ago

Hi Ralf,

I thought I had solved this by creating a grid of latitudes using ArcGIS, then exporting to NetCDF. However there are problems with that approach, so I will investigate the suggestions you have made.

Thanks for your assistance.

David

RE: Solar radiation accumulated over different dates - Added by David Gobbett over 10 years ago

Hi Theodoros,

I don't have a deep knowledge of many CDO operators, but will add my suggestion since you're not had other responses here.

I can't think of any CDO operator or combination that will do what you want to do in a single call. My approach to this problem would be to create a loop that incremented over the date range, starting with the 10th Jun, and call CDO functions such as timselsum, consecsum and ifthen operators to incrementally calculate the degree days, to create the mask you need.

I run CDO under Cygwin so I would use a bash script to do this. However if you run cygwin via windows, Python etc they you'll need to use a different approach to create a loop.

This is not a complete solution, but I hope it is of some help.

David

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