Monthly SIS data from CM SAF

Monthly SIS data from CM SAF

от Joao Carreiras -
Количество ответов: 3

Hi everyone,

I just dowloaded the full monthyly CM SAF SIS dataset (1983-2005) in NetCDF format (12 months x 23 years). I want to create mean SIS values per month for the period 1983-2005, and then use it in a project that will produce agro-climatic indicators in a specific region in Africa. I'm trying to use IDL to read the NetCDF files and to calculate the monthly averages for the period 1983-2005. I can read, extract and calculate the monthly averages, but the images appear upside-down and with some kind of mirror effect. Please find below two jpeg from December 1983, the original returned from the IDL code and the other (correct?!) using a rotation of 270º and transpose operation.

Has anyone used IDL to read NetCDF data and observed this issue?

Many thanks and best wishes

João

 

 

В ответ на Joao Carreiras

Re: Monthly SIS data from CM SAF

от Anke Kniffka -

Hi João,

can you plot the data with the lat-lon-information included in the netcdf-file? The image should have the correct orientation afterwards. When ploting just the image in idl, using the rotate(image_data,7) function is correct.

Cheers,

Anke

 

В ответ на Anke Kniffka

Re: Monthly SIS data from CM SAF

от Joao Carreiras -

Hi Anke,

many thanks for your reply. Yes, that's what I did, rotation(image_data, 7). I guess I'm not that smart :) reading the NetCDF in IDL and needed to perform that rotation to get the image right.

The IDL code to read the NetCDF file that I wrote to create a multiband image with SIS data for each month across the 1983-2005 period was something like:

FOR ifn=0, (dimages-1) DO BEGIN

id =NCDF_OPEN('D:\Public\IICT\PNUD\Datasets\Climate\Baseline_SAF_CM\Dec\'+fnames(ifn))

SISid = NCDF_VARID(id, "SIS")

NCDF_VARGET, id, SISid, SISimage

NCDF_CLOSE, id

input(*, *, ifn) = rotate(SISimage, 7)

ENDFOR

 

All is fine now, I guess.

Many thanks again and best wishes

João

В ответ на Joao Carreiras

Re: Monthly SIS data from CM SAF

от Jörg Trentmann -

Dear João,

glad to see that the problem with plotting the data in IDL has been solved.

From the CM SAF Training Team we are supporting the use of the climate data operators (cdo) and R for analysing and visualising the CM SAF data.

In case you are flexible on the software you want to use for data analysis you might want to have a look at the 'Introduction to the Software Tools' Section and check out the CM SAF Toolbox and its Instructions. You will find software scripts based on these free software tools to calculate and display multi-annual monthly averages of the CM SAF data, which you might find helpful for your application.

Kind regards,
Jörg