Solar radiation flux at 5 minute interval using GRASS GIS r.sun

Question

I have been trying to estimate instantaneous total solar irradiance(w/m2) at five minute interval for a day (eg. 21 sept). I can do this in SAGA GIS by using "moment, mode 1" and running the solar module for 12*24 time.

Therefore, for automation purpose I want to stick to GRASS. I have looked into r.sun and r.sun.hourly however I am unable to use these function to produce output at 5 minute interval.

Here is the sample code from r.sun.hourly

r.sun.hourly -t elevation=example_data@PERMANENT start_time=6 end_time=18 
             time_step=.08 day=277 year=2011 beam_rad_basename=beam
             diff_rad_basename=dif glob_rad_basename=tot nprocs=6

Answer 1

GRASS GIS addin r.sun.hourly can be used to calculate instantaneous solar radiation flux(w/m2) at an specified interval. By default it is set to run at an hourly instance however by changing the 'time_step' parameter can change the time instant for the run. For eg if you want the total irradiance every two minutes, this is how the parameters would look like.

r.sun.hourly -t elevation=dem@filtered linke_value=2 start_time=6 end_time=18 
             time_step=.01 day=265 year=2008 glob_rad_basename=tot nprocs=6

You might also want to check creating time-space object in the parameters as it will help other operations much easier.