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openclimatefix / metoffice_ec2

Subset Met Office MOGREPS-UK and UKV on AWS EC2
MIT License
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Find out which irradiance field to use #39

Open tomwhite opened 4 years ago

tomwhite commented 4 years ago

In https://github.com/openclimatefix/predict_pv_yield_nwp we build a baseline model for predicting PV yield from the NWP irradiance field. This uses the GRIB data, where the field is called "Downward short-wave radiation flux" or dswrf.

In #34 we use the irradiance data from the AWS feed in NetCDF/Zarr format. The field names are different (see https://github.com/openclimatefix/metoffice_ec2/issues/2#issuecomment-635930273), but surface_downwelling_shortwave_flux_in_air seems like it might be the corresponding field.

Is this correct? (Tagging @tv3141 for possible insight here.)

(Of course, in the future we will use the data from the AWS feed in NetCDF/Zarr format, so this problem will go away.)

tv3141 commented 4 years ago

Yes surface_downwelling_shortwave_flux_in_air should be the right variable for this purpose.

From http://cfconventions.org/Data/cf-standard-names/71/build/cf-standard-name-table.html:

surface_downwelling_shortwave_flux_in_air alias: surface_downwelling_shortwave_flux The surface called "surface" means the lower boundary of the atmosphere. Downwelling radiation is radiation from above. It does not mean "net downward". The sign convention is that "upwelling" is positive upwards and "downwelling" is positive downwards. The term "shortwave" means shortwave radiation. Surface downwelling shortwave is the sum of direct and diffuse solar radiation incident on the surface, and is sometimes called "global radiation". When thought of as being incident on a surface, a radiative flux is sometimes called "irradiance". In addition, it is identical with the quantity measured by a cosine-collector light-meter and sometimes called "vector irradiance". In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.

tomwhite commented 4 years ago

Thanks @tv3141 that's very helpful!