Clarification on integral_wrt_time_of_surface_direct_downwelling_shortwave_flux_in_air_1hour_Accumulation.nc

[chiaral]

Hello! I need some clarifications on the variable:

integral_wrt_time_of_surface_direct_downwelling_shortwave_flux_in_air_1hour_Accumulation.nc

The name suggests that is "direct" only. However when I look at the metadata I have as name variable ssrd

ssrd corresponds to this variable which explicitly states: This parameter comprises both direct and diffuse solar radiation.

Moreover, the units of this variable, based on the metadata, are J/m2 ; I don't think I have found within ERA5 documentation a variable that is representative of direct radiation that comes in J/m2, all those that mention direct are in W/m2.

Can anyone clarify this? perhaps it was a simple naming error, and indeed this quantity is ssrd which includes both direct and diffuse radiation.

Thanks!

[aluhamaa]

Hi @chiaral

I cannot check the direct vs direct + diffuse at the moment, however, the J/m2 should just reflect the fact that it is integral/accumulated variable and not flux.

Regards Andres

[chiaral]

Hi Andres!

Thanks so much for your quick reply, and of course for putting these data in AWS!

Yes, indeed, J/m2 vs W/m2 could be just a matter of units. So I guess if you could check which was the original variable corresponding to this specific quantities on the cloud would be great.

I am happy to open a PR to fix the documentation after. Have a great day!

[etoodu]

Hi @chiaral,

I am so sorry for the wait. I checked and this variable seems to correspond to Surface solar radiation downwards variable, which in short is ssrd and units are J m-2.

[chiaral]

Thanks so much! I really appreciate your help on this. I had done a quick comparison between these data and the ssrd, in fact, and things seemed to line up pretty well. Thanks for double checking and confirming the source! Best,