Doubts regarding GR-SR validation

i am working on this observation which is fulfilling all criteria for validation matching.

this is the result when gr S band is converted to ku band . which is coming good.
but when sr frequency converted to gr (s band ) . all reflectivity data is missing.

combined result

what could be the reason behind the missing reflectivity data?

Hi @Jagdish_jena,

I’ll ask a colleague for help on this one.

Would you be able to provide the GR data for that particular event?


I have a guess, but for that we would need at least the date or orbit number of your overpass. The problem here comes from the brightband detection of the DPR. During the transformation from GR(S) to GR(KU), an average value of the entire GPM swath is used for the brightband altitude. This height can also be calculated from just a few measurements (see your last plot). This height is important for the frequency transformation between GR and SR, because it needs to know whether we are in rain, wet snow or snow. If the transformation from SR(Ku) to SR(S) is now made, the brightband heights of the individual DPR scans (columns) are used. It is now possible that the DPR algorithm has not detected the brightband or that it is very close to the ground/clutter region (e.g. in winter) and cannot be detected. This is why the transformation fails in these cases.


Thanks Veli!

Welcome to openradar discourse, your expertise is much appreciated!


Thank you very much @V.Pejcic @kmuehlbauer. i have attached both gpm and gr file . please check.

Here are a few vertical slices of your case. Here it looks like the detected precipitation is very “flat” (zFactorFinal) but the zero degree level is very high (~5km). Thus, the DPR cannot detect a brightband signature or only with great difficulties, because the vertical reflectivity information is simply not sufficient. We already have an idea how we can handle such cases in the future and will work on it.

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