Calculating wind direction from CARRA u, v grids

Datasets and Usage
1

Hi everyone,

I’m trying to calculate wind direction from u and v wind components following the instructions in section 5.3 here:

https://confluence.ecmwf.int/display/CKB/Copernicus+Arctic+Regional+Reanalysis+(CARRA)%3A+Data+User+Guide#CopernicusArcticRegionalReanalysis(CARRA):DataUserGuide-Variablesat10-metreheight

I can follow the steps and run the python code to get the grid of alpha values, but I’m not sure how to interpret equation (4). Is the variable U (capital u) the wind speed from equation 3? And I’m confused as to the meaning of V (capital v) ?

Many thanks for your help! And apologies if I’m missing something obvious,

Best wishes,

Talfan

2

I see the equation has been updated and makes more sense now, many thanks for looking into it!

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3

Dear Talfan,

Indeed, we had a discussion on this issue behind the scenes and we realised that the original details were not correct (in the original equation it should have been U instead of V and the link to the code for computing alpha was not correct neither).

For any case as you have spotted yesterday, we updated the Data User Guide, see at Copernicus Arctic Regional Reanalysis (CARRA): Data User Guide - Copernicus Knowledge Base - ECMWF Confluence Wiki.

We hope this is indeed clearer and precise.

Thank you very much for spotting this issue.

Best regards

Andras Horanyi

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