Surface windspeed in tavg1_2d_flx_Nx (M2T1NXFLX): Surface Flux Diagnostics

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Surface windspeed in tavg1_2d_flx_Nx (M2T1NXFLX): Surface Flux Diagnostics

by EarthdataForumContributor » Fri May 22, 2020 3:39 pm America/New_York

Hello,

In this dataset there exists a surface windspeed measurement. What is the height that you would consider to be the surface: 2m or 10m ?

Intuitively, I took it as being 2m. However, it is inconsistent with another data source I am using that has winds at 2 m.

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Re: Surface windspeed in tavg1_2d_flx_Nx (M2T1NXFLX): Surface Flux Diagnostics

by GES DISC - jimacker » Fri May 22, 2020 3:45 pm America/New_York

From the GES DISC / GSFC Subject Matter Expert on MERRA-2 data:
"The Variable called SPEED (and its companion SPEEDMAX) are computed from the lowest model level data in the 3D data, and saved as a 2D variable. This is the windspeed needed to compute surface fluxes in the surface layer parameterization. The lowest model level varies in height in time and space, but is generally around 60m above the surface. The variable HLML in the single level collection is that height exactly.

If you need 2m or 10m wind speed, the accurate way is to compute magnitude from the vector components U,V at the 1 hourly interval, then average up to daily or monthly, depending on your needs."

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