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WRF with MERRA2

WRF required fields: http://www2.mmm.ucar.edu/wrf/OnLineTutorial/Basics/UNGRIB/ungrib_req_fields.htm

  • 3D, pressure levels: Temperature=T, Winds=U, V, Relative Humidity=RH, Geopotential Height=PHIS
  • 2D: Surface Pressure=PS, Sea Level Pressure=SLP, Skin Temperature=TS, 2-meter Temperature=T2M, 2-meter specific humidity=QV2M, 10-meter U,V=U10M,V10M
  • Constant: LANDSEA mask=FRLAND, Soil Height, PHIS
  • Optional: Soil Temperature and Soil Moisture, needed for Noah LSM. Water equivalent snow depth=PRECSNOLAND.

Area I download for GFS forecasts: leftlon=-55, rightlon=20, toplat=70, bottomlat=30

MERRA2 Data info from File Specification by Bosilovich et al. here: https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/docs/

  • inst3_3d_asm_Np (M2I3NPASM): Assimilated Meteorological Fields
    • RH : relative humidity after moist, 1
    • T : air temperature, K
    • U : eastward wind, m/s
    • V : northward wind m/s
    • PHIS : surface geopotential height,  m2/s2
  • inst1_2d_asm_Nx (M2I1NXASM): Single-Level Diagnostics
    • PS : surface pressure, Pa
    • SLP : sea level pressure, Pa
    • TS : surface skin temperature, K
    • T2M : 2-meter air temperature, K
    • QV2M : 2-meter specific humidity, kg/kg
    • U10M : 10-meter eastward wind, m/s
    • V10M : 10-meter northward wind, m/s
  • const_2d_asm_Nx (M2C0NXASM): Constant Model Parameters
    • FRLAND : fraction of land, 1
    • PHIS : surface geopotential height, m2/s2

To download data, start here: https://disc.gsfc.nasa.gov/uui/datasets?keywords=”MERRA-2″

Then type in the dataset name in the search box. Select the dataset. Click on Subset > Subsetter. Enter lat/lon values. Download list of files. Issue wget command:

wget --load-cookies ~/.urs_cookies --save-cookies ~/.urs_cookies --auth-no-challenge=on --keep-session-cookies --content-disposition -i myfile.dat

The constants files are different, download those directly from the online archive. Downloading requires earthdata login.