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Assimilation of Accumulated Precipitation Data

 

Reference: Precipitation Data Assimilation in the WRFDA Users' Guide

  • Read the paper: Ban et al., 2017
  • Source code

    Get the pre-compiled code, if you have not done so.

    WRFDA/var/build/da_wrfvar.exe is the executable that will be used in this practice session.

    Working directory

    We recommend you create a new working directory for this exercise:

    mkdir /home/ec2-user/workdir/rainfall
    cd /home/ec2-user/workdir/rainfall

    Input data

    The test data for this rainfall tutorial case can be found in /home/ec2-user/test_data/Rainfall

    This test case is the same domain as the 3dvar test case (continental US, February 5, 2008), but at a lower resolution due to the constraints of the classroom computers

    ln -fs /home/ec2-user/test_data/Rainfall/ob/ob.rain.2008020518.06h ob07.rain
    ln -fs /home/ec2-user/test_data/Rainfall/rc/wrfinput_d01 ./fg
    ln -fs /home/ec2-user/test_data/Rainfall/rc/wrfinput_d01 .
    ln -fs /home/ec2-user/test_data/Rainfall/rc/wrfbdy_d01 .
    ln -fs /home/ec2-user/test_data/Rainfall/be/be.dat .

    These are the observation, first guess, boundary, and background error files, respectively. It is necessary to link a few more files for a 4D-VAR precipitation run

    Domain of this test case

    ln -fs /home/ec2-user/compiled_code/WRFDA-v4.1.2/run/RRTM_DATA_DBL ./RRTM_DATA
    ln -fs /home/ec2-user/compiled_code/WRFDA-v4.1.2/run/*.TBL .

    Edit namelists

    A very basic namelist.input file for running this tutorial case is available at /home/ec2-user/test_data/Rainfall/namelist.input.

    cp /home/ec2-user/test_data/Rainfall/namelist.input .
    vi namelist.input

    Pay special attention to the following namelist variables, making sure they are set to these values:

    &wrfvar1
    var4d=true,
    Remember: precipitation DA only works with 4DVAR.
    var4d_lbc=false,
    var4d_bin=3600,
    var4d_bin_rain=21600,
    ...
    /
    ...
    &wrfvar4
    use_rainobs=true,
    thin_rainobs=true,
    thin_mesh_conv=20.,
    /

    Run 4D-VAR with Accumulated Rainfall Observations

    mpirun -np 6 /home/ec2-user/compiled_code/WRFDA-v4.1.2/var/build/da_wrfvar.exe

    Note! In the provided namelist, we have set a small limit 5 for ntmax (maximum number of iterations of the cost function minimization) like we did for some other exercises. Therefore, on the AWS node this case will take ~3 minutes.


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