QUESTION: initial sounding files of WRF AWR v.4.0 test cases

I want to know whether there is a test case which uses an input sounding file based on GATE phase 3 observation.

I'm new to WRF model. I’m planning a radiation-convection equilibrium experiment with initial mean vertical profile of GATE observation, if a preset is available. I searched around user documents and READMEs of preset test cases, but some test cases do not seem to contain descriptions regarding how each sounding profile is produced.

There is no test case using a GATE sounding. Single sounding initializations are used in a number of test cases where they are read from an editable ascii file, including the 2D squall-line test cases and the 3D supercell test case. You will need to edit (or generate in some fashion) the sounding file such that it contains the GATE sounding you want. The sounding file is called "input_sounding" and the format for this file is described in the MPAS tutorial slides found at https://www2.mmm.ucar.edu/wrf/users/tutorial/202001/skamarock_ideal.pdf, slide 10. Make sure the sounding in the input_sounding file extends beyond the top of the WRF configuration so that the interpolation routines do not have to extrapolate. You also may want to initialize with a random perturbation to the temperature field (see the em_les test case) in addition to having latent and sensible heat fluxes (see the em_les, the em_seabreeze2d_x and the em_tropical_cyclone test cases).