This code is designed for HAILCAST to be embedded in the Weather Research and Forecasting model, version 3.6 or later (WRF).

Instructions for using HAILCAST in WRF (v4.0):

The most updated HAILCAST is already available within WRF v4.0, available here.

  1. Set hailcast_opt=1 in the &phys namelist for the domain over which you want to run HAILCAST. HAILCAST can only be run in domains with the cumulus parameterization turned off.

  2. Set haildt to how frequently you want HAILCAST called, in seconds. If set to 0, it runs every WRF timestep. We recommend setting it no higher than 60 seconds.

  3. Output will consist of a HAILCAST_DIAM_MAX variable containing the maximum hail size (mm) predicted since the last history output file.

Instructions for using HAILCAST in WRF (v3.9):

  1. Download the code here.

  2. The files in the tarball are designed to modify the following files in WRFv3.9 or later:
    • REPLACE phys/module_diag_hailcast.F
    • Follow the instructions to MODIFY phys/module_diagnostics_driver.F.
    • ADD TO Registry/Registry.EM_COMMON
    After modifying those files, clean and recompile the WRF code.

  3. Follow steps outlined for WRF v4.0 above.

Use of HAILCAST in earlier versions of WRF should follow a similar process. Slight changes in the code might be necessary to ensure compatibility with earlier WRF versions.

Instructions for embedding HAILCAST in any CAM:

HAILCAST can be run inside of any convection-allowing model. In this tarball, module_diag_hailcast.F code is the file needed. The subroutine that contains the bulk of the hail model is called hailstone_driver. This subroutine requires as input the following fields:

For a discussion of the updraft duration, refer to Section 3a of Adams-Selin and Ziegler (2016). The code in the main subroutine, before the call to hailstone_driver, can show you how we handled determining updraft duration within WRF.

The hailstone_driver subroutine outputs 5 different hail sizes (mm), corresponding to the hail size produced by 5 different initial embryos. We recommend retaining the maximum of these 5 sizes. We also recommend retaining and outputting the maximum hail size at any grid point since the last output file.