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Cloud Resolving Model Radar Simulator

The idea behind CR-SIM is to create an accurate radar forward model operator consistent with several microphysics schemes that converts the model variables into the form of radar observations and thus to enable the direct comparison between numerical weather model output and radar observations. The CR-SIM can be applied in order to reproduce characteristic (polarimetric) signatures commonly found in (polarimetric) radar and lidar observations and examine the performance of different microphysical schemes and the assumptions related to scattering characteristics of observed cloud and precipitation systems.

The current version of CR-SIM uses input from the high resolution Weather Research and Forecasting (WRF) Model (WRF) for several microphysical schemes (Morrison double-moment scheme, Milbrandt and Yau double-moment scheme, and the fast spectral bin scheme) and computes “idealized” forward modeled scanning (or vertical-pointing) radar observations and profiling lidar observables. The CR-SIM can be easily configured to work on other models and microphysics schemes. The latest version can use the inputs from the ICOsahedral Non-hydrostatic general circulation model (ICON), the Regional Atmospheric Modeling System (RAMS), and System for Atmospheric Modeling (SAM). The CR-SIM is written in FORTRAN and uses as input the model prognostic mass and number variables in the case of double-moment microphysics schemes or the explicit (bin) microphysics for the fast spectral bin scheme.

The CR-SIM employs the T-matrix method for computation of scattering characteristics for cloud water, cloud ice, rain, snow, graupel and hail and allows the specifications of the following radar frequencies for scattering calculations: 3 GHz, 5.5 GHz, 9.5 GHz, 35 GHz and 94 GHz. For the lidar variable simulations, the T-matrix computation also provides scattering characteristics for cloud water (for ceilometer and micro pulse lider simulations) and cloud ice (for micro pulse lider simulations) at wavelengths of 905 nm for ceilometer and 353 and 532 nm for micro pulse lider.

The polarimetric variables simulated include reflectivity at vertical and horizontal polarization, differential reflectivity, specific differential phase, specific attenuation at horizontal and vertical polarization, specific differential attenuation, and linear depolarization ratio. Also simulated are the vertical reflectivity weighted velocity, mean Doppler velocity and spectrum width. The computation of fall velocities is consistent with the computational method used in the specific microphysical package. The simulated lidar variables includes true and attenuated backscatter, extinction coefficient, lidar ratio, true and attenuated aerosol backscatter, aerosol lidar ratio, and molecular backscatter.

The CR-SIM includes an optional package to emulate additional observational products from the simulated radar and lidar variables. The current version compute liquid water path considering the microwave radiometer field of view and the Active Remote Sensing of Cloud Locations (ARSCL) products.

Version 3.21 is now available (April 10, 2019):

The major changes since the last release (v.3.1) of the model include:

  1. Incorporated SAM TAU two-moment bin microphysics (liquid only) (MP_PHTSICS=70).
  2. Incorporated SAM Morrison 2-moment microphysics (MP_PHYSICS=75).
  3. Incorporated Doppler spectra generator.
  4. Incorporated a retrieval of particle size distribution parameters which are used in the Thompson scheme’s reflectivity calculation in WRF instead of those described in Thompson et al. (2008 & 2004).
  5. Introduced the parameter maxNumOfHydroTypes equal to the maximal number of hydrometeor types allowed (currently 8 for RAMS, MP=40). Corrected dimension for those variables whose dimension was not updated (i.e. was equal to less than maxNumOfHydroTypes).
  6. Added a new module phys_param_mod.f90 that should include all the physical parameters and constants used throughout the CR-SIM. The idea is to gradually exclude the use of hard-coded values.
  7. Fixed bug in test script when reporting if the test passes or fails.
  8. Added the new test with RAMS 2-moments microphysical scheme.
  9. Modified files so that ‘make clean’ does not remove configuration files.
  10. Updated processor version (
  11. Introduced progress messages in percentage.
  12. The main code and file crsim_subrs.f90 cleaned and introduced indentation.


If you use the CR-SIM software to simulate WRF data used in publication, an acknowledgment would be appreciated. If you have any comments, suggestions for improvements, bug fixes or you need help to interface CR-SIM with your model output, please contact us (;;;

We would like to thank Dr. H. Morrison, Dr. Z. Feng and Dr. J. Fan, Dr. T. Matsui, and Dr. A. Fridlind for providing the WRF output data and for their valuable comments, suggestions and encouragement. Thanks are extended to Dr. M. Mech, Dr. P. Marinescu, and Dr. T. Yamaguchi for providing the ICON, RAMS, and SAM output data, respectively, and for their valuable comments. We also would like to thank Dr. J. Vivekanandan for his Mueller-matrix-based code and Dr. M. I. Mishchenko for making his T-matrix codes public and freely available for research purposes.

Download Latest Software (v3.2) User Guide (v3.2)