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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) and the Regional Atmospheric Modeling System (RAMS). 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 3.0 is now available (August 22, 2017):

The major changes since the initial release of the model include:

  1. Computation of simulated measured radial Doppler velocity and spectrum width (in addition to "vertical"). Doppler velocities are defined positive away from the radar (radar convention).
  2. The three radar coordinates (range, azimuth, elevation) are computed for every WRF grid point and reported out.
  3. The spectrum width contributions due to turbulence, wind shear in radar volume and cross-wind in radar volume are also computes in addition to the spectrum width due to different hydrometeor terminal velocity of different sizes. All spectrum width variables are reported in the output.
  4. Includes computation of radar sensitivity limitation with range.
  5. Includes computation of simulated ceilometer and micro pulse lider measurements.
  6. Few severe bugs found and corrected.
  7. The structure of the output NetCDF file(s) modified.
  8. Parallel computing using OpenMP is available.
  9. The ICOsahedral Non-hydrostatic general circulation model (ICON) and the Regional Atmospheric Modeling System (RAMS) data can be input.
  10. The ARM Value Added Products (e.g., liquid water path, ARSCL) are optionally computed.


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

Download Latest Software (v3.1) User Guide (v3.1)