CFODD diagnostics code
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CFODD: Cloud Microphysical Process Metrics

CFODD (Contoured Frequency by Optical Depth Diagram) is a model diagnostic metric that evaluates warm rain formation microphysical processes against satellite observations. The methodology combines satellite cloud observables (e.g. radar reflectivity, cloud optical depth and cloud-top effective particle radius) to construct a particular statistics that "fingerprint" signatures of the warm rain formation process in the form of a contoured frequency diagram of radar reflectivity by in-cloud optical depth. The statistics are typically classified according to different ranges of the cloud-top particle size to depict how vertical microphysical structures tend to transition from non-precipitating clouds to precipitating clouds as a fairly monotonic function of the cloud-top particle size. The corresponding statistics are constructed from output of a given model for comparisons with the satellite-based statistics to expose how the model realistically represents the warm rain formation process in a statistical sense. The methodology is applicable to both global climate models and cloud-resolving models.


Fortran 90 codes for constructing the metric are available at the directory "code/fortran" in this repository. There are two codes: one for satellite-based statistics using CloudSat and MODIS data product and the other for model-based statistics using GFDL-CM3 sample output. The satellite and model data required to run the codes are available upon request to Kentaroh Suzuki at The data will be shared through Google Drive, to which the user will be given a permission to access. The sample results obtained from the code and data comparing the satellite-based and model-derived statistics are included in the directory "images".

Related publications (selected)

Suzuki, K., G. Stephens, A. Bodas-Salcedo, M. Wang, J.-C. Golaz, T. Yokohata, and T. Koshiro, 2015: Evaluation of the warm rain formation process in global models with satellite observations. J. Atmos. Sci., 72, 3996-4014, doi:10.1175/JAS-D-14-0265.1.

Suzuki, K., J.-C. Golaz, and G. L. Stephens, 2013: Evaluating cloud tuning in a climate model with satellite observations. Geophys. Res. Lett., 40, 4464-4468, doi:10.1002/grl.50874.

Suzuki, K., G. L. Stephens, S. C. van den Heever, and T. Y. Nakajima, 2011: Diagnosis of the warm rain process in cloud-resolving models using joint CloudSat and MODIS observations. J. Atmos. Sci., 68, 484-503, doi:10.1175/JAS-D-10-05026.1.


Frequency Duration Variables Dimension CMOR labels Unit File Format
6 hourly 3 months Cloud Optical Thickness (liquid) 2D tau Unitless nc
Cloud-top Effective Droplet Radius 2D reffclwtop m nc
Stratiform In-Cloud Optical Depth 3D dtaus Unitless nc
Radar Reflectivity 3D+Subcolumn N/A dBZ nc
Fracout 3D+Subcolumn N/A Unitless nc

*CMOR labels denoted "N/A" indicate that the variable is not available in current archive of CMIP.

*Radar Reflectivity is CloudSat radar reflectivity, which is computed and named "cfad_ze" in COSP.

*Fracout is the integer denoting the subcolumn scene type defined in COSP as "frac_out": =0 (Clr), =1 (St) and =2 (Cu)


The output is the occurrence frequency of radar reflectivity normalized at each in-cloud optical depth in the form of the contoured frequency by optical depth diagram. The sample results obtained from GFDL CM3 model output and satellite observations are provided as "cfodd_gfdl_sg_std_jan_4class.txt" and "cfodd_r21_5class_djf.txt" in the "code/fortran" directory. These are visualized to be displayed as "cfodd_sat_gfdl.png" in the "image" directory.


The diagnostic code:

code/fortran/analysis_cfodd_gfdl.f90 (Model: GFDL CM3)

code/fortran/analysis_cfodd_sat.f90 (Satellite)

The visualization script:

code/fortran/draw_cfodd.exe for Gnuplot

Data availability

The sample data from satellite and model required to create this diagnostic are available upon request to Kentaroh Suzuki at