Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 9, 2533-2547, 2016
https://doi.org/10.5194/gmd-9-2533-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Development and technical paper
27 Jul 2016
Numerical framework and performance of the new multiple-phase cloud microphysics scheme in RegCM4.5: precipitation, cloud microphysics, and cloud radiative effects
Rita Nogherotto, Adrian Mark Tompkins, Graziano Giuliani, Erika Coppola, and Filippo Giorgi The Abdus Salam International Centre for Theoretical Physics ICTP, Strada Costiera 11, 34151 Trieste, Italy
Abstract. We implement and evaluate a new parameterization scheme for stratiform cloud microphysics and precipitation within regional climate model RegCM4. This new parameterization is based on a multiple-phase one-moment cloud microphysics scheme built upon the implicit numerical framework recently developed and implemented in the ECMWF operational forecasting model. The parameterization solves five prognostic equations for water vapour, cloud liquid water, rain, cloud ice, and snow mixing ratios. Compared to the pre-existing scheme, it allows a proper treatment of mixed-phase clouds and a more physically realistic representation of cloud microphysics and precipitation. Various fields from a 10-year long integration of RegCM4 run in tropical band mode with the new scheme are compared with their counterparts using the previous cloud scheme and are evaluated against satellite observations. In addition, an assessment using the Cloud Feedback Model Intercomparison Project (CFMIP) Observational Simulator Package (COSP) for a 1-year sub-period provides additional information for evaluating the cloud optical properties against satellite data. The new microphysics parameterization yields an improved simulation of cloud fields, and in particular it removes the overestimation of upper level cloud characteristics of the previous scheme, increasing the agreement with observations and leading to an amelioration of a long-standing problem in the RegCM system. The vertical cloud profile produced by the new scheme leads to a considerably improvement of the representation of the longwave and shortwave components of the cloud radiative forcing.

Citation: Nogherotto, R., Tompkins, A. M., Giuliani, G., Coppola, E., and Giorgi, F.: Numerical framework and performance of the new multiple-phase cloud microphysics scheme in RegCM4.5: precipitation, cloud microphysics, and cloud radiative effects, Geosci. Model Dev., 9, 2533-2547, https://doi.org/10.5194/gmd-9-2533-2016, 2016.
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Short summary
The paper presents a new cloud scheme for regional climate model RegCM4.5. The new scheme treats microphysical processes occurring within stratiform clouds and with respect to the pre-existing scheme is able to allow a more physically realistic representation of cloud microphysics and distribution, improving the representation of the longwave and shortwave components of the cloud radiative forcing.
The paper presents a new cloud scheme for regional climate model RegCM4.5. The new scheme treats...
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