Observational and modeling studies of cloud and associated rainfall processes

An operational cloud verification system is being developed at the Joint Center for Satellite Data Assimilation, aiming towards validating the cloud simulations in the operational models. The system collects satellite-retrieved cloud products such as liquid water and ice paths (LWP/IWP), precipitable water (PW), surface rain rate, cloud top pressure and temperature, cloud amount and the others from Microwave Surface and Precipitation Products System (MSPPS), Advanced Television InfraRed Observation Satellite (TIROS) Operational Vertical Sounder (ATOVS), Clouds from Advanced Very High Resolution Radiometer (AVHRR) (CLAVR) from Polar Operational Environmental Satellites (POES) and Automated Surface Observing System (ASOS) from Geostationary Operational Environmental Satellites (GOES). Consistence Checks of the LWP and IWP retrieved from MSPPS and CLAVR_x are carried out. It is found that the differences between two sets of satellite-retrieved cloud products are significantly large. Such significant differences suggest that a caution should be exercised when the cloud products are chosen for the validation purposes. The comparison study of PW, LWP, and IWP between the simulations from NCEP/Global Forecast System (GFS) and satellite-retrievals from MSPPS is conducted. The RMS difference of the PW over cloudy regions has the similar magnitude of the mass-integrated mixing ratios of cloud hydrometeors. Further study of surface rainfall processes indicates that the surface rain rate is the sum of sources/sinks of water vapor and cloud hydrometeors. The cloud-resolving simulations show that the inaccurate simulations of atmospheric water vapor affect the calculation of surface rain rate directly and by changing cloud microphysical processes indirectly. A cloud ratio is defined as the ratio of the IWP to LWP over the cloudy region, and is used to identify the convective and stratiform clouds and associated surface rainfall. The surface rainfall and its relationship with cloud hydrometeors in MSPPS data and model simulations are studied to show significantly different relationship between the satellite retrieved data and cloud model. The cloud microphysical processes are examined to determine the dominant rainfall processes.