Evaluation of cloud ice and snow size distributions and fallspeeds in CAM5 using observations

 

Authors

Trude Eidhammer — National Center for Atmospheric Research
Hugh Clifton Morrison — University Corporation for Atmospheric Research
Andrew Gettelman — National Center for Atmospheric Research (NCAR)
Aaron Bansemer — National Center for Atmospheric Research (NCAR)
Andrew Heymsfield — National Center for Atmospheric Research (NCAR)

Category

Cloud Properties

Description

The representation of ice microphysics in clouds remains a key uncertainty in climate models. Detailed in situ measurements of hydrometeor size distributions and fall speeds from several measurements have been compiled for comparison with model simulations. We focus here on two field campaigns: the 2000 ARM Spring Cloud IOP (Intensive Operational Period) in March 2000 over Oklahoma and the NASA TC4 (Tropical Composition, Cloud and Climate Coupling) mission in 2007, conducted in the tropical eastern Pacific. The moments of size distributions and weighted mean fall speeds determined from the measurements are compared with moments from modeled size distributions and fall speeds from simulations with Community Atmosphere Model (CAM) 5.1. We compare cloud ice mass and number concentrations with the measurements and to determine how well the CAM model represents the microphysical behavior in clouds. Preliminary results indicate that the measured and modeled moments are within the same order of magnitude; however, there are some differences in the trends of the moments as a function of temperature.