08/01/2013
Evaluation of Precipitation in Climate Models Using ARM Data
Summary
Precipitation is one of the most poorly parameterized physical processes in global climate models (GCMs). Scientists often utilize a single grid-box column of a GCM, or a single-column model (SCM), to more efficiently study and test the process representations or parameterization schemes in GCMs. The SCM approach is also a key strategy of the Department of Energy’s (DOE) Atmospheric Radiation Measurement (ARM) Facility and Atmospheric System Research (ASR) activity. However, most of the SCM intercomparison studies organized by ARM have been focused on special cases, or week-to-month-long periods. To make a statistically meaningful comparison and evaluation on modeled precipitation, three-year-long SCM simulations of seven GCMs participating in the FASTER project at the ARM Southern Great Plains site have been carried out by DOE scientists at Brookhaven National Laboratory. The results show that although most SCMs can reproduce the observed average precipitation reasonably well, there are significant differences in their details, including differences (both among models and between models and observations) between daytime and nighttime, between warm and cold seasons, between frequency and mean precipitation intensity, and between convective and stratiform partition. Further analysis reveals distinct meteorological backgrounds for large underestimation and overestimation precipitation events. The former occur in strong ascending regimes with negative low-level horizontal heat and moisture influx, whereas the latter occur in the weak or moderate ascending regimes with positive low-level horizontal heat and moisture influx. The different SCM performances and associations with large-scale conditions provide useful insights on how to improve representation of convection in climate models as well as improved approaches for future testing.
References
Song, H., W. Lin, Y. Lin, A. B. Wolf, R. Neggers, L. J. Donner, A. D. Del Genio, and Y. Liu. 2013. “Evaluation of Precipitation Simulated by Seven SCMs Against the ARM Observation at the SGP Site,” Journal of Climate 26, 5467-92. DOI:10.1175/JCLI-D-12-00263.1.