9:30 AM - 9:45 AM
[AAS08-03] The too fast, too frequent precipitation simulated in GCMs
Keywords:cloud, precipitation, auto-conversion, GCMs, Satellites
The cloud-to-precipitation transition process is represented in GCMs by bulk auto-conversion schemes. A sensitivity test with two widely used auto-conversion schemes in the global cloud-resolving model shows that a more realistic auto-conversion scheme significantly improved the model representation of cloud-to-precipitation transition process: the typical cloud radius where precipitation occurs is shifted close to the observations. However, precipitation occurrence frequency is still overestimated, implying that the parameterization of cloud particle size, besides the auto-conversion scheme, also contributes to the model bias of precipitation occurrence.
Results here demonstrate that both auto-conversion and the growth of non-precipitating cloud particles need to be better represented to achieve realistic precipitation rate and frequency.