Convective/Large-scale Rainfall Partitions of Tropical Heavy Precipitation in CMIP6 Atmospheric Models

Abstract

Convective/large-scale (C/L) precipitation partitions are crucial for achieving realistic rainfall modeling and are classified in 16 phase 6 of the Coupled Model Intercomparison Project (CMIP6) atmospheric models. Only 4 models capture the feature that convective rainfall significantly exceeds the large-scale rainfall component in the tropics while the other 12 models show 50%–100% large-scale rainfall component in heavy rainfall. Increased horizontal resolution generally increases the convective rainfall percentage, but not in all models. The former 4 models can realistically reproduce two peaks of moisture vertical distribution, respectively located in the upper and the lower troposphere. In contrast, the latter 12 models correspond to three types of moisture vertical profile biases: (1) whole mid-to-lower tropospheric wet biases (60%–80% large-scale rainfall); (2) mid-tropospheric wet peak (50% convective/large-scale rainfall); and (3) lower-tropospheric wet peak (90%–100% large-scale rainfall). And the associated vertical distribution of unique clouds potentially causes different climate feedback, suggesting accurate C/L rainfall components are necessary to reliable climate projection.