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The convective-to-total precipitation ratio and the “drizzling” bias in climate models
  • Di Chen,
  • Aiguo Dai,
  • Alex Hall
Di Chen
University of California, Los Angeles

Corresponding Author:dichen@atmos.ucla.edu

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Aiguo Dai
University at Albany, State University of New York
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Alex Hall
University of California Los Angeles
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Overestimation of precipitation frequency and duration while underestimating intensity, i.e., the “drizzling” bias, has been a long-standing problem of global climate models. Here we explore this issue from the perspective of precipitation partitioning. We found that most models in the Climate Model Intercomparison Project phase 5 (CMIP5) have high convective-to-total precipitation (PC/PR) ratios in low latitudes. Convective precipitation has higher frequency and longer duration but lower intensity than non-convective precipitation in many models. As a result, the high PC/PR ratio contributes to the “drizzling” bias over low latitudes. The PC/PR ratio and associated “drizzling” bias increase as model resolution coarsens from 0.5o to 2.0o, but the resolution’s effect weakens as the grid spacing increases from 2.0o to 3.0o. Some of the CMIP6 models show reduced “drizzling” bias associated with decreased PC/PR ratio. Thus, more reasonable precipitation partitioning, along with finer model resolution should alleviate the “drizzling” bias within current climate models.
27 Aug 2021Published in Journal of Geophysical Research: Atmospheres volume 126 issue 16. 10.1029/2020JD034198