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Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

The Convective‐To‐Total Precipitation Ratio and the “Drizzling” Bias in Climate Models

TitleThe Convective‐To‐Total Precipitation Ratio and the “Drizzling” Bias in Climate Models
Publication TypeJournal Article
Year of Publication2021
JournalJournal of Geophysical Research: Atmospheres
Volume126
Number16
Abstract / Summary

Overestimation of precipitation frequency and duration while underestimating intensity, that is, 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 0.5° to 2.0°, but the resolution's effect weakens as the grid spacing increases from 2.0° to 3.0°. 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.

URLhttp://dx.doi.org/10.1029/2020jd034198
DOI10.1029/2020jd034198
Journal: Journal of Geophysical Research: Atmospheres
Year of Publication: 2021
Volume: 126
Number: 16
Publication Date: 08/2021

Overestimation of precipitation frequency and duration while underestimating intensity, that is, 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 0.5° to 2.0°, but the resolution's effect weakens as the grid spacing increases from 2.0° to 3.0°. 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.

DOI: 10.1029/2020jd034198
Citation:
Chen, D, A Dai, and A Hall.  2021.  "The Convective‐To‐Total Precipitation Ratio and the “Drizzling” Bias in Climate Models."  Journal of Geophysical Research: Atmospheres 126(16).  https://doi.org/10.1029/2020jd034198.