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Representation of Diurnal Cycle of Precipitation in CMIP6 Models

Presentation Date
Tuesday, December 8, 2020 at 4:00am



The diurnal cycle of precipitation simulated from CMIP6 models is evaluated globally between 60°S and 60°N, and at ten selected geographical locations representing three categories of diurnal cycle of precipitation: (1) afternoon precipitation over land, (2) early morning precipitation over ocean, and (3) nocturnal precipitation over land. The ensemble mean of CMIP6 models shows that the model diurnal phase appears 3 to 4 hours earlier over land and 1 to 2 hours earlier over ocean, when compared with the latest satellite products. These biases are in line with what were found in previous versions of climate models but reduced compared to the CMIP5 ensemble mean. Analysis at the selected locations complimented with in-situ measurements reinforces these results. Several CMIP6 models have shown a significant improvement in the diurnal cycle of precipitation compared to their CMIP5 counterparts, notably on delaying afternoon precipitation over land. This can be attributed to the use of more sophisticated convective parameterizations. Most models are still unable to capture the nocturnal peak associated with propagating mesoscale convective systems, with a few exceptions that allow convection to be initiated above the boundary layer to capture nocturnal elevated convection. This study uses five different satellite and surface-based precipitation measurements to evaluate climate models. We quantify an encouraging consistency between these products that exists despite differing spatiotemporal resolutions and sampling periods, which provides confidence in using them to evaluate the simulated diurnal and semi-diurnal cycle of precipitation.

Funding Program Area(s)