Understanding future increases in precipitation extremes in global land monsoon regions

This study investigates future changes in daily precipitation extremes and the involved physics over the global land monsoon (GM) region using climate models from phase 6 of the Coupled Model Intercomparison Project (CMIP6). The daily precipitation extreme is identified by the cutoff scale, measuring the extreme tail of the precipitation distribution. Compared to the historical period, multimodel results reveal a continuous increase in precipitation extremes under four scenarios, with a progressively higher fraction of precipitation exceeding the historical cutoff scale when moving into the future. The rise of the cutoff scale by the end of the century is reduced by 57.8% in the moderate emission scenario relative to the highest scenario, underscoring the social benefit in reducing emissions. The cutoff scale sensitivity, defined by the increasing rates of the cutoff scale over the GM region to the global mean surface temperature increase, is nearly independent of the projected periods and emission scenarios, roughly 8.0% K−1 by averaging all periods and scenarios. To understand the cause of the changes, we applied a physical scaling diagnostic to decompose them into thermodynamic and dynamic contributions. We find that thermodynamics and dynamics have comparable contributions to the intensified precipitation extremes in the GM region. Changes in thermodynamic scaling contribute to a spatially uniform increase pattern, while changes in dynamic scaling dominate the regional differences in the increased precipitation extremes. Furthermore, the large intermodel spread of the projection is primarily attributed to variations of dynamic scaling among models.

Chang M., B. Liu, B. Wang, C. Martinez-Villalobos, G. Ren, and T. Zhou, 2022: Understanding future increases in precipitation extremes in global land monsoon regionsJ. Climate, 35(6)1839-1851https://doi.org/10.1175/JCLI-D-21-0409.1

Figure 7. Multi-model mean (a) precipitation extremes and (b) full scaling of extreme precipitation derived using (4) for all days with daily precipitation exceeding PM in 1995-2014. Multi-model mean of fractional changes relative to the period 1995-2014 of (c) precipitation extremes and (d) full scaling for all days with daily precipitation exceeding PM in the long-term under SSP2-4.5 scenario. The red lines denote the boundaries of global land monsoon region.

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