The peak structure and future changes of the relationships between extreme precipitation and temperature

Theoretical models predict that, in the absence of moisture limitation, extreme precipitation intensity could exponentially increase with temperatures at a rate determined by the Clausius-Clapeyron (C-C) relationship. Climate models project a continuous increase of precipitation extremes for the twenty-first century over most of the globe. However, some station observations suggest a negative scaling of extreme precipitation with very high temperatures, raising doubts about future increase of precipitation extremes. Here we show for the present-day climate over most of the globe, the curve relating daily precipitation extremes with local temperatures has a peak structure, increasing as expected at the low-medium range of temperature variations but decreasing at high temperatures. However, this peak-shaped relationship does not imply a potential upper limit for future precipitation extremes. Climate models project both the peak of extreme precipitation and the temperature at which it peaks (T peak) will increase with warming; the two increases generally conform to the C-C scaling rate in mid- and high-latitudes, and to a super C-C scaling in most of the tropics. Because projected increases of local mean temperature (T mean) far exceed projected increases of T peak over land, the conventional approach of relating extreme precipitation to T mean produces a misleading sub-C-C scaling rate.