Projected Changes in the Annual Range of Precipitation Under Stabilized 1.5°C and 2.0°C Warming Futures

Abstract

Abstract Changes in hydrological cycle under 1.5°C and 2.0°C warming are of great concern on the post‐Paris Agreement agenda. In particular, the annual range of precipitation, that is, the difference between the wet and dry seasons, is important to society and ecosystem. This study examines the changes in precipitation annual range using the Community Earth System Model low‐warming (CESM‐LW) experiment, designed to assess climate change at stabilized 1.5°C and 2.0°C warming levels. To reflect the exact annual range in different regions, wet and dry seasons are defined for each grid point and year. Based on this metric, the precipitation annual range would increase by 3.90% (5.27%) under 1.5°C (2.0°C) warming. The additional 0.5°C of warming would increase annual range of precipitation by 1.37%. The enhancement is seen globally, except in some regions around the subtropics. Under the additional 0.5°C of warming, a significant increase in the annual range occurs over 15% (22%) of the ocean (land) regions. The increase is associated with the enhanced precipitation during wet season. Moisture budget analysis shows that the enhancement in annual range is dominated by vertical moisture advection, which includes thermodynamic (TH, moisture) and climate dynamic (CD, circulation changes) terms. The TH term plays a dominant role, while the CD term partly offsets the effects of the TH term. The TH term dominates over most regions except for part of the tropical ocean and some of the land regions, where the CD term is also remarkable. Thus, the enhancement of the annual range of precipitation is mainly caused by the increase in moisture.