Increased Tibetan Plateau vortex activities under 2℃warming compared to 1.5℃warming:NCAR CESM low-warming experiments

The Tibetan Plateau vortices(TPVs)are the major rain-producing systems over the Tibetan Plateau(TP).The activities of TPVs are closely related to TP's water source,which supplies fresh water to millions of people in Asia.Projection of the TPVs can increase understanding about the future of water supply in Asia under global warming.In this study,the possible activities of TPVs under 1.5℃and 2℃warming scenarios above the pre-industrial level are evaluated through the NCAR CESM(Community Earth System Model)Low-warming(CESM-LW)Experiments.The results show that the CESM-LW well reproduces the spatio-temporal characteristics of TPVs in the historical run from 1985 to 2000.The CESM-LW suggests TPVs in warm season(May-September)increase by 15%due to the additional 0.5℃warming by the end of this century(2071—2100).It implies the greater importance of TPVs to the precipitation over the TP in the future.The changes of TPVs are closely related to the large-scale circulations adjustments.The additional 0.5℃warming strengthens the temperature difference between the TP and its surrounding areas,which results in an enhanced convergence near the TP's surface and divergence in the upper troposphere by about-0.1×10^(-6)and 0.22×10^(6)s^(-1),respectively.The assessment of future TPVs provides a synoptic dynamic perspective on the climate change of precipitation and water resources.

Regional changes in extreme heat events in China under stabilized 1.5℃ and 2.0℃ global warming

Extreme heat events(EHEs)have a significant impact on the social economy and human health.China is a country with a large population and diverse terrain,and it is necessary to project future extreme heat changes in the sub-regions.This study used a specially designed dataset,the Community Earth System Model(CESM)simulations,namely CESM low-warming,to investigate the EHEs in China under 1.5℃ and 2.0℃ global warming.The results indicate that the regional mean warming over China will exceed the global average,about 1.63℃ and 2.24℃ in 1.5℃ and 2.0℃ warmer futures.Compared to the present-day(1976–2005),the frequency and duration of the EHEs in South China are projected to increase the most among the sub-regions.For example,the frequency of EHEs in South China at 1.5℃ and 2.0℃ warming will exceed 3 and 3.5 times the present-day level.However,when global warming rises from 1.5℃ to 2.0℃,the increased impacts relative to the 1.5℃ warming level will be the lowest in South China(less than 40%),and the highest increased impacts are projected to appear in Northeast China(53%-84%)and Northwest China(53%–107%).The main reason for this situation is that compared with the 1.5℃ scenario,the upper zonal westerly in northern China weakens and the continental high pressure enhances under the 2.0℃ scenario.Therefore,limiting global warming at 1.5℃ instead of 2.0℃ is beneficial for eliminating extreme heat events,especially for Northeast China and Northwest China.