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Interdecadal variation in the frequency of extreme hot events in Northeast China and the possible mechanism
Atmospheric Research ( IF 4.5 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.atmosres.2020.105065 Haixu Hong , Jianqi Sun , Huijun Wang
Atmospheric Research ( IF 4.5 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.atmosres.2020.105065 Haixu Hong , Jianqi Sun , Huijun Wang
Abstract Based on the daily maximum temperature data from Chinese metrological stations, the frequency of extreme hot event (EHE) in Northeast China (NEC) over the period from 1960 to 2018 is investigated. The results show that the EHE frequency in summer (June and July) experienced a significant interdecadal increase around the mid-1990s. The analysis of the possible mechanism indicates that the interdecadal strength of the summer geopotential height in the mid-to-upper troposphere over the Mongolian region could be directly responsible for the interdecadal increase in the NEC EHE frequency. The enhanced geopotential height can weaken the subtropical East Asian westerly jet and lead to anomalous convergence and subsidence over NEC. Consequently, there were less cloud cover, favoring more incoming short-wave solar radiation to warm the land surface of NEC. Under such a background, there are more outgoing sensible heat, latent heat, and long-wave radiation from the land surface to warm the overlying atmosphere, favoring more EHE frequency over NEC. Further analysis indicates that the interdecadal variation in the summer geopotential height over the Mongolian region is related to a barotropic stationary Rossby wave train at the midlatitude from the North Atlantic to East Asia. Dynamic diagnosis and numerical simulation both suggest that the Atlantic Multidecadal Oscillation (AMO) can excite the pronounced Rossby wave train and further influence the interdecadal change in the geopotential height over the Mongolian region, finally contributing to the interdecadal increase in the NEC EHE frequency around the mid-1990s.
更新日期：2020-11-01
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