选取近57 a宁夏20个气象站夏季逐日最高气温、NCEP/NCAR再分析及北极海冰资料,利用气候统计诊断方法,分析了宁夏夏季极端高温的气候异常特征及其与北极海冰的联系。结果表明：宁夏夏季极端高温总强度、事件频次及最长持续日数自1961年以来总体呈增加趋势,尤其1990s后期至2000s中期是年代际增加最快的时段;极端高温总强度偏强年,宁夏处于500 hPa位势高度场正中心的南边,北边冷空气不易入侵,有利于宁夏夏季极端高温偏强;前期春季格陵兰海、巴伦支海、喀拉海地区海冰密集度偏高时,激发500 hPa位势高度距平场上出现正负相间的波列自北向南、自西向东往欧亚地区稳定传播,造成乌拉尔山高压脊减弱,使得欧亚中高纬地区以纬向环流为主,导致宁夏夏季极端高温强度偏强。本研究结果旨在为宁夏夏季极端高温预测提供理论依据。

The study of the relationship between the extremely high temperature in the Ningxia area and Arctic sea ice within the current climate change scenarios is a great significance to reveal the impact of Arctic sea ice on summer extreme temperatures. Based on maximum temperature data derived from meteorological stations in Ningxia, NCEP/NCAR reanalysis and Arctic sea ice data from 1961 to 2017, the extremely high temperature index was calculated, and its threshold was defined as the 90^th percentile of daily maxima, centered on a 31 day window. Subsequently, the climatic characteristics of the summer extremely high temperature in Ningxia, and its relationship with Arctic sea ice were analyzed using the statistical methods of regression, correlation, resultant and so on. Results show that, in the area, the total intensity, frequency of events and the longest lasting days with extremely high temperature in summer had a significantly increasing trend since 1961, and presented obvious interdecadal changes. In particular, the period from the late 1990s to the mid-2000s was the fastest growing interval. After the late 2000s, the increasing trend slowed down, but the interannual variation rate remained high. In addition, the above mentioned extremely high temperature index in summer generally increased across Ningxia, and strengthened in the 2000s and 2010s, in particular, the increase in the northern region was greater than that in the central and southern regions. In the intenser year of extremely high temperature intensity in Ningxia, the northern region of China was control under the positive anomaly field with 500 hPa geopotential height field, and Ningxia was in the south of it. This impeded the cold air in the north from flowing through, which resulted in high temperature detected in summer in Ningxia. In the weak year, the circulation mode over Ningxia was high in the west and low in the east, which was advantageous to the high latitude cold air inflowed southward, but disadvantageous to enhanced extremely high temperature. In the early spring, when the sea ice density in the Greenland Sea, Barents Sea, and Kara Sea is high, to excited the wave train on the 500 hPa geopotential height field steadily propagated from north to south and west to east, that resulting in the Ural Mountain High Ridge weakened, and the middle and high latitude area of Eurasia dominated by zonal circulation, and then caused the strong summer extremely high temperature intensity in Ningxia. The present study aimed to deepen the understanding of the variation of summer extremely high temperature in the Ningxia region, as well as to provide atheoretical basis for their prediction.