1979—2017年冬半年京津冀区域大风的变化及其环流背景分析

利用1979—2017年冬半年(从11月至次年3月)站点的日平均风速和ERA-Interim再分析资料,分析了京津冀冬半年区域大风的变化及其环流背景。结果表明,研究时段共计有556次区域性大风日,风向以偏北风为主(约占90%)。近40 a资料显示：区域性大风日频次在显著减少,线性趋势达-1.77 d·(10 a)^-1 (P<0.1);同时大风平均风速也在减弱-0.07 m·s^-1·(10 a)^-1,P<0.05]。同期北半球大气环流的异常显示,东亚西风急流强度偏强时大风日频次易偏多;同时,大风日频次的变化与北半球对流层中低层大尺度的环流异常存在明显相关,北大西洋和欧亚大陆存在多个显著异常中心,其中北大西洋地区南北向的偶极子型异常与大风日频次及风速的相关系数均接近0.30(P<0.1)。表明京津冀区域性大风的变化,不仅与东亚地区大气环流有关,还可能受上游地区环流及北半球大尺度环流的影响。这对理解风速逐渐减小的原因具有重要的参考价值。

Regional strong winter wind events over Beijing-Tianjin-Hebei and the associated atmospheric circulation changes during 1979-2017

In this study, the variability of the strong wind events in the Beijing-Tianjin-Hebei (BTH) region during the period 1979 to 2017 and its relationship with atmospheric circulation were analyzed, by employing the daily average wind speed records from the meteorological stations and the ERA-Interim reanalysis data. The analysis boreal winter months cover November to March of the following year. During 1979-2017, there were 556 strong wind events, and nearly 90% of them were dominated by northerly winds. The frequency of strong wind events has decreased significantly at a rate of -1.77 d·(10 a)^-1 (P<0.1), and the mean wind speed for these events has weakened with a trend of -0.07 m·s^-1·(10 a)^-1 (P<0.05). The regional and hemispheric atmospheric circulation anomalies were also analyzed. It was found that the East Asian westerly jet has a significant positive correlation with the frequency of strong wind events. The North Atlantic region has a negative-positive stratospheric circulation anomaly distribution in the north-south direction, and its correlation coefficients with both the frequency and mean wind speed of strong wind events are close to 0.30. These analyses suggest that the wind variability in northern China is related to the regional atmospheric circulation over East Asia, the large-scale circulation in the northern hemisphere, and the upstream circulation in the North Atlantic