Subjects: Geosciences >> Atmospheric Sciences submitted time 2023-12-16 Cooperative journals: 《干旱区研究》
Abstract： Based on daily temperature observation data and reanalysis data of the geopotential height, sea levelpressure, and wind field from 1961 to 2020, the characteristics of spatial and temporal change of cold waves,strong cold waves, and exceptionally strong cold waves lasting 24 h, 48 h, and 72 h were studied in Ningxia overthe past 60 years. The causes of atmospheric circulation anomalies of cold waves were also revealed. The resultsshow the following: (1) In the past 60 years, cold waves of different intensities and different durations in Ningxiaconsistently showed the distribution characteristics of“shifting eastwards and northwards.”(2) The cumulativefrequencies of cold waves, strong cold waves, and exceptionally strong cold waves in the region accounted for71.7%, 22.6%, and 5.7% of the total annual cold wave frequencies, respectively, among which cold wavesdominated by process lasting 24 h and 48 h. The proportions of various durations for strong cold waves andexceptionally strong cold waves were equivalent. They mainly occured in October to April, during which theaccumulated cold waves, strong cold waves, and exceptionally strong cold waves in the region accounted for99%, 98%, and 95% of those throughout the year, and there was a decreasing trend from January to April andincreasing trend from October to December. (3) In the past 60 years, the cold waves, strong cold waves, andexceptionally strong cold waves have been decreasing at a rate of 4.5, 2.8, and 0.18 per station every 10 years,respectively. Among them, the frequencies of waves of 24 h and 48 h as short durations were decreasing, but thatof waves of 72 h as a long duration was decreasing. All types of cold waves decreased from the 1960s to the1990s, reaching a minimum in the 1990s and increasing since the 2000s, with a sudden change around 1990. (4)Under the influence of global warming, the atmospheric circulation showed completely the opposite distributioncharacteristics between before and after the sudden change of cold waves in Ningxia. The key systemsinfluencing cold waves in Ningxia are consistent. When the blocking high pressure in the Ural Mountains wasstronger, the East Asian trough was deeper, the west Pacific subtropical high was weaker, the western side ofLake Baikal was dominated by cyclonic circulation, and cold high pressure at the ground was active, this wasconducive to the southward movement of cold air in middle and high latitudes, and more cold waves in Ningxia.
Subjects: Geosciences >> Geography submitted time 2021-06-13 Cooperative journals: 《干旱区研究》
Abstract：利用1981—2018年西藏地区38个气象站点的逐日气象观测资料，采用联合国粮农组织Food and Agricul⁃ture Organization of the United Nations（FAO）推荐的Penman-Monteith公式估算了各站点的潜在蒸散量（ET0），分别从趋势性、突变性以及周期性分析了ET0的时空变化格局及其影响因素。结果表明：在时间尺度上，西藏地区ET0均表现出先“下降”后“升高”的趋势，其中“下降”阶段ET0整体呈显著的降低趋势（除冬季外），“升高”阶段呈显著的增加趋势（除春、夏季）。在空间尺度上，春、夏季表现出减少和秋冬季、年际表现出增加的趋势。发生突变的站点主要分布在中南部和东北部区域，时间集中在20世纪80年代；年均ET0变化的第一主周期为33 a（2013年）。此外，平均风速和相对湿度是影响年及季节ET0的主要因素，同时平均风速、相对湿度和最高温度对ET0的影响趋势具有很强的一致性。
Subjects: Geosciences >> Atmospheric Sciences submitted time 2021-02-28 Cooperative journals: 《干旱区地理》
Abstract： 利用 1961 年以来美国国家环境预报中心（NCEP）月平均再分析风场、高度场、NOAA 重构 海表温度以及西北地区中部 54 个气象站 6 月逐日降水资料、1979 年以来北极 10 个区域的海冰面积，通过分析 2019 年 6 月西北地区中部降水异常的成因，揭示出对该区域 6 月降水具有显著影响的 关键海区海冰面积及时段、北大西洋三极子（NAT）关键影响时段，结合厄尔尼诺-南方涛动（ENSO） 事件，分析其协同作用及影响机制。结果表明：1990 年以来春季 3—4 月楚科奇海海冰面积异常容 易激发欧亚中高纬度 EU2（欧亚 2 型）遥相关型（即夏季 EU（欧亚）遥相关型），有利于西北地区中部 降水异常，1992 年以来春季 NAT 对 EU2 遥相关型有明显影响，但其影响小于楚科奇海海冰面积的 影响；当楚科奇海海冰面积偏少和 NAT 正位相（海冰面积偏多和 NAT 负位相）协同作用时，西北地 区中部降水偏多（偏少）的概率明显增大；ENSO 事件对西北地区中部 6 月降水无明显直接影响，但 厄尔尼诺事件次年使得副热带高压异常偏强、偏西。2019 年楚科奇海海冰面积异常偏少，春季 NAT 异常偏强，两者协同作用下使得 EU2 遥相关型正异常（“+ - + -”），尤其使得贝加尔湖附近的 阻塞高压异常偏强，鄂霍次克海和乌拉尔山附近低压异常深厚，厄尔尼诺事件使副热带高压异常 偏强、偏西，将西太平洋的水汽输送至北太平洋，与鄂霍次克海附近的深厚低压相接，充足的冷空 气和水汽导致西北地区中部出现异常降水。研究成果可为短期气候预测提供依据，同时，气-冰- 海之间的相互作用需要更进一步研究。
Subjects: Geosciences >> Geography submitted time 2020-06-02 Cooperative journals: 《干旱区地理》
Abstract： 利用宁夏全域5个地市1980-2018年逐日白昼气温、相对湿度、风速、日照时数等气象资料，运用温湿指数、风寒指数、着衣指数和综合舒适指数模型，计算出旅游气候适宜期天数，并对其变化趋势及变化原因进行分析。综合舒适指数模型结果表明:石嘴山、银川、吴忠、中卫4市的旅游气候适宜期较为一致，为3月10日一11月7日，持续时长为243 d。固原的旅游气候适宜期为3月27日一10月29日，持续时长为217 d;石嘴山、吴忠、中卫全年旅游适宜天数变化不显著，是由始期、终期适宜天数增加幅度与“凹”面期适宜天数的减少幅度相当所致。银川、固原全年旅游适宜天数显著增加，主要是始期、终期适宜天数增加幅度大于“凹”面期适宜天数的减少幅度所致;各地始期、终期适宜天数显著增加是由气温升高、相对湿度降低和其他要素的差异变化共同作用所致。“凹”面期适宜天数显著减少是由气温升高(高温日数增多),相对湿度降低和其他要素的差异变化共同作用所致;各地始期、终期、“凹”面期，气温的显著变化对适宜天数显著变化的影响权重最大，达到50%以上，相对湿度、风速、日照时数的影响权重各有差异。
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