庐山雨凇积冰日数变化特征及其与海气场关系

利用江西省气象信息中心提供的1970-2016年逐日庐山站电线积冰、NOAA重构延长的逐月海表温度(SST)及NCEP再分析风场等资料,采用线性趋势分析、Man-Kendall检验、Morlet小波分析、合成分析等方法,研究了庐山雨凇积冰日数的变化特征及其与海气场的关系,结果表明:1)庐山雨凇积冰基本发生在当年11月至次年3月。2)雨凇积冰日数总体呈显著下降趋势,且在1981年和2001年分别存在一显著突变,即1970-1980年庐山雨凇积冰日数异常偏多,1981-2001年庐山雨凇积冰均值基本接近常年,2001-2005年庐山雨凇又异常偏少。3)庐山雨凇积冰日数存在2~4年、6~8年及20年左右的振荡周期,2~4年周期变化在20世纪70年代、80年代末到90年代末及2005年以后振荡显著。4)庐山雨凇积冰异常偏多年代,前期410月整个热带太平洋海温异常偏低,同期113月庐山受贝加尔湖异常反气旋东南侧东北气流和来自东太平洋偏南气流的共同影响,有利于出现雨凇积冰。

Variation Characteristics of Glaze Icing Days in Lushan Mountain and Its Relationship with Ocean-Air Field

Wind shear refers to the vector difference of wind between two points in space. Wind shear is divided into horizontal wind shear and vertical wind shear. In aviation meteorology, low level wind shear usually refers to vertical wind shear below 600 m above the surface. Low level wind shear seriously endangers the safety of aviation activities, especially during the take off and landing stages of aircraft. In order to improve the forecast accuracy and early warning time of low level wind shear, the characteristics of low level wind shear in Dalian airport are summed up by using the Dalian Airport discourse mode reports. The most frequent seasons of low level wind shear at Dalian Airport are late autumn and spring, when the low level wind shear caused by strong northwest and north winds is the most typical wind shear. Such shear often occurs near the observation time, accompanied by surface wind with 9 m·s-1 average wind speed or 16 m·s-1 gust speed in 360° or 350° direction. In this paper, three examples of typical low level wind shear weather in Dalian airport are selected, and the characteristics of typical low level wind shear weather at Dalian airport are analyzed based on the NCEP/NCAR FNL 1°×1°data. Besides, the WRF model output data are used and the characteristics of the wind field at the bottom of the typical low level wind shear in Dalian Airport are analyzed. The analysis results denote that the wind field changes of the WRF model output are small and cannot reflect the mutation characteristics of low level wind shear. The calculation of the I value reflecting the deviation wind, calculated by using the model output data has a significant correlation with the occurrence of wind shear. When I is greater than 0.5 and gradually increases, low level wind shear is prone to occur; when I is less than 0.5 and gradually decreases, low level wind shear is not easy to occur. Therefore, the I value and its changes can be used in the forecasting and early warning of low level wind shear events.