不同天气形势下山东半岛南部沿海大风特征及其成因

以山东半岛南部沿海为例,利用旋转T模态主成分分析方法和欧洲中期天气预报中心第5代大气再分析资料(ERA5)对大风的环流形势和成因进行研究。结果表明:(1)形成大风的天气型有5种,按大风日数从多到少依次为西北路冷高压型、低压槽后型、低压槽前型、江淮气旋型和北路冷高压型,与不同天气型下大风发生的概率大小顺序一致。(2)冷高压型(包括西北路冷高压型和北路冷高压型)的冬季大风最多,低压槽型(包括低压槽前型和低压槽后型)的春季大风最多,江淮气旋型的春、秋季大风最多。(3)高空冷平流、地面冷高压和动量下传是西北路冷高压型大风的成因;高空冷平流和地面冷高压是北路冷高压型大风的成因;高空暖平流、入海高压和东北低压是低压槽前型大风的成因;高空冷平流、地面冷高压和东北低压是低压槽后型大风的成因;受高空正涡度平流和暖平流影响,气旋发展并向东北方向移动在半岛南部形成大的气压梯度是江淮气旋型大风的成因。

Characteristics and Causes for Gale at Southern Shandong Peninsula Coast of Different Circulation Patterns

Taking the southern Shandong Peninsula coast as an example, the circulation patterns and the causes of the gale are explored using the obliquely rotated T mode Principal Component Analysis and the fifth generation ECMWF reanalysis data (ERA5). There are five main circulation patterns for gale, and the order is the northwest path of the high pressure type, behind trough low pressure trough type, before trough low pressure trough type, Jianghuai cyclone type, and north path of the high pressure type according to the number of gale days, which is consistent with the order of the gale probability for different types. Winter holds the most gale days of high pressure type (northwest and north path types), spring holds the most gale days of low pressure trough (before and behind trough types), and spring and autumn hold the most gale days of Jianghuai cyclone type. The causes of the northwest path of high pressure type gale are the combination of the cold advection, cold high pressure and the momentum downward transporting. The cause of the north path of high pressure type gale is the combination of the cold advection and cold high pressure. The cause of the before trough low pressure type gale is the combination of the warm advection, the high pressure at the ocean and the northeast China low. The cause of the behind trough low pressure trough type gale is the combination of the cold advection, the cold high pressure and the northeast China low. The vorticity advection and warm advection before the trough are the key factors for the development and movement of the low pressure. The Jianghuai cyclone moves northeast and results in a large pressure gradient at the south of the Shandong Peninsula, causing the Jianghuai cyclone type gale.