【摘要】 利用1961-2013年3-5月的逐日降水、气温和高度环流场资料,计算了月季降水、气温序列、气象干旱指数序列、高原地面加热场强度指数序列,研究了春季旱涝急转的主要特征及其规律,解释了2013年青海省春季降水前期偏少、后期偏多和旱涝急转的成因.结果表明:2013年3月1日-4月27日青海大部分地区降水偏少、气温偏高,出现了大范围不同程度的气象干旱,海北大部分地区出现50 a一遇的特大气象干旱,西宁大部分地区出现25 a一遇的严重气象干旱;4月28日-5月20日青海大部分地区降水偏多,气温偏高幅度开始逐步减小,前期的干旱得到缓解,并出现了大范围不同程度的渍涝,旱涝急转的台站达21个.通过对比分析发现,若极涡面积偏小、中亚和西亚低压槽维持时间长、冷空气主要在欧洲东部和亚洲西部地区堆积、进入中国的冷空气路径偏西、高原位势高度场偏低、东亚槽位置偏东、西太平洋副热带高压北界位置偏北时,青海降水偏多,容易出现渍涝.在相反的环流形势下,青海降水偏少,容易发生干旱.4月干旱和5月渍涝处在青海高原降水长期变化的大气候背景之下,前期1-3月青藏高原地面加热场强度偏强、春夏季过渡时间提前也有助于青海5月异常降水的形成.更多还原

【Abstract】 Based on the daily precipitation,temperature and geopotential high data in spring from 1961 to 2013,the series of precipitation,air temperature and meteorological drought index were calculated. Then after analyzing the characteristics and cause of sudden turn of drought and flood with the climate diagnosis methods. It is summarized as follow s: from 2013. 3. 1 to 2013. 4. 27 greater part of the province had less rainfall and higher temperature,and then appeared a large range meteorological drought with different degree,and in greater part of Xining and Haibei appeared the meteorological drought with frequencies of 1-in-25 years and 1-in-50 years,respectively. Then from 2013. 4. 28 to 5. 20 greater part of the province had more rainfall,and the higher temperature shifted to low er one gradually,so the drought relieved and waterlogging appeared in a large range with different degree. There were 21 stations had the records of sudden turn of drought and flood. Composition analysis shows that when the polar vortex area is smaller than ordinary,the central and west Asia trough has longer duration,the cold air cumulates in eastern Europe and western Asia regions,the cold air into China inclines to the west,the plateau potential height field inclines to low,the east Asian trough inclines to east and the western Pacific subtropical high inclines to north,Qinghai Province will have more precipitation and more prone to waterlogging,and vice versa. The drought in April and the waterlogging in May is under the climate background of long-term variation in Qinghai plateau,characterized by the Tibetan Plateau surface heating field with high intensity in the early stage of January to March. The transient time from spring to summer in advance will be conducive to abnormal precipitation in May in the province.更多还原