1997-2002年华北持续性干旱气候诊断分析

利用1957-2002年华北地区104个气象站实测的月降水量、月平均气温等气候资料,以及美国NCEP/NCAR的850 hPa矢量风和500 hPa位势高度等再分析资料,分析了1997-2002年逐月降水距平变化特征、干旱持续性特征、干旱强度分布特征;基于干旱区域性特征,提出了一个描述区域性干旱的指数(spatial drought index,SDI);此外,从东亚大气环流系统中的冬季东亚大槽、贝加尔湖反气旋环流场、西太平洋副热带高压以及东亚夏季风等系统的变化等方面,探讨了对这一持续性干旱的影响.研究表明:华北地区1997-2002年的干旱具有全区强度大的特征,区域平均干旱指数达到了65%以上.而东亚地区冬季东亚大槽持续偏弱,夏季贝加尔湖地区高压又持续偏高,东亚夏季风持续偏弱,西太平洋副热带高压持续偏东等的综合作用,是引起华北地区这一阶段持续性干旱的主要原因.

Analysis on Climatic Diagnosis of Persistent Drought in North China during the Period from 1997 to 2002

Severe drought occurred in north China during the period from 1997 to 2002 except first half of 1998.The persistent drought brought about the remarkable impacts on daily life of local residents and the social and economic development.In this paper,the essential factors resulting in such drought during this period,such as the monthly precipitation anomaly and the duration,distribution and intensity of drought,are analyzed using the NCEP/NCAR reanalysis data including vector wind at 850 hPa,geopotential height at 500 hPa and meteorological data(monthly precipitation and temperature) observed by 104 meteorological stations in north China.A spatial drought index(SDI)is put forward based on the regional features in the study area so as to quantify the regional drought characteristics.Some other factors resulting in the persistent drought are investigated in the aspects of East Asian atmospheric circulation,deep trough over East Asia in winter,Baikal Lake anticyclonic circulation,west Pacific subtropical high,and East Asian monsoon.The results reveal that the drought intensity in north China during the period from 1997 to 2002 was high,and the SDIwas as high as over 65%.It is considered that the persistent drought in north China during this period was jointly affected by the persistently weak deep trough over East Asia in winter,persistent high over the Baikal Lake in summer,persistent weak East Asian monsoon,eastward duration of west Pacific subtropical high,etc.