春季北方气旋活动的气候特征及与气温和降水的关系

利用1948-2002年NCEP／NCAR再分析逐日海平面气压资料以及中国160站的降水和气温资料，分析了春季北方气旋活动频数和强度的时空变化特征，以及两者与中国降水和气温的相关关系。结果表明：春季北方气旋活动频繁，存在明显的两个高值中心，分别位于蒙古国的中部和我国东北北部地区。春季北方气旋活动频数和强度均存在明显的年际和年代际变化。伴随着一次全球性的年代际气候跃变，20世纪70年代中后期无论是频数还是强度均出现了显著的突变。春季北方气旋活动频数主要对我国北方地区的降水和气温有一定影响，活动频数多(少)年，我国华北大部、新疆北部降水偏少(多)；北疆地区气温回升(下降)，甘、宁、陕、内部分地区偏冷(暖)。80-90年代春季北方气旋活动频数的偏少，强度的减弱，导致我国北方地区沙尘暴次数比70年代减少.

Climatic Characteristics of Northern Cyclone Activity in Spring and Their Relationship to Rainfall and Temperature in China

By use of the NCEP/NCAR daily reanalysis sea level pressure data from 1948 to 2002 and monthly rainfall and air temperature of 160 stations in China,the spatial and temporal variations of the frequency and intensity of spring Northern Cyclones have been computed,and relationships between spring Northern Cyclones and the temperature and precipitation over China also analyzed.Results show that in spring Northern Cyclones have high frequencies and there are two distinct high value centers:one locates in the middle of Mongolia;the other in the north of northeast china.There are obvious interannual and interdecadal variations in spring Northern Cyclones frequencies and intensities.With the decadal climatic catastrophe in global scale,there was a abrupt change in both frequency and intensity in the mid-last of 1970s,i.e.the frequencies and intensities of Northern Cyclones decreased from 1980s to 1990s.The frequencies of spring Northern Cyclones mainly have important influence on rainfall and air temperature in the north of china.When the spring Northern Cyclones are active(inactive),the rainfall is less(more) in the most part of North china as well as the north of Sinkiang;and the temperature is higher(lower) in the north of Sinkiang,whereas the temperature is lower(higher) in part of Gansu,Ningxia,Shanxi and Neimeng.In spring,the frequency-descending and the intensity-weakening of Northern Cyclones from 1980s to 1990s are responsible for the reduction of frequencies of sandstorms in compansion to the 1970s.