影响我国北方冬半年气旋的气候特征及年际变率

Climatology and Interannual Variability of Extratropical Cyclones in the Winter Half-Year in Northern China

本文首先对气旋进行了客观定义,实现了气旋的自动识别与跟踪算法,利用NCEP/NCAR再分析资料建立了近60年(1951～2010)我国北方冬半年气旋活动数据集。对气旋的气候特征与年际变率进行了探讨。结果表明:蒙古国中西部、雅布洛诺夫山脉东麓等为主要气旋源地;蒙古国东南部、内蒙古东南部、松嫩平原是气旋活跃区;内蒙古东南部、东北地区中北部为气旋消亡区与快速填塞区;初春、仲秋季节气旋较活跃,冬季气旋最少;随季节推移,气旋活动区域向南、向东推进;气旋移动以偏东路径居多,其次是东南、东北路径;700hPa风场对气旋移动趋势具有较好的指示意义;24h标准加深率大于0.5Bergeron的快速发展气旋,位于内蒙古东部、东北地区中北部、日本海中部等地;爆发性气旋则主要位于日本海附近,我国大陆极少;极端最强气旋主要集中在1980年代以前的仲秋与初春;1980年代以来,气旋频次相对较少,强气旋有逐渐增加的趋势;气旋频次减少与东亚中高纬度大气低层斜压性减弱有关。

Using the objective definition and auto-identification and tracking technique, the database of extratropical cyclones （ECs） in the winter half-year in northern China from 1951 to 2010 is built on the basis of the NCEP/NCAR reanalysis data. Furthermore, the climatology and interannual variability of ECs are studied. The results show that cyclogenesis is mainly focused in the central-west region of Mongolia and the eastern foot of Yablonoi Mountains. ECs are active mostly over southeast of Mongolia, southeast of Inner Mongolia, and the Songnen Plain; however, cyclolysis and rapid decay of ECs occur over the southeast of inner Mongolia and central-north of Northeast China. The frequency of ECs is the highest in early spring and middle autumn and the lowest in winter. With seasonal evolution, the active region of ECs moves eastward and southward. The eastward path is the most common track of ECs, after which comes the southeastward track, and then the northeastward one. Horizontal winds at 700 hPa can be considered as the steering flow of ECs. The rapid growth of ECs, whose standard deepening rate is greater than 0.5 Bergeron for 24 h, is mainly active over the east of Inner Mongolia, central-north of Northeast China, and the central Japan Sea. However, explosive ECs are spread mainly over the Japan Sea and marginally over the continent of China. The extremely strong EC eventsoccurred mostly in the early spring and mid autumn before the 1980s. However, frequency of ECs was relatively low, the frequency of extremely strong ECs has increased since the 1980s. The decrease of ECs is related to the weakening of the baroclinicity in the lower troposphere of Northeast Asia.