东北地区汛期降水异常的大气环流特征分析

Analyses on General Circulation Character of Precipitation Anomaly in Northeast China Flood Season

针对东北地区汛期（7～8月）的情况，分析了造成汛期降水异常的大气环流特征，结果表明：汛期多（少）雨年，低层850hPa蒙古东南的气旋（反气旋）式距平环流、我国大陆东部的西南风（东北风）距平气流及日本南面的反气旋（气旋）式距平环流的共同作用加强（减弱）了低层西南暖湿气流在东北地区的辐合；多（少）雨年，中层500hPa中高纬西风带经向运动加强（减弱），从贝加尔湖以北的高纬地区到日本附近的高度场呈＋-＋（-＋-）的波列分布。8月的环流形势比7月更容易造成严重旱涝，下游鄂霍茨克海和日本海阻塞高压的发展和减弱是造成8月降水异常的重要因子。考虑7月旱涝流型演变时，应着重关注南北向＋-＋的“波列”；而考虑8月旱涝流型演变时，则更应着重关注东西向-＋-＋-的“波列”配置。多、少雨年，高、低层的散度场、垂直速度场及水汽条件等物理量场都有明显的差异。

To better understand and predict the flood season （July-August） precipitation in Northeast China, the general circulation in the years with above- and below the normal precipitation is analyzed. The results show that, on lower layer （850 hPa）, the common action of cyclonic （anti-cyclonic） anomaly circulation in Southeast of Mongolia, the southwest（northeast） wind anomaly in East of China and anti-cyclonic （cyclonic） anomaly circulation in south of Japan have strengthened（weakened） the convergence of southwest warm and humid air flows of low layer in Northeast China region in more rain year of flood season. On middle layer （500 hPa）, the meridional movement of westly belt in high-middle latitudes strengrhen （weakened）, there are ＋-＋-wave train distributions from the high latitude region to the north of Baikal to the height field near Japan. The circulation pattern in August is easier resulting in severe drought and flooding than in July. The developing and weakening of blocking highs in low reach of Okhotsk and Japan seas are to cause an important facter of precipitation anomaly in August. Considering with the evolution of drought and flooding patterns, we have special attention to the ＂wave train＂ allocation of -＋-＋- westeast-ward. There are obvious differences for the divergence, vertical velocity felids, and vapour condition of high-and low-layers in more and less rain years.