中文摘要：

利用区域自动站加密观测资料、NCEP/CFSR 0.5°×0.5°再分析资料以及0.01°×0.01°全球地形资料等,对2013年夏季发生在川西高原东侧两次对流暴雨天气过程中偏东气流的作用和特征进行了对比分析,重点研究两次过程中中低层偏东气流的活动特征、风场的垂直结构和温湿特征及其在对流暴雨中的作用等。结果表明：（1）7月3日过程高原东侧偏东风活动在850 hPa以下,持续时间约20 h,风速平均为2 m·s^-1;8月6日过程偏东风活动在700 hPa以下,持续时间也能达到20 h,风速约为4 m·s^-1;两次过程均是在天气尺度的西风槽东移与地形的共同作用下,诱生了高原东侧对流层中低层偏东气流,偏东气流形成时间比对流降水发生时间早约12 h。（2）两次过程偏东气流具有高相当位温属性,在其上方存在干冷空气活动,形成了有利的对流不稳定层结。相比较而言,后一次过程偏东气流出现的高度和风速明显增强后,与偏西风形成了更大的低层垂直风切变,暖湿能量局地集中特征更为显著,对于水汽和能量持续输送能力更强,因而引发的对流降水强度明显更大。（3）前一次过程盆地内起伏波动的偏东风与辐合中心及气旋性涡度中心配置关系较差,只是当偏东风受强迫抬升后,在地形附近激发出对流,并使降水主要位于地形附近;后一次过程盆地内平直的偏东风与辐合中心及涡度中心配置关系较好,尺度相当,因此激发出的对流强度和范围有明显增大,强降水沿地形向盆地西部发展。

英文摘要：

Using intensive surface observation,NCEP/CFSR 0.5°×0.5° reanalysis data and 0.01°×0.01°global terrain data etc.,the contrast role and characteristics of the easterly air stream in two convection rainstorms in the terrain transition zone of Western Sichuan Plateau in the summer of 2013 was analyzed in this paper.The activity characteristics,vertical structure and temperature and humidity characteristics,and the role in the two convective rainstorms were focused on.The results showed that：（1）The easterly activity on 3 July 2013 is below 850 hPa,lasting for about 20 h with wind speed averaged 2 m·s^-1 in Sichuan Basin,while easterly activity on 6 August is below 700 hPa,also with duration 20 h but wind speed is about 4m·s^-1.Both of the two processes are composed of westerly trough moving eastward and the effect of terrain,which induce the easterly air stream.The easterly airflow forms about 12 h earlier than convective precipitation appears.（2） The easterly flows of the two processes have high equivalent potential temperature property with the dry cold air activities in the mid-upper troposphere,thus,forming the favorable convective unstable stratification.In contrast,after the height and wind speed of the easterly flow in the later process is obviously enhanced,much stronger low-level vertical wind shear is formed together with the west wind,and the local concentration characteristics of the warm-wet energy is more significant,more beneficial for the sustained delivery of water vapor and energy.So the induced convective precipitation is more intensive.（3） The undulated easterly air stream,convergence center and cyclonic vorticity center are poorly related in the previous process,except when the easterly wind forces the uplift and inspires convecfion making the rainfall near the terrain.However,the straight easterly air stream has good relations with the convergent center and vorticity center during the second process,with almost equivalent scales.Therefore,severe convection intensifies to lar