莱芜瀛汶河流域短时强降水特征分析

Analysis on Short-time Heavy Rainfall Characteristics in Yingwen River Basin of Laiwu City

利用瀛汶河流域8个区域自动气象站2009~2014年5~9月份的逐时降水资料,统计分析了瀛汶河流域短时强降水的时空分布规律,利用常规的地面和高空观测资料对该流域短时强降水个例进行天气学分析,总结出了该流域短时强降水的特征信息。结果表明,瀛汶河流域短时强降水的空间分布具有明显的地域性,局地性强,对暴雨的贡献较大,从西南部平原到东北部山区呈递增趋势。该流域短时强降水的年际频次变化大,集中出现在7~8月份,7月上旬至8月中旬是该流域短时强降水的高发期。该流域的短时强降水日变化明显,一日中有傍晚和清晨两个峰值,夜雨特征突出。流域内山区的短时强降水多在午后到夜间形成,且频次多,强度大;平原区多在夜间和早晨形成,频次少,强度小,山区傍晚的短时强降水峰值比平原提前1 h。由强对流系统造成的短时强降水过程,高空冷空气、低层暖湿输送等热力条件较好,持续时间短;暴雨过程中的短时强降水动力和水汽条件好,持续时间长,容易诱发北部山区山洪、泥石流等地质灾害,应给予高度关注。

Temporal and spatial distribution characteristics are analyzed statistically by using timely precipitation data from 8automatic weather stations in the Yingwen River region between May and September from 2009 to 2014 and characteristic information of short-time heavy rainfall in this basin is summarized according to the synoptic analysis of several short-time heavy rainfall examples by using surface and high altitude observation data. The results showed that the spatial distribution of short-time heavy rainfall in the basin had a remarked regional characteristic, which greatly contributed to the heavy rainfall,and an increasing trend existed from the plain area in the southwest to the mountainous region in the northeast. The short-time heavy rainfall in the basin displayed a large annual variation in frequency, concentrating in July and August, and the peak period came up from early July to mid August and there was a clear daily variation. Two rainfall peaks in a day appeared in the evening and in the morning, and the characteristic that rainfall occurred at night was obvious. Short-time heavy rainfall in the mountainous region often took shape in the afternoon and at night, which was frequent and intense.However, short-time heavy rainfall in the plain area often came out at night and morning, which was less frequent and intense.The peak of short-time heavy rainfall in the mountainous region was 1 hour earlier than that in the plain area. Short-time heavy rainfall caused by strong convective system in a short time in spite of some good thermodynamic conditions such as high altitude cold air and low-level warm wet transmission. Due to beneficial power and water vapor conditions in the process of heavy rainfall, short-time heavy rainfall during the process lasted a long time, which inclined to induce flash floods, landslides and other geological disasters, so it should be paid more attention.