大型人工湖气候效应观测研究——以密云水库为例

应用近5 a自动气象站观测资料,分析了华北地区最大人工湖——密云水库的局地气候效应。结果表明：① 密云水库库区相比于附近平原地带具有气温偏低、湿度偏高、风速偏弱、降水量偏大等特点。水库对区域气候的影响范围约在10 km内,离水库越近的地方,受影响越大。② 密云水库的气候效应主要体现在夏半年,尤以气温和降水最为明显。③ 水库南、北两侧受到的局地环流的影响具有明显的差异,库区东西方向的年平均局地风速约为0.14 m/s,南北方向约为 0.10 m/s。下垫面属性的热力差异及特殊地形条件使得密云水库附近同时存在山谷风和湖陆风现象,其叠加效应是导致区域内不同位置间气象要素出现季节性及日变化差异的主要原因。

Observational Study on Climate Effect of Large Artificial Lake: Taking Miyun Reservoir as an Example

There exists lake-land breeze that wind blowing onshore from lake to land during the day and offshore in the evening around lake area, due to differences in air pressure mainly caused by different heat capacities between lake and land. Generally speaking, the closer to the lake, the more remarkable the lake climate effects. For studying the lake climate effects, it is not only important for understanding the characteristics of local climate and atmospheric circulation, but also helpful for analyzing and forecasting meso-and micro-scale weather processes. Miyun Reservoir (MYR), which located at 15 km north of Miyun District of Beijing city, is the largest artificial lake in North China. Up to now, there are seldom reports on the influence of MYR on local weather and climate. Based on hourly observation data obtained by 77 automatic weather stations surrounding MYR from 2011 to 2015, local climate effects of MYR were explored and discussed in the present work. The results showed that: 1) comparing with peripheral plains, climate effects of MYR were characterized by the facts that lower air temperature, higher humidity, slightly weaker wind speed and larger rainfall. As far as regional climate was concerned, the MYR had a modulate effect on the local climate and the spatial extent of the effect is about 10 km. The closer to the MYR, the more notable the MYR climate effects. 2) The MYR climate effects were mainly occurred in the summer, especially for temperature and rainfall. In detail, averaged air temperature was lower of 0.96℃ and averaged rainfall amount was higher of 13.3% in MYR than in the adjacent plains, where has the same elevation with MYR away from 10km. In addition, there were significant differences in diurnal variations of meteorological factors between the south and north regions of the MYR. 3) Excluding the impact of the large-scale background wind field, local wind presented the characteristics of monthly variation, i.e., mountain breeze was dominant from April to September, especially in summer; while in other months, valley breeze was more prevailing, especially in the wintertime. In general, annual averaged local wind speed was about 0.14 m/s in the east-west direction, which was slightly larger than that of 0.10 m/s in the north-south direction around the MYR. 4) In summer, there existed significant differences in wind vectors at the south and north regions of the MYR, due to the influence of local circulation. In most time of the whole day, component anomalies were usually in the same phase, while component anomalies presented out of phase at the south and north regions of the MYR. Lake-land breeze and mountain-valley breeze had the same/opposite directions at the north/south regions of the MYR, and thus these correspondingly formed the overlaying/counteractive effects. Due to lake-land differences in heat capacities and topography effects, lake-land breeze and mountain-valley breeze in the areas around MYR usually existed at the same time, which mainly caused the differences in seasonal and diurnal variations of meteorological elements at different locations around the MYR region.