一次干冷空气过境对鄂陵湖地区大气边界层过程的影响

Influence of Incursion of Dry Cold Air on Atmospheric Boundary Layer Process in Ngoring Lake Basin

利用2012年夏季黄河源区鄂陵湖的GPS探空资料，分析了一次千冷空气过境前后该地区大气边界层位温、比湿和风速风向的垂直分布及其与地表热力作用的关系。结果表明，冷空气过境前的晴天时，湖区白天对流边界层高度不足100m，远小于陆地，而夜间可以达到400～600m；伴随着冷空气的到来，湖区对流边界层迅速增长，夜间达到2000m以上，超过了平时的陆地边界层高度。冷空气过境前后，陆地与湖泊的感热通量此消彼长；冷空气入侵后，水气温差迅速增加而地气温差急剧减小，湖面感热的日累积值迅速增大，风速增加并且垂直方向的风切变增强，这些都为湖泊对流边界层的急剧增长提供了充足的动力。

GPS radiosonde data observed in Ngoring Lake Basin in the summer of 2012 were used to investigate the vertical distribution of potential temperature, specific humidity and wind field in the atmosphere before and after the incursion of the cold, dry air, as well as the relation between them and the surface heat flux. The results showed that the depth of the convective boundary layer was less 100 m in Ngoring Lake during the daylight, be- fore the incursion of cold, dry air, far lower than that over land, but it can reach 400 - 600 m at night. Along with the arrival of cold air, the convective boundary layer increased rapidly and reached above 2000 m at night, more than the depth of the boundary layer over land. During the incursion of the cold, dry air, the accumulated sensible heat flux over land fell, but rose over the lake. After cold air arriving, the vertical temperature differ- ence increased rapidly over the lake and decreased sharply over land, and the accumulated sensible heat flux in- creased rapidly over the lake, along with enhancing of the wind speed and the wind shear, these factors provided plenty of power to the rapidly growth of convective boundary layer.