夏季巴丹吉林沙漠区域残留层与对流边界层的关系研究

There has been reported that a convective boundary layer with its maximum depth more than 4000 m, as well as a residual layer with its top above 3000 m height during daytime can exist over arid region in Northwest of China. The deep convective layer was usually considered to be responsible for the appearance of the deep residual layer existing in the nighttime. However, if the residual layer can exist until the next day, then it may affect the development of convective boundary layer significantly as well. Unfortunately, since it is difficult to monitor the atmospheric motion and thermal characteristics near the top of a planetary boundary layer, such process has not been well concerned. In order to confirm the relationship of the convective boundary layer and the residual layer above, by using the observation data over Badanjilin desert, the reanalysis data, and the large eddy simulation results, four objects are planning to discuss during the implementation of this project: 1,the vertical structure of the lower atmosphere when there was a residual layer capping on a convective boundary layer; 2, the essential condition for that the residual layer can hold until next day; 3, the frequency of occurrence for a residual layer capped on a convective layer in the region; 4, the characteristics of the development of convective boundary layer when it was coupling with the residual layer. The effect of residual layer on the diurnal cycle of development of the planetary boundary layer over a desert should be more explicit when the project was accomplished. Furthermore, a more reasonable explanation for the existence of a so deep convective boundary layer over the desert can be given.

中国西北干旱地区白天经常观测到最大厚度超过4000m的对流边界层，同时在白天也观测到顶部位于3000m以上的残留层。通常认为白天深厚对流边界层是夜间深厚残留层出现的前提，但由于观测条件的限制，白天残留层对对流边界层的发展所起的作用还没有充分的研究。为了进一步明确沙漠地区对流边界层与残留层之间的关系，本项目利用在巴丹吉林沙漠的探空观测资料与再分析资料，结合大涡模拟，重点分析如下4个问题：1，对流边界层上覆盖有残留层的整体大气垂直结构；2，夜间残留层维持至白天的必要条件；3，当地对流边界层上残留层的出现频率；4，对流边界层与残留层发生耦合时所表现出的结构变化特征。通过这样的分析，探讨沙漠地区夜间残留层在整个边界层发展的日循环中的作用，从而对当地白天深厚对流边界层的成因给出更加完整的认识。