Lake-Related Cloud Dynamics on the Tibetan Plateau: Spatial Patterns and Interannual Variability

Abstract

he scarcity of meteorological observations has hitherto prevented spatially comprehensive and complete assessments on regional and local-scale atmospheric processes such as breeze systems on the Tibetan Plateau (TiP). Because of the high abundance of lakes, the steep topography, and the intense insolation of the TiP, lake breeze and land breeze systems might, however, contribute substantially to the local climatic and hydrological variability. The presented study aims at unveiling the influence of the lake effect over the whole TiP by using a novel high-mountain satellite cloud product, based on Meteosat Indian Ocean Data Coverage (IODC) data from 1999 to 2012, focusing on 70 lake systems larger than 72 km2. Of particular interest are the spatial and interannual variability of lake-related cloud dynamics during boreal summer and autumn. For both seasons, a significant effect of lakes on cloudiness is shown during the early morning. Its mean strength is mainly determined by each basin?s temperature difference between lake and surroundings. For boreal summer the large-scale influences of tropical and extratropical circulation pattern on the interannual variability of the lake effect are also investigated. The results show that the Arctic and North Atlantic Oscillations (AO and NAO) inhibit convective activity above lakes in the northern and central-eastern domain. A positive polarity of the Southern Oscillation index (SOI), in contrast, is in phase with enhanced convective activity. The variability of the Indian summer monsoon circulation does not affect cloud dynamics at more than two locations. Case studies are employed to illustrate interactions between cloud activity and the SOI and NAO. For this purpose satellite data are combined with the modeled 10 km ? 10 km High Asia Refined Analysis dataset on a daily basis.