The Hydrological Cycle on the Tibetan Plateau - Observed by Multisensoral Remote Sensing Methods

Abstract:

Climate change and its potential effects are of global interest. Lake ice and snow coverage act as effective indicators of climate change due to their sensitivity to climate elements (like air temperature in the case of the lake ice), and can be observed on a large-scale with the help of remote sensing. The lakes on the Tibetan Plateau are important indicators for the development of the high mountain ecosystems facing the impacts of future climatic warming on runoff from snow and ice. Many of these Tibetan lakes are remote and hard to access, so multi-sensoral remote sensing is a valuable tool to generate hydrological relevant information as modeling input (land cover, soil moisture, trends in mountain lake ice cover, etc.) or validation base (lake level changes) . Tibetan lakes are remote and hard to access. For the monitoring of the lake ice, the first and the last day of the partial ice cover and the period of total ice cover are defined on the basis of temporal high temporal resolution MODIS data. The larger lakes were compared and put into regional groups in order to delineate and define different local trends. For obtaining a better spatial resolution for the calculation of the ice covered area, additional medium and high resolution optical and microwave data (ERS-1, ERS-2, ENVISAT A-SAR, LANDSAT, Kompsat-2, RapidEye) were considered, which at the same time, have a smaller temporal resolution. By means of correlation of the different data, the respective advantages of each data type are merged and were then exploited for the exaction of the iced surface and calculation of its area extent calculation. The study is enhanced by the use of passive microwave data (SSM/I, AMSR-E) which provides very high temporal resolution information as validation input. Simultaneously TerraSAR-X ScanSAR data was analysed for the whole winter period 2011 (December until April) in order to derive the spatial distribution of different ice types. The snow cover is an important intermediate storage of water and plays a crucial role in the water budget of the Tibetan endorheic lakes. However little is known about it since their contribution to runoff is mostly unknown as well as the losses through sublimation.