. The Tibetan Plateau includes a large system of endorheic (closed basin) lakes. Lake ice phenology, i.e. the timing of freeze-up and break-up and the duration of the ice cover may provide valuable information about climate variations in this region. The ice phenology of 59 large lakes on the Tibetan Plateau was derived from Moderate Resolution Imaging Spectroradiometer (MODIS) 8-day composite data for the period from 2001 to 2010. Ice cover duration appears to have a high variability in the studied region due to both climatic and local factors. Mean values for the duration of ice cover were calculated for three groups of lakes defined by clustering, resulting in relatively compact geographic regions. In each group several lakes showed anomalies in ice cover duration in the studied period. Possible reasons for such anomalous behaviour are discussed. Furthermore, many lakes do not freeze up completely during some seasons. This was confirmed by inspection of high resolution optical data. Mild winter seasons, large water volume and/or high salinity are the most likely explanations. Trends in the ice cover duration derived by linear regression for all the studied lakes show a high variation in space. A correlation of ice phenology variables with parameters describing climatic and local conditions showed a high thermal dependency of the ice regime. It appears that the freeze-up tends to be more thermally determined than break-up for the studied lakes.

/pdf/analysis-of-ice-phenology-of-lakes-on-the-tibetan-plateau-3bqlnop8bf.pdf

Analysis of ice phenology of lakes on the Tibetan Plateau from MODIS data

Near-nadir interferometric imaging SAR (Synthetic Aperture Radar) techniques are promising in measuring global water extent and surface height at fine spatial and temporal resolutions. The concept of near-nadir interferometric measurements was implemented in the experimental Interferometric Imaging Radar Altimeters (InIRA) mounted on Chinese Tian Gong 2 (TG-2) space laboratory. This study is focused on mapping the extent of high mountain lakes in the remote Qinghai–Tibet Plateau (QTP) areas using the InIRA observations. Theoretical simulations were first conducted to understand the scattering mechanisms under near-nadir observation geometry. It was found that water and surrounding land pixels are generally distinguishable depending on the degree of their difference in dielectric properties and surface roughness. The observed radar backscatter is also greatly influenced by incidence angles. A dynamic threshold method was then developed to detect water pixels based on the theoretical analysis and ancillary data. As assessed by the LandSat results, the overall classification accuracy is higher than 90%, though the classifications are affected by low backscatter possibly from very smooth water surface. The algorithms developed from this study can be extended to all InIRA land measurements and provide support for the similar space missions in the future.

https://www.mdpi.com/2072-4292/10/9/1418/pdf

Mapping High Mountain Lakes Using Space-Borne Near-Nadir SAR Observations

Remote Sensing of the Environment: 19th National Symposium on Remote Sensing of China

Sponsored by Committee of Remote Sensing for Geology, The Geological Society of China • Association on Environment Remote Sensing of China • Committee on Ocean Remote Sensing, Chinese Society of Oceanography • Committee on Satellite Meteorology and Space Weather, China Meteorological Society • Committee on Space Remote Sensing, Chinese Society of Space Research • Committee on Photogrammetry and Remote Sensing, Chinese Society of Geodesy, Photogrammetry, and Cartography • Committee on Space Remote Sensing, Chinese Society of Aeronautics and Astronautics • Technical Committee on Avionics, Chinese Society of Aeronautics • Committee on Telemetry, Remote Sensing, and Control, Chinese Association of Automation • Committee on Software Industry, China Association for Geographic Information System • Committee on Remote Sensing, Chinese Society for Optical Science Committee on Remote Sensing, Chinese Hydraulic Engineering Society • Affiliated Society of Land Information and Remote Sensing, Chinese Land Society • Committee on Remote Sensing for Land and Resources, Chinese Association of Remote Sensing Applications • National Remote Sensing Center of China • CNCRS—Chinese National Committee for Remote Sensing

Remote Sensing of the Environment: 16th National Symposium on Remote Sensing of China

Using the topographic data at the scale of 1:100000 in 1960´s, and Landsat MSS in 1970´s, Landsat TM in 1990´s, Landsat ETM+ in 2000´s, we carried out the survey of the lake distribution and its dynamic changes on Tibetan Plateau. The result indicates that there are 3 lakes within the area more than 1000km 2 , 74 lakes within area more than 100km 2 , 382 lakes within the area more than 10km 2 , 1260 lakes with the area more than 1km 2 , 6882 lakes within the area more than 0.1km 2 , and the total area of lakes is about 43186.4km on Tibetan Plateau. The area of lakes has taken place significantly changes during the past 30 years. The total area of lakes has increased 1610.01km 2 . The area of increased lakes are 157 lakes with in area more than 1km 2 , 5411 lakes within area more than 0.1km 2 and small lakes increased in hundreds and thousands. The area and amount of lakes increase most obviously in Qiangtang Plateau and Kunlun Mountains, and decrease most obviously in Qaidam basin, Hexi Corridor, Yellow River Basin, Yarlung Zangbo River Basin. The expanded and newborn lakes are distributed in the inner Plateau and disappeared and decreased lakes in the surrounding area of the Plateau. The increase and decrease of lake area has some related with climate changes, but mainly related to the local topography controlled by neo-tectonic. Keywords: Topographic map ÷ Landsat data ÷ lake ÷ lake area change ÷ Tibetan Plateau Tibetan Plateau is the most concentrated area of lake and wet land in China

Qigang Jiang

Papers

Dynamic changes of lakes and the geo-mechanism in Tibet based on RS and GIS technology