Effect of lake surface temperature on the summer precipitation over the Tibetan Plateau

There are numerous lakes on the Tibetan Plateau(TP),but the role of lake temperature in precipitation over the TP remains unclear.Here the Weather Research and Forecasting(WRF) model was used to detect the impact of lakes on summer rainfall.Three test cases were used to evaluate the effect of lakes surface temperature(LSTs) on precipitation variability.The three cases used different methods to determine initial LSTs,including using sea surface temperature data(SST),the WRF inland water module(avg_tsfc),and a lake model.Results show that when precipitation was stimulated over the TP,LSTs cannot be initialized using SST,which led to large discrepancies of precipitation.Compared with the simulations,the simulated precipitation were improved obviously with LSTs using avg_tsfc,indicating that LSTs have an considerable influence on determining precipitation over the TP.Due to a lack of observational data,the lake scheme does not improve on rainfall simulation,but does effectively simulate precipitation pattern over lakes,such as rainfall over the lakes was dominated by convection during the nighttime.Though the simulated precipitation using SST to initialize LSTs caused largediscrepancies,it suggested that precipitation increase especially convective precipitation with increase in LSTs,which confirmed that the moisture from lakes cannot be neglected over the TP.Generally,it was necessary to monitor the LSTs for accurate weather and climate prediction over the TP.

Simulation on the Release of TP from Wensi Lake Sediment into Water

[Objective]The study aimed to analyze the release of total phosphorous from Wensi Lake sediment into water.[Method]Though simulation experiments in a laboratory,we studied the effects of various environmental factors like water-soil ratio,water temperature,pH,disturbance and dissolved oxygen（DO） on TP release from Wensi Lake sediment.[Result]The higher the water-soil ratio,the less TP released from the sediment;temperature increase sped up TP release from the sediment;when pH of overlying water was 6,the amount of released TP was the lowest;disturbing the overlying water accelerate TP release from the sediment;the lower the DO content,the larger the released TP.[Conclusion]The research could provide scientific references for controlling the pollution of Wensi Lake.

Spatial-temporal patterns of vegetation dynamics and their relationships to climate variations in Qinghai Lake Basin using MODIS time-series data

Global warming has led to significant vegetation changes in recent years. It is necessary to investigate the effects of climatic variations（temperature and precipitation） on vegetation changes for a better understanding of acclimation to climatic change. In this paper, we focused on the integration and application of multi-methods and spatial analysis techniques in GIS to study the spatio-temporal variation of vegetation dynamics and to explore the vegetation change mechanism. The correlations between EVI and climate factors at different time scales were calculated for each pixel including monthly, seasonal and annual scales respectively in Qinghai Lake Basin from the year of 2001 to 2012. The primary objectives of this study are to reveal when, where and why the vegetation change so as to support better understanding of terrestrial response to global change as well as the useful information and techniques for wise regional ecosystem management practices. The main conclusions are as follows：（1） Overall vegetation EVI in the region increased 6% during recent 12 years. The EVI value in growing seasons（i.e. spring and summer） exhibited very significant improving trend, accounted for 12.8% and 9.3% respectively. The spatial pattern of EVI showed obvious spatial heterogeneity which was consistent with hydrothermal condition. In general, the vegetation coverage improved in most parts of the area since nearly 78% pixel of the whole basin showed increasing trend, while degraded slightly in a small part of the area only.（2） The EVI change was positively correlated with average temperature and precipitation. Generally speaking, in Qinghai Lake Basin, precipitation was the dominant driving factor for vegetation growth; however, at different time scale its weight to vegetation has differences.（3） Based on geo-statistical analysis, the autumn precipitation has a strong correlation with the next spring EVI values in the whole region. This findings explore the autumn precipitation is an important indicator, and then, limits the plant growth of next spring.