Trends in extreme temperature indices in the Poyang Lake Basin, China

Based on daily maximum and minimum temperature records at 78 meteorological stations in the Basin of China's largest fresh water lake (Poyang Lake Basin), the temporal and spatial variability of 11 extreme temperature indices are investigated for the period 1959-2010. The analysis indicates that the annual mean of daily minimum temperature (T-min) has increased significantly, while no significant trends were observed in the annual mean of daily maximum temperature (T-max), resulting in a significant decrease in the diurnal temperature range. Trends and percentages of stations with significant trends in T-min-related indices are generally stronger and higher than those in T-max-related indices; however, no significant trends can be found in T-max-related indices (TXMean, TX90p, TXx and TX10p) at both seasonal and annual time scale. Low correlations with Global-SST ENSO index are also detected in T-max-related indices. Significant positive relationships can be found in T-min-related indices (TNMean, TNx, TNn and TN90p), however, the most significant negative coefficient was also found in cold nights (TN10p) with the Global-SST ENSO index. Singular value decomposition (SVD) correlating extreme temperatures over the Poyang Lake Basin and the North Pacific SST indicates the East China Sea, Western Pacific and Bering Sea to be stronger linked with T-min than T-max with the first mode (SVD-1) explaining 90 and 94 % of annual T-max and T-min respectively.