Temporal and Spatial Changes in Climate Extremes and their Connection with Runoff in the Yellow River Basin between 1961 and 2010

Abstract

This study analyzes the temporal and spatial distribution of the extreme values of eight climate indices, based on observational data from a hundred and forty-three (143) meteorological stations across the basin. The eight core indices selected from the STARDEX projects reflect rather moderate extremes. The relationship between the eight indices and observed run-off from six hydrological stations was analyzed. Results showed that the annual and seasonal indices of temperature extremes for the period 1961 to 2010 increased most significantly for txq90, tnq10, and hxw90, which increased by about 0.8 to 1.3°C, 2.5 to 3.9°C, and 0.6 to 2.7 days, respectively, while the number of frost days decreased by 14.8 to 26.5 days. Sharp increases in txq90, tnq10, and txhw90 occurred in the late 1980s and 1990s, and decreases in tnfd occurred in the 1990s. The rainfall extremes are significantly different to the temperature series between 1961 and 2010. From the result, no significant increasing or decreasing trends in rainfall extremes was observed. Out-of-phase variations in annual temperature extremes are evident between the middle and north–south regions, the west and east regions, and the northwest and southeast regions. The spatial distribution of rainfall also shows an out-of-phase pattern, but the trends are weaker than those of the temperature indices. Furthermore, the four temperature indices (txq90, tnq10, tnfd and txhw90) and two of the rainfall indices (pnl90 and px5d) are more closely related to the observed run-off than the other two rainfall extremes.