Trends and variability of daily temperature extremes during 1960-2012 in the Yangtze River Basin, China

Authors: GUAN, YINGHUI - Northwest Agricultural & Forestry University; Zhang, Xunchang; ZHENG, FENLI - Northwest Agricultural & Forestry University; WANG, BIN - Beijing Forestry University

Submitted to: Global and Planetary Change
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2014
Publication Date: 11/26/2014
Citation: Guan, Y., Zhang, X.J., Zheng, F., Wang, B. 2014. Trends and variability of daily temperature extremes during 1960-2012 in the Yangtze River Basin, China. Global and Planetary Change. 124:79-94.

Interpretive Summary: The variability of temperature extremes has been the focus of attention during the past few decades, and may exert a great influence on the global hydrologic cycle and energy balance through thermal forcing. Based on daily minimum and maximum temperature observed by the China Meteorological Administration at 143 meteorological stations in the Yangtze River Basin (YRB), a suite of temperature indices recommended by the Expert Team on Climate Change Detection and Indices, with a primary focus on extreme events, were computed and analyzed for three periods 1960-1985, 1986-2012 and 1960-2012. The results showed widespread significant changes in all temperature indices associated with warming in the YRB during 1960-2012. On the whole, cold-related indices, i.e., cold nights, cold days, frost days, icing days, and cold spell duration index significantly decreased by -3.45, -1.03, -3.04, -0.42 and -1.6 days/decade, respectively. In contrast, warm-related indices such as warm nights, warm days, summer days, tropical nights, and warm spell duration index significantly increased by 2.95, 1.71, 2.16, 1.05, and 0.73 days/decade. And minimum TN, maximum TN, minimum TX, and maximum TX increased significantly by 0.42, 0.18, 0.19 and 0.14 ºC/decade. Because of a faster increase in minimum temperature (TN) than maximum temperature (TX), the diurnal temperature range exhibited a significant decreasing trend of -0.09 ºC/decade for the whole YRB during 1960-2012. However, the increasing trend though insignificant was observed in mid-eastern YRB and was more pronounced during 1986-2012. Geographically, stations in the eastern Tibet Plateau and northeastern YRB had stronger trends. The trends during the two periods of 1960-1985 and 1986-2012 illustrated that there were a cooling period before the mid-1980s and an accelerated warming period, during which changes in trends doubled those of 1960-2012 in most cases. In general, it was the warming especially during 1986-2012 that contributed most to the long term warming in the YRB. Strong relationships between temperature trends and elevation were detected in this study. The warming rates increased with elevation when elevation is above 350m, but decreased with elevation when elevation is below 350m. These findings will be useful for evaluating projections of Global Climate Models and Regional Climate Models in the study basin. They will also be useful to decision makers for developing emergency management plans for combating extreme temperature events in the region.

Technical Abstract: The variability of temperature extremes has been the focus of attention during the past few decades, and may exert a great influence on the global hydrologic cycle and energy balance through thermal forcing. Based on daily minimum and maximum temperature observed by the China Meteorological Administration at 143 meteorological stations in the Yangtze River Basin (YRB), a suite of temperature indices recommended by the Expert Team on Climate Change Detection and Indices, with a primary focus on extreme events, were computed and analyzed for three periods 1960-1985, 1986-2012 and 1960-2012. The results showed widespread significant changes in all temperature indices associated with warming in the YRB during 1960-2012. On the whole, cold-related indices, i.e., cold nights, cold days, frost days, icing days, and cold spell duration index significantly decreased by -3.45, -1.03, -3.04, -0.42 and -1.6 days/decade, respectively. In contrast, warm-related indices such as warm nights, warm days, summer days, tropical nights, and warm spell duration index significantly increased by 2.95, 1.71, 2.16, 1.05, and 0.73 days/decade. And minimum TN, maximum TN, minimum TX, and maximum TX increased significantly by 0.42, 0.18, 0.19 and 0.14 ºC/decade. Because of a faster increase in minimum temperature (TN) than maximum temperature (TX), the diurnal temperature range exhibited a significant decreasing trend of -0.09 ºC/decade for the whole YRB during 1960-2012. However, the increasing trend though insignificant was observed in mid-eastern YRB and was more pronounced during 1986-2012. Geographically, stations in the eastern Tibet Plateau and northeastern YRB had stronger trends. The trends during the two periods of 1960-1985 and 1986-2012 illustrated that there were a cooling period before the mid-1980s and an accelerated warming period, during which changes in trends doubled those of 1960-2012 in most cases. In general, it was the warming especially during 1986-2012 that contributed most to the long term warming in the YRB. Strong relationships between temperature trends and elevation were detected in this study. The warming rates increased with elevation when elevation is above 350m, but decreased with elevation when elevation is below 350m.