Due to the impact of climate change and human activities, the upper and middle reaches of the Tao＇er River have become an ecologically sensitive area in Northeast China. It is important to evaluate the contributions ...Due to the impact of climate change and human activities, the upper and middle reaches of the Tao＇er River have become an ecologically sensitive area in Northeast China. It is important to evaluate the contributions of climate change and human activities to water suitability in the Tao＇er River area. From the perspective of water and heat balance, the water suitability index （Cr） was used to analyze the water suitability of the upper and middle reaches of the river. The nonparametric Mann-Kendall, moving t-test and cumulative anomaly methods were used to detect abrupt changes in Taonan station runoff from 1961 to 2012. Three inflexion years were detected. Thus, the entire time period was divided into four periods： 1961-1974, 1975-1983, 1984-1998, and 1999-2012. In order to estimate the impacts of climate change and human activities on runoff, the slope change ratio of cumulative quan- tity （SCRCQ） was adopted. Finally, the contribution of climate change and human activity to Cr was transformed from the contribution of climate change and human activity to runoff by the sensitivity coefficient method and SCIRCQ method. The results showed that the water suitability index （cr） had a decreasing trend 1961-2012. Fac- tors influencing cr, such as net radiation and runoff, also exhibited a decreasing trend, while precipitation exhibited an increasing trend over the past 52 years. The trends of Cr, net radiation and runoff were obvious, which passed the Mann-kendall test of significance at a=0.05. Human activities were the main factors that affected runoff, al- though the degree of impact was different at different times. During the past 52 years, the biggest contributor to the change in Cr was precipitation.展开更多
As the position of the transition zone changes obviously, that is, as the transition zone migrates to the north or the south from present position, it affects water or heat balance between the land and the atmosphere ...As the position of the transition zone changes obviously, that is, as the transition zone migrates to the north or the south from present position, it affects water or heat balance between the land and the atmosphere in a considerable degree and has a profound influence on climate in North China. The experiment results in this paper indicate whether in the dry case or in the wet case of the large-scale climatological background field, the surface air temperature in a wide range of the transition zone migration and its surrounding decreases as the transition zone migrates northward. Moreover, the net upward fluxes of the surface long wave radiation and the sensible heat decrease, and the evaporation to the atmosphere increases. As the transition zone migrates southward, the results are opposite. This kind of significant thermal forcing between the land and the atmosphere can excite secondary circulation or circulation cells, which interact with the large-scale circulation systems, changing the atmospheric motion, affecting the water vapor transportation and consequently having an effect on the precipitation.展开更多
基金National Natural Science Foundation of China(41201568,41202134)
文摘Due to the impact of climate change and human activities, the upper and middle reaches of the Tao＇er River have become an ecologically sensitive area in Northeast China. It is important to evaluate the contributions of climate change and human activities to water suitability in the Tao＇er River area. From the perspective of water and heat balance, the water suitability index （Cr） was used to analyze the water suitability of the upper and middle reaches of the river. The nonparametric Mann-Kendall, moving t-test and cumulative anomaly methods were used to detect abrupt changes in Taonan station runoff from 1961 to 2012. Three inflexion years were detected. Thus, the entire time period was divided into four periods： 1961-1974, 1975-1983, 1984-1998, and 1999-2012. In order to estimate the impacts of climate change and human activities on runoff, the slope change ratio of cumulative quan- tity （SCRCQ） was adopted. Finally, the contribution of climate change and human activity to Cr was transformed from the contribution of climate change and human activity to runoff by the sensitivity coefficient method and SCIRCQ method. The results showed that the water suitability index （cr） had a decreasing trend 1961-2012. Fac- tors influencing cr, such as net radiation and runoff, also exhibited a decreasing trend, while precipitation exhibited an increasing trend over the past 52 years. The trends of Cr, net radiation and runoff were obvious, which passed the Mann-kendall test of significance at a=0.05. Human activities were the main factors that affected runoff, al- though the degree of impact was different at different times. During the past 52 years, the biggest contributor to the change in Cr was precipitation.
文摘As the position of the transition zone changes obviously, that is, as the transition zone migrates to the north or the south from present position, it affects water or heat balance between the land and the atmosphere in a considerable degree and has a profound influence on climate in North China. The experiment results in this paper indicate whether in the dry case or in the wet case of the large-scale climatological background field, the surface air temperature in a wide range of the transition zone migration and its surrounding decreases as the transition zone migrates northward. Moreover, the net upward fluxes of the surface long wave radiation and the sensible heat decrease, and the evaporation to the atmosphere increases. As the transition zone migrates southward, the results are opposite. This kind of significant thermal forcing between the land and the atmosphere can excite secondary circulation or circulation cells, which interact with the large-scale circulation systems, changing the atmospheric motion, affecting the water vapor transportation and consequently having an effect on the precipitation.
