Spatio-temporal Variations Of Water Vapor And Its Hydrological Response Under Changing Environment In The Yellow River Basin

Under the background of climate change and human activities,the water cycle of Yellow River Basin has significant changes in the recent decades,followed by the frequent occurrences of flood and drought.The investigation of influence of climate change and human activities is important to the preventing of flood and drought.Based on the wavelet analysis and EOF analysis,the study investigated the spatial-temporal distribution of the precipitation of Yellow River Basin.The results shows that the interannual variances annual precipitation of the Yellow River Basin is significant.It can be found that the southeastern of the basin has a decreased precipitation while an opposite trend was found in the western part of the basin.The precipitation of the basin was cyclical and the main cycle is around 20 years.Based on the atmospheric water vapor movement,the study investigated the atmospheric conditions which influenced the precipitation of Yellow River Basin.The results shows that there are significant differences of precipitation among different seasons and the atmospheric water vapor movements are different.There are significant decadal variations of the atmospheric water vapor movements of Yellow River Basin.The increasing water vapor from south of the basin is the main reason of the increasing precipitation.Based on the Mann-Kendall analysis,the study investigated the spatial-temporal variations of runoff in different time scales.And the cyclical characteristics of runoff were investigated by the wavelet analysis.The results shows that runoff is mainly decreased in most of the basin,which is especially significant after the middle of 1980 s.The main cyclical periods of runoff is different among different stations.Based on the observed runoff data from 1960-2014,Budyko based hydrothermal balance model is used to evaluate quantitatively fractional contribution of climate changes and human activities to streamflow changes.And combined the FAO Penman-Monteith potential evapotranspiration,the sensitivities of runoff change to the climatic factors(e.g.precipitation,speed and relative humidity)and underlying surface factors(land use and land cover changes)are calculated,then the contribution rate of those influence factors for the runoff reduction are estimated quantitatively.Precipitation and relative humidity have the positive driving effects on the change of runoff,and maximum temperature,minimum temperature,global radiation,speed,and surface factors have the negative driving effects on the change of runoff.The special distribution of climatic factors elasticity is consistent with the LULC elasticity,showing that climate,hydrology and vegetation in the Yellow river basin have nicer spatial correlation.The special distribution of climatic factors elasticity is consistent with the LULC elasticity,showing that climate,hydrology and vegetation in the Yellow river basin have nicer spatial correlation.