In recent decades,the "warming and wetting" in Northwest China has become the consensus of the scientific community,and much research has been conducted regarding water and heat transport between land and atmosphere.Station observations show that the annual precipitation has been increasing since the early 1980s under the land surface warming background.As a notable arid-semiarid regions,the social and economic developments in Northwest China is strongly dependent on water resources.The land water availability (LWA),which is the residual of precipitation and evaporation,typically denotes natural water resources.However,the long-term characteristics and decadal variability of LWA in Northwest China are not clear,due to the lack of a reliable and long-term evaporation dataset.In our previous work,a long-term 0.25 deg daily land surface hydrological and fluxes dataset (referred as to VIC-CN05.1) was developed,and has provided a high quality evaporation dataset for exploring LWA variability.In the present study,we analyze the long-term and decadal characteristics of the land water budget in the northwestern region during the 1961-2016 warm season (May-September).The station observational meteorology dataset (CN05.1) VIC-CN05.1 and atmospheric reanalysis (JRA55) are used.The Mann-Kendal mutation test is adopted to test the LWA time series,and two abrupt change points in 1979 and 2008 are detected.Next,the studied period is divided into three sub-periods (P1:1961-1978;P2:1979-2008;P3:2009-2016) for further analysis.The main conclusions of the study are as follows:From 1961 to 2016,the LWA in the Northwest China warm season shows an upward tendency.The regional mean LWA time series exhibits obvious decadal characteristics,and the LWA anomaly percentage in the three periods are -5.45%,-0.46% and 13.99%,respectively,showing a general characteristic of "decreasing-invariable-increasing".The spatial distributions of the LWA change are significantly different in the three periods,particularly in central Xinjiang,eastern Gansu and Shaanxi Provinces.Sufficient water vapor and rising motion are the necessary conditions for precipitation,and the atmospheric circulation has a major influence on precipitation change in Northwest China.The changes in water vapor flux transport and vertical velocity in Northwest China are basically consistent with the decadal variation characteristics of precipitation overall,with obvious regional difference distribution characteristics.Evaporation in Northwest China is closely related to near-surface meteorological elements,and is mainly affected by precipitation,downward longwave radiation and wind speed.It should be noted that we treat the Northwest China region as a whole,although this region exhibits a high degree of LWA spatially heterogeneity.In the future,it is necessary to analyze the LWA change in different sub-regions.Moreover,the effects of land use change and human activities on water resources must also be considered.