Effect of climate change on reference evapotranspiration and aridity index in arid region of China

Temporal variations in reference evapotranspiration (ET0) and aridity index (AI) were comprehensively investigated for 23 meteorological stations during 1955–2008 in the northwest China. The quantitative contributions of the major meteorological variables to the ET0 and AI trends were evaluated and the possible causes were also investigated. The results showed that in the past 50 years annual temperature, humidity and precipitation had significant increasing trends with time, and wind speed and radiation had decreasing trends. ET0 had a significant decreasing trend with an averagely value of about 3 mm per year, and AI had also witnessed a decreasing trend; For ET0, wind speed was the most sensitive meteorological variable, followed by relative humidity, temperature and radiation and for AI, precipitation was the most sensitive meteorological variable. The contribution of wind speed to the decrease of ET0 is more than that of other meteorological variables. The increase of precipitation contributes more than the decrease of ET0 to decrease of AI in past 50 years. This study provides an understanding of the effect of recent climate change on drought in arid northwest China.