西北旱区1961-2011年参考作物蒸散量的时空分异

全球变化背景下分析参考作物蒸散量的变化特征,对于农业生产和水资源管理等有重要指导意义。根据西北旱区152个气象站点1961—2011年气象资料计算参考作物蒸散量(ET0),分析了其空间分布及时间变化趋势,并探讨了其变化原因。1961—2011年西北旱区年均ET0为1100.4 mm/a,但存在空间变异,低值出现在黄土高原南部区域,高值出现在西北部沿东南-西北方向的条带上。ET0整体呈不显著的上升趋势,但64和36个站点分别呈显著的上升和下降趋势;西北旱区ET0发生突变的年份东部较西部晚。ET0的时空变异是气象因子时空变化的组合效应,ET0对相对湿度和最高温度的变化最敏感,但过去50a ET0变化中风速和最高温度的贡献率最大。西北旱区ET0的变化发生了重要改变,由2000年以前的下降趋势转变为目前的上升趋势,可能加剧该区的水资源短缺状况,需引起足够的重视。

Spatiotemporal variations of the reference crop evapotranspiration in the arid region of northwest China during 1961-2011

Reference crop evapotranspiration(ET₀)is wide lyconsidered to be one of the best means to evaluate agriculture water use,which is of great importance for crop production. The agriculture in the arid region of northwest China has suffered from severe water shortage and imbalance between water quantity and land area. Under the background of global warming, it is necessary to evaluate the spatiotemporal characteristics of ET₀as it is sensitive to climate change. Observed daily data during 1961-2011 from 152 meteorological stations, including temperature, relative humidity, wind speed and sunshine hours,are used to calculate the ET₀ based on Penman-Monteith equation.Mann-Kendall, Pettitt and Inverse Distance Weighted Interpolation are used to analyze the spatiotemporal characteristics of ET₀.Results show that the annual mean ET₀is1100.4 mm/a with obvious spatial variations. Values in the south region of the Loess Plateau are the smallest, while those in a southeast-northwest strip beside the Loess Plateau are the greatest.ET₀ shows a insignificant upward trend during 1961-2011 for the whole region,and the annual increase is 0.45 mm/a; however, significant upward and downward trends are detected for 64 and 36stations, respectively.ET₀has occurred abrupt changes from 1970s to 1990s;however, the years occurring abrupt changes in the eastern part are later than those in the western part. Sensitive coefficients and contribution rates are calculated to analyze the reasons of the spatiotemporal pattern for ET₀.Results show that the spatiotemporal characteristics of ET₀are from the combined effects of climatic factors. Relative humidity and maximum temperature is the most sensitive factors for ET₀; however, wind speed and maximum temperature have the greatest contribution rates for the changes of ET₀ during the past 50 years.The changes of ET₀ in the arid region of northwest China have transformed from downward trend to upward trend since 2000s, which will exacerbate the water shortage of this region. Therefore, more attentions should be paid to it and some countermeasures should be planned.