气候变化情景下渭河流域潜在蒸散量时空变化特征

Spatiotemporal characteristics of potential evapotranspiration in the Weihe River basin under future climate change

根据渭河流域20个气象站1959~2008年逐日气象资料,以FAO Penman-Monteith法计算的各站逐日潜在蒸散量作为标准值,对基于气温的Hargreaves法进行参数校正以使其适用于渭河流域。应用统计降尺度模型SDSM将HadCM3输出数据降尺度到各站点,生成A2,B2两种情景下各站未来日最高、最低气温数据,将其输入校正参数后的Hargreaves模型,从而分析未来气候变化情景下渭河流域潜在蒸散量以及最高、最低气温的时空变化趋势。结果表明：各站校正后Hargreaves法可用于估算未来情景下渭河流域潜在蒸散量;两种情景下流域日最高、最低气温和年潜在蒸散量较基准期均呈现明显上升趋势,且B2情景低于A2情景下增幅;各区域年潜在蒸散变化量在未来3个时期均呈现明显递增趋势,增幅较大地区主要分布在渭河南岸,而渭河北岸大部分变幅较小。

The parameters in the temperature-based Hargreaves method for the estimation of potential evapotranspiration（ETP） are calibrated by the FAO Penman-Monteith method and daily data during the period 1959-2008 at 20 meteorological stations in the Weihe River basin.To study the impact of climate change on potential evapotranspiration,the projected daily maximum and minimum air temperature（Tmax/Tmin） of HadCM3 GCM under A2 and B2 scenarios are first downscaled onto local meteorological stations using the statistical downscaling model（SDSM）.Using the calibrated Hargreaves method,the future ETP,Tmax and Tmin time series under A2 and B2 scenarios can then be calculated.The spatiotemporal characteristics of these series are analyzed.Results show that the calibrated Hargreaves method reproduces well the observed potential evapotranspiration at each of the 20 meteorological stations;upward trends in daily Tmax and Tmin and annual ETP could be significant compared to that of the baseline period 1961-1990 under both scenarios;the increase in meteorological variables would be greater under A2 than B2;over different regions of the Wei River basin,the annual ETP could be gradually increasing for the three future periods,the 2010-2039,the 2040-2069 and the 2070-2099;and the greatest increase of ETP could be expected in the south bank of the basin,while the lowest increase might be found in the north bank.