Selecting the Liuyuankou irrigation area in Henan Province as the representative area ,the Valiantzas e-quation with the air relative humidity ( RH ) as the input parameter is improved and that based on the characteristic tem-perature was also established in this paper .Using the multiple regression method ,an improved Valiantzas equation with the input of characteristic temperature and daily ordinal number was established ,and the accuracy of the model was veri-fied .Compared with original equation ,the improved Valiantzas equation had a 12 .4％ reduction in the relative error and a 37 .4％ in root mean square deviation .In addition ,the correlation coefficient was increased by 13 .4％ .Therefore ,the improved Valiantzas equation could provide basic information about crop water requirement forecast at ten-day scale .%根据黄河调度旬方案编制对作物需水量逐旬预报的要求,分析了参考作物需水量计算方法.以河南省柳园口灌区为典型,对以空气相对湿度等为输入参数的Valiantzas方程进行了改进,研究建立了基于特征气温的空气相对湿度预测方法.采用多元回归方法,建立了以特征气温、日序数为输入的改进Valiantzas方程,并对模型精度进行了验证.研究表明,改进的Valiantzas方程的相对误差比原方程可减少12.4％,均方根偏差降低37.4％,相关系数提高13.4％.同时,改进的Valiantzas方程能够实现对未来10 d作物需水量的预测,符合黄河水量旬精细调度对基础数据中期预报的要求.
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