a_s和b_s取值对参考作物蒸发蒸腾量计算结果的影响

Penm an-Monte ith公式中as和bs是计算净辐射不可缺少的参数,采用江苏射阳2002年日气象资料,分别采用FAO56推荐值和邻近地区南京市的校正值进行计算,得到了日参考作物蒸发蒸腾量和相应的太阳辐射与净辐射资料。分全年、夏半年和冬半年等不同情况分析了2种取值方案计算结果的差异。结果表明:采用邻近站点推荐值计算得到的参考作物蒸发蒸腾量ET0和净辐射Rn计算结果与FAO推荐值计算结果相比偏大,并且在计算值较小的冬半年误差也相对较大。与此相反,采用邻近站点推荐值计算得到太阳辐射Rs的计算结果偏小,并且在计算值较大的夏半年误差更大。因此,参数as和bs的选择对于参考作物蒸发蒸腾量计算结果的影响是不可以忽略的,尤其在辐射较低、蒸腾较弱的冬半年,根据实测的辐射资料进行校正是很有意义的。

Influence of as and bs Values on Determination of Reference Crop Evapotranspiration by Penman-Monteith Formula

The parameters of a_s and b_s are necessary in the calculation of net radiation in the Penman-Monteith formula.Based on the daily meteorological data of Sheyang Jiansu Province,daily reference crop evapotranspiration,solar radiation and net radiation were calculated,according to the different value of a_s and b_s which are derived from FAO56 and Nanjing station respectively.Differences were analyzed in complete year,summer half year and winter half year.Results of reference crop evapotranspiration and net radiation calculated by parameter from Nanjing are bigger than results by FAO recommended parameter,especially in the winter half year when the calculate results are relatively small.On the contrary,the results of solar radiation calculated by parameter from Nanjing are smaller than results by FAO,and with a greater error in summer half year when the results are much bigger.So the error is not ignorable in the determination of reference crop evapotranspiration by using different value of a_s and b_s,especially in the winter half year with a lower radiation and evaporation,it is quiet important to calibrate the value of a_s and b_s by radiation measurement.