Li-cor仪器太阳辐射测量单位定量变换的应用研究

因研究的角度不同，辐射研究结果有能量、亮度、量子数等方面的量纲，实践中不同单位之间换算很有必要。该文研究了太阳辐射测定中几个单位的定量变换方法，得出了相应的变换系数；并实测了植物冠层上和冠层内太阳辐射，并对单位变换系数进行了检验，结果表明：在冠层上，单位变换差异晴天仅为7%，阴天为2%，处在仪器测定辐射的相对误差范围内；在植物冠层内，线状辐射仪和辐照度仪同时采样，以线状辐射仪测得结果为基准，相同时刻辐照度仪测得结果经换算成辐射量子流密度单位后，与线状辐射仪对比差异全天平均达25%，远大于冠层上；光斑作用使LI－200辐照度仪在群体内测光产生较大误差。除中午辐射最大值，光斑最多时段以外，线状传感器能消除光斑的影响。

Application of quantum unit conversion in solar radiation measurement using Li-cor instruments

Due to the different research angles, researches on the radiation often have different units of the energy, the illumination, and the quantum amounts, which are necessary to be conversed into each other practically. The authors studied the methods of the units in solar radiation measurement, and obtained some conversion coefficients. The conversion coefficients were tested by the actual measured results of solar radiation above and under the different plant canopies using the most advanced radiation instruments made by Li-cor of U.S.A. The results show that the relative errors of conversion above the plant canopies are 7% and 2% in clear and cloudy weather, respectively, which are within the relative error range of the radiation instruments. Under the plant canopies, when the LI-191 and LI-200 are used to sample simultaneously and the results measured by LI-200 are conversed into quantum unit, the average difference between the results of the two sensors during the whole day is 25%, which is much greater than those above the canopies. The great errors of LI-200 sensor under the plant canopies are caused by the facula. The line sensor eliminated the facula effect except when too many are there during the noon period.