自然与农田状态下照度计测光的偏差分析

根据色度基本原理，推导并计算了不同天气类型下照度的换算因数，并在不同天气类型下，对自然光和小麦群体不同高度透光情况进行了测定，将照度计实测照度换算出的辐射强度与实测辐射强度进行对比。结果表明：①前两种照度计可以在1、2级日光状况下用于太阳辐射测定而在3、4级日光状况下误差较大。②在作物田中，实测照度换算为辐射光量子数时，内活动面偏差比在0.2左右，而外活动面因光斑阴影作用，偏差较大，实测时应增加重复。

The Deviation Analysis of Light Measuring with Illuminometersunder Natural Sunlight and on Farmland

The conversion factors of illumination in different weather type are deduced and calculated according to the basic principle of chroma, the light penetrates through the canopy at different high level above ground are measured, and the measured radiation intensities are compared with converted ones. The results are: (1) the two illuminometers can be used to natural sunlight measured at 1 and 2 classes sunlight but not at 3 and 4 classes; (2) the deviation ratios of the quantum converted from measured illuminations are about 0 2 at the inner active surface level on farmland, meanwhile at outer active surface level the deviation ratios are higher because of the effect of light spots and drop shadows, so it naturally needs more repetitions.