华北地区光合有效辐射的计算方法研究

2004年9月—2006年10月，选择华北地区的4个观测站开展了太阳辐射（光合有效辐射PAR、可见光辐射VIS、总辐射Q等）、气象参数等的综合测量，得到了PAR、VIS等的变化特征，结果表明：PAR/Q、VIS/Q、PAR/VIS相对稳定，有明显的日、逐日和季节变化，并受到水汽、散射因子、云等因素的影响。2004—2006年禹城、栾城、香河、兴隆地区VIS/Q，PAR/Q和PAR/VIS的平均值分别为0.39，1.95 mol/MJ和4.97 mol/MJ；0.39，1.94 mol/MJ和4.95 mol/MJ；0.43，2.16 mol/MJ和4.97 mol/MJ；0.42，2.03 mol/MJ和4.89 mol/MJ。建立了计算华北地区实际天气PAR、VIS小时累计值的经验公式及PAR与VIS转换关系式，计算值与观测值符合得都比较好。考虑水汽和散射因子时，PAR、VIS计算值与观测值的相对偏差分别为13.0%、12.4%。由于某些站点可能缺少直接或散射辐射，也可以只考虑水汽因子，此时，PAR、VIS的相对偏差分别为13.2%、12.8%。对于PAR、VIS的传输和计算来说，水汽因子的作用最为重要；散射因子的作用虽弱于水汽因子，但也不应该忽视。

Calculating photosynthetically active radiation in North China

The variations of PAR and VIS were analyzed, in terms of the observation data of solar radiation (photosynthetically active radiation (PAR), visible radiation (VIS), global radiation (Q), and etc.) and meteorological factors from four stations in North China from September 2004 to October 2006. The results show that the ratios of hourly sums of PAR/Q, VIS /Q and PAR/VIS are relatively stable. The diurnal, daily and seasonal variations of them are obvious, which are influenced by water vapor, scattering factor, cloud, and etc. The averages of hourly VIS/Q, PAR/Q and PAR/VIS in Yucheng, Luancheng, Xianghe and Xinglong from 2004 to 2006 are 0.39, 1.95 mol/MJ, 4.97 mol/MJ; 0.39, 1.94 mol/MJ, 4.95 mol/MJ; 0.43, 2.16 mol/MJ, 4.97 mol/MJ; 0.42, 2.03 mol/MJ, 4.89 mol/MJ. The empirical formulae calculating hourly sums of PAR and VIS under weather conditions in North China and conversion formulae between PAR and VIS are established. The calculated values of PAR and VIS are in good agreement with the measured, and their relative biases are 13.0% and 12.4%, respectively, if water vapor and scattering factor are both considered. Considering the limitation of direct or scattering radiations at some stations, only water vapor factor can be selected, so the relative biases between the calculated and the observed are 13.2% and 12.8%, respectively. Water vapor is an important factor controling the transmission and the simulation of PAR and VIS. At the same time, the scattering factors are also important.