光合有效辐射是生物、生态和农业常用的重要参数,常规气象资料中没有该资料,实测结果也比较少,以往多采用经验气候学计算获得。论文基于固城站观测辐射资料,对光合有效辐射特征分析的结果表明:光合有效辐射（PAR）占总辐射（Q）的比值(η_PAR)分布呈近似钟型,有60%的比值分布在0.35～0.45之间。η_{PARPARPARPARPAR})与Q的关系为:全年Q_PAR=0.40Q,生长季Q_PAR=0.41Q,这一结果与以往国内一些实测结果相近。论文用此值重新评估华北平原光合生产潜力的结果表明,以往估算光合生产潜力常采用η_PAR

The photosynthetic active radiation(Q_PAR)is an important parameter in biology,ecology and agriculture,but in routine meteorological data no Q_PAR is observed and the observation data are also relatively less.So,the previous calculation of Q_PAR often uses experiential climatology method.In this paper,the characteristics of photosynthetic active radiation are analyzed by using radiation data from Gucheng Experimental Station.The results show that the ratio of photosynthetic active radiation to global radiation(η _PAR)presents an approximate campanulas distribution with 60% ofη _PAR ranging between 0.35-0.45.The tendency of daily variation forη _PAR in sunny day presents a single-peak pattern that theη _PAR is high at noon and low in morning and evening.At the same time,in cloudy day,the daily variation of theη _PAR fluctuates while the cloud cover changes,and theη _PAR in cloudy day is higher than that in sunny day.In addition,the yearly variation ofη _PAR presents a tendency that it is lower in winter and spring but higher in summer and autumn.Q_PAR and Q show an evident tendency of single-peak patterns.The mean annual value ofη _PAR is 0.40 and 0.41 during growth period.The relationships of Q_PAR and Q are as follows: for a whole year,Q_PAR=0.40Q;and for a growth period,Q_PAR=0.41Q.Generally,the result is similar to some measurement results in China.The potentiality of photosynthetic production is evaluated by using theη _PAR in this paper.The results shows that the potentiality of photosynthetic production evaluated previously by usingηPAR(0.47～0.50) is obviously higher than the measurement results.In addition,the causes of the variation of the photosynthetic active radiation are related to the solar altitude,cloud cover,water vapor and dust in atmosphere.In conclusion,some causes are very complicated,so further studies are needed.