The photosynthetic active radiation(QPAR)is an important parameter in biology,ecology and agriculture,but in routine meteorological data no QPAR is observed and the observation data are also relatively less.So,the previous calculation of QPAR 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.QPAR 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 QPAR and Q are as follows: for a whole year,QPAR=0.40Q;and for a growth period,QPAR=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.
MA Jin-yu, LIU Jing-miao, LI Shi-kui, LIANG Hong, JIANG Chao-yang, WANG Bing-zhong .
Study on the Features of the Photosynthetic Active Radiation (PAR) with Experimentations and Measurements[J]. JOURNAL OF NATURAL RESOURCES, 2007, 22(5): 673-682 https://doi.org/10.11849/zrzyxb.2007.05.001