Effects of cloud,atmospheric water vapor,and dust on photosynthetically active radiation and total solar radiation in a Mongolian grassland

作     者：Tserenpurev BAT-OYUN Masato SHINODA Mitsuru TSUBOn 

作者机构：Meiji UniversityTokyo168-8555Japa Arid Land Research CenterTottori UniversityTottori 680-0001Japan 

出 版 物：《Journal of Arid Land》 (干旱区科学（英文版）)

年 卷 期：2012年第4卷第4期

页      面：349-356页

核心收录：

学科分类：0830[工学-环境科学与工程（可授工学、理学、农学学位）] 090503[农学-草业科学] 0909[农学-草学] 0905[农学-畜牧学] 09[农学] 0903[农学-农业资源与环境] 

基　　金：supported by the Global Center of Excellence for Dryland Science Program of the Japanese Society for the Promotion of Science 

主　　题：clearness index dust storm photosynthetically active radiation total solar radiation water vapor pressure 

摘      要：Photosynthetically active radiation （PAR） is an important input parameter for estimating plant produc- tivity due to its key role in the growth and development of plants. However, a worldwide routine network for sys- tematic PAR measurements is not yet established, and PAR is often calculated as a constant fraction of total solar radiation （SR）. Although the ratio of PAR to SR （PAR/SR） has been reported from many places, few studies have been performed for dry regions. The present study was therefore carried out in an arid region of Mongolia to obtain PAP-JSR and examine its dependency on sky clearness （the clearness index）, water vapor in the atmosphere and aeolian dust. Continuous measurements of PAR and SR were taken every one second using quantum and pyranometer sensors, respectively, and the readings were averaged and recorded at intervals of 30 minutes for a period of 12 months. The lowest monthly mean daily PAR/SR occurred in April （0.420）, while the highest ratio was observed in July （0.459）. Mean daily PAR/SR during plant growing season （May-August） was estimated to be 0.442, which could be useful for modeling plant productivity in the study area. The annual mean daily PAR/SR （0.435） was lower than the values reported in many previous studies. This difference could be explained with the regional variation in climate： i.e. drier climatic condition in the study area. PAR/SR was negatively correlated with the clearness index （r= -0.36, P〈0.001）, but positively with atmospheric water vapor pressure （r=0.47, P〈0.001）. The average PAR/SR was significantly lower （P=0.02） on the dusty days compared to the non-dust days. Water vapor in the atmosphere was shown to be the strongest factor in the variation of PAR/SR. This is the first study examining PAR/SR under a semi-arid condition in Mongolia.