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

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.

Analysis of Meteorological Elements and Distribution Characters of Surface Solar Radiation in Guangxi

[Objective] The aim was to study the relation between solar radiation distribution and meteorological elements in Guangxi. [Method] Based on the observed data of solar radiation in Guangxi from 1995 to 2009, the total radiation, solar distribution and interannual changes in Guangxi were analyzed. By dint of observed data in Nanning station, the annual, seasonal and monthly changes of net radiation in Nanning and the linear relation between total radiation, solar distribution characteristics and interannual changes were discussed. [Result] The global radiation of surface solar radiation in the low latitude was higher tan the high latitude, as Beihai>Nanning>Guilin. The solar radiation changes and the seasonal changes in different places varied, as summer>autumn>spring>winter. The total radiation and solar radiation hours were consistent. The total solar radiation and the low cloud was in negative relation, but was in positive relation with sunny weather. The total solar radiation was in positive relation with ground temperature, except in winter. [Conclusion] The study provided effective theoretical basis and data reference to the study of climate and development of solar energy.

怒江流域近30年太阳总辐射变化趋势(英文)

Based on the data of sunshine duration,cloud cover and relative humidity from 9 stations in 1981-2008,the spatial and temporal distribution and change trend of total solar radiation in river valley basin of Nujiang were analyzed,as well as its impact factors.The results showed that annual solar radiation decreased obviously in Nujiang basin from 1981 to 1997,with the rate of-161.1 MJ/(m2·10 a),while it went up after 1997 at the rate of 111.3 MJ/(m2·10 a).Annual total cloud cover showed significant decrease trend with the rate of 1.8%/10 a,but annual low cloud cover increased at the rate of 3.2%/10 a.Contrary to the change trend of annual solar radiation,relative humidity rose at the increase of 3.1%/10 a from 1981 to 1997 and decreased significantly at the rate of 5.6%/10 a in 1997-2008.The change of water vapor pressure was consistent with relative humility change.Low cloud cover was the main impact factor of total solar radiation and had a negative correlation with total solar radiation.

East Asian summer monsoon changes in subtropical China since late Pleistocene:Evidence from the Ailuropoda-Stegodon fauna

Previous studies on the amplitude of East Asian summer monsoon(EASM)changes mainly focused on northern China(represented by the Loess Plateau).However,a rare investigation centered on the subtropical zone of southern China,where the important route for EASM moved northward or southward,especially addressing a lack of the research on mammals.The Ailuropoda-Stegodon fauna is a representative mammal fauna in southern China since the late Pleistocene.It indicates the southern mid-subtropicaltropical forest environment with tropical climate characteristics,and its southward or northward movements in the subtropical zone imply the changes of EASM intensity.Based on previous research,combined with the species characteristics and distribution range of the Ailuropoda-Stegodon fauna with tropical animals during the marine isotope stage 5(MIS5),MIS3,MIS2,and MIS1 Megathermal periods,this paper mainly investigates its evolution and the fluctuations of EASM.The conclusions include:(1)The distribution geometric centers in the MIS5,MIS3,MIS2,and MIS1 Megathermal periods are(26°14′N,111°22′E),(24°35′N,107°30′E),(22°48′N,112°01′E),and(26°19′N,112°25′E),respectively.(2)Compared with the MIS5 period,the EASM of the MIS3 and MIS2 moved 180 km and 380 km southwards,and that of the MIS1 Megathermal period moved about 10 km northwards.The EASM movement indicated by the fauna migration happened synchronous with the climate records of stalagmites in subtropical China,the sporopollen from eastern China,and oxygen isotopes from Sulu Sea.They also correspond to the peaks and valleys of the total solar radiation at 35°N in the winter half-year.This suggests that the migrations of the Ailuropoda-Stegodon fauna are consistent with the changes of the global climate,and the driving force is mainly from the changes of total solar radiation at 35°N in the winter half-year.