Spatial and temporal variation of solar radiation in recent 48 years in North China

Abstract

Solar radiation, being the primary energy source for all the biological processes on the earth, is an important factor concerned in many applications due to its essential role as a driving input to agronomic, ecological, hydrological and soil vegetation atmosphere transfer models. Climate change is generally accepted to be one of the most critical problems faced by mankind and it is intricately linked to solar radiation which, as the primary energy source for all of earth's living organisms, is a major determinant of the productivity of biological systems. North China, as a very important food producing region, is seriously affected by climate change, especially by the changes in solar radiation. Given the above background, the overwhelming emphasis of this study aims to establish the spatial and temporal variation of solar radiation in North China. Based on data of the Chinese Meteorological Administration (CMA) from 1961 to 2008, the geographical coordinates of 120 meteorological stations and the global digital elevation map (GT0P030, DEM), we estimated the solar radiation duration between 1961 and 2008 and analysed the spatial pattern and the change in average annual solar radiation in North China. The results showed that the annual solar radiation varied between years, and that there was a linear decreasing trend over the last 48 years: solar radiation was relatively high in 1960s after which it fell by an average of 7.72 MJ•m-2•a-1, During the period analysed, maximum annual solar radiation occurred in 1965 which is about 5173.72 MJ•m-2•a-1, while the minimum occurred in 2003 which is around 4382.51 MJ•m-2•a-1 The result of Mann-Kendall analysis indicated a mutation point in 1981, after which annual solar radiation decreased significantly in North China by an average of 203.92 MJ•m-2•a-1, with a trend that continued until 2008. Solar radiation decreased in most parts of North China with the greatest reductions of more than 300 MJ•m-2•a-1 in central and southern region of North China. There were large spatial differences in the reduction of solar radiation: where as the average decline was 7.72 MJ•m-2•a-1, where as in Beijing, Tianjin, Northern Shandong and Northern Hebei, the average annual reduction was 15 MJ•m-2•a-1, The spatial and temporal variation of solar radiation is complex and affected by many factors, including the process of industrialization and urbanization in this region. At same time, the analysis of spatial and temporal variation of solar radiation in the past 48 years in North China can play an important role in the study of potential agricultural productivity, rational prediction of changes in climate, and corresponding decision-making. Considering all these aspects, an attempt should be made to reveal the solar radiation characteristics of main crops in different growth stages in the further work, with the purpose of improving the utilization of agricultural climate resource.