Homogenization and trend analysis of the 1958-2016 in-situ surface solar radiation records in China1

AbstractThis paper presents a method to homogenize China’s surface solar radiation (SSR) data and uses the resulting homogenized SSR data to assess the SSR trend over the period 1958-2016. Neighboring surface sunshine duration (SSD) data are used as reference data to assess the SSR data homogeneity. A Principle Components Analysis is applied to build a reference series, which is proven to be less sensitive to occasional data issues than using the arithmetic mean of data from adjacent stations. A relative or absolute test is applied to detect change points, depending on whether or not a suitable reference series is available. A Quantile-Matching method is used to adjust the data to diminish the inhomogeneities.As a result, 60 out of the 119 SSR stations were found to have inhomogeneity issues. These were mainly caused by changes in instrument and observation schedule. The non-climatic changes exaggerated the SSR change rates in 1991-1993 and resulted in a sudden rise in the national average SSR series, cau...