| Shanxi Province is situated in the east of the Loess Plateau and to the west of the North China Plain, between latitudes34°34’ and40°43’N and longitudes110°14’and114°33’E, with an average elevation of about900m above sea level and an area of about15.63×104km2. It is featured by a continental monsoon climate. The specific location and topography may have resulted in a complicated pattern of climate change. A thorough analysis of climate change across Shanxi is paramount for local policymakers and communities to fully understand the basic characteristics of climate change, and to explore further its causes and effects, and devise more effective management strategies.Within this context, the primary objective of this study is to explore the temporal trends and spatial patterns of climate change over the period1959-2008in Shanxi Province in terms of annual mean temperature, annual precipitation, temperature and precipitation extremes, frost-free and frost seasons and annual sunshine duration. The analysis is performed based on the data of air temperature and precipitation from all61available stations, and the data of last spring frost date and first fall frost date, and sunshine duration from all62available stations. At the same time, to clarify the possible differences in the long-term trends of climatic change between Shanxi and the NNCP (the northern half of the North China Plain)(i.e. the latitudinal range of the North China Plain corresponding to that of Shanxi), the change trends for annual mean temperature, annual precipitation, temperature and precipitation extremes, and annual sunshine duration are analyzed for the NNCP. Additionally, the change trends for air temperature and precipitation, air temperature and precipitation extremes and sunshine duration over the period1959-2010in Shanxi are updated since additional data for the recent two years (2009-2010) have become available, and the consistency of the change trends between the50-and52-year periods is examined at the same time.The results show that a significant increasing trend is found for the annual mean air temperature over the period1959-2008in Shanxi. The province-averaged annual mean air temperature has increased at a rate of0.24℃/10year, with a50-year trend of1.20℃, well above the Northern Hemisphere average (0.75℃) or global average (0.65℃) during the same period. The warming has mainly occurred since1987, and it has accelerated since1997. Winter, spring and autumn have experienced the greatest, second and third increases in mean air temperature, respectively. Spatially, there is an enhanced warming trend from south to north across Shanxi, and the most remarkable warming occurs in the northern area. A significant drying trend for the annual precipitation over the period1959-2008in Shanxi is detected. The province-average annual precipitation has decreased by99.2mm, at a drying rate of19.84mm/10year over this period. The decrease in annual precipitation in Shanxi is mostly caused by precipitation decline in rainy season (June-September). An abrupt decrease in annual precipitation is found in1979, with the precipitation in sub-series1979-2008having decreased by51.58mm. Spatially, there is a decreasing drying trend from south to north across Shanxi, and the most remarkable drying occurs in the southern area.Significant and symmetric increasing trends for the annual mean maximum and mean minimum temperatures (TXam, TNam) are revealed, and no significant decrease trend for the annual diurnal temperature range (DTR) is detected over the past50years in Shanxi. Significant increasing trends for warm days and nights (TX90p, TN90p), the highest and lowest maximum and minimum temperatures (TXx, TXn, TNx, TNn) and the growing season length (GSL) are found, while the significant decreasing trends for cold days and nights (TX10p, TN10p) and frost days (FD) are detected. Significant decrease trends for the number of heavy precipitation days (RIOmm) and wet day precipitation (PRCPTOT) are also found. However no significant trends have been identified for maximum1-day precipitation (RX1day), maximum5-day precipitation (RX5day), simple daily intensity index (SDⅡ), very heavy precipitation days (R20mm), torrential rainfall days (R50mm), very wet day precipitation (R95pTOT) and extremely wet day precipitation (R99pTOT).Significant advancing trend for the last spring frost date (LSFD) and a non-significant delaying trend for the first fall frost date (FFFD) over the period1959-2008in Shanxi are found. Consequently, significant lengthening trend for the frost-free season (FFS) is detected over the past50years in Shanxi. The province-averaged annual mean frost-free season has lengthened by13.2days over past50years. The changing for the LSFD, FFFD and FFS mainly occurred since1998. Spatially, there is an enhanced lengthening FFS trend, with an enhanced advancing (delaying) trend of LSFD (FFFD), from south to north across the province.Significant decreasing trend for the annual sunshine duration over the period1959-2008in Shanxi is found. The province-average annual sunshine duration has decreased by327.0hours over past50years. The decreasing for the annual sunshine duration mainly occurred since1983. Spatially, there are stronger decreasing trends for the annual sunshine duration in Xinzhou-Dingxiang basin, Taiyuan basin, Linfen basin and Yuncheng basin, and weaker decreasing trends in southernmost and northernmost areas within the province.Although the entire area of Shanxi and NNCP have been grouped into the North China region and assessed together in some of the previous studies for China, the results of the present study demonstrate that climate change trend for the NNCP are obviously different from that for Shanxi. The annual mean temperature increase is higher over the NNCP (1.50℃/50year) than Shanxi (1.20℃/50year). All seasons have experienced significant increases in mean air temperature over the NNCP. The regional-averaged annual precipitation has no significant decrease over the past50years. The warming rate of the annual mean minimum is nearly three times that of the mean maximum temperatures over the past50years in the NNCP. Consequently, the diurnal temperature range (DTR) has decreased significant in this region. The warming trends for the nighttime indices (TN90p, TN10p, TNx, and TNn) are stronger than those for the daytime indices (TX10p, TX90p, and TXx). The annual growing season length (GSL) has a larger increase over the NNCP (18.8d) than Shanxi (13.3d) during the past50years. The non-significant decreasing trends for the heavy rainfall days (R10mm) and wet day precipitation (PRCPTOT) are detected over NNCP. In addition, the annual sunshine duration decrease is higher over the NNCP (472.5h) than Shanxi (327.0h) during the past50years.The temporal trends in climatic indices over the last52years (1959-2010) are highly consistent with those for the last50years (1959-2008) in Shanxi. The province-averaged annual mean air temperature has increased at a rate of0.25℃/10year, with a52-year trend of1.32℃, and the annual precipitation has decreased at a rate of-13.66mm/10year, with a52-year trend of-71.02mm. No significant trend in DTR has been identified over the past52years. Significant increasing trends have been found for TX90p and TN90p; TXx, TXn, TNx and TNn; and GSL over the52-year period, while significant decreasing trends have been detected for TX10p, TN10p and FD over the same period. Significant decreasing trends have been revealed for R10mm and PRCPTOT over the52-year period. Similarly, no significant trends have been seen for RXlday, RX5day, SDII, R20mm, R50mm, R95pTOT and R99pTOT over the last52years. Additionally, the province-averaged annual sunshine duration has decreased at a rate of-70.08h/10year, with a52-year trend of-364.42h. |
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