榆林地区1970-2010年气候因子变化特征分析

榆林位于陕西省黄土高原和内蒙古毛乌素沙地的交接地带,是我国北方农牧交错带的典型地区,地理环境复杂多样,致使该地区生态环境比较敏感,极易受到气候变化和人类活动的影响和干扰。为探讨榆林地区气候变化的发展趋势和特征,基于1970-2010年气象资料,对榆林地区5个气象指标(平均最低气温、平均最高气温、平均气温、降水量和太阳辐射)进行空间插值,进而分析了各指标的季节和年际变化特征,即趋势变化、周期性变化、突变特征。结果表明,榆林地区气温呈现上升的趋势,春季和冬季的气温增幅对全年的增温贡献较大;降水量波动变化较大,夏季降水量减少比其他季节明显。20世纪80年代的降水量较大,90年代前期和中期降水量减少,而90年代后期降水量出现了回升趋势;41 a来的太阳辐射呈现下降的趋势,夏季太阳辐射的减少对全年太阳辐射的减少贡献较大。5个气象指标的周期性变化在大时间尺度上(如25～32 a)变化比较稳定,在小时间尺度上差异比较明显;降水量和平均最低气温在三类时间尺度(如5～15 a、15～25 a和25～30 a)上的周期比较明显。另外,除春季降水量外,其他季节的气象因子在1970-2010年期间变化频率有增加、时间间隔减少的趋势,说明最近10～20 a榆林地区气候变化比较活跃。对榆林地区气候变化特征进行分析,为进一步揭示气候变化下榆林地区农业生产系统的影响机理提供理论基础,为当地政府制定农业生产政策提供决策支持。

Characteristics of climate factor change in Yulin Region during 1970 -2010

Yulin locates on a typical agro pastoral ecotone of North China between Loess Plain in Shaanxi Province and Mu Us sandy land in Inner Mongolia Autonomous Region. In order to understand the development trend and characteristic of climate change in Yulin region, the paper used spatial interpolation to analyze seasonal and inter annual trend and characteristic of climate in Yulin on the basis of meteorological data in Yulin during 1970-2010. Five meteorological indexes (such as, average minimum temperature, average maximum temperature, precipitation, and solar radiation) were used for the analysis of climatic characteristics, for example, change trend, periodic variation, and abrupt change. Five meteorological indexes were interpolated into raster layers by using of Kring method, and further clipped by the administrative line of Yulin region. The average value of five metrological indexes in Yulin region were abstained from raster layers based on spatial overlay analysis at last. Then, regression analysis and moving average method were used for trend analysis, Mann-Kendall method and Moving WTBX]tWTBZ]-test technique for abrupt change, and wavelet analysis for periodic analysis. Through the analysis above, the results indicate that the average temperature in Yulin increased during 1970-2010. The temperature in spring and winter contributes relatively higher to the rising of annual temperature than that in summer and autumn. Annual and seasonal precipitation fluctuated obviously during this period. The precipitation in summer reduced relatively higher than that in other season. As well, the precipitation increased before 1990s, decreased at the beginning and middle of 1990s, and picked up since the late 1990s. The solar radiation in past 41 years had a downward trend, and reduction of the solar radiation in summer showed higher contribution to the decreasing of annual solar radiation. The periodic variation of five meteorological indexes was much stable in the lager time scale, such as 25-32 years. Precipitation and average minimum temperature in the four seasons owned obvious periodic characteristic at three kinds of time scale. In addition, except for precipitation in spring, the frequency of meteorological factors in other seasons during 1970-2010 had a rising trend, and the time interval decreased. Thus, the climate change was much active during the last 10 or 20 years in this region.