黄土高原半干旱区降水量对当地气候变化的响应

利用毛乌素沙漠边缘的丘陵沟壑区的观测站降水量资料,通过Mann-Kendall法等数理统计方法,分析陇东北部地区降水量对当地气候变化的响应特征。从56 a的降水量统计来看,降水呈现出逐年减少的趋势,其中年降水量、春季降水量、秋季降水量序列的线性倾向率分别为-7.36、-2.27、-6.35 mm/10 a,夏季降水量序列的线性倾向率为0.69 mm/10 a,这说明四季当中只有夏季降水量呈现出上升的变化趋势。通过对降水量的多时间尺度分析发现,年降水量存在着至少3个尺度的变化结构,主要的变换集中在5、10~15、25~30 a的尺度,在25~30 a的时间尺度上最为显著,降水量经历了偏多-偏少-偏多-偏少的交替变化,1970年前、1984~1997年降水量较多,1970~1984、1997~2007年降水量较少,2007年之后降水量又开始趋于增多,根据降水量的小波方差分析,确定25~30 a是降水量序列变化的第一主导周期。通过Mann-Kendall突变检验发现降水量在1968年之后减少的趋势明显,确定突变点为1968年。通过研究降水量与其他气象要素的相关性发现,夏季气温、秋季的日照时数,春季的地表温度伴随着相应时间段降水量的变化,均表现出负相关的变化特征,只有秋季降水量与相对湿度表现为正相关的变化规律。秋季相对湿度与降水量的变化关系最为密切,相关系数最大达到0.71,其后依次是秋季降水量和日照时数的0.60、春季降水量与地表温度的0.36,夏季气温与降水量的0.35。关系模型的建立说明通过降水量的变化情况在一定程度上可以反映出其他气象要素的变化规律,其共同影响着当地的气候环境。

Response of Precipitation to Local Climate Change in Semi-arid Region of Loess Plateau

Using the observation in hilly and gully area of Maowusu desert station, climatic characteristics of precipitation and temperature and sunshine hours, through the Mann-Kendall and other methods of mathematical statistics, the response characteristics of the precipitation in the northeast of Gansu local climate change was analysised. From 56 a of precipitation statistics, the precipitation showed a trend of decreasing year by year. The linear tendency rate of annual precipitation, spring precipitation and autumn precipitation series were -7.36, -2.27, -6.35 mm/10 a, respectively. The linear tendency rate of summer precipitation series was 0.69 mm/10 a, which showed that only in the four seasons of summer precipitation showed a rising trend. Based on the multi time scale analysis of precipitation: There were at least three scale changes in precipitation. The main transformation was concentrated in 5, 10~15, 25~30 a scale, the most significant in the time scale of 25~30 a. Precipitation had experienced more, less, more, less change process, 1970 years ago, 1984~1997 precipitation were more, 1970~1984, 1997~2007 precipitation were less, in 2007 after the precipitation began to increase. According to the wavelet variance analysis of precipitation, determination of 25~30 a was the first dominant period of the change of precipitation series. Through the Mann-Kendall mutation test, it was found that the precipitation decreased trend was obvious after 1968, and the mutation point was 1968. By studying the correlation between precipitation and other meteorological elements, it was found that summer temperature and sunshine hours in autumn, the surface temperature in spring were accompanied with the change of precipitation in the corresponding time period, all of which showed a negative correlation. Only the positive correlation was shown between the fall precipitation and relative humidity. It was clear that the relationship between the relative humidity and precipitation was the most closely, and the correlation coefficient was 0.71. Then, it was the autumn precipitation and sunshine hours of 0.60, spring precipitation and surface temperature of 0.36, summer air temperature and precipitation of 0.35. The establishment of the relationship model showed that the change of the other meteorological factors could be reflected by the change of precipitation, which together affected the local climate environment.