北京地区汛期降雨时空演变特征及城市化影响研究

近年来伴随着城市化的快速发展,世界各大城市汛期极端降雨事件频发,洪涝造成的社会经济损失日益严重,在此背景下,分析中国首都北京各城市化阶段汛期降雨变化显得非常有必要。论文基于30个雨量站1963—2012年汛期降雨资料,运用线性回归、滑动平均以及ArcGIS空间分析等方法对北京汛期降雨时空特征进行分析,通过对比城区和近郊区汛期降雨之间的差异来研究城市化对汛期降雨特征的影响,同时利用北京不同城市化阶段土地利用数据分析了城市下垫面变化对降雨的影响,得出以下主要结论：① 北京各区域汛期降雨时间上整体呈现下降趋势,空间上整体表现为由东向西呈逐渐减小的趋势。② 北京山区最容易发生小雨和中雨;城区则更容易发生中雨以上等级降雨事件,特别是暴雨和大暴雨;近郊区发生小雨和中雨概率与城区接近,但大雨以上等级降雨事件发生可能性小于城区;远郊发生各等级降雨事件的可能性均较大。③ 相对于北部近郊而言,在不同城市化发展阶段,城区降雨比南部近郊更大,但城市化增雨效应在城区与北部近郊之间也有所体现。④ 随着城市化的发展,北京城区和郊区城镇建设用地面积持续增长,原有下垫面条件被改变;由于城区城市化进程比近郊区更快,下垫面条件的改变使得城区汛期降雨量大于近郊区,且更易发生大雨以上等级降雨事件。

Temporal and spatial features of precipitation and impact of urbanization on precipitation characteristics in flood season in Beijing

In the process of urbanization, the original landform is inevitably changed, which directly affects the dynamic characteristics of the underlying surface of cities. On the other hand, with the increase of population, high density of buildings, and the emission of all kinds of waste and heat to the atmosphere, the thermodynamic characteristics of the underlying surface and the air above the city, as well as the condensation nucleus of the atmospheric cloud induced rain are all changed, which directly affect rainfall. Beijing as the capital city of China has experienced rapid development of urbanization in the recent decades. Extreme rainfall events and heavy floods in flood seasons have become more frequent and the socioeconomic losses caused by floods have become increasingly serious. In this case, it is very necessary to study the relationship between urbanization and rainfall. Based on the precipitation data of 30 stations during 1963-2012, the temporal and spatial features of precipitation in Beijing flood season were analyzed by linear regression, sliding average, and ArcGIS spatial analysis. In addition, the data were used to research the impact of urbanization on precipitation characteristics in flood season by comparing the differences between urban and suburban areas. Land-use data of different urbanization stages in Beijing were used to analyze the effect of the change of urban underlying surface on rainfall. The results indicate that: 1) Precipitation in the flood season showed a downward trend and the overall spatial pattern is gradual decrease from east to west. 2) Light rain and moderate rain were most likely to occur in Beijing mountainous areas, while urban areas were more prone to moderate rain and heavy rain events, especially rainstorm and heavy rain. The frequency of light rain and moderate rain in the suburbs was close to that in the urban area, but the frequency of rainfall events above the heavy rain level was less than that in the urban area. The frequency of all grade rainfall events in the far suburbs was higher. 3) Compared with the northern suburb, the rainfall in the urban area was greater than that in the southern suburb at different stages of urbanization, but the effect of urbanization was also reflected in the rainfall difference between the urban area and the northern suburb. 4) With the development of urbanization, the area of urban construction land in Beijing and suburban areas continues to increase. However, because the urbanization of urban areas is faster than that of peri-suburbs, the situation of the underlying surface of urban areas also changes more, which makes the rainfall in flood season in urban areas higher than that in the suburbs and rainfall events above the grade of heavy rain are more likely to occur.