湘江流域城市化对夏季降水的影响研究

The Impact of Urbanization on Summer Precipitation in the Xiangjiang River Basin

摘要: 本研究基于1965~2020年湘江流域内78个国家级气象站点的逐日降水数据，采用动态城乡站点分类法，结合线性趋势拟合、S-T检验、分数位分析等方法，量化了城市化对流域夏季降水及不同强度降水的影响特征。结果表明：① 湘江流域城市化进程呈显著的阶段性，2000年前发展缓慢，2010~2020年进入高速扩张期。② 1965~2020年湘江流域夏季总降水量呈显著增加趋势，城乡站点降水均呈增长特征，城市站点增长速率(24.77 mm/10年)略高于农村站点(24.16 mm/10年)。③ 城市化对不同强度降水的影响存在明显差异，对小雨、中雨等弱降水影响微弱，对极端降水增强效应最为突出。城市站点极端降水增幅(12.45 mm/10年)为农村站点(7.59 mm/10年)的1.64倍，且流域强降水增加高值区与长株潭城市群等城市化核心区高度耦合。④ 流域降水总量增加主要由高分位数(P70~P100)强降水驱动，城乡降水趋势差异随分位数升高而扩大，降水结构呈现“小雨占比持续下降、强降水占比逐步上升”特征，2000年后快速城市化进一步拉大了城乡强降水占比差距。

Abstract: Based on the daily precipitation data from 78 national meteorological stations in the Xiangjiang River Basin during the year of 1965 to 2020, this study quantified the impact characteristics of urbanization on summer precipitation and different precipitation intensities in the basin by adopting the dynamic urban-rural station classification method, combined with the methods of linear trend fitting, Student’s t-test and quantile analysis. The results show that: 1) The urbanization process of the Xiangjiang River Basin presented obvious phased characteristics, with slow development before 2000 and a rapid expansion period during 2010 to 2020. 2) The total summer precipitation in the Xiangjiang River Basin showed a significant increasing trend from 1965 to 2020, and the precipitation at both urban and rural stations presented a growing feature. The growth rate at urban stations (24.77 mm per decade) was slightly higher than that at rural stations (24.16 mm per decade). 3) Urbanization had distinct impacts on different precipitation intensities, with a negligible effect on light precipitation, while the enhancement effect on extreme precipitation was the most prominent. The growth rate of extreme precipitation at urban stations (12.45 mm per decade) was 1.64 times of that at rural stations (7.59 mm per decade), and the high-value areas of increased heavy precipitation in the basin were highly coupled with urbanization core areas in the Changsha-Zhuzhou-Xiangtan Urban Agglomeration. 4) The increase in the total precipitation was mainly driven by heavy precipitation in the high quantiles (P70~P100). The difference in precipitation trends between urban and rural areas expanded with the rise of quantiles, and the precipitation structure presented the characteristic of “a continuous decline in the proportion of light rain and a gradual rise in the proportion of heavy precipitation”. The rapid urbanization after 2000 further widened the gap in the proportion of heavy precipitation between urban and rural areas.