气候变化对城市年径流总量控制率分区的影响

城市地区强降水发生频次和强度的增加容易诱发内涝现象,年径流总量控制率作为海绵城市的重要设计参数,更是直接受到降水变化的影响。以江苏省为例,利用全省70个国家级气象观测站1961—2019年最新的日降水量资料评估了气候变化对城市年径流总量控制率分区的影响。研究发现,有效降水的年代际变化十分明显,1991—2019年降水日数、降水量、降水强度均比其他时间段上更多、更强;太湖流域的设计雨量较小,连云港地区的设计雨量较大,南北差异随着控制率的提高而扩大,当控制率为85%时,全省设计雨量平均值为38.1 mm,最大值是最小值的1.7倍;气候变化对年径流总量控制率分区影响明显,江苏的苏南、江淮南部大部分地区的分区变大,导致全省IV区所占面积明显增加。不同等级降水的变化趋势是影响年径流控制率分区的关键因素,大雨以上的雨日、雨量在有效降水中占比增加,则分区变大。

Influence of climate change on the volume capture ratio of annual rainfall’s partition

The increase in frequency and intensity of heavy precipitation is prone to flooding in urban areas. The volume capture ratio of annual rainfall is an important design parameter of sponge city, which is directly affected by changes in precipitation. In this paper, the impact of climate change on the volume capture ratio of annual rainfall’s partition is assessed by using the latest daily precipitation data from 70 national meteorological stations in Jiangsu province from 1961 to 2019. The spatial distribution of multi-year average effective precipitation days and effective precipitation in Jiangsu province shows that they are more in the southern region, less in the northern region, more in the coastal areas and less inland areas. The effective precipitation intensity increases from southeast to northwest. In the past 59 years, the number of effective precipitation days, precipitation amount and precipitation intensity in Sunan region have been increasing, with changes of 2.0 d/(10 a), 45.0 mm/(10 a) and 0.2 mm/d per decade, respectively. Effective precipitation has a very obvious multi-decadal characteristics. In 1991-2019, the number of precipitation days, precipitation amount, precipitation intensity are more and stronger than those in other 30-year periods. The design rainfall depth increases with the volume capture ratio of annual rainfall, it is 38.1 mm on average while the volume capture ratio of annual rainfall is 85%. The design rainfall depth in Taihu Lake is small, and it is large in Lianyungang. With the improvement of volume capture ratio of annual rainfall, the difference of the design rainfall depth between the north and the south becomes greater. When the volume capture ratio of annual rainfall is 85%, the largest design rainfall depth is 49.3 mm in Ganyu, and is the smallest 29.0 mm in Dongshan. The former is 1.7 times higher than the later. In the past 59 years, the volume capture ratio of annual rainfall’s partition in the north of the Yangtze River in Jiangsu province is zone IV, and most of Sunan area is zone III. The spatial distribution of the minimum design rainfall depth is more fragmented. The minimum design rainfall depth in the southwestern and southeastern parts of Jiangsu is less than 22 mm, and it is larger than 26 mm in Ganyu. The maximum design rainfall depth is gradually increasing from south to north. The proportion of precipitation of different intensity is the key factor that affects the zoning of volume capture ratio of annual rainfall. While the proportions of rain days and rainfall above heavy rain in the effective precipitation increase, the partition of volume capture ratio of annual rainfall rises. The area of zone IV of volume capture ratio of annual rainfall increases significantly in Jiangsu because of the influence of climate change.