2024年8月27日，香港大学Francis C Y Tam团队在《大气科学进展》杂志发表论文，该研究揭示了城市化对华南大湾区极端降水的影响——前季风期间对天气系统的敏感性。

该研究调查了城市化对季风前降雨的影响，使用每小时一次的气象站观测，以及采用单层城市冠层模型(WRF-SLUCM)模拟了高站观测和天气研究与预报模型。观测显示，GBA城市季风前极端降水强于周边农村地区，城市热岛(UHI)增强了城市降雨强度和概率。极端情况分为锋面型和切变线型暖扇区型。

在切变线和暖扇形系统下，由于UHI而增加的城市降雨更为明显。使用WRF-SLUCM，对四个锋面和四个切变线情况进行了动态缩小尺度，并进行了四个平行实验："Nourban"(城市被耕地取代)，“AH0”、“AH100”,和“AH300"(正常土地利用，SLUCM中的每日最大人为热量(AH)分别设置为0,100和300W/m²)。

在锋面情况下，AH0中的城市降雨量的显著减少是由于与农田相比，城市的地面蒸发(风辐散)减少(增强)。在降水过程中，强偏北风和冷空气侵入抑制了AH0和AH100的UHI；城市降雨增强只发生在AH300。相反，在切变线情况下，城市摩擦和UHI促进了当地对流和风辐合，与城市相比，在所有城市实验中都显著增加了城市降雨量。总体而言，城市化对SC季风前极端降雨的影响对天气系统的类型高度敏感，因此有必要对该季节的城市降雨进行进一步调查。

附：英文原文

Title: Urbanization Impacts on South China Greater Bay Area Extreme Rainfall - Sensitivity to Synoptic Systems during Pre-monsoon Period

Author: Chenxi Hu, Francis C Y Tam, Ziqian Wang, Xiaoyi Fang, Zong-Liang Yang

Issue&Volume: 2024-08-27

Abstract: Urbanization’s impact on pre-monsoon extreme rainfall in the Greater Bay Area (GBA), coastal South China (SC), and its relation to different synoptic systems remains understudied. This research investigates urbanization effects on pre-monsoon rainfall using hourly station observations and the Weather Research and Forecasting model with the Single Layer Urban Canopy Model (WRF-SLUCM) simulations. Observations show stronger pre-monsoon extreme rainfall in GBA cities than surrounding rural areas, with the urban heat island (UHI) intensifying urban rainfall intensity and probability. Extreme cases were classified into frontal and shear-line warm-sector types. Enhanced urban rainfall due to UHI was more pronounced under shear-line and warm-sector systems. Four frontal and four shear-line cases were dynamically downscaled using WRF-SLUCM, and four parallel experiments were conducted: "Nourban" (urban areas replaced by cropland), "AH0," "AH100," and "AH300" (normal land use, with diurnal maximum anthropogenic heat (AH) set to 0, 100, and 300 W/m² in SLUCM, respectively). In frontal cases, significantly reduced urban rainfall in AH0 is due to decreased (enhanced) surface evaporation (wind divergence) in cities compared to cropland. Strong northerly winds and cold air intrusion suppress UHI in AH0 and AH100 during the rainfall process; enhanced urban rainfall occurs only in AH300. In contrast, for shear-line cases, urban friction and UHI promote local convection and wind convergence, increasing urban rainfall significantly in all urban experiments compared to Nourban. Overall, urbanization’s influence on SC’s pre-monsoon extreme rainfall is highly sensitive to the type of synoptic systems, necessitating further investigation of urban rainfall in this season.

DOI: 10.1007/s00376-024-4114-x

Source: http://www.iapjournals.ac.cn/aas/en/article/doi/10.1007/s00376-024-4114-xviewType=HTML