热岛与海风相互作用对珠三角午后强降水影响的观测和模拟研究  

OBSERVATIONAL AND NUMERICAL STUDY OF IMPACTS OF INTERACTIONS BETWEEN HEAT ISLAND AND SEA-BREEZE ON THE LATE-AFTERNOON SEVERE PRECIPITATION OVER PEARL RIVER DELTA

作　　者：蒙伟光[1] 郑艳萍[2,3] 王宝民[3] 张艳霞[1] 蒋德海[1] 袁金南[1] 罗聪 

机构地区：[1]中国气象局广州热带海洋气象研究所/广东省区域数值天气预报重点实验室,广东广州510080 [2]广东省气象信息中心,广东广州510080 [3]中山大学大气科学系,广东广州510275 [4]广州市气象台,广东广州511430

出　　处：《热带气象学报》2014年第6期1011-1026,共16页Journal of Tropical Meteorology

基　　金：国家自然科学基金项目(41105006);公益性行业(气象)科研专项(GYHY200906026)共同资助

摘　　要：通过地面风场加密观测及雷达回波分析表明,2011年6月21日午后海风引发对流首先出现在珠江口,之后随着海风向内陆深入并与珠三角地区热岛环流相互作用,引起对流发展强度增强,为广州市带来了一次雨强达60 mm/h的强降水过程。在对观测资料进行分析的基础上,应用具有云分辨尺度的CR-WRF模式并耦合城市冠层模式,模拟研究了珠三角城市地表对海风发展及其与城市热岛相互作用对强降水过程的影响。与观测结果相对比,尽管模拟最大降水与观测比较仍有一定差距,但模拟结果反映出了海风发展与热岛相互作用对强降水的影响过程。对比模拟试验结果表明城市地表的影响可在城市区形成更高的温度,热岛与海风相互作用可导致广州城区南部降水增多15 mm以上,接近总降雨量的30%。无城市地表影响时,模拟的海风可更早影响到城市区并到达更北位置,造成降水落区偏北。对其影响物理机制的分析表明,受城市热岛影响,边界层中可形成干暖"盖"对流稳定层,抑制不稳定能量过早释放,使对流系统一旦发展起来后表现更激烈,并在边界层形成更强的外流。强降水对流系统在边界层形成的外流与热岛入流一起共同对海风形成阻挡作用,是导致广州城区南部降水增强的重要影响因子。Intensive observations of surface wind field and analysis of radar echo indicate that, in the afternoon of June 21,2011, sea-breeze induced convection ftrst appeared in the Pearl River estuary, then as the sea-breeze moved inland and interacted with the urban heat island （UHI） circulations over PRD （Pearl River Delta）, it enhanced the convection and brought to Guangzhou severe precipitation with hourly rainfall of nearly 60 mm. Based on observational analysis, cloud-resolving CR-WRF numerical simulations coupled with an urban canopy model were carried out to investigate the PRD urban land surface effects on the sea-breeze and impacts of heat island interacting with sea-breeze circulation on the precipitating convective systems. Though the maximum precipitation amount was simulated a bit small as compared to the observation, the model captured most characteristics of interactions between the sea-breeze and UHI and their impacts on the late afternoon rain event. Model sensitivity study revealed that the urban land surface was able to produce higher temperature around the city and lead to an enhanced precipitation totals by 15mm, about 30% of the total rainfall amount, to the south of Guangzhou city. Lacking urban land surface impacts, the simulated sea-breeze should affect the city earlier and get through the urban areas, causing the precipitation to fall northward to the observation. Mechanism analysis shows that a warm and dry ＂lid＂, a stable convective cap, was created by the urban effect in the middle layers of the atmosphere above the surface, which was able to confine the earlier release of unstable energy and initiate violent convection, leading to more intensive boundary outflows. Besides, it was suggested that these strong outflows from the precipitating convective systems and UHI southward inflows may play an important role, by blocking the inland-moving sea-breeze, in rainfall increase in or upwind of the central urban area.

关 键 词：强降水 城市热岛 海风 数值模拟 

分 类 号：P435[天文地球—大气科学及气象学]