湖泊对长江中下游地区降水影响的特征及机理研究

Lake has a significant impact on regional weather and climate due to its water and thermal properties different from surrounding land area. The middle and lower reaches of Yangtze River is one of the most concentrated area of freshwater lakes in China. Thus, to study the lake effect precipitation in the middle and lower reaches of Yangtze River is of great significance to economic development and people's living in this region. Due to the common effects of global warming and human activities, in recent decades the area of the lake is generally on a declining trend, but the impact of this change on regional precipitation is still unclear. In this study, a high resolution regional climate model which interactively coupled with a physically sound lake module will be used. In order to improve the simulation capability of the lake-atmosphere coupled model in the middle and lower reaches of Yangtze River, lake water temperature observation data and convectional meteorological data in this area will be used to optimize the key parameters that depended on lake type in the lake module. On this basis, the optimized lake-atmosphere coupled model will be used to study the characteristic and mechanism of lake effect precipitation in this region, as well as the possible impact on regional precipitation due to the shrink of lake. This research result can help us better understand the mechanism of lake-atmosphere interactions, and provide scientific basis for the quantitative understanding the lake effect on regional weather and climate in the middle and lower reaches of Yangtze River.

湖泊因其水热性质与周围陆地迥异，对区域天气和气候有着显著的影响。长江中下游是我国淡水湖泊分布最为密集的地区之一，研究湖泊对长江中下游降水的影响对该区的经济发展和人民生活具有重要意义。由于全球变暖和人为因素的共同影响，近几十年来该地区的湖泊面积总体呈逐渐萎缩的态势，但这种变化对区域降水的影响至今尚不清楚。本研究拟利用耦合了物理过程完善的湖面模块的高分辨率区域气候模式，充分利用该地区的湖泊观测资料和常规气象观测资料，优化该湖面模块中依赖于湖泊类型的关键参数，提升湖气耦合模式在该地区模拟能力。在此基础上，利用优化后的湖气耦合模式，研究长江中下游地区湖泊效应降水的特征和机理，以及湖泊萎缩对区域降水可能产生的影响。以期能够更好地理解该地区湖气相互作用的机理，为定量认识该地区湖泊的区域天气气候效应提供科学依据。

湖泊因其水热性质与周围陆地迥异，对区域天气和气候有着显著的影响。长江中下游是我国淡水湖泊分布最为密集的地区之一，研究湖泊对长江中下游降水的影响对该区的经济发展和人民生活具有重要意义。本研究利用耦合了物理过程完善的湖面模块的高分辨率区域气候模式，利用太湖梅梁湾所获得的铁塔观测资料、近地面空气温度以及水温等观测资料，实施集合模拟，找出了适合于该区域水体的关键湖泊参数，提高了该耦合模式对长江中下游太湖地区的模拟能力。为了识别长江中下游地区太湖的湖泊效应对当地降水的影响，我们用该优化后的湖气耦合模式在长江中下游太湖地区开展了三重嵌套高分辨率的模拟，设计了两组（有湖和无湖）对照试验。结果表明，夏季太湖水体的存在总的来说减少了当地降水，并且降水减少的区域主要发生在湖泊的下风方向。为了揭示夏季降水减少的内在物理机制，我们选取太湖湖泊效应减少降水的典型区域对进行综合的动力和热力学分析。得到的主要结论如下：夏季白天，太湖水体的存在导致降低的空气温度和潜热通量以及加强的辐散和下沉运动共同作用使该地区的边界层高度降低,对流抑制能量增加。从而使得该地区低层大气稳定度增强，抑制了热力对流活动的发展，最终导致该地区夏季降水的减少。该研究为更好地理解长江中下游地区湖气相互作用的特征和机理，以及定量认识该地区湖泊的区域天气气候效应提供了科学依据。