海雾中毛毛雨的形成机制及其对雾水沉降通量估算模型的影响

It is extremely significant to study the development of sea fog droplet collision-coalescence growth and deposition to enhance the overall understanding of the warm cloud precipitation and the coastal ecological water cycle process, since the sea fog water deposition is an important microphysical process to evaluate the life history of the fog. However, the researches involved are barely reviewed, while the quantitative understanding of the effect of the deposition estimation is still insufficient. A comprehensive spring observing project on sea fog will be conducted in Zhanjiang Donghai Island. Firstly, use drizzle / fog droplet spectrum data to divide the sea fog into two categories with / without drizzle; secondly, from the comparative analysis of water mass（water vapor + liquid droplets）balance and energy budget balance, gravity collision, turbulent diffusion and collision, boundary layer thermal and dynamical structure by the macro and micro perspective, in order to analyze the similarities and differences of the sea fog droplet spectrum broaden and deposition process of the two categories, and to reveal the mechanism of formation and maintenance of generating drizzle during sea fog periods, to establish a quantitative relationship between the sea fog and drizzle with micro-physical values; finally to be applied to parameterization of WRF/fog Deposition Estimation Scheme (FogDES) to simulate the sea fog process with / without drizzle, by contrasting with observations, eventually to assess the estimation accuracy. The results will improve the parameterization scheme of sea fog water deposition process.

海雾雾水沉降是评估雾生命史的重要微物理过程，开展海雾雾滴碰并增长和沉降过程研究，不仅对暖云降水研究具有借鉴意义，而且能增强对海滨生态水循环过程的整体认识。但目前海雾研究涉及于此还较少，且对雾滴谱中大液滴或毛毛雨滴的形成机制及其对雾水沉降估算影响的定量理解仍显不足。本项目拟选择湛江东海岛开展两期春季海雾观测。首先利用雨/雾滴谱数据将海雾过程分为有/无毛毛雨两类；其次从水（水汽+液水）质量和能量平衡、重力碰并、湍流碰并、边界层热力动力结构等宏微观角度着手，对比分析两类海雾雾滴谱拓宽和沉降过程的异同点，揭示海雾中毛毛雨的形成机制及维持条件，探究毛毛雨与海雾微物理量之间的定量关系 ，并建立雾中毛毛雨通量的参数化方案；最后将该方案应用于WRF/雾水沉降估算方案（FogDES）中，并通过模拟和实测对比验证，评估海雾及毛毛雨对FogDES估算精度的影响，所得结果将改进海雾雾水沉降过程的参数化方案。

在项目执行过程中，项目组成员围绕项目研究计划开展了项目研究工作。将我国浓雾按区域划分为陆地雾 (城市雾、山地雾)和海雾进行研究，分析雾滴谱、气溶胶、能见度以及常规气象资料，并结合其他地区结果，对比分析城市与高山、海边浓雾微物理结构以及能见度参数化方案的区域特征。相比广东湛江东海岛和广东茂名博贺地区岸边海雾个例，海上海雾水汽充足，雾滴偏大。海雾属于酸性海雾，pH值变化范围为2.51~3.50，海雾后的雨水样本pH 值则为4.05。海雾发生初期电导率比其它阶段高很多，说明海雾发生的初始阶段雾水溶解了大量的气溶胶。海上雾水中Na+和Cl-浓度最高，浓度分别为32 535 μmol/L和53 466 μmol/L，K+浓度远高于Mg2+和Ca2+，而东海岛岸边海雾相反。对海雾过程中毛毛雨进行了分析，探讨了海雾雾滴和毛毛雨微物理特征之间的联系，对海雾过程进行了模拟研究，揭示海雾中毛毛雨的形成机制及维持条件，探究毛毛雨与海雾微物理量之间的定量关系，建立雾中毛毛雨通量的参数化方案，并通过模拟和实测对比分析。