多组分气溶胶活化及其对云和降水影响的数值研究

Aerosols have an important effect on atmospheric chemistry throughout the troposphere and lower stratosphere. They influence the radiative budget of Earth directly and indirectly by the modification of the cloud droplet size spectrum and precipitation at the surface. Researchers are beginning to incorporate these effects into the most sophisticated weather and climate models for shallow clouds. This is because aerosol-cloud interactions are seen as one of the most important single forces that drive weather and climate change, but there are big uncertainties in the current understanding of these processes. One reason is that the aerosol model and cloud models have been paralleled developed for relatively long time. At presents, both are with very complex physics processes i.e. nucleation, condensation, coagulation and deposition etc., and so for the cloud physics which still have phase changes. To make things more difficult, there are different scale interactions from nanometers to thousand miles in terms of the aerosol effect on weather system, Let alone the climate models. So cloud physicists commonly classify the characteristics of aerosols and clouds into "maritime" and "continental" regimes, where "continental" has become synonymous with "aerosol-laden and polluted." But the fact is that there are huge variations as to the aerosol components and horizontal and vertical distributions in different regions. Most results of aerosol and cloud interactions came from the researches in Europe and North American where the aerosol concentrations are almost one order lowere than those in China. Things will be quite different in China for the aerosol indirect effect. ..In this project, a parameterization scheme on multi-components and multi-size-bins aerosol activations will be developed in terms of different aerosol composite's physics characterizations, i.e., hyperopic growth and mixing state. This scheme will be incorporated into a weather model with on-line coupled sectional aerosol modules and a two-moment cloud physics schemes. Through the activation scheme in the on-line model system time variational cloud condensation nuclei (CCN) will take the place of the constant CCN in the cloud physics. Then, the scheme will be carefully evaluated and improved with the aerosol activation measurements over China. Researches on aerosol's effect on cloud formation, precipitation and the thermal and dynamic effect on the atmospheric circulations will be carried on later. Feedbacks from the aerosol activation and the changes in the cloud, precipitation and circulation to the aerosol wet deposition will also be investigated finally.

在在线耦合了多组分分档气溶胶模式的天气模式中，研究不同的气溶胶组分排放进入大气，经过老化、相互作用之后，在不同的水汽条件下的活化机制。开发多粒径多组分的气溶胶活化成云凝结核（CCN）的参数化方案，为云物理过程提供动态的CCN谱，将气溶胶的三维分布及转化与云物理过程联系起来。通过研究动态CCN谱对云的微观特征、云中微物理过程以及降水的影响，深入理解多组分气溶胶活化与云以及中尺度天气的相互作用。同时研究气溶胶活化、与云相互作用反过来对与云和降水关系密切的气溶胶湿沉降过程的影响，提高气溶胶的模拟精度。

在中国气象局化学天气数值预报系统GRAPES/CUACE中，研发了分档多组分的气溶胶活化方案HG。HG方案与观测验证显示该方案适合我国组成复杂浓度较高的气溶胶的活化。在GRAPES/CUACE中，引进能更好的反映气溶胶和云的关系的双参云物理方案WDM6，利用HG方案，将实时活化的CCN输入到WDM6中。由于对流降水可占总降水量90%以上，本研究还将气溶胶引入对流参数化中，利用HG方案为对流云提供实时活化的CCN，最终建立了从排放-气溶胶-CCN-层云/对流云-降水的完全的气溶胶和云的完全的相互作用关系。利用此完全的气溶胶和云的关系研究了我国气溶胶对云和降水的影响机制，结果显示实时活化的气溶胶，增加了云水含量和云滴数浓度，减小了云滴半径。气溶胶对降水的影响必须综合不同的因素，只有当活化之后的云粒子collection增长加强，气溶胶才真正意义上促进降水，反之，则是抑制降水。研究还发现，实时活化的气溶胶对云的影响改进了GRAPES模式的降水模拟效果，6小时降水TS评分提高了33%，同时还一定程度上降低了模式低层温度误差。本研究结果已经在ACP杂志上发表。. 综上所述本研究在自主的模式中开发了分档多组分气溶胶活化方案，建立了物理基础较好的完全的气溶胶-云和降水的反馈关系，研究了我国气溶胶对云和降水的影响机制。本研究完成了既定的任务，也为在自主的数值模式中进一步研究我国气溶胶对云和降水的研究打下了基础。