探究全球尺度下强对流对气溶胶的垂直输送效率

Convective transport often dominates the vertical transport of aerosols and trace gases. Parameterizations of convective transport in atmospheric chemistry and climate models have large uncertainties. In this study, we show that the default parameterization scheme in the NSF/DOE Community Earth System Model (CESM) produces a factor of 10-1000 discrepancy in the aerosol mass for black carbon and sea salt in the middle and upper troposphere when compared with observations from a number of field campaigns. The discrepancy severely limits our ability in predicting the temporal and spatial distributions of aerosols and other tracer gases. It also prevents reliable prediction on the interactions of aerosol, clouds and radiation. A modified transport scheme, which considers aerosol activation processes above the cloud-base and aerosol-cloud interaction on the convective scale, improves model performance dramatically. Recent studies find that aerosols can be quickly activated to cloud condensations in the deep convections, and removed in cloud with precipitations. However, the default convective transport scheme fails to consider the secondary activation process, and therefore overestimates the aerosol concentration in the atmosphere. This study will introduce the secondary activation process within the deep convection to the default convective transport scheme in climate models. We anticipate that the modified scheme can better reproduce the aerosol’s vertical transport. Based on the climate model (CESM-CARMA) I developed in the recent eight years, I plan to introduce the secondary activation into the default convective transport scheme. The modified scheme is expected to provide us better prediction on aerosol’s temporal-spatial distribution, and its interactions with clouds and radiation.

强对流在通常情况下决定了大气中气溶胶和其他污染物质的垂直传输效率。在气候模式中，对流传输的参数化方案具有很大的不确定性。根据NASA和NOAA近10年的航测数据，我们发现气候模式中参数化方案大幅高估了大气中的黑碳和海盐气溶胶的的浓度高达10到1000倍。这将严重制约着我们对大气中气溶胶时空分布的预测能力，妨碍了我们定量气溶胶与云和辐射的相互作用以及评估其气候效应。最近的科学研究发现强对流中的气溶胶粒子可以被迅速核化行成云滴，并在云中随降水被清除。然而现有的对流传输模型中并没有考虑该物理过程，因而大幅高估气溶胶粒子在高层大气中的浓度。本课题将以气候模式里现有的对流传输参数化方案为基础，引入气溶胶粒子在强对流中的二次核化过程。申请人将使用自主开发的气溶胶气候耦合模式，结合多种航测数据，着眼于粒子在对流云内成核等物理过程，以此提高模式对气溶胶与云和辐射相互作用的模拟能力。

强对流在通常情况下决定了大气中气溶胶和其他污染物质的垂直传输效率。在气候模式中，对流传输的参数化方案具有很大的不确定性。本课题在气候模式里现有的对流传输参数化方案为基础，引入气溶胶粒子在强对流中的二次核化过程，结合多种航测数据，探究了粒子在对流云内成核等物理参数话过程，大幅提高模式对气溶胶与云和辐射相互作用的模拟能力，尤其是在对流层中层和上层，气候模式对气溶胶的模拟精度提高了1-2个数量级，大幅提高模式对气溶胶与云和辐射相互作用的模拟能力。模式中引入了该参数化方案后，大幅高估了大气气溶胶（例如黑碳和海盐）的模拟能力。