Breakout Summary Report
ARM/ASR User and PI Meeting
19 - 23 March 2018
Aerosols--deep convection interaction
19 March 2018
4:00 PM - 6:00 PM
30
U. Anber and J. Fan
19 March 2018
4:00 PM - 6:00 PM
30
U. Anber and J. Fan
Breakout Description
A growing body of evidence suggests a potentially significant impact of aerosols on deep convective dynamical and microphysical processes in some geographical regions, yet a comprehensive picture of this interaction is far from being fully understood due to its complex nature. For example, the impact of aerosol loading on convective dynamics and precipitation depends on environmental factors such as thermodynamic stability and wind shear as well as microphysical factors such as terminal fall velocity and ice particle size. In order to fully assess the effect of aerosol on deep convection, feedbacks from multi-scale interacting components must be accounted for. The strong coupling between cumulus convection and the large-scale environment implies that microphysical perturbations on the convective scale due to changes in aerosol propertie-scale processes. This breakout session aims to summarize recent progress in observational and modeling work on the interaction between aerosol and deep convection. It also discusses modeling approaches accounting for the interactions of large-scale dynamics and convective-scale processes towards assessing the impact of aerosol on deep convection.Main Discussion
(a) Concepts of convective invigoration and cloud invigoration.(b) Co-variability of aerosols with environmental variables.
(c) Important issues related to observational data.
Key Findings
• Observational and modeling studies suggest that aerosols can potentially lead to deep convective invigoration in warm and humid environments such as those during the GoAmazon and TWP-ICE campaigns, and ship lanes over tropical and subtropical oceans.• A new study following Li et al., 2011 (Nature Geoscience) showed that the increase of cloud top height with aerosol concentration at SGP over a long-term period results from correlation between aerosol concentration and thermodynamic conditions, suggesting current SGP observational data are insufficient to untangle significant relationships between aerosols and convective activity.
• Results of simulated aerosol impacts depend on the choice of cloud microphysical parameterizations. Bin schemes and bin-emulating schemes are generally simulating the invigoration effect on convection, while idealized simulations with two-moment bulk schemes suggest suppression of precipitation despite increase in cloud fraction (cloud invigoration).
• Environment plays an important role in determining the invigoration response: warm and humid tropics in which convective invigoration tends to occur versus dryer and colder mid-latitudes where convective invigoration does not occur easily.
• The resulting enhanced updrafts and super-cooled liquid could potentially lead to enhancement of lightening.
Issues
Despite significant progress over the last decade, aerosols-deep convection interaction research is still in its infancy. Remaining important challenges and needs include:• More locations and long-term field measurements design at warm and humid regions (preferably tropical) will help tackle the aerosol-deep convective clouds interactions more robustly and systematically with key quantity measurements such as CCN, updraft velocity, supersaturation, and microphysical properties at convective cores.
• Due to large variability in CRM/LAM model results, a model intercomparison study should be helpful, particularly with well-observed convective cases such as GoAmazon.
Needs
Despite significant progress over the last decade, aerosols-deep convection interaction research is still in its infancy. Remaining important challenges and needs include:• More locations and long-term field measurements design at warm and humid regions (preferably tropical) will help tackle the aerosol-deep convective clouds interactions more robustly and systematically with key quantity measurements such as CCN, updraft velocity, supersaturation, and microphysical properties at convective cores.
• Due to large variability in CRM/LAM model results, a model intercomparison study should be helpful, particularly with well-observed convective cases such as GoAmazon.
Decisions
The session was useful and important, and should be continued. More for discussion is needed in future sessions. Se need to organize sessions of a similar theme to monitor progress and tackle challenges.Future Plans
Organizing sessions of a similar theme to monitor progress and tackle challenges.Action Items
- The (critical) need for a dedicated field campaign targeting key measurements of the interaction between aerosols and deep convection.- Consensus on a model intercomparison project to evaluate models and address their deficiencies.