Suggestion of observation-based framework designed for the study of aerosol-cloud-precipitation interactions

Description

The scale of aerosol-cloud microphysics ranges from submicron to at most millimeter scale of drizzle drop, whose interactions seem to be resolvable with in situ measurements only, or possibly ground-based remote sensing measurements such as those gathered by the ARM Climate Research Facility. The basic assumption for the observation-based aerosol-cloud interactions (ACI) study is that the horizontal variability of clouds and aerosols is trivial with the assumption of homogeneous stratiform clouds and flat surfaces so that it could provide researchers with better opportunities for the study of aerosol effects only. Even aerosol-cloud interactions are strongly modulated and controlled by environmental conditions like stability, updraft velocity, and humidity, which can be in part classified by adiabaticity (Kim et al. 2008, 2012). Extending the subject to precipitation, Lee and Feingold (2010) and Lee et al. (2012) recently emphasized and demonstrated the possible aerosol influence on cloud system organization and distributions of cumulus precipitation as well as aerosol modification of cloud microphysical properties. Cloud-aerosol-precipitation interactions (CAPI) have so complicated feedback mechanisms that it is difficult to differentiate aerosol impacts accompanying instability-driven forcing from response results such as changes in circulation and precipitation, etc., based on the general framework of ground-based remote sensings.

Probably, if mean horizontal wind is predominant, it will be possible to separate CAPI response field from aerosol forcing domain. Ground-based remote sensings would be arranged with help of an available ARM Mobile Facility, considering suitable properties for each forcing and response domain, respectively. Temporal resolution and spatial distance of selected instruments should be identified in advance by carefully designed simulations with varying environmental conditions—mean advection wind, updraft velocity, cloud-top height, temperature profile, etc. The response area (or distance) can be determined by comparing advection and updraft time scales. Certainly, synthesizing ground and satellite remote sensings and simulations for the forcing and response domains will be ideal in monitoring changes in dynamic fields and eventually for the fundamental understanding of CAPI.