Seasonal Influences of Aerosol Type on Low-Level Cloud Microphysical Properties under Different AirMasses at the ARM-SGP site

The seasonal influences of aerosols on low-level clouds are being examined using a combination of surface-based and reanalysis data retrieved from the DOE Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site and second NASA Modern Era Retrospective Reanalysis for Research (MERRA-2) platforms during the period 2007-2016. Based on the 10-yr data set, a relationship between aerosol physical and chemical data retrieved from the ARM-SGP Aerosol Observation System (AOS) and aerosol component data from MERRA-2 was evident. In particular, a strong mineral dust aerosol signature was observed during the spring months due to the long-range transport from Asia. Weaker dust signals were also apparent in any given month as a result of continental airmass transport from arid regions to the west and south of the ARM SGP site. Sulfate pollution aerosols were typically observed during the summer months. Biomass burning smoke aerosols were observed primarily during the spring months (March-May) likely originating from Mexico and Central America and transported by marine airmasses originating from the Gulf of Mexico. A second maximum during the warm season months of August and September was observed as a result of a combination of regional fire activity and source regions primarily to the west, north, and south. The impacts of these three aerosol types on low-level cloud microphysical properties are also being examined in terms of the cloud condensation nuclei (CCN) number concentration (NCCN). While biomass burning smoke and sulfate aerosols readily activate as CCN and tend to be well correlated with higher NCCN values, the opposite is true for mineral dust though all three types are associated with an increase in total aerosol number concentration (NCN). Selected cases will be investigated to demonstrate the influences of various aerosol types on low-level cloud development under different airmass conditions during the 10-yr period.