Physicochemical Measurements of Trade Wind Aerosol to Elucidate Seasonal Differences in Marine Boundary Layer-Free Troposphere Exchange
Abstract
PROJECT SUMMARY/ABSTRACTApproved for Public ReleaseThis project leverages a collaboration between the University of Miami, the Naval Research Laboratory, the University of Wisconsin, and the University of Michigan in response to the Direct Research Initiative (DRI): #Moisture and Aerosol Gradients/Physics of Inversion Evolution (MAGPIE)#. We will combine in situ measurements of aerosol size, mixing state, and morphology with both aerosol radiative measurements as well as high spectral resolution lidar (HSRL) of aerosol and cloud vertical profiles including in the near surface environment at high spatial resolution. These measurements address the DRI science question #How do warm, moist, and aerosol laden air parcels originating near the surface travel through the boundary layer, clouds, and exchange with the free troposphere? And #How do cloud processes influence MABL motions down to the ocean#s surface?#. As such, our proposed measurements provide insight into #how inversions, aerosol/cloud particulates, and moisture fluxes interact as a holistic system#. We propose to use the Ragged Point atmospheric research site operated by the University of Miami to execute our proposed measurements. The site is a receptor for locally emitted sea spray aerosol in addition to dust and smoke transported at altitude from Africa that demonstrate strong seasonality. The overall goal of our proposal is to probe the impact of long-range dust and smoke transport events on airmass mixing and exchange in the marine boundary layer as well as the impact of dust and smoke on vertical gradients in radiation, cloud structure, and inversions. In achieving this goal, we will test several hypotheses including: 1) Sea salt scatters light less than expected due to organic coatings on the particles while African dust and smoke strongly increase aerosol absorption, 2) Dust transported at lower altitudes in winter and spring will be more aged compared to summertime dust and co-transported with smokeincreasing cloud fraction in the near-surface environment, 3) HSRL measurements validated with in situ aerosol measurements will show more frequent dust and smoke transport events, especially in the marine boundary layer and near surface, than predicted by current remote sensing products, and 4) Aerosol mixing state and source can be used as fingerprints of airmass mixing through up and down drafts. To test our hypotheses, we will perform continuous measurements of dust, light absorbing carbonaceous aerosol, aerosol optical depth (AOD), and particle size distributions. Intensive measurements of aerosol mixing state will be performedduring dedicated field studies in summer (when dust transport is at an annual maximum), and winter and spring (when dust and smoke co-transport events peak). We will then compare our in-situ aerosol measurements to the HSRL and NRL#s radiative measurements in order to elucidate the exchange of air masses that help mix the boundary layer through up and downdrafts as well as the impact of sea spray aerosol and African smoke and dust on aerosol radiative properties, cloud structure, and inversions that can suppress convective mixing. Our aerosol measurements will also provide insight into whether dust undergoes chemical aging during transport, which critically affects dust-cloud interactions as well as dust radiative properties. Further, our measurements of size and particle sphericity will validate aerosol classification data products from the HSRL and remote sensing products. The proposed work will generate multiple benefits for ONR including an improved understanding of: 1) aerosol-cloud interactions that affect cloud structure and formation, 2) the aerosol radiation budget, and 3) the role of aerosols in maintaining inversions over the North Atlantic Basin. This work will lead to improvements in the next generation of naval models of aerosols and clouds and improvements to remote sensing aerosol retrievals.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 13, 2023
- Source ID
- N000142312861
Entities
People
- Cassandra Gaston
Organizations
- Office of Naval Research
- United States Navy
- University of Miami