AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Cold Fronts Promote New Particle Formation over Mid-latitude Remote Oceans
GUANGJIE ZHENG, Yang Wang, Michel Jensen, Chongai Kuang, Isabel McCoy, Rob Wood, Alyssa Matthews, Fan Mei, Jason Tomlinson, Ewan Crosbie, Luke Ziemba, Richard Moore, Jian Wang, Washington University in St. Louis
Abstract Number: 647 Working Group: Aerosols, Clouds and Climate
Abstract The indirect effects of aerosols on clouds remain highly uncertain in predicting the future climate. Among the major contributions to this uncertainty is poor understanding of the formation, evolution, and transport of aerosols in the remote marine environment, where the albedo and lifetime of low clouds are highly susceptible to perturbations in aerosol properties. Globally, new particle formation (NPF) represents an important source of aerosol and cloud condensation nuclei (CCN). Model simulations show that nearly half of the global CCN in the planetary boundary layer may be formed through NPF.
In this study, aerosol properties and processes over the Eastern North Atlantic (ENA) are examined using measurements onboard the US Department of Energy Gulfstream-1 (G-1) research aircraft during the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) campaign and long-term observation at the Atmospheric Radiation Measurement (ARM) ENA site on Graciosa Island. NPF was observed in lower free troposphere (FT) and upper decoupled layer within the marine boundary layer (MBL) following the passage of cold front, which is often associated with convective clouds and intense precipitation. The convective clouds transport ocean-emitted gas precursors upward to the upper decoupled layer and lower FT, and aerosol surface area concentrations are reduced due to wet deposition, leading to NPF. In addition, reduced temperature and relatively lower cloud fraction (i.e., stronger radiation and therefore photochemical activities) following the cold front passage also facilitate NPF. Following the passage of a cold front, the newly formed particles in the upper decoupled layer are transported downwards into the surface mixed layer, where they grow and may become CCN. The influence of post cold front NPF on the population of MBL aerosols and CCN budget will be discussed.