Assessing the Removal of Particles by Precipitation and Quantifying Their Wet Deposition Rates

CHRISTOS STAMATIS, Chenyang Bi, Gabriel Isaacman-VanWertz, Virginia Tech

     Abstract Number: 185
     Working Group: Aerosols, Clouds and Climate

Abstract
Secondary organic aerosol (SOA) levels in the atmosphere are affected by the thermodynamic equilibrium between reactive organic gases and particles. Therefore any processes such as wet and dry deposition that removes particles, will affect the thermodynamic equilibrium and the formation of SOA. Unfortunately, there are few direct observational constraints on the wet deposition of particles and their timescales of removal, leading to significant uncertainty regarding the impact of precipitation on aerosols. In this work we will present observationally constrained estimates of wet deposition timescales for particles. Precipitation size distribution data from globally distributed sites in the Department of Energy Atmospheric Radiation Measurement (ARM) network and in Blacksburg, VA provided highly detailed measurements of precipitation characteristics, collocated with measurements of wet scavenging of particle size distributions. Direct observations of removal are combined with precipitation data to calculate scavenging coefficients that are size-dependent for particles. Using data from Lamont, Oklahoma (2017-2023) and Manacapuru, Brazil (2014 - 2015) we quantify removal rates as a function of particle size during rain events. Wet scavenging of particles is similar at both sites across the measured submicron size range, with an interesting and complex size dependence. We examine scavenging at diverse geographical locations and compare to theoretical scavenging equations to better understand wet deposition timescales for particles and how precipitation parameters such as precipitation duration, intensity and droplet size distribution affects aerosol wet deposition.