A one‐dimensional sectional aerosol model integrated with mesoscale meteorological data to study marine boundary layer aerosol dynamics

Abstract

The dynamics of aerosols in the marine boundary layer are simulated with a one‐dimensional, multicomponent, sectional aerosol model using vertical profiles of turbulence, relative humidity, temperature, vertical velocity, cloud cover, and precipitation provided by 3‐D mesoscale meteorological model output. The Naval Research Laboratory's (NRL) sectional aerosol model MARBLES (Fitzgerald et al., 1998a) was adapted to use hourly meteorological input taken from NRL's Coupled Ocean‐Atmosphere Prediction System (COAMPS). COAMPS‐generated turbulent mixing coefficients and large‐scale vertical velocities determine vertical exchange within the marine boundary layer and exchange with the free troposphere. Air mass back trajectories were used to define the air column history along which the meteorology was retrieved for use with the aerosol model. Details on the integration of these models are described here, as well as a description of improvements made to the aerosol model, including transport by large‐scale vertical motions (such as subsidence and lifting), a revised sea‐salt aerosol source function, and separate tracking of sulfate mass from each of the five sources (free tropospheric, nucleated, condensed from gas phase oxidation products, cloud‐processed, and produced from heterogeneous oxidation of S(IV) on sea‐salt aerosol). Results from modeling air masses arriving at Oahu, Hawaii, are presented, and the relative contribution of free‐tropospheric sulfate particles versus sea‐salt aerosol from the surface to CCN concentrations is discussed. Limitations and benefits of the method are presented, as are sensitivity analyses of the effect of large‐scale vertical motions versus turbulent mixing.