Development of an aerosol microphysical module: Aerosol Two-dimensional bin module for foRmation and Aging Simulation (ATRAS)

摘要

Number concentrations, size distributions, and mixing states of aerosols areessential parameters for accurate estimations of aerosol direct and indirecteffects. In this study, we develop an aerosol module, designated the AerosolTwo-dimensional bin module for foRmation and Aging Simulation (ATRAS), thatcan explicitly represent these parameters by considering new particleformation (NPF), black carbon (BC) aging, and secondary organic aerosol(SOA) processes. A two-dimensional bin representation is used for particleswith dry diameters from 40 nm to 10 μm to resolve both aerosol sizes(12 bins) and BC mixing states (10 bins) for a total of 120 bins. Theparticles with diameters between 1 and 40 nm are resolved using additionaleight size bins to calculate NPF. The ATRAS module is implemented in the WRF-Chemmodel and applied to examine the sensitivity of simulated mass, number, sizedistributions, and optical and radiative parameters of aerosols to NPF, BCaging, and SOA processes over East Asia during the spring of 2009. The BCabsorption enhancement by coating materials is about 50% over East Asiaduring the spring, and the contribution of SOA processes to the absorptionenhancement is estimated to be 10–20% over northern East Asia and 20–35% over southern East Asia. A clear north–south contrast is alsofound between the impacts of NPF and SOA processes on cloud condensationnuclei (CCN) concentrations: NPF increases CCN concentrations at highersupersaturations (smaller particles) over northern East Asia, whereas SOAincreases CCN concentrations at lower supersaturations (larger particles)over southern East Asia. The application of ATRAS in East Asia also showsthat the impact of each process on each optical and radiative parameterdepends strongly on the process and the parameter in question. The modulecan be used in the future as a benchmark model to evaluate the accuracy ofsimpler aerosol models and examine interactions between NPF, BC aging, andSOA processes under different meteorological conditions and emissions.