Sign up & Download
Sign in

Estimating the direct and indirect effects of secondary organic aerosols using ECHAM5-HAM

by D. O'Donnell, K. Tsigaridis, J. Feichter
Atmospheric Chemistry and Physics ()

Abstract

Abstract. Secondary organic aerosol (SOA) has been introduced into the global climate-aerosol model ECHAM5/HAM. The SOA module handles aerosols originating from both biogenic and anthropogenic sources. The model simulates the emission of precursor gases, their chemical conversion into condensable gases, the partitioning of semi-volatile condenable species into the gas and aerosol phases. As ECHAM5/HAM is a size-resolved model, a new method that permits the calculation of partitioning of semi-volatile species between different size classes is introduced. We compare results of modelled organic aerosol concentrations against measurements from extensive measurement networks in Europe and the United States, running the model with and without SOA. We also compare modelled aerosol optical depth against measurements from the AERONET network of grond stations. We find that SOA improves agreement between model and measurements in both organic aerosol mass and aerosol optical depth, but does not fully correct the low bias that is present in the model for both of these quantities. Although many models now include SOA, any overall estimate of the direct and indirect effects of these aerosols is still lacking. This paper makes a first step in that direction. The model is applied to estimate the direct and indirect effects of SOA under simulated year 2000 conditions. The modelled SOA spatial distribution indicates that SOA is likely to be an important source of free and upper tropospheric aerosol. We find a negative shortwave (SW) forcing from the direct effect, amounting to 0.31Wm2 on the global annual mean. In contrast, the model indicates a positive indirect effect of SOA of +0.23Wm2, arising Correspondence to: D. ODonnell from the enlargement of particles due to condensation of SOA, together with an enhanced coagulation sink of small particles. In the longwave, model results are a direct effect of +0.02Wm2 and an indirect effect of 0.03 Wm2

Cite this document (BETA)

Authors on Mendeley

  1. Kostas Tsigaridis
    Researcher (at an Academic Institution)
    New York, New York, United States

Readership Statistics

16 Readers on Mendeley
by Discipline
 
 
 
by Academic Status
 
25% Post Doc
 
19% Researcher (at an Academic Institution)
 
13% Doctoral Student
by Country
 
13% United States

Sign up today - FREE

Mendeley saves you time finding and organizing research. Learn more

  • All your research in one place
  • Add and import papers easily
  • Access it anywhere, anytime

Start using Mendeley in seconds!

Already have an account? Sign in