Pacific Northwest National Laboratory
The organic aerosol component (OACOMP) VAP performs a multivariate analysis of the organic aerosol spectra measured by the Aerosol Chemical Speciation Monitor (ACSM). This multivariate analysis deconvolved the organic aerosol (OA) mass spectrum into factors (e.g., OOA, HOA, BBOA) that represent OA with different sources, formation and evolution processes, and potentially physicochemical properties.
The OACOMP VAP inputs are the time-varying organic aerosol component of the recorded mass spectra and the corresponding error matrix describing the measurement uncertainty. The key outputs of the VAP are the concentration-time series and the mass spectra of the OA factors derived from the multivariate analysis algorithm. Data are available at the same time resolution of the native ACSM data; typically 30 minutes for the quadrupole-ACSMs and 10-30 minutes for the time-of-flight ACSMs.
The OACOMP VAP is useful for addressing the sources, lifecycle, and properties of OA. Since the sum of all the OA factors adds up to ~100% of the total OA mass, the concentration results are particularly useful for (1) closure studies on aerosol optical and cloud condensation properties and (2) evaluating model predictions of sources and processes (e.g., primary emissions, secondary formation, biomass burning) that contribute to total OA. Estimates of the organic components in the atmosphere will help improve the representation of OAs in models that will subsequently reduce the uncertainties associated aerosol direct and indirect forcing in climate models.
Currently, preparation and QA/QC control of the organic mass spectral matrix and the error matrix requires significant manual input from the mentor. Therefore, this VAP is currently in the evaluation stage as we investigate methods to better automate the process. For total OA loading below approximately 1 ug/M3, the VAP output will have significantly higher uncertainty. Please see the technical report for more information.