Development of the high-order decoupled direct method in three dimensions for particulate matter: enabling advanced sensitivity analysis in air quality models

W Zhang,S L Napelenok,A G Russell,A Nenes,S L Capps,Y Hu

doi:10.5194/gmd-5-355-2012

W Zhang, S L Napelenok + Show 4 more

Open Access

https://doi.org/10.5194/gmd-5-355-2012

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Abstract

Abstract. The high-order decoupled direct method in three dimensions for particulate matter (HDDM-3D/PM) has been implemented in the Community Multiscale Air Quality (CMAQ) model to enable advanced sensitivity analysis. The major effort of this work is to develop high-order DDM sensitivity analysis of ISORROPIA, the inorganic aerosol module of CMAQ. A case-specific approach has been applied, and the sensitivities of activity coefficients and water content are explicitly computed. Stand-alone tests are performed for ISORROPIA by comparing the sensitivities (first- and second-order) computed by HDDM and the brute force (BF) approximations. Similar comparison has also been carried out for CMAQ sensitivities simulated using a week-long winter episode for a continental US domain. Second-order sensitivities of aerosol species (e.g., sulfate, nitrate, and ammonium) with respect to domain-wide SO2, NOx, and NH3 emissions show agreement with BF results, yet exhibit less noise in locations where BF results are demonstrably inaccurate. Second-order sensitivity analysis elucidates poorly understood nonlinear responses of secondary inorganic aerosols to their precursors and competing species. Adding second-order sensitivity terms to the Taylor series projection of the nitrate concentrations with a 50% reduction in domain-wide NOx or SO2 emissions rates improves the prediction with statistical significance.

Highlights

Airborne particulate matter (PM), or aerosol, is a major pollutant in the atmosphere
The performance of HDDM-3D/PM is evaluated in both the stand-alone ISORROPIA and the Community Multiscale Air Quality (CMAQ) model for inorganic species
The input concentrations of total sodium and chloride are 0.5 and 1 μmol·m−3, respectively (Table 2). These inputs are consistent with the typical chemical composition of inorganic aerosols (Nenes et al, 1998b) and are over a wide range allowing each subcase in ISORROPIA to be tested

Summary

Introduction

Airborne particulate matter (PM), or aerosol, is a major pollutant in the atmosphere. An alternative approach to BF is the decoupled direct method in three dimensions (DDM-3D) This method operates integrally within a chemical transport model (CTM) and simultaneously computes local sensitivities of pollutant concentrations to perturbations in input parameters (Dunker, 1984; Yang et al, 1997; Cohan et al, 2005, 2010; Napelenok et al, 2006). DDM-3D has been extended to calculate high-order sensitivities of gaseous species by Hakami et al (2003) within the Multiscale Air Quality Simulation Platform (MAQSIP) (Odman and Ingram, 1996) They calculated second- and third-order sensitivities using DDM-3D and showed that the approach could accurately capture the nonlinear response of ozone concentration to NOx and VOC emission changes. HDDM3D/PM is implemented in the Community Multidimensional Air Quality model, version 4.5 (CMAQ4.5)

Model description

Results and discussion

Conclusions