10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Characterizing the Climate Impacts of Brown Carbon over California
ANIKENDER KUMAR, Michael Kleeman, Christopher Cappa, Lynn Russell, University of California, Davis
Abstract Number: 1015 Working Group: Aerosol Modeling
Abstract Brown carbon (BrC) is an important component of the atmospheric radiation budget. Past studies analyzing the effects of BrC on climate change have been conducted at the global scale with limited ability to resolve regional details associated with targeted emissions control programs. These global studies have necessarily used simplified aerosol chemistry to represent the complex interactions between aerosols, clouds, and radiation. These features make it difficult for California to fully evaluate the climate effects of emissions control programs that seek to reduce ambient concentrations of BrC.
In this study we examine the effect of BrC absorption on regional scale over California. The source-oriented WRF/Chem (SOWC) model is used to track a six dimensional aerosol variable (X, Z, Y, Size bin, Source type, Species) through explicit simulations of atmospheric chemistry and physics. To the best of our knowledge, this is the first study to track BrC using source-oriented air quality model with external mixing. In source oriented external-mixture representations, particles of the same size can age to display different chemical compositions that depend on the chemical and hygroscopic properties of the primary seed particles initially emitted from different sources. A new mechanism is incorporated into this framework for formation of SOA from the reactions of phenol, glyoxal and methylglyoxal on aqueous aerosols in winter.
The SOWC model is applied for one year from Aug, 2014 to July, 2015 with 12 km resolution over California. Simulations are based on the regional emission inventory provided by the California Air Resources Board (CARB). Major BrC sources are identified as biomass burning, incomplete combustion of fossil fuels and secondary organic aerosols (SOA). The model results are compared with observed concentrations of biomass burning-organic aerosol (BBOA) and nitrate-related oxidized organic aerosols (NOOA) measured with an Aerodyne aerosol mass spectrometer (AMS) at Fresno, California. The direct effect of regionally emitted / formed BrC on radiative forcing at the top of the atmosphere is calculated. The influence of regional emissions control programs to reduce BrC and climate forcing are estimated.