DOI: 10.7910/dvn/6cowhj
title: Harvard EPA-ACE Center GEOS-Chem Model Output, 2000-2017

description: This dataset contains North American surface and vertical air quality outputs from the GEOS-Chem global 3-D chemical transport model. We conducted a 2000-2017 
simulation with GEOS-Chem model version 11-02c (http://www.geos-chem.org) using NASA MERRA-2 assimilated meteorological data (Gelaro et al., 2017). We use the nested North American version of GEOS-Chem at the native MERRA-2 0.5°x0.625° horizontal resolution over North America and adjacent oceans (10–70°N, 140–40°W) with dynamic boundary conditions from a global simulation with 4°x5°horizontal resolution. The simulation includes detailed NOx-hydrocarbon–aerosol chemistry as described in Travis et al. (2016), Fisher et al. (2016) and Marais et al. (2016). US anthropogenic emissions are distributed spatially following the NEI2011 inventory (EPA, 2018). NEI2011 is scaled for individual years using national annual totals (EPA, 2018), and we decrease non-EGU NOx emissions by 60%, as in Travis et al. (2016), for all years. Open fire emissions are from the daily Quick Fire Emissions Database (QFED; Darmenov and da Silva, 2013) with diurnal variability from the Western Regional Air Partnership (Air Sciences, 2005). Soil NOx emissions, including emissions from fertilizer application, are computed according to Hudman et al. (2012), with a 50% reduction in the midwestern US for summertime based on a previous comparison with OMI NO2 observations (Vinken et al., 2014). Lightning NOx emissions are described
by Murray et al. (2012) with a horizontal distribution matching climatological observations of lightning flashes, interannual variability driven by MERRA-2 convection, and most of the release at the top of convective updrafts (Ott et al., 2010).
The NOx yield per flash is 260 mol to the south of 35°N and 500 mol to the north (Hudman et al., 2007; Huntrieser et al., 2008, 2009; Ott et al., 2010; Travis et al., 2016).
description: MDA8_03.05x0625_NA.20**.nc: calculated MDA8 ozone for each day; daily values given at each gridbox for surface concentrations in ppb. // 
NO2.05x0625_NA.20**.nc: daily averaged NO2 at each gridbox, surface concentrations in ppb. //
PM25.05x0625_NA.20**.nc: all species given in units of ug/m3 where the conversion from ppb to ug/m3 is done at standard temperature and pressure; PM2.5 and component species defined as follows:
PM25: calculated at 35% RH with the following scale factors applied: OC x 2.1 (account for non-carbon mass); SO4,NIT,NH4 x 1.33 (account for aerosol water); OCPI,SOA x 1.12 (account for aerosol water); SALA x 1.86 (account for aerosol water); DST2 x 0.38 (only include aerosols smaller than 2.5 um); includes primary and secondary organic aerosol. Components are defined as: SO4: sulfate / NH4: ammonium / NIT: nitrate / BC: black carbon / OA: organic aerosol / DUST: dust (&lt;= 2.5 ug/m3) / SALT: sea salt / TSOA: terpene SOA / ISOA: isoprene SOA (volatility pathway) / ASOA: aromatic and intermediate volatility organic compounds / 
ISOAAQ: isoprene SOA (aqueous formation) / H2O: aerosol water
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AOD.05x0625_NA.20**.nc: daily average AOD for each gridbox, unitless; Total AOD and individual components as follows: TOT = total AOD (SO4+BC+OC+SALA+SALC+DUST) / SO4 = sulfate AOD / BC = black carbon AOD / OC = organic carbon AOD / SALA = accumulation mode sea salt AOD / SALC = coarse mode AOD / DUST = total dust AOD
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PM25_NO2_O3.PROFILE.05x0625_NA.20**.nc: vertical profiles (47 model layers) of PM2.5 (+ components, described above), NO2, and O3 at monthly mean time resolution