Jennifer Logan (PI)
Harvard University
jal@io.harvard.edu

Development, Evaluation, and Applications of the Tropospheric Chemistry Simulation Capability of the Global Modeling Initiative

We propose a 3 year program of research to support development of the NASA Global Modeling Initiative (GMI) model for tropospheric chemistry, and to apply GMI to three assessments relevant to air quality and climate. To support GMI development, we propose to:  (1) Provide updated state-of-the-art modules for the GMI tropospheric chemistry simulation including anthropogenic and biogenic emissions, dry deposition, and chemical mechanism; (2) Conduct global evaluations of GMI tropospheric simulations with observations, using different new configurations of the model including new meteorological fields and modules.  Our objective is to test the ability of the new configurations to reproduce well-known aspects of atmospheric composition and improve upon previous simulations. We will use objective scoring criteria to measure the ability of the simulations to reproduce observed statistics for ozone, CO, and other gases.  Results from simulations with simple tracers will be used to investigate dynamical differences. We will also evaluate the new GMI stratosphere-troposphere (Strat-Trop) model using near-tropopause and tropospheric observations.   We will apply the unique capabilities of GMI to conduct assessments addressing two ESE questions: (a) What are the effects of regional pollution on the global atmosphere, and the effects of global chemical and climate change on regional air quality? (b) How well can future atmospheric chemical impacts on ozone and climate be predicted? (1) Assessment of intercontinental transport of ozone and aerosol pollution, focusing initially on Asian influence on the U.S. Differences between GMI simulation pairs, with vs. without anthropogenic emissions in East Asia, will be used to quantify Asian pollution enhancements over the U.S.  The analysis will be done with different GMI model configurations, and this ensemble will provide a first assessment of intercontinental pollution to inform policy makers. Results will be evaluated with observed concentration statistics from surface sites and aircraft, and with satellite data (MOPITT, AIRS, MODIS).  (2) Assessment of continental emissions using inverse analyses of satellite and aircraft data. We will focus on North American emissions during the INTEX-A aircraft mission (Jul-Aug 2004). This work will build on ongoing inverse analyses in our group using the GEOS-CHEM CTM. We will use the GMI model in different configurations as forward model for inverse analyses of (a) NOx and isoprene emissions using SCIAMACHY and GOME observations of tropospheric NO2 and HCHO columns; (b) CO sources using MOPITT and AIRS observations. The resulting ensemble will improve the constraints and the characterization of errors for (a) air mass factors for tropospheric NO2 and HCHO column retrievals; (b) relationships of NO2 columns to NOx emissions, and HCHO columns to isoprene emissions; (c) Jacobians for Bayesian inversion of CO sources.  (3) Assessment of stratospheric influences on 1970-present tropospheric ozone trends, using the Strat-Trop version of the GMI model and taking advantage of its capability for simulation of cross-tropopause transport. We believe that current models may underestimate stratospheric influence on tropospheric ozone because they do not describe cross-tropopause transport correctly. Better understanding is crucial for assessments of climate sensitivity to future chemical change. We will use simulations with stratospheric halogens, SSTs etc. and tropospheric emissions for the mid-1990s vs. the early 1970s. Simulations will be conducted for both warm and cold arctic winters. We will use a tagged tracer of stratospheric ozone to assess stratospheric influence on tropospheric ozone concentrations and trends.

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