Jennifer A. Logan
HINDCASTS - HOW WELL DO WE UNDERSTAND RECENT TRENDS AND VARIABILITY IN TRACE GASES?
Methane and tropospheric ozone are radiatively important trace gases that impact climate, and recent observations show trends and interannual variability (IAV). Ozone precursors, NOx and CO, also show trends and IAV. Models are used to project how these gases will evolve over the coming century. Hindcasts – model simulations of past behavior – are essential to test the models which incorporate our state of knowledge of processes affecting trace gases and aerosols. We used the GEOS-Chem model to conduct hindcasts, investigating the causes of trends and IAV in CH4, CO, and tropospheric ozone.
Hindcasts use meteorological fields for the appropriate time period, and time dependent emissions. We developed interannual and seasonally dependent biomass burning emissions using the TOMS Aerosol Index, ATSR and AVHRR fire counts (Duncan et al., 2003 [PDF]) and a climatology for biomass burning developed by J. A. Logan and R. M. Yevich (Lobert et al. 1999 [PDF]) as part of this work.
Global budget and trends in CO, 1988-1997 (Duncan et al., 2007)
Analysis of the slowdown and interannual variability in the CH4 growth rate, 1988-1997 (Wang et al., 2004).
Tropospheric Ozone Trends in 1970-1995 (Fusco and Logan, 2003).
Duncan, B. N., J. A. Logan, I. Bey, I. A. Megretskaia, R. M. Yantosca, P. C. Novelli, N. B. Jones, and C. P. Rinsland, The global budget of CO, 1988-1997: Source estimates and validation with a global model, J. Geophys. Res., 112, D22301, doi:10.1029/2007JD008459, 2007. [PDF]
Duncan, B.N., R.V. Martin, A.C. Staudt, R. Yevich, J.A. Logan, Interannual and Seasonal Variability of Biomass Burning Emissions Constrained by Satellite Observations, J. Geophys. Res., 108 (D2), 4040, doi:10.1029/2002JD002378, 2003. [PDF]
Fusco, A.C. and J.A. Logan, Analysis of 1970-1995 Trends in Tropospheric Ozone at Northern Hemisphere Midlatitudes with the GEOS-CHEM Model, J. Geophys. Res., 108(D15), 4449, doi:10.1029/2002JD002742, 2003. [pdf]
Wang, J.S., J.A. Logan, M.B. McElroy, B.N. Duncan, I.A. Megretskaia, and R.M. Yantosca, A 3-D model analysis of the slowdown and interannual variability in the methane growth rate from 1988 to 1997, Global Biogeochem. Cycles, 18, GB3011, doi:10.1029/2003GB002180, 2004. [PDF]
SUPPORT: NSF, NASA