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TES thermal IR satellite observations for 2006, seasonal means at 500 hPa. Maximum values at northern mid-latitudes in spring-summer due to anthropogenic pollution; High values in tropical regions affected by seasonal biomass burning; Minimum values over tropical oceans due to chemical loss .
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TES thermal IR satellite observations for 2006, seasonal means at 500 hPa • Maximum values at northern mid-latitudes in spring-summer due to anthropogenic pollution; • High values in tropical regions affected by seasonal biomass burning; • Minimum values over tropical oceans due to chemical loss GLOBAL DISTRIBUTION OF TROPOSPHERIC OZONE Zhang et al. [2010]
OBSERVED RISE IN TROPOSPHERIC OZONEOVER 20th CENTURY Models underestimate the observed trend Preindustrial ozone models } Observations at mountain sites in Europe [Marenco et al., 1994]
RADIATIVE FORCING BY TROPOSPHERIC OZONE COULD BE MUCH LARGER THAN IPCC VALUE Global simulation of late 19th century ozone observations [Mickley et al., 2001] Standard model: DF = 0.44 W m-2 “Adjusted” model (lightning and soil NOx decreased, biogenic hydrocarbons increased): DF = 0.80 W m-2
GLOBAL OZONE AND OH TRENDS Ozone, ppb Mean mass-weighted tropospheric values computed from GEOS-Chem model for present-day (PD), pre-industrial (PI), and last glacial maximum (LGM) OH, 105 molecules cm-3 PD PI LGM two different climate reconstructions Lee Murray, Harvard
MODEL INTERCOMPARISON OF OH TRENDS LGM to pre-industrial Pre-industrial to present
Using long-term trends of methylchloroform to infer trends in OH concentrations Montzka et al. 2011
TRENDS IN GLOBALTROPOSPHERIC OHinferred from methylchloroform observations Montzka et al., 2011 IPCC, 2007
TRENDS IN GLOBALTROPOSPHERIC OHusing observations of other gases Montzka et al. [2011]