Extended Abstract (268K)8.1
Radiative forcing of tropospheric ozone
W. F. J. Evans, Trent University, Peterborough, ON, Canada; and C. R. Ferguson and E. Puckrin
There has been little experimental verification of the radiative forcing from tropospheric ozone. This paper reports on the progress which has been made towards validating the predictions of the climate forcing associated with tropospheric ozone. Measurements have been taken over the last three years with a new technique which was developed to measure the greenhouse radiative fluxes from greenhouse gases beneath clouds. These measurements are valuable since there are large spatial and temporal variations in some gases which make it difficult to quantify their climate forcing. As a result of the poor state of knowledge of the radiative forcing associated with tropospheric ozone, its reduction has been omitted in the Kyoto protocol for the reduction of greenhouse gases as are other prime constituents of smog such as nitric acid or PAN. In our technique, measurements of the surface radiative forcing from the gases below the cloud are taken against the cold black body background of the cloudy sky. Radiative fluxes from ozone, carbon monoxide, nitrous oxide, nitric acid and aerosols have been measured. Measurements of the tropospheric ozone surface forcing made for a number of summer days during the past three years have shown that the average surface forcing is about 0.23 W/m2. This translates to a radiative forcing of about 0.3 W/m2 ; it is interesting to note that this value is consistent with the value of 0.3 W/m2, which is cited in the IPCC 2001 report. A comparison of the measured surface forcing with the corresponding radiative trapping is also conducted; the radiative trapping was calculated with MODTRAN 4 . The average of the measured radiative trapping fluxes from 30 days at 45 N is about 0.4 W/m2 ; this is close to the global forcing estimate for tropospheric ozone reported in the 2001 IPCC report. Our measurements have been made at 44N over all four seasons. In order to decrease the uncertainty of the tropospheric ozone forcing measurements further, many more measurements need to be made at different latitudes and climates.
Session 8, Radiative Forcing of the Climate: Observations (Room 608)
Wednesday, 14 January 2004, 8:30 AM-9:30 AM, Room 608
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