Effects of 1997 Indonesian forest fires on tropospheric ozone enhancement,radiative forcing, and temperature change over the Hong Kong region

Tropospheric ozone enhancements were measured over Hong Kong (22.2 degrees N, 114.3 degreesE) by electrochemical concentration cell ozonesondes during the 1997 period when many forest fires were burning in Indonesia. The enha ncements have a maximum ozone concentration of up to 130 ppbv and an ozone- enhanced layer depth of 10 km. We used Total Ozone Mapping Spectrometer, ad vanced very high resolution radiometer satellite image, and back air trajec tory to identify the source region and the transport pattern of ozone. The strong tropospheric ozone enhancements covered all of tropical Southeast As ia and subtropical south China. They were due to photochemical ozone buildu p from the biomass burning emissions from the Indonesian fires. The ozone-r ich air mass was transported to Hong Kong following the east Asia local Had ley circulation and an abnormal anticyclonic flow related to the El Nino ph enomenon in the tropical western Pacific. A rough estimation of the radiati ve forcing due to the ozone enhancement was carried out for two cases in Oc tober and December in 1997 using a normalized tropospheric ozone radiative forcing parameter derived from the Unified Chemistry-Climate model [Mickley et al., 1999]. The ozone enhancements induced an additional radiative forc ing of 0.26 and 0.48 Wm(-2) compared to the normal total forcing of 0.48 an d 0.39 Wm(-2) in October and December over the Hong Kong region. Estimation of the associated surface temperature change suggests that enhanced ozone from biomass burning on the scale of the 1997 Indonesian fires may have sig nificant impact on regional surface temperature change.