Tuesday, 18 November 2003: 2:00 PM
A natural fire experiment in central Russia: meteorology, radiative and optical properties of atmosphere and resulting effects on sub-boreal forest plants
July through September 2002 in Central Russia was characterized by severe fire smoke conditions that led to high concentrations of atmospheric aerosols and gaseous species. A combination of a unique meteorological regime exacerbated the occurrence of the fire events in Moscow area and led to smoke conditions in Moscow itself. During the smoke episode, a complex program of aerosol, surface ozone, and broadband solar radiation measurements (UV-B <0.32mkm, UV-A <0.38mkm, visible light 0.4-0.7mkm, and short wave 0.34-4.5mkm) was in operation at the Meteorological Observatory of Moscow State University (MOMSU). Changes in aerosol, ozone and other gas concentrations in the lower atmosphere are presented for clear sky and fire smoke conditions using data from the Moscow ecological monitoring service and MOMSU. Using fire smoke atmospheric properties as input parameters to model simulations, the impact of aerosol and several gaseous components (i.e., surface ozone, SO2, NO2, and organic components) on attenuation of solar irradiance in different spectral ranges was compared with experimental radiative measurements. The effects of gaseous absorption in the UV and visible range and the absorption properties of fire smoke aerosol were verified by fitting model and measured solar irradiance attenuation. Using model calculations, the radiative forcing of the fire-smoke conditions observed in 2002 was calculated. The results were then compared with natural fire experiments in other geographical regions (Brasil, Africa, North America). The fire smoke conditions of summer 2002 also led to significant observed changes in forest herbaceous plant phenology and induced plant injury. Several bioindicator plants species sensitive to ozone are widely spread throughout the Moscow region. During the fire events of 2002, corresponding high levels of surface ozone resulted in impact on bio-indicator plants in the Moscow area including measured impacts to Alnus incana, Physocarpus opulifolius, and Sambucus racemosa. Changes in the seasonal development of Central Russian sub-boreal forest plants were also observed. These were expressed in missing phenophases as well as in modified phenorhythmotypes, and changed sequence of seasonal development phases accompanied by plant mortality. These changes are postulated to be a result of a combination of specific changes in weather regime, resulting micro-climatic drift at observation sites, and possible direct ozone damage. The occurrence of this unique Moscow smoke intrusion event can thus be examined from both an atmospheric and plant ecology consequence viewpoint. The work was supported in part by USDA Forest Service International Programs and North Central Research Station.