A case study on biomass burning aerosols: effects on aerosol optical properties and surface radiation levels

[摘要] In spring 2006, biomass burning aerosols from eastern Europe weretransported extensively to Finland, and to other parts of northernEurope. They were observed as far as in the European Arctic. Inthe first part of this paper, temporaland spatial evolution and transport of these biomass burningaerosols are monitored with MODIS retrieved aerosol opticaldepth (AOD) imagery at visible wavelengths (0.55 μm). Comparison of MODISand AERONET AOD is conducted at Tõravere, Estonia. Then trajectoryanalyses, as well as MODIS Fire Mapper products are used to better understandthe type and origin of the air masses. During the studied four-weekperiod AOD values ranged from near zero up to 1.2 at 0.55 μmand the linear correlation between MODIS and AERONET was very high(~0.97). Temporal variability observed within this four-weekperiod was alsorather well explained by the trajectory analysis in conjunctionwith the fire detections produced by the MODIS Rapid ResponseSystem. In the second part of our study, the surface measurementsof global and UV radiation at Jokioinen, Finland are usedto study the effect of this haze episode on the levels of surfaceradiation. We found reductions up to 35% in noon-time surface UV irradiance(at 340 nm) as compared to typical aerosol conditions. For global(total solar) radiation, the reduction was always smaller, in linewith the expected wavelength dependence of the aerosol effect.

[学科分类] 大气科学