Proceedings Article | 4 November 2003
KEYWORDS: Aerosols, Combustion, Ultraviolet radiation, Atmospheric particles, Ozone, Atmospheric optics, UV optics, Clouds, Visible radiation, Absorption
Ground-based visible and UV irradiances at 11 wavelengths were measured in order to characterize the wavelength dependence of aerosol optical depth during the biomass burning period (October~November 2002) with a visible/ultraviolet multifilter rotating shadowband radiometer (vis-MFRSR, UV-MFRSR) at Gwangju (35.13°N, 126.53°E), South Korea. UVMFR has 7 wavelengths of 2 nm FWHM centered on, 299, 305, 310, 317, 323, 331, and 367 nm, and vis-MFRSR has 6 channels of 10 nm FWHM on 415, 500, 615, 673, 870 and 930 nm. Measurement outputs from the MFRSRs were sampled at 20 seconds interval and saved every minute as a mean value into a YESDAS data logger. In order to calculate aerosol optical depth at the visible and UV range, total column ozone should be considered because the surface UV radiation, especially UV-B radiation, is highly absorbed by atmospheric ozone. Ozone optical depths were calculated using TOMS (Total ozone mapping spectrometer) daily total column ozone (DU) and WMO (1985) ozone absorption coefficients. Exceptionally, UV radiation at 367.4 nm is free from ozone absorption. Rayleigh optical depth was highly dependent on the wavelength and was calculated using surface pressure information provided by the KMA (Korea Meteorological Administration). This study shows the results on October and November 2002 when both ground-based spectral AOD at visible/UV range and aerosol measurements and chemical analysis were executed simultaneously. AOD varied 0.16 ~ 0.64 dependent on the wavelengths during the measurement period and the AOD values had an anticorrelation with wavelength. On November 12, 2002 both biomass burning and Asian dust were observed simultaneously. The AOD analysis results showed that AOD increased 100~200% dependent on the wavelength when Asian dust and biomass burning were observed compared to the days when no events occurred. Aerosol measurement confirmed this from the increase of mass concentration of aerosol on this date. Aerosol optical parameters were compared with aerosol chemical composition.
