Radiative effects of Pinatubo aerosols in the middle latitudes of the Northern Hemisphere |
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| Authors: | B Wu D Lu Q Fu |
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| Institution: | (1) Institute of Atmospheric Physics, Beijing, China;(2) Department of Meteorology, The University of Utah, Salt Lake City, Utah, USA |
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| Abstract: | Summary Using scattering coefficient profiles of the Pinatubo aerosols derived from the observation of skylight polarization and lidar backscattering ratio in Beijing, the radiative effect of Pinatubo aerosols in middle latitudes is assessed by a delta-four-stream radiative transfer model. It is shown that the Pinatubo aerosols significantly change the radiation field. Due to the presence of the volcanic aerosols, the downward short wave flux at the surface decreases with a maximum of 8 W/m2 while the upward short wave flux at the top of the atmosphere increases with a maximum of 6.5 W/m2. The volcanic aerosols are injected into the region bounded below by the tropopause and up by the 25 km level. The upward and downward radiative fluxes are changed in opposite directions at those two boundaries. Downward short wave fluxes below the tropopause are 7–9 W/m2 less than background values and downward long wave fluxes below the tropopause are 2 W/m2 more than background values. Upward short wave fluxes above 25 km level is 5–7 W/m2 more and upward fluxes above there are about 3 W/m2 less.The effects of the Pinatubo aerosols on heating rates are also significant. The maximum increase in the short wave heating rate can be as large as 0.2 K/day at 22 km. The increase in the long wave heating rate is less with a maximum amplitude of about 0.15 K/day. The maximum increase of the total heating rate is about 0.35 K/day, which is comparable with the heating rate caused by the ozone 9.6 µm band in this region.Results of this study are compared with studies of Lacis et al. (1992) and Russell et al. (1993) as well as ERBE measurements. The results generally agree well. Causes for the differences are analyzed.Based on the numerical study, it is also found that the LOWTRAN fresh volcanic model is not representative for the Pinatubo aerosols.With 9 Figures |
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