On the impact of Pacific Ocean free tropospheric background aerosols at the surface of the earth-atmosphere system



Individual tropospheric particles (0.03 to several um in diameter) were sampled using wire impactors on a DC-8 64 aircraft along and within Pacific Rim, from 125ºE to 120ºW and 70ºS to 70ºN, during the November 1989 and May 1990 Global Backscattering Experiment (GLOBE) deployments of NASA. A simple radiative balance model was used to determine the first order radiative effect of this aerosol layer at the surface. The results indicate that: (i) The background (optical thickness of ≈0.005) tropospheric aerosols between 2.4 - 12.2 km exert a warming tendency on surfaces with albedos > ≈0.02 in both the visible and infrared, (ii) There is an apparent increase in the coarse mode sulfur containing aerosol abundance compared to ≈15 years ago, suggesting that the background aerosol layer exerted a stronger tendency of planetary warming ≈15 years ago.

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