摘要：In this paper, the main microphysical characteristics of clouds developing in polluted and
clean conditions in the biomass-burning season of the Amazon region are examined, with
special attention to the spectral dispersion of the cloud droplet size distribution and its
potential impact on climate modeling applications. The dispersion effect has been
shown to alter the climate cooling predicted by the so-called Twomey effect. In
biomass-burning polluted conditions, high concentrations of low dispersed cloud droplets
are found. Clean conditions revealed an opposite situation. The liquid water content
(0.43 ± 0.19 g m−3) is shown to be uncorrelated with the cloud drop number concentration, while the effective
radius is found to be very much correlated with the relative dispersion of the size distribution
(R2 = 0.81). The results suggest that an increase in cloud condensation nuclei concentration from
biomass-burning aerosols may lead to an additional effect caused by a decrease in relative
dispersion. Since the dry season in the Amazonian region is vapor limiting, the dispersion
effect of cloud droplet size distributions could be substantially larger than in other polluted
regions.
