A study of the direct and indirect effects of aerosols using global satellite data sets of aerosol and cloud parameters

Abstract

[1] The present study investigated the correlations between aerosol and cloud parameters derived from satellite remote sensing for evaluating the radiative forcing of the aerosol indirect effect. The global statistics showed that the effective particle radius and the optical thickness of low clouds correlate well with the column number concentration of the aerosol particles, indicating an aerosol indirect effect. A correlation of the cloud fraction with the aerosol number was also seen, whereas we could not find a significant correlation of the cloud-top temperature with the column aerosol number. Furthermore, the regional statistics presented that positive correlations between the cloud optical thickness and cloud fraction with the aerosol column number concentration exist in most regions consistent with the global mean statistics. However, the effective cloud particle radius showed a tendency similar to the global correlation only around the seashore regions. Using these correlations and assuming that the aerosol column number concentration has increased by 30% from the preindustrial era, the total radiative forcing of the aerosol indirect effect was evaluated to be about À0.6 to À1.2 W m À2 . The radiative forcing of the aerosol direct effect from the satellite-retrieved parameters was also evaluated as À0.4 W m À2 over the ocean. The cloud-top temperature was found to be insensitive to the change in the aerosol number, although there was a distinct negative correlation between the aerosol number and cloud temperature at which the cloud particle grows to a radius of 14 mm. This particular dependency of the cloud temperature suggests that aerosols acts on clouds so as to change cloud particle size near the cloud top, optical thickness, and fraction but to keep their cloud-top temperature without causing a significant longwave radiative forcing.

Spatio-Temporal Distribution of Aerosol and Cloud Properties over Sindh Using MODIS Satellite Data and a HYSPLIT Model

“…Some southern most sites are insensitive to changes in CTT with changing aerosol concentrations. The anthropogenic aerosols increase CTT by the induced secondary circulation, and thus change the cloud top temperature (Santer et al, 1995;Sekiguchi et al, 2009;Balakrishnaiah et al, 2012).…”

Impact of cloud horizontal inhomogeneity and directional sampling on the retrieval of cloud droplet size by the POLDER instrument

“…Actual clouds may not satisfy the homogeneity assumption (Schutgens and Roebeling, 2009). Moreover, the coarse resolution limits the usage in certain aerosol-cloud interaction studies (Sekiguchi, 2003;Gryspeerdt et al, 2014). Based on the above analysis, the following two questions are the focal points of this study.…”

Predicting decadal trends in cloud droplet number concentration using reanalysis and satellite data

“…CC BY 4.0 License. al., 2006;Nakajima et al, 2001;Sekiguchi et al, 2003), although whether aerosol affects cloud lifetime is still debated (McCoy et al, 2017b;Malavelle et al, 2017;Gryspeerdt et al, 2016). Studies have utilized the natural laboratory provided by transient degassing volcanoes to study cloud responses to changes in aerosol (Mace and Abernathy, 2016;Gassó, 2008;Yuan et al, 2011;McCoy et al, 2017b;Malavelle et al, 2017).…”