Ocean temperature forcing by aerosols across the Atlantic tropical cyclone development region

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Abstract

[1] Recent work has shown a statistical climatological link between African dust outbreaks and North Atlantic tropical cyclone frequency and intensity. However, a definite causal link between year-to-year changes in African dust and Atlantic tropical cyclones has yet to be proven. Here we show that variability in Atlantic dust cover is linked to changes in tropical cyclone activity through the aerosols' surface radiative forcing, which has a net cooling effect on tropical Atlantic Ocean temperatures. In this manuscript we describe a new methodology for incorporating more than 25 years of satellite observations of aerosols into a simple model that estimates the aerosol direct effect and its impact on tropical eastern Atlantic Ocean temperatures. The output from our model suggests that African dust outbreaks play a nonnegligible role in the evolution of eastern Atlantic Ocean temperatures. Using the strong relationship between temperatures in the so-called main development region and the seasonal power dissipation index (PDI), we estimate that about one third of the increase in PDI over the last 25 years can be attributed to decreases in dust loadings over the same period. Our results imply that efforts aimed at attributing causality to past variability of, or at predicting future changes in, North Atlantic tropical cyclone activity must consider the important radiative influence of African dust.

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