Abstract
How anthropogenic forcing could change tropical cyclones (TCs) is a keen societal concern owing to its significant socio-economic impacts. However, a global picture of the anthropogenic aerosol effect on TCs has not yet emerged. Here we show that anthropogenic aerosol emission can reduce northern hemisphere (NH) TCs but increase southern hemisphere (SH) TCs primarily through altering vertical wind shear and mid-tropospheric upward motion in the TC formation zones. These circulation changes are driven by anthropogenic aerosol-induced NH-cooler-than-SH and NH-increased versus SH-decreased meridional (equator to mid-latitudes) temperature gradients. The cooler NH produces a low-level southward cross-equatorial transport of moist static energy, weakening the NH ascent in the TC formation zones; meanwhile, the increased meridional temperature gradients strengthen vertical wind shear, reducing NH TC genesis. The opposite is true for the SH. The results may help to constrain the models’ uncertainty in the future TC projection. Reduction of anthropogenic aerosol emission may increase the NH TCs threat.
Highlights
How anthropogenic forcing could change tropical cyclones (TCs) is a keen societal concern owing to its significant socio-economic impacts
We used the historical aerosol-forced simulations (Methods) from 13 coupled model intercomparison project phase 6 (CMIP6) models (Supplementary Table 1) to investigate the impact of anthropogenic aerosol forcing on global TCs
Our analysis reveals an northern hemisphere (NH)-southern hemisphere (SH) asymmetric response of TC genesis frequency (TCGF) to the historical anthropogenic aerosol
Summary
How anthropogenic forcing could change tropical cyclones (TCs) is a keen societal concern owing to its significant socio-economic impacts. We show that anthropogenic aerosol emission can reduce northern hemisphere (NH) TCs but increase southern hemisphere (SH) TCs primarily through altering vertical wind shear and mid-tropospheric upward motion in the TC formation zones. These circulation changes are driven by anthropogenic aerosol-induced NH-cooler-than-SH and NH-increased versus SH-decreased meridional (equator to mid-latitudes) temperature gradients. The regional TCs respond sensitively to the NH-concentrated, spatially, and temporally variable anthropogenic aerosol emission[17] It is still unknown whether the anthropogenic aerosol alters the global TC frequency, aerosols can change the global climate by mediating sea surface temperature changes[18,19]. The TC frequency is suppressed over the NH and increased over the SH, forming a hemisphere-asymmetric TC frequency pattern
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