Abstract
Abstract. This paper examines the feasibility of mitigating the intensity of hurricanes by enhancing the CCN concentrations in the outer rainband region. Increasing CCN concentrations would cause a reduced collision and coalescence, resulting in more supercooled liquid water to be transported aloft which then freezes and enhances convection via enhanced latent heat of freezing. The intensified convection would condense more water ultimately enhancing precipitation in the outer rainbands. Enhanced evaporative cooling from the increased precipitation in the outer rainbands would produce stronger and more widespread areal cold pools which block the flow of energy into the storm core, ultimately inhibiting the intensification of the tropical cyclone. We designed a series of multi-grid for which the time of the "virtual flights" as well as the aerosol release rates are varied. A code that simulates the flight of a plane is used to increase the CCN concentrations as an aircraft flies. Results show a significant sensitivity to both the seeding time and the aerosol release rates and support the aforementioned hypothesis.
Highlights
Many studies examined various possible mechanisms of convective intensification due to aerosol indirect effects
The delay in the formation of raindrop growth and ice alters the vertical profile of latent heat release and is sufficient to cause invigoration of cloud dynamics
While aerosol modulation of outer rainband convection is much more subtle than shear-induced changes, our results show a storm response that is consistent with that driven by wind shear
Summary
The cold-pool downdraft emanating from the peripheral rainbands can potentially act to cut off the inflow of warm low-level air, a requisite in maintaining the energetics of the system (Wang, 2002; Frisius and Hasselbeck, 2009) For this reason and motivated by Zhang et al’s simulations, Cotton et al (2007) hypothesized that seeding hurricanes with pollution-sized aerosols could lead to a chain of responses leading to the eventual mitigation of the storm intensity. In the outer rainbands, increasing CCN concentration results in reduced collision/coalescence, increased supercooled water aloft, enhanced convection (latent heat of freezing) and enhanced precipitation and low level cooling (evaporation).
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