Evidence of much more intense land convection in the Southern than in the Northern tropics and implications for climate change. (ePoster)

Abstract : Convective overshooting over tropical land areas is key contributor to the troposphere-to-stratosphere exchange, shown to inject in the lower stratosphere adiabatically cooled air (Pommereau and Held 2007, Khaykin et al., 2012), trace and chemically active gases (Ricaud et al 2007, 2010), ice crystals (Corti et al 2007, Nielsen et al. 2007, Khaykin et al. 2009) and tropospheric clean air diluting the aerosols (Vernier et al., 2011). However, the altitude reached by those events differs dramatically with the hemisphere. They are observed to reach 20-21 km on average in the Southern tropics during the southern summer in contrast to the Northern tropics where they are limited to the tropopause level., indicating that convective overshoots are far less intense in the North. This difference is consistent with the indirect aerosols effect due to the known larger anthropogenic aerosols and desert dust concentrations in the northern hemisphere troposphere, shown by Cloud Resolving Models (CRM) to increase the number and reducing the size of droplets or growlers, resulting in lighter rainfall and reduced convective vertical velocity, that is weaker overshooting. Asides from the reduced cross-tropopause transport reported by all above observations, the lighter rainfall due to the increase anthropogenic pollution and desertification in the industrial era in the North has strong implications for climate change differences between the two hemispheres. Shown in the presentation will be the evidence of the large difference of convective intensity between the two hemispheres from the various satellite observations, followed by an illustration of the difference in tropospheric aerosols loading, and a short discussion on the impact of such contrast between the two hemispheres on their respective past climate evolution.
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Submitted on : Friday, April 5, 2013 - 2:43:34 PM
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  • HAL Id : hal-00808462, version 1

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Jean-Pierre Pommereau, Sergey Khaykin, Jean-Paul Vernier, P. Ricaud. Evidence of much more intense land convection in the Southern than in the Northern tropics and implications for climate change. (ePoster). AGU Fall Meeting, Dec 2012, San Francisco, United States. ⟨hal-00808462⟩

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