Moisture plumes above thunderstorm anvils and their contributions to cross.doc

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Moisture plumes above thunderstorm anvils and theircontributions to cross-tropopause transport of water vapor inmidlatitudesPao K. WangDepartment of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison,Madison, Wisconsin, USAAbstract[1] Water vapor in the lower stratosphere may play significant roles in the atmosphericradiative budget and atmospheric chemistry; hence it is important to understand itstransport process. The possibility of water vapor transport from the troposphere to thestratosphere by deep convection is investigated using three-dimensional, nonhydrostatic,quasi-compressible simulations of a Midwest severe thunderstorm. The results show thatthe breaking of gravity waves at the cloud top can cause cloud water vapor to be injectedinto the stratosphere in the form of plumes above a thunderstorm anvil. Meteorologicalsatellites and aircrafts have observed such plumes previously, but the source of watervapor and the injection mechanism were not identified. The present results reveal thatthere are two types of plumes, anvil sheet plumes and overshooting plumes, in thisinjection process and that the process is diabatic. A first-order estimate of this plumetransport of water vapor per day from the upper troposphere to the lower stratosphere wasmade assuming that all thunderstorms behave the same as the one simulated. Other tracechemicals may also be similarly transported by the same mechanism.Received 28 May 2002; revised 1 December 2002; accepted 15 January 2003; published28 March 2003.Keywords: cross-tropopause exchange, anvil top plumes, stratosphere-troposphereexchange of water vapor, moisture in the stratosphere, gravity wave breaking, cloud topgravity waves.Index Terms: 0341 Atmospheric Composition and Structure: Middle atmosphere—constituent transport and chemistry (3334); 3314 Meteorology and AtmosphericDynamics: Convective processes; 3362 Meteorology and Atmospheric Dynamics:Stratosphere/troposphere interactions.Citation: Wang, P. K., Moisture plumes above thunderstorm anvils and their contributionsto cross-tropopause transport of water vapor in midlatitudes, J. Geophys. Res., 108(D6),4194, doi:10.1029/2002JD002581, 2003.
Copyright 2003 by the American Geophysical Union.1. Introduction[2] Water vapor is important to the radiative budget of the atmosphere, and hence toclimate studies, because of its strong absorption of infrared (IR) radiation [e.g.,Liou,1992;Goody and Yung, 1989]. It is also the main source of ozone-destroying HOxradicals in the lower stratosphere. In the condensed phase, as exemplified by the recentlyobserved anvil-top plumes [Setvak and Doswell, 1991;Levizzani and Setvak, 1996] to bediscussed in detail later, it serves as a catalytic surface for heterogeneous reactionsinvolving NOxand halogen species [e.g.,Solomon, 1999]. It is clear that the distributionof water substance in the upper troposphere/lower stratosphere (UT/LS) region hassignificant impacts on the global climate process.

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