11.2 DEEP CONVECTIVE CLOUD PHENOMENA IN THE UPPER TROPOSPHERE/LOWER STRATOSPHERE – A NEW DEVELOPMENT IN CLOUD SCIENCE Pao K. Wang* University of Wisconsin-Madison, Madison, Wisconsin 1. INTRODUCTION Recent discoveries of a few new phenomena atop many Midlatitude deep convective storms open up a new area for cloud research. The elucidation of these phenomena will not only help unraveling the physical processes involved in them, but also understanding the impacts of deep convective clouds on the large-scale and global atmospheric processes. This paper will give a summary of these findings and their implications to other fields. 2. STORM TOP PLUMES This phenomenon was first discovered by meteorological satellite images that reveal the existence of chimney plume-like clouds atop the anvils of some severe thunderstorms (Setvak and Doswell, 1991; Levizzani and Setvak, 1996). Fig. 1 shows such an example. The plumes are generally about 3 km above the anvils. Since the anvils in some of these storms are already at the tropopause level, the plumes are thus most likely in the lower stratosphere. It was then unknown where the source of the moisture is for these plumes. The moisture could have been pre- existent in the stratosphere or could be transported from the storm below. Fig.1. NOAA-12 AVHRR channels 1, 2 and 4 composite image of a thunderstorm on 11 September 1996 1724 UTC at Balearic Islands, Spain, showing the cirrus plume above the anvil. (Courtesy of M. Setvak) _______________________________________ * Corresponding author address: Pao K. Wang, Dept. of Atmospheric and Oceanic Sciences, University of Wisconsin- Madison, Madison, WI 53706. e-mail: pao@windy.aos.wisc.edu . To determine the plume moisture source, a 3-D nonhydrostatic quasi-compressible cloud model with explicit cloud microphysics, WISCDYMM (see Johnson et al., 1993, 1995; Lin et al., 2005), was used to perform simulations of a few severe thunderstorm cases typical of the US Midwest and Plains. The sounding used to initiate the simulation is the same as that in Johnson et al. (1993). The results of the simulated CCOPE supercell that occurred on 2 Aug 1981 in Montana will be used here for the discussion. The model results clearly demonstrate that the water vapor forming the plume comes from the storm below. Fig. 2 shows the simulated RHi (relative humidity with respect to ice) 30% contour surface. It demonstrated that the plume phenomenon is well- simulated and the size of the plume (as represented by the RHi iso-surface) is consistent with the observation. The general orientation is also consistent with the observed plumes, namely, along the central line of anvil and in the general direction of the upper level wind shear. The plume shown here appears to emanate from the overshooting top, which is also consistent with observation. Fig. 3 also shows the possibility of more than one plumes, which was also observed sometimes from satellite images (Levizzani and Setvak, 1996). Fig.2. Simulated RHi = 30% surface of the CCOPE supercell storm at t = 112 min, top view. The upper level winds are generally from upper right to the lower left (westerly) in the figure, i.e., along the orientation of the anvil top plume. Fig. 3 shows the central (y = 27 km) east-west cross-sectional of the simulated storm. It is seen that the plume emanates from the overshooting