Basic Convective and Mesoscale Research

NSSL Project 6 – Investigation of Synoptic and Mesoscale Meteorological Processes Associated with Hazardous Weather: Formation and Dynamics of Mammatus and Thunderstorm Outflow Anvils

Schultz and Kanak (co-primary – CIMMS at NSSL and CIMMS at OU), Straka, Trapp, Gordon, Zrnic, Bryan, Durant, Garrett, Klein, Lilly

Funding Type: CIMMS Task II

Objectives
Review the state of the art knowledge of mammatus clouds; numerically investigate the dynamics and microphysics of mammatus clouds associated with cirrus outflow anvils and compare the results with observations and theory; isolate the conditions under which mammatus clouds form and are detectable, make case studies of mammatus events, and to continue to collect soundings, photographs and other observations of mammatus events.

Accomplishments
Numerical simulations of mammatus-like clouds have been completed and a paper has been published in Atmospheric Science Letters. A portion of a cirrus outflow anvil was simulated including ice microphysical processes. A new paper that extends these results to explore more of the parameter space is in preparation for submission to the Journal of Atmospheric Sciences. The results show that mammatus-like clouds (see figure below) form when soundings obtained near observed mammatus are used to initialize the simulations and do not form when other soundings are used. Furthermore, it is shown that sublimation is necessary but not sufficient for the formation of simulated mammatus.

A review paper of mammatus clouds is in press at the Journal of the Atmospheric Sciences. Observations, formation theories, and numerical simulation results, relevant to mammatus are presented and discussed. Observations of mammatus reported in the literature range from early aircraft penetration and visual observations from the 1940s, to recent polarimetric radar data. Formation theories remain speculative as mammatus clouds typically exist on short times scales and are thus difficult to measure. In addition, because they are benign entities, the observations that have been obtained have been mostly serendipitous, or tangential to other field program objectives. The plausibility of various theories is evaluated in light of the more recent observations, limited numerical simulations, and some new proximity soundings. Although mammatus are rarely studied, they remain an enigma and an intriguing problem of basic atmospheric fluid dynamics. It is hoped that this paper, which summarizes the current state of knowledge of the microphysics and dynamics of mammatus clouds and the environments in which they form, will motivate others to study mammatus.

This project is ongoing.

Publications
Kanak, K. M. and J. M. Straka, 2006: An idealized numerical simulation of mammatus-like clouds. Atmos. Sci. Letters, 7(1), 2-8. DOI: 10.1002/asl.121.

Kanak, K. M., Straka, J. M. and D. M. Schultz, 2007: Numerical simulation of mammatus. J. Atmos. Sci., accepted.

Schultz, D. M., K. M. Kanak, J. M. Straka, R. J. Trapp, B. A. Gordon, D. S., Zrnic , G. H. Bryan, A. J. Durant, T. J. Garrett, P. M. Klein, and D. K. Lilly, 2006: The mysteries of mammatus clouds: Observations and formation mechanisms. J. Atmos. Sci., 63, 2409-2435.

Kanak, K. M., J. M. Straka, and D. M. Schultz: 2006: Numerical simulation of mammatus-like clouds in cirrus outflow anvils. 12th Conference on Cloud Physics, Madison, WI, Amer. Meteor. Soc.

Schultz, D. M., K. M. Kanak, J. M. Straka, R. J. Trapp, B. A. Gordon, D. S. Zrnic , G. H. Bryan, A. J. Durant, T. J. Garrett, P. M. Klein, and D. K. Lilly, 2006: What causes mammatus? 12th Conference on Cloud Physics, Madison, WI, Amer. Meteor. Soc.

Schultz, D. M., K. M. Kanak, J. M. Straka, 2007: What causes mammatus? Fourth European Conference on Severe Storms, Trieste, Italy.

Schultz, D. M., K. M. Kanak, J. M. Straka, R. J. Trapp, B. A. Gordon, D. S. Zrnic , G. H. Bryan, A. J. Durant, T. J. Garrett, P. M. Klein, and D. K. Lilly, 2007: What causes mammatus? European Geophysical Union General Assembly 2007, Vienna, Austria, EGU.

XZ cross-sections of snow diameter contours at t = 26 min, y = 125 m for S1. Minimum value (gray) is 0.0 to maximum value (red) 0.58 mm with interval of 0.04 mm. Left panel: whole domain; right panel: expanded region within whole domain with velocity vectors in white.