May 26 - July 31
Physical and Dynamical Ingredients Required for the Development of Above-Anvil Cirrus Plumes
Joel McAuliffe, Cameron Homeyer, and Andrew Dzambo
What is already known:
- The formation of above-anvil cirrus plumes results in increased concentrations of water vapor in the lower stratospheric region, causing climatic effects regarding ozone destruction and the radiation budget.
- These plume-producing storm systems are known to be severe and are associated with the fall of significant sized hail.
What this study adds:
- Directional wind shear between the upper level detrainment and cell motion is needed in order to produce these above-anvil plumes; no correlation was found for temperature structure and wind speed shear.
- Plume development requires tropopause-penetrating convection.
- A possible lead time for hail events was established by studying the depth of the overshooting top, which a pattern of leveling off or decrease in peak altitude of convection depth 5 - 15 minutes prior to a hail event was found.
Abstract:
The formation of above-anvil cirrus plumes atop deep convection is an important contributor to water vapor transfer from the troposphere to the lower stratosphere. It has been observed that these plume features have been associated with severe weather activity. However, the factors contributing to the development of these cirrus plumes are unknown. Here we show that the main ingredients required for this process are directional wind shear between cell motion and upper level detrainment and penetration of the tropopause using a combination of geostationary satellite imagery, high-resolution three-dimensional radar observations, and radiosonde observations. Temperature and vertical wind speed shear do not show consistent characteristics for environments conducive to the development of above-anvil cirrus. Some plume cases show fluctuations in cloud top heat signatures when analyzed with infrared satellite imagery, indicating mixing of the plume into the lower stratosphere. Our results demonstrate how environmental and physical characteristics affect plume formation and support assertions in previous studies on the relevance of above-anvil cirrus plumes for increases in stratospheric water vapor content, which is relevant to predictions of future climate. We also present a relationship between hail occurrence and overshooting top depth that may result in an increase in lead time for warnings of severe storms.