Understanding the Formation, Maintenance, and Climate Impact of Above-Anvil Cirrus Plumes

The formation, maintenance, and climate impact of above-anvil cirrus plumes (AACPs) in extratropical convection typical during spring and summertime was examined using idealized simulations with the CM1 Large-Eddy Simulation (LES) model. This study is the first to utilize coarse resolution and extended periods (4 hours) in CM1 simulations and successfully capture the dynamic evolution of deep convection and the overshooting top (OT) region. This study highlights the importance of understanding dynamic and thermodynamic processes in AACPs and convective systems. The study presents new findings indicating that the storm evolves into a split cell configuration and that the orientation of the cells depends on the background shear profile. Furthermore, results indicate that hydraulic jumps and the lofting of the above-anvil cirrus plumes significantly enhance water vapor in the stratosphere, which is maintained by gravity waves and turbulent mixing in the lee side of the overshooting top. Intense deep convection leads to significant hydration of the lower stratosphere, whereas simulations without hydraulic jumps show weaker plumes and reduced post-convection mass. Lastly, we examine the influence of the above-anvil cirrus plumes on the cloud radiative effects in the Upper Troposphere and Lower Stratosphere. Understanding the fraction of stratospheric water vapor injected into the stratosphere and its radiative impact is crucial. To quantify the role of radiation on the time evolution of stratospheric water injected by overshooting tops, we run CM1 with (Rad) and without radiation (Rad off). Results shows that radiation slightly impacts water vapor injection due to radiative cooling on longer timescales (> 2 hours), which is critical for middleworld hydration. A plausible hypothesis for the reduced overworld water injection is that radiative cooling near the cloud top is balanced by adiabatic heating from subsidence. This radiatively balanced subsidence would oppose water injection into the overworld.