Ambrogio Volonte : Current Research : UoR, Dept Of Meteorology

Current Research

PhD Project: Title Dynamics of Sting Jets and their relations to larger-scale drivers

Supervisors: Prof. Peter Clark and Prof. Suzanne Gray

(A scientific peer-reviewed publication is in preparation)

Birth and Life of a Sting Jet: the case of Windstorm Tini

Here you can find the slides presented at the Lunchtime Seminar at Department of Meteorology - University of Reading on 16th May 2017, summarising the work of my PhD (pdf version, contact me if you want to download the animations).

Poster presented at EGU 2017

Brief Description

Sting jets (SJ) occur as an additional region of low-level strong winds present in some Shapiro-Keyser extratropical cyclones. While it is now widely accepted that those winds are not part of the warm or cold conveyor belts (WCB-CCB), the precise mechanisms responsible for their occurrence are yet to be fully understood. The key aspect of the current research concerns the dependence of SJ generation and strengthening upon the release of mesoscale instabilities and upon the balanced dynamics in the frontolytic region. text

3D (lon-lat-pressure) view of SJ (green) and CCB(below) airstreams from model simulations of Windstorm Tini, showing the substantial descent of the SJ causing the strongest wind at low-levels in storm Tini (windspeed at 850 hPa, contours)


The main analysis performed in my project up to now refers to a case study, namely Windstorm Tini (12th February 2014), in which a SJ has been identified. The investigation is carried out through simulations run with the MetUM and Lagrangian trajectories are used to gain further information on the dynamics of the SJ.

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Same as above but in a system-relative framework, in order to higlhight the motion of the two airstreams with respect to the cyclone centre. The SJ airstreams rises up into the cloud head before descending in the frontal fracture, while the CCB stays at low-levels wrapping around the cyclone


Particular attention is devoted to the evolution of mesoscale atmospheric instabilities (e.g. symmetric and inertial instabilities) in the region where the descending airstream originates. The analysis of frontogenesis field, along with the use of vorticity budgets and of potential vorticity tracers, highlights the processes leading to the development of these instabilities and the banded structure in the cloud head. The results of this case study suggest that the SJ undergoes a process of destabilisation that enhances its descent and acceleration, adding to the strong winds already generated by the balanced dynamics. The same destabilisation does not occur in a coarser-resolution simulation, resulting in a weaker wind jet in the frontolytic region. This analysis thus reveals the synergy between the balanced dynamics and mesoscale instabilities in SJ formation.

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Timeseries (UTC) of pressure (colours indicate relative humidity wrt ice) and diagnosis of instability conditions along the trajectories. A large part of the trajectories composing the SJ gets unstable to various atmospheric instabilities, that are then released during the descent of the airstream

A different approach is necessary to perform more extensive sensitivity studies and test the robustness of the mechanisms outlined. Thus, the Met Office Idealised Model (periodic channel configuration with baroclinic lifecycles) has been prepared to be ready to use now. This simpler and more general framework will favour sensitivity experiments on initial parameters, large-scale environmental conditions and physical processes. See link