Far-flung influences on midlatitude climate and weather extremes: The stratospheric pathway

Teleconnections are processes which link variations in weather and climate between different parts of the globe, often many thousands of kilometres apart. They are important for making reliable predictions of weather and climate at the regional scale, from weeks to decades ahead, particularly in the midlatitudes where billions of people live. Recently there has been much speculation that the stratosphere may play a significant role in these teleconnections, despite its thin air and high altitude.

More specifically, climate variability in both the tropics and the Arctic may influence the stratospheric polar vortex, a region of intense winds at above 10 km in altitude, encircling the winter pole. In extreme cases, this vortex may temporarily break down in dramatic events known as sudden stratospheric warmings, with impacts propagating downwards to the Earth's surface (see this explainer video: https://youtu.be/VnlFFaF_l7I).

There is still much to be understood about the mechanisms underlying this potential 'stratospheric pathway'. Open research questions include, but are not limited to, how tropical and polar influences interact, how these remote influences affect the 3D structure of the stratospheric polar vortex (as illustrated above), how stratospheric signals are communicated down to the surface, and how they impact the risk of extreme weather. This project will use cutting-edge computational and data analysis tools to tackle these important problems.

Project Aims and Methods:

The student will have the opportunity to join a major new collaboration on Arctic teleconnections which also includes scientists at the Universities of Bristol, Oxford, Reading, Bangor, Southampton, and the National Oceanography Centre. This will give them the opportunity to build a wider network of collaborators, and to discuss and present results at regular project meetings. To make progress in this significant research area, the student will use the Isca climate modelling framework, recently developed within our group (https://execlim.github.io/IscaWebsite/index.html). Isca is a relatively simple and uniquely flexible model that can be used for simulating the atmosphere at varying levels of complexity and is therefore ideal for probing fundamental mechanisms. Knowledge gained from these experiments will be applied to the analysis of observed climate records, state-of-the-art 'large ensemble' climate projections, as well as seasonal-to-decadal predictions from collaborators at the UK Met Office. With support from the supervisors, the candidate will be encouraged to shape the focus of research to suit their interests.