Projects
VORTEX: The role of the polar VORTex on the predictabIlity of Extreme events in the Northern Hemisphere.
|
Weather and climate extreme events include unexpected, unusual or severe weather, this is, weather at the extremes of the historical distribution. Extremes have significant impacts on human health and mortality as well as on society and natural ecosystems. The devastating consequences that climate extremes can have and the fact that they are increasing in frequency and intensity with global warming, makes it essential to increase our ability to predict severe weather conditions at temporal scales beyond the usual 7-10 days. While numerous components of the atmosphere-ocean system have been identified for their capacity to improve predictability on time scales ranging from weeks to decades, the stratosphere is another factor with great potential to increase our predictive capability. Changes in the stratosphere occur much more slowly and predictably than in the troposphere and their influence on the troposphere can lead to persistent impacts on the surface.
In recent years, evidence has emerged regarding the impact of the stratosphere on climate and weather extremes. Particularly, in the extratropical northern hemisphere, weak or strong stratospheric polar vortex events tend to precede a switch towards anomalous and persistent weather conditions lasting up to 2 months, which makes the stratospheric polar vortex the best-established phenomenon that gives rise to the predictability of surface climate from the stratosphere. So far, studies on the relationship between the polar vortex and the occurrence of extremes have focused mainly on the impact of sudden stratospheric warmings, with the exception of a few studies on specific extremes related to other anomalous states of the vortex. However, the connection and mechanisms linking climate extremes and the stratosphere are far from being firmly established. The identification of new links between climate extremes and the stratosphere is essential to establish more robustly the conditions that enable these connections and to understand the underlying mechanisms.
In this project we propose a recently developed methodology, based on the adaptation and extension of mathematical results from dynamical systems theory, and apply it to the study of the relation between anomalous states of the polar vortex and the occurrence of precipitation and temperature extremes. The application of this methodology aims to diagnose the dynamic characteristics of the linkage between the vortex and the extremes in precipitation and temperature and to determine the role of the vortex in the predictability of these extremes. This technique, unlike the classical composite-based methodology, allows the analysis of the dependence structure between instantaneous configurations of different variables making it possible to characterise each vortex-extreme event separately in terms of its recurrence, persistence and predictability, and to classify these events in relation to these parameters in order to analyse the underlying dynamics.
The application of the dynamical systems theory that we propose for VORTEX has not been exploited yet and may offer important advantages for improving current sub-seasonal to seasonal modelling since, by determining the intrinsic predictability of the stratospheric patterns related to extreme events, it will be possible to focus future model development on the improvement of the representation of the most relevant patterns.
Key words: Polar Vortex, stratosphere, Predictability, Dynamical Systems Theory
Research funded by the Spanish Ministry of Science, Innovation and Universities through the project PID2023-150798NB-I00
|
|
