SD4SP · Stratospheric Dynamics for Seasonal Prediction

Stratospheric Dynamics for Seasonal Prediction

The aim of this project, Stratospheric Dynamics for Seasonal Prediction – SD4SP, is to improve understanding of dynamical processes in the winter stratosphere to formulate more reliable seasonal forecasts in the North Atlantic-European region. The relevance of making available trustworthy information at seasonal timescales is recognized by the WMO Global Framework for Climate Services Seasonal forecasting, which is a field with enormous potential influence in different socio-economic sectors, such as agriculture, health, water management, insurance and particularly energy. Despite the chaotic nature of the climate system, seasonal prediction is feasible because atmospheric variability on seasonal timescales is modulated by slowly-varying boundary conditions, such as sea surface temperature (SST), and can retain memory from internal processes with very slow relaxation rates, such as those in the stratosphere. These fluctuations are not noticeable in day-to-day weather conditions but become evident in seasonal averages, e.g. two or three-month means. Seasonal prediction has improved considerably in the last decades, but the tropics remain the region where seasonal forecasts are most successful. In most of the extratropics, and in particular for the North Atlantic-European (NAE) winter, General Circulation Model (GCM)-based seasonal forecasts have generally added little information over a prediction based on climatology or persistence, due to the large internal atmospheric variability – dominated by the North Atlantic Oscillation (NAO). Several recent studies have claimed that a better representation of the stratosphere-troposphere coupling in GCMs could improve seasonal forecasts over NAE since the surface signature of both, polar stratospheric anomalies and tropical-extratropical stratospheric teleconnections project strongly on the NAO. Yet, the impact of resolving the stratosphere and simulating stratospheric processes is unclear and needs to be properly assessed in a forecast context. SD4SP will address the separate contribution of the tropical stratosphere and the polar stratosphere to the prediction skill of the NAE during winter. This will be achieved by performing sensitivity seasonal forecast experiments with suppressed variability in the two stratospheric regions, using two independent state-of-the-art GCMs. The goal of SD4SP is not only to identify key sources of predictability but also to advance knowledge and simulation of the mechanisms responsible for that predictability. The project deals with extratropical teleconnections, via the stratosphere, associated with the two main modes of interannual variability at low latitudes: El Niño-Southern Oscillation (ENSO) in the tropical troposphere, and the Quasi-Biennial Oscillation (QBO) in the tropical stratosphere, both of which represent suitable phenomena to enhance regional predictability. SD4SP will improve prediction of the ENSO/QBO-NAE teleconnections by gaining new insight into the stratospheric dynamics at play and by identifying model biases in the relevant stratospheric processes. The outcomes will be of great interest to the climate modelling community and will also provide valuable information to forecast providers and decision makers that use seasonal forecast products.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз