Abstract
The drive to develop environmental prediction systems that are seamless across both weather and climate timescales has culminated in the development and use of Earth system models, which include a coupled representation of the atmosphere, land, ocean and sea ice, for medium-range weather forecasts. One region where such a coupled Earth system approach has the potential to significantly influence the skill of weather forecasts is in the polar and sub-polar seas, where fluxes of heat, moisture and momentum are strongly influenced by the position of the sea ice edge. In this study we demonstrate that using a dynamically coupled ocean and sea ice model in ECMWF Integrated Forecasting System, results in improved sea ice edge position forecasts in the northern hemisphere in the medium-range. Further, this improves forecasts of boundary layer temperature and humidity downstream of the sea ice edge in some regions during periods of rapid change in the sea ice compared to forecasts in which the sea surface temperature anomalies and sea ice concentration do not evolve throughout the forecasts. Challenges and limitations, such as the quality of ocean and sea ice initial conditions or analyses, and the inability of the coupled system to capture the rate of sea ice concentration change during periods of ice advance and retreat will also be discussed.
Highlights
Dynamic sea ice and ocean have long been recognised as important components in the Earth System Models used to generate climate projections (Holland and Bitz, 2003; Manabe and Stouffer, 1980) and more recently in seasonal forecasts (Guemas et al, 2016; Koenigk and Mikolajewicz, 2009; Tietsche et al, 2014)
Since the forecast experiments were performed for winter (DJFM), which is a period of ice expansion in the northern hemisphere, persisting sea ice, results in negative ice concentration (Fig 1a) and extent (Fig 2) biases which grow with lead-time
4.Conclusions A set of 10-day coupled atmosphere-ocean-sea ice forecasts with the European Centre for Medium-Range Weather Forecasts (ECMWF) forecasting system have been evaluated and 310 compared with uncoupled forecasts with both persisted and updated ocean and sea ice surface fields to determine the benefits of dynamic sea ice coupling for medium-range Numerical Weather Prediction (NWP)
Summary
Dynamic sea ice and ocean have long been recognised as important components in the Earth System Models used to generate climate projections (Holland and Bitz, 2003; Manabe and Stouffer, 1980) and more recently in seasonal forecasts (Guemas et al, 2016; Koenigk and Mikolajewicz, 2009; Tietsche et al, 2014) This is to meet the societal demand for information on the future state of the sea ice itself (e.g. Melia et al, 2017; Stephenson et al, 2013) and to capture important climate feedbacks and the remote influence of sea ice on atmospheric circulation (Balmaseda et al, 2010; e.g. Screen, 2017).
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