Hemispheric Impact of North Atlantic SSTs in Subseasonal Forecasts. Issue 4 (20th February 2021)

• Record Type: Journal Article
• Authors: Roberts, C. D.; Vitart, F.; Balmaseda, M. A.
• Is Part Of: Geophysical research letters. Volume 48:Issue 4(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-02-20
• Subjects: earth system models -- North Atlantic -- ocean‐atmosphere coupling -- sea‐surface temperature biases -- subseasonal prediction; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL091446
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Coupled Earth system models of the type used for weather and climate predictions suffer from sea‐surface temperature (SST) biases associated with errors in the location and structure of the Gulf Stream. Here, we show that such SST biases can have a significant impact on initialized forecasts at the subseasonal time range. In the European Center for Medium‐Range Weather Forecasts (ECMWF) subseasonal forecast system, correcting these errors with an online SST bias‐correction scheme improves the mean state of the North Atlantic region and has a significant positive impact on forecasts of atmospheric circulation anomalies. Improvements to forecast skill extend beyond the North Atlantic into Europe and along the northern hemisphere subtropical waveguide. These impacts provide important evidence for the potential benefits to initialized coupled forecast systems of higher‐resolution ocean models that can better resolve the position of the Gulf Stream. Plain Language Summary: The complex mathematical models used to make climate and weather forecasts include a time‐evolving representation of the 3D ocean state. However, these models do not get the position of important ocean currents such as the Gulf Stream exactly right, which can cause errors in the simulation of ocean temperatures. This study uses a bias‐correction method to demonstrate that such errors in the North Atlantic can have an impact on the quality of extended‐range weather forecasts during the northern hemisphere winter. The resulting impacts extend beyond the North Atlantic region, leading to improved forecasts over Europe and along the northern hemisphere jet stream. The results of this study provide important evidence for the potential benefits of more sophisticated representation of the ocean in weather and climate models. Key Points: North Atlantic SST biases have a significant impact in subseasonal forecasts Correcting these errors improves the model mean state and simulation of atmospheric circulation anomalies Improvements to forecast skill extend beyond the Atlantic region into Europe and along the subtropical waveguide