Teleconnection-based evaluation of seasonal forecast quality
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Teleconnection‑based evaluation of seasonal forecast quality Danila Volpi1,2 · Lauriane Batté1 · Jean‑François Guérémy1 · Michel Déqué1 Received: 12 November 2019 / Accepted: 4 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In response to the high demand for more skillful climate forecasts at the seasonal timescale, innovative climate prediction systems are developed with improved physics and increased spatial resolution. Alongside the model development process, seasonal predictions need to be evaluated on past years to provide robust information on the forecast performance. This work presents the quality assessment of the Météo-France coupled climate prediction system, taking advantage of an experiment performed with 90 ensemble members over a 37-year re-forecast period from 1979 to 2015. We focus on the boreal winter season initialised in November. Beyond typical skill measures we evaluate the model capability in reproducing ENSO and NAO teleconnections on precipitation and near surface temperature respectively. Such an assessment is carried out first through a composite analysis, and shows that the model succeeds in reproducing the main patterns for near surface temperature and precipitation. A covariance method leads to consistent results. Finally we find that the teleconnection representation of the model is not affected by shortening the verification period and reducing the ensemble size and therefore can be used to evaluate operational seasonal forecast systems. Keywords Seasonal climate prediction · Teleconnection · ENSO · NAO
1 Introduction Seasonal predictions provide climate information for timescales ranging from 1 month to 1 year. Several studies have proven that state-of-the-art coupled climate models are able to produce skillful extra-tropical predictions at such time scales (e.g. Riddle et al. 2013; Scaife et al. 2014; Kang et al. 2014; Dunstone et al. 2016). The sources of seasonal predictability rely upon the existence of slow components of the natural climate variability, associated with variations of soil moisture, snow cover, sea-ice, and ocean surface temperature (Doblas-Reyes et al. 2013; Smith et al. 2012). El Niño Southern Oscillation (ENSO) is the main process that contributes to the forecast quality in the Tropics (Scaife et al. 2017), as well as in large parts of the world, due to its expanded remote impacts (Shaman 2014). Teleconnections with the Tropics and the Arctic (Jung et al. 2016), as well as * Danila Volpi [email protected] 1
Centre National de Recherches Météorologiques, MétéoFrance, CNRS, Toulouse, France
Present Address: Istituto di Scienze dell’Atmosfera e del Clima, ISAC-CNR, Bologna, Italy
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variations in soil moisture and snow (Douville 2010), also contribute to climate predictability over the extra-tropics. Seasonal predictability also arises from the interactions between the troposphere associated with the tropospheric vortex (Waugh et al. 2017), and the stratosphere associated with the quasi-biennial oscillation (Marsha
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