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Publications

Ortega, Pablo; Cristini, Luisa; APPLICATE Consortium

Abstract of the poster presented at the EGU 2019 highlighting the key APPLICATE outcomes in the first part of the project

Full Article: https://www.zenodo.org/record/3565532#.XhMW92XAO70

Ortega, Pablo

Update on seasonal and decadal prediction activities done at the BSC with EC-Earth3 (including those within APPLICATE) on the Ec-Earth Meeting of 2019, held in Reading

Full Article: https://www.zenodo.org/record/3565487#.XhMWoGXAO70

Ortega, Pablo; Jung, Thomas

Slides of the presentation on the APPLICATE project at the ASSW2019 conference.

Full Article: https://www.zenodo.org/record/3565496#.XhMWPWXAO70

Xavier J. Levine; Pablo Ortega Montilla; Markus G. Donat; Ivana Cvijanovic

Over the past decades, the Arctic has experienced rapid warming and extensive loss of sea ice cover. These high-latitude changes have been accompanied by extreme weather events over the Arctic and mid-latitude regions (e.g. Scandinavian 2018 summer heat wave). Yet links between the Arctic sea ice cover changes and extreme weather events (droughts, floods, cold outbreaks, heatwaves, extreme snowfall), remain poorly understood. More generally, it is unclear whether Arctic sea ice variability contributes significantly to interannual variations in extreme weather events in mid- and high-latitude regions.

Full Article: https://www.zenodo.org/record/3564164

Acosta Navarro, Juan Camilo; Hunter, Alasdair; Guemas, Virginie; Ortega, Pablo; García-Serrano, Javier; Tourigny, Etienne; Cruz-García, Rubén; Doblas-Reyes, Francisco;

The Arctic region has suffered a transformation in the past decades that will very likely continue in the future. Since the late 1970s, declining trends in pan-Arctic sea ice extent and volume, and increasing trends in air and sea surface temperature have been observed. However, the region has a large natural climate variability that can usually be mistaken for a long-term forced response. Furthermore, this natural Arctic variability has been linked to mid-latitude weather extremes in the northern hemisphere, both as a cause and a as response. Disentangling natural variability and forced response is of critical importance from a climate change perspective.

Full Article: https://www.zenodo.org/record/3560614#.XhMVM2XAO70

Marta Terrado; Dragana Bojovic; Juan Acosta; Linus Magnusson; Morten Køltzow; Thomas Jung;

The APPLICATE project releases its second case study that describes an extreme precipitation event that occurred in Svalbard in November 2016. This event was responsible of several landslides and avalanches. We try to illustrate how a better understanding of weather and climate information could improve the preparedness of local populations to deal with events that can be catastrophic, keeping in mind that adaptations that settlements and the environment in Svalbard would demand could set the scene for the rest of the globe. At the same time, this case study also contributes to understanding the linkages between the Arctic and mid-latitudes.

Full Article: https://www.zenodo.org/record/3560164

Marta Terrado; Dragana Bojovic; Isadora Christel; Juan Acosta; Pablo Ortega; Marcus Donat; Llorenç Lledó; Albert Soret; Halldór Jóhannsson; Thomas Jung;

Energy case study: Effects of Arctic sea ice on energy production in mid-latitudes. Winter 2016-17 event identified as relevant by stakeholders in the energy sector

Full Article: https://www.zenodo.org/record/3560148

Massonnet, François

Here, we review the foundations of this emerging notion with five cases borrowed from the field of polar prediction with a focus on sea ice (sub-seasonal to centennial time scales). We suggest that climate models, besides their usual purposes, can be used to objectively prioritize future observational needs – if, of course, the limitations of the realism of these models have been recognized. This idea, which has been already extensively exploited in the context of Numerical Weather Prediction, reinforces the notion that observations and models are two sides of the same coin rather than distinct conceptual entities.

Full Article: https://www.zenodo.org/record/3550961

Day, Jonathan

Understanding the linkages between the Arctic and mid-latitudes is important to motivate improvements in the NWP capabilities in the Arctic. Recent studies have suggested that Arctic teleconnections affect the weather of the mid-latitudes on timescales relevant for medium-range weather forecasting.

In this study, we use several numerical experimentation approaches with a state-of-the-art global opera- tional numerical weather prediction system to investigate this idea further. Focusing on boreal winter, we investigate whether the influence of the Arctic on mid-latitude weather, and the impact of the current Arctic observing system on the skill of medium-range weather forecasts in the mid-latitudes is more pronounced in certain flow regimes. Using so called Observing System Experiments, we demonstrate that removing in-situ or satellite observations from the data assimilation system, used to create the initial conditions for the forecasts, deteriorates mid-latitude synoptic forecast skill in the medium-range, particularly over northern Asia. By looking at the day-to-day variations in the linkages, we find that this deterioration is largest during Scandinavian Blocking episodes. The mechanisms behind the impact is 1) enhanced error growth in the European-Arctic sector of the Atlantic, as a result of increased baroclinicity in the region, and 2) high amplitude planetary waves allow errors to propagate from the Arctic into mid-latitudes. These conclusions are corroborated by numerical experimentation in which the Arctic is relaxed towards the best estimate of the atmospheric state. We also demonstrate that the linkage is enhanced during the Scandinavian blocking regime through a diagnostic analysis spanning several winters of the ERA5 reanalysis and reforecasts.

Full Article: https://www.zenodo.org/record/3548339

Day, Jonathan; Sandu, Irina; Magnusson, Linus; Rodwell, Mark; Lawrence, Heather; Bormann, Neils; Jung, Thomas

Recent studies have suggested that Arctic teleconnections affect the weather of the midlatitudes on time‐scales relevant for medium‐range weather forecasting. In this study, we use several numerical experimentation approaches with a state‐of‐the‐art global operational numerical weather prediction system to investigate this idea further. Focusing on boreal winter, we investigate whether the influence of the Arctic on midlatitude weather, and the impact of the current Arctic observing system on the skill of medium‐range weather forecasts in the midlatitudes is more pronounced in certain flow regimes. Using so‐called Observing System Experiments, we demonstrate that removing in situ or satellite observations from the data assimilation system, used to create the initial conditions for the forecasts, deteriorates midlatitude synoptic forecast skill in the medium‐range, particularly over northern Asia. This deterioration is largest during Scandinavian Blocking episodes, during which: (a) error growth is enhanced in the European‐Arctic, as a result of increased baroclinicity in the region, and (b) high‐amplitude planetary waves allow errors to propagate from the Arctic into midlatitudes. The important role played by Scandinavian Blocking, in modulating the influence of the Arctic on midlatitudes, is also corroborated in relaxation experiments, and through a diagnostic analysis of the ERA5 reanalysis and reforecasts.

Full Article: https://www.zenodo.org/record/3548329