Seasonal predictability of Mediterranean weather regimes in the Copernicus C3S systems

Giuntoli, Ignazio; Fabiano, Federico; Corti, Susanna

doi:10.1007/s00382-021-05681-4

Cited by 14 publications

(5 citation statements)

References 55 publications

(73 reference statements)

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“…Sub-synoptic contribution has been emphasized as being important in winter, while frequency changes in thermal lows dominate Mediterranean cyclones' variability in spring and summer [37]. Recently, the seasonal predictability of the Mediterranean has been studied, identifying weather regimes and their precursors through teleconnections with sea surface temperature (SST) anomalies, showing that current predictions systems are able to represent these links with increased accuracy during extreme SST years (ENSO) [38]. On the other hand, recently, the impact on AMOC strength due to Mediterranean Sea changes in stratification, through increased precipitation and runoff discharges has been studied as a long-term mechanism of coupled variability [39].…”

Section: Introductionmentioning

confidence: 99%

Recent Changes in Storm Track over the Southeast Europe: A Mechanism for Changes in Extreme Cyclone Variability

et al. 2021

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Recent changes in cyclone tracks crossing Southeast Europe are investigated for the last few decades (1980–1999 compared with 2000–2019) using a developed objective method. The response in number, severity, and persistence of the tracks are analyzed based on the source of origin (the Mediterranean Sea sub-domains) and the target area (Romania-centered domain). In winter, extreme cyclones became more frequent in the south and were also more persistent in the northeast of Romania. In summer, these became more intense and frequent, mainly over the south and southeast of Romania, where they also showed a significant increase in persistence. The regional extreme changes are related to polar jet displacements and further enhanced by the coupling of the sub-tropical jet in the Euro-Atlantic area, such as southwestwards shift in winter jets and a split-type configuration that shifts northeastwards and southeastwards in the summer. These provide a mechanism for regional variability of extreme cyclones through two paths, respectively, by shifting the origins of the tracks and by shifting the interaction between the anomaly jet streaks and the climatological storm tracks. Large-scale drivers of these changes are analyzed in relation to the main modes of atmospheric variability. The tracks number over the target domain is mainly driven during the cold season through a combined action of AO and Polar–European modes, and in summer by the AMO and East-Asian modes. These links and the circulation mode’s recent variability are consistent with changes found in the jet and storm tracks.

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Section: Introductionmentioning

confidence: 99%

Recent Changes in Storm Track over the Southeast Europe: A Mechanism for Changes in Extreme Cyclone Variability

et al. 2021

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“…We adopted European Centre for Medium-Range Weather Forecasts (ECWMF) fifth generation prediction system (ECMWF-SEAS5) reforecast dataset (Johnson et al 2019) to analyse the early summer season (May-June; MJ) SAT prediction skill over WSA using the April initial condition (Lead-1 season). Total 25 ensemble members, based on "burst mode" method, where all members are initialized with similar start date conditions but from perturbed initial states (Giuntoli et al 2022) are available for each year for the period of 1981-2016, while 2017-2022 forecast for 25members is also considered to extent the analysis to do the 1981-2022 period. The model, reanalysis and observations are re-gridded to a common 1°×1° horizontal grid.…”

Section: Datasets and Methodologymentioning

confidence: 99%

Predictability of the Early Summer Surface Air Temperature over Western South Asia

Rashid¹,

Abid

Osman

et al. 2023

Preprint

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The Surface Air Temperature (SAT) variability over Western South Asia (WSA) is highest during the early summer (May-June) season, which leads to frequent seasonal heatwaves over the region. Therefore, it is important to understand the model’s ability in predicting the regional anomalous temperature conditions, which is the focus of this study using the European Centre for MediumRange Weather Forecast fifth generation (ECMWF-SEAS5) seasonal prediction system dataset for the period 1981-2022. The model skilfully predicts the El Niño-Southern Oscillation (ENSO) related interannual variability of the SAT over WSA compared to the reanalysis, mediated through the upper-level positive 200-hPa geopotential height anomalies, that lead to warm conditions over the regions during the negative ENSO phase. A negative ENSO-SAT relationship shows that warmer extreme temperature events are more frequent during La Niña, while the opposite may happen for El Niño years. The model shows a reasonable actual prediction skill of the SAT anomalies over the WSA region compared to the higher resolution observational and reanalysis datasets, while a low skill is noted for coarser resolutions, which shows that a choice of the observational dataset is important for the estimation of the model skill. Overall, the Potential Predictability of the SAT is comparable to its actual prediction skill over the WSA region. Moreover, the higher Potential Predictability of the SAT over WSA is noted during La Niña compared to El Niño, which is mainly contributed through the higher signal compared to the noise.

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“…However, in the tropical and subtropical regions, all models (especially UK-Met and Météo-France models) exhibit relatively better performance (lower bias) in capturing extreme events, compared to extratropical regions, when 75 th and 95 th percentile thresholds were used in the indices as additional constraints. This is attributed to the model's predictive skill in grasping large-scale teleconnection patterns (Giuntoli et al, 2022). Figure 2 shows the standardized precipitation anomalies of the five models across the four seasons.…”

Section: Global Analysis Of Model Biasmentioning

confidence: 99%

Impact-based Skill Evaluation of Seasonal Precipitation Forecasts

Nikraftar,

Mbuvha,

Sadegh

et al. 2023

Preprint

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Forecasting hydroclimatic extremes holds significant importance considering the increasing trends in natural cascading climate-induced hazards such as wildfires, floods, and droughts. This study evaluates the performance of five Copernicus Climate Change Service (C3S) seasonal forecast models (i.e., CMCC, DWD, ECCC, UK-Met, and Météo-France) in predicting extreme precipitation events from 1993 to 2016 using 28 extreme precipitation indices reflecting timing and intensity of precipitation in a seasonal timescale. We design indices using various precipitation thresholds to reflect model skill in capturing the distribution and intensity of precipitation over a season. We use percentage bias, the Kendall Tau rank correlation, and ROC scores for skill evaluation. We introduce an impact-based framework to evaluate model skill in capturing extreme events over regions prone to natural disasters such as floods and wildfires. The performance of models varies across regions and seasons. The model skill is highlighted primarily in the tropical and inter-tropical regions, while skill in extra-tropical regions is markedly lower. Elevated precipitation thresholds correlate with heightened model bias, revealing deficiencies in modelling severe precipitation events. The impact-based framework analysis highlights the superior predictive capabilities of the UK-Met and Météo-France models for extreme event forecasting across many regions and seasons. In contrast, other models exhibit strong performance in specific regions and seasons. These results advance our understanding of an impact-based framework in capturing a broad spectrum of extreme climatic events through the strategic amalgamation of diverse models across different regions and seasons, offering valuable insights for disaster management and risk analysis.

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Seasonal predictability of Mediterranean weather regimes in the Copernicus C3S systems

Cited by 14 publications

References 55 publications

Recent Changes in Storm Track over the Southeast Europe: A Mechanism for Changes in Extreme Cyclone Variability

Recent Changes in Storm Track over the Southeast Europe: A Mechanism for Changes in Extreme Cyclone Variability

Predictability of the Early Summer Surface Air Temperature over Western South Asia

Impact-based Skill Evaluation of Seasonal Precipitation Forecasts

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