Georgios Fragkoulidis

• PhD
• Research Associate at National Observatory of Athens

This study investigates the medium‐range predictability of warm and cold extremes in the Northern Hemisphere and the role that upper‐tropospheric circulation biases play in this regard. Deterministic ERA5 reforecasts for the period 1979–2019 are evaluated based on the ERA5 reanalysis of the respective period, thus providing a large sample for verif...

Heatwaves that occur simultaneously over several regions, termed concurrent heatwaves, pose compounding threats to society and the environment. Amplified quasi-stationary circumglobal Rossby wave patterns (CGWPs) and high-amplitude transient non-circumglobal Rossby Wave Packets (RWPs) have been proposed as two possible explanations for the occurren...

The summer of 2018 was an extraordinary season in climatological terms for northern and central Europe, bringing simultaneous, widespread, and concurrent heat and drought extremes in large parts of the continent with extensive impacts on agriculture, forests, water supply, and the socio-economic sector. Here, we present a comprehensive, multi-facet...

The ongoing global yet spatially inhomogeneous warming prompts the inspection of decadal variability in the extratropical upper-tropospheric circulation properties. This study provides observational evidence in this regard by utilizing reanalysis data to examine the past interannual-to-decadal variability and unveil trends in the probability distri...

The summer of 2018 was an extraordinary season in climatological terms for northern and central Europe, bringing simultaneous, widespread, and concurrent heat and drought extremes in large parts of the continent with extensive impacts on agriculture, forests, water supply, and socio-economic sector. We present a comprehensive, multi-faceted analysi...

Under the influence of global warming, heatwaves are becoming a major threat in many parts of the world, affecting human health and mortality, food security, forest fires, biodiversity, energy consumption, as well as the production and transportation networks. Seasonal forecasting is a promising tool to help mitigate these impacts on society. Previ...

The connection between weather extremes and Rossby wave packets (RWP) has been increasingly documented in recent years. RWP propagation and characteristics can modulate the midlatitude weather, setting the scene for temperature and precipitation extremes and controlling the geographical area affected. Several studies on extreme precipitation events...

Extreme precipitation events (EPEs) are meteorological phenomena of major concern for the densely populated regions of northern and central Italy. Although statistically rare, they tend to be recurrent in autumn and share common characteristics in the large-scale dynamical evolution responsible for their generation. Past studies on EPEs have report...

Transient Rossby wave packets (RWPs) are a prominent feature of the synoptic to planetary upper-tropospheric flow at the mid-latitudes. Their demonstrated role in various aspects of weather and climate prompts the investigation of characteristic properties like their amplitude, phase speed, and group velocity. Traditional frameworks for the diagnos...

Weather and climate variations on subseasonal to decadal time scales can have enormous social, economic, and environmental impacts, making skillful predictions on these time scales a valuable tool for decision-makers. As such, there is a growing interest in the scientific, operational, and applications communities in developing forecasts to improve...

This study investigates the synoptic circulation patterns associated with temperature extremes in southeastern (SE) Europe. Using ERA-Interim reanalysis data we report on the typical patterns that characterize the middle and upper tropospheric flow a few days before and during hot and cold extremes. The analysis is done separately for each season,...

Upper tropospheric Rossby wave packets (RWPs) are important dynamical features, because they are often associated with weather systems and sometimes act as precursors to high impact weather. The present work introduces a novel diagnostic to identify RWPs and to quantify their amplitude. It is based on the local finite amplitude wave activity (LWA)...

This paper analyses the late summer heat wave over Europe in 2016. Primarily central, western and southwestern Europe were affected by high temperatures. Seville (Spain), for example, registered the highest September temperature on record on 5 September 2016 topping at 44.8°C, as well as Trier with temperatures reaching 34.2°C on 13 September 2016....

The present work investigates the statistical linkage between upper-tropospheric transient Rossby wave packets (RWPs) and lower-tropospheric temperature extremes on the Northern Hemisphere during the period 1979–2015. Data from ERA-Interim reanalyses are used for the diagnosis of RWP amplitude and temperature anomalies as well as the systematic exa...

This paper introduces a newly compiled set of feature-based climatologies identified from ERA-Interim reanalyses (1979–2014). Two categories of flow features are considered: (i) Eulerian climatologies of jet streams, tropopause folds, surface fronts, cyclones and anticyclones, blocks, and potential vorticity (PV) streamers and cutoffs, and (ii) Lag...