Ioannis Stergiou

Mr. Ioannis Stergiou

Mechanichal Engineering, University of Western Macedonia, Kozáni, Dytikí Makedonía, Greece
orcid

Research Focus & Metrics

Academic Career Length

10Years (2017-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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17 July 2017 in Proceedings
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Conference Paper
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Ioannis StergiouIoannis Stergiou
Ioannis Stergiou
Efthimios TagarisEfthimios Tagaris
Efthimios Tagaris
Rafaella - Eleni P. SotiropoulouRafaella - Eleni P. Sotiropoulou
Rafaella - Eleni P. Sotiropoulou
Evaluation of the performance of the parameterization schemes used in the WRF model is assessed for temperature and precipitation over Europe at 36 km by 36 km grid resolution using gridded data from the ECA & D 0.25° regular grid. Simulations are performed for a winter (i.e., January 2015) and a summer (i.e., July 2015) month using the two way nesting approach. A step-wise decision approach is followed, beginning with 18 simulations for the various microphysics schemes followed by 45 more, concerning all of the model’s PBL, Cumulus, Long-wave, Short-wave and Land Surface schemes. The best performing scheme at each step is chosen by integrating the entropy weighting method ‘Technique for Order Performance by Similarity to Ideal Solution’ (TOPSIS). The concluding scheme set consists of the Mansell-Ziegler-Bruning microphysics scheme, the Bougeault-Lacarrere PBL scheme, the Kain-Fritsch cumulus scheme, the RRTMG scheme for short-wave, the New Goddard for long-wave radiation and a seasonal-variable sensitive option for the Land Surface scheme.

19 February 2021 in Atmosphere
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Journal Article
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Ioannis StergiouIoannis Stergiou
Ioannis Stergiou
Efthimios TagarisEfthimios Tagaris
Efthimios Tagaris
Rafaella - Eleni P. SotiropoulouRafaella - Eleni P. Sotiropoulou
Rafaella - Eleni P. Sotiropoulou
The grid size resolution effect on the annual and seasonal simulated mean, maximum and minimum daily temperatures and precipitation is assessed using the Advanced Research Weather Research and Forecasting model (ARW-WRF, hereafter WRF) that dynamically downscales the National Centers for Environmental Prediction’s final (NCEP FNL) Operational Global Analysis data. Simulations were conducted over central Europe for the year 2015 using 36, 12 and 4 km grid resolutions. Evaluation is done using daily E-OBS data. Several performance metrics and the bias adjusted equitable threat score (BAETS) for precipitation are used. Results show that model performance for mean, maximum and minimum temperature improves when increasing the spatial resolution from 36 to 12 km, with no significant added value when further increasing it to 4 km. Model performance for precipitation is slightly worsened when increasing the spatial resolution from 36 to 12 km while further increasing it to 4 km has minor effect. However, simulated and observed precipitation data are in quite good agreement in areas with precipitation rates below 3 mm/day for all three grid resolutions. The annual mean fraction of observed and/or forecast events that were correctly predicted (BAETS), when increasing the grid size resolution from 36 to 12 and 4 km, suggests a slight modification on average over the domain. During summer the model presents significantly lower BAETS skill score compared to the rest of the seasons.

22 December 2022 in Atmosphere
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Journal Article
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Ioannis StergiouIoannis Stergiou
Ioannis Stergiou
ETEfthimios Tagaris
Efthimios Tagaris
Rafaella - Eleni P. SotiropoulouRafaella - Eleni P. Sotiropoulou
Rafaella - Eleni P. Sotiropoulou
WRF is used to simulate eight extreme precipitation events that occurred over the regions of Schleswig–Holstein and Baden–Wurttemberg in Germany. The events were chosen from the German Weather Service (DWD) catalog and exceeded the DWD’s warning level 3 (i.e., rainfall > 40 mm/h). A two-way nesting approach is used with 9 and 3 km spatial resolutions. Initial and boundary conditions are obtained from the ERA5 dataset at 0.25° × 0.25°. To model each event, thirty different parameterization configurations were used, accounting for all possible combinations of five microphysics (MP), three cumulus (CU), and two planetary boundary layer (PBL) parameterization methods, yielding a total of 240 simulations. TOPSIS multicriteria analysis technique is employed to determine the performance skill of each setup and rank them, using six categorical and five statistical metrics. Resolution increase from 9 to 3 km did not improve forecasting accuracy temporally or in intensity. According to TOPSIS ranking, when treating each event individually, the ideal parameterizations combination is spatiotemporally dependent, with certain members ranking higher. When all events are considered, the Morrison double-moment MP–Grell–Freitas CU–YSU PBL combination works best with a frequency of occurrence in the top five performing scenarios of 30%, 47.5%, and 57.5% respectively.

15 October 2025 in Agriculture
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DPDimitris Κ. Papanastasiou
Dimitris Κ. Papanastasiou
Athanasios GelasakisAthanasios Gelasakis
Athanasios Gelasakis
GPGiorgos Papadopoulos
Giorgos Papadopoulos
Dimitrios MelasDimitrios Melas
Dimitrios Melas
KDKostas Douvis
Kostas Douvis
Nikolaos KatsoulasNikolaos Katsoulas
Nikolaos Katsoulas
It is well established that exposure to heat-stress conditions significantly impacts the physiology, health, welfare, and productivity of both sheep and cattle. The aim of this study was to apply the Temperature Humidity Index (THI) in order to assess the impact of future climate conditions on the thermal stress exposure of sheep and cattle in Greece. The Weather Research and Forecasting (WRF) model was used as a high-resolution regional climate model to simulate climate conditions for two decades in Greece at a 10 Km spatial resolution and a 1 h temporal resolution. The WRF model was applied to two emission scenarios, namely SSP2-4.5 (intermediate) and SSP5-8.5 (worst-case). Projections were made for the near-future decade (2046–2055), with the decade (2005–2014) serving as the reference period for comparative analysis. The data analysis indicated that under the SSP2-4.5 emission scenario, the mean temperature is projected to increase by 1.2–1.4 °C and 1.4–1.6 °C across 38% and 58% of the country’s territory, respectively. Increases higher than 1.6 °C are projected across 32% of the Greek territory under the SSP5-8.5 emission scenario. The mean THI (sheep) and mean THI (adj) (cattle) are projected to increase by 5–10% and by 4% across 74% and 82% of the Greek territory, respectively, when considering the SSP2-4.5 emission scenario. Slightly more severe mean heat-stress conditions were projected when considering the SSP5-8.5 emission scenario. The analysis of the hourly THI values showed that sheep and cattle are expected to experience heat-stress conditions during extended periods in the future, in which hot weather will prevail. Specifically, the number of severe/danger heat-stress hours is projected to double in the greater part of the country. To mitigate the adverse effects of climate-change-induced thermal stress on animal productivity, health, and welfare, the implementation of adaptation measures and best management practices is strongly recommended for sheep and cattle farmers. These measures encompass improvements in breeding strategies, livestock housing and microclimate management, nutritional interventions, and the adoption of precision livestock farming technologies. Given the outstanding economic, social, and environmental importance of sheep and cattle farming in Greece, effective adaptation to and mitigation of climate change impacts represent urgent priorities to ensure the long-term sustainability and resilience of the livestock sector.

17 June 2025 in Atmosphere
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Journal Article
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Ioannis StergiouIoannis Stergiou
Ioannis Stergiou
NTNektaria Traka
Nektaria Traka
Dimitrios MelasDimitrios Melas
Dimitrios Melas
Efthimios TagarisEfthimios Tagaris
Efthimios Tagaris
Rafaella - Eleni P. SotiropoulouRafaella - Eleni P. Sotiropoulou
Rafaella - Eleni P. Sotiropoulou
Accurate air quality forecasting is essential for environmental management and health protection. However, conventional air quality models often exhibit systematic biases and underpredict pollution events due to uncertainties in emissions, meteorology, and atmospheric processes. Addressing these limitations, this study introduces a hybrid deep learning model that integrates convolutional neural networks (CNNs) and Long Short-Term Memory (LSTM) for ozone forecast bias correction. The model is trained here, using data from ten stations in Texas, enabling it to capture both spatial and temporal patterns in atmospheric behavior. Performance evaluation shows notable improvements, with a Root Mean Square Error (RMSE) reduction ranging from 34.11% to 71.63%. F1 scores for peak detection improved by up to 37.38%, Dynamic Time Warping (DTW) distance decreased by 72.77%, the Index of Agreement rose up to 90.09%, and the R2 improved by up to 188.80%. A comparison of four loss functions—Mean Square Error (MSE), Huber, Asymmetric Mean Squared Error (AMSE), and Quantile Loss—revealed that MSE offered balanced performance, Huber Loss achieved the highest reduction in systematic RMSE, and AMSE performed best in peak detection. Additionally, four deep learning architectures were evaluated: baseline CNN-LSTM, a hybrid model with attention mechanisms, a transformer-based model, and an End-to-End framework. The hybrid attention-based model consistently outperformed others across metrics while maintaining lower computational demands.

22 August 2022 in Atmosphere
Verified
Journal Article
Open access
PDF file
Ioannis StergiouIoannis Stergiou
Ioannis Stergiou
Efthimios TagarisEfthimios Tagaris
Efthimios Tagaris
Rafaella - Eleni P. SotiropoulouRafaella - Eleni P. Sotiropoulou
Rafaella - Eleni P. Sotiropoulou
The Weather Research and Forecasting (WRF) mesoscale meteorological model is used to dynamically downscale data from the Goddard Institute for Space Studies (GISS) atmospheric general circulation model (GCM) CMIP5 version (Model E2-R) over Europe at a 0.25° grid size resolution, for the period of 1951 to 2010. The model configuration is single nested with grid resolutions of 0.75° to 0.25°. Two 30-year datasets are produced for the periods of 1951–1980 and 1981–2010, representing the historic and current periods, respectively. Simulated changes in climate normals are estimated and compared against the change derived from the E-OBS gridded dataset at 0.25° spatial analysis. Results indicate that the model consistently underpredicts the temperature fluctuations observed across all subregions, indicative of a colder model climatology. Winter has the strongest bias of all seasons, with the northeastern part of the domain having the highest. This is largely due to the land–atmosphere interactions. Conversely, spring and summer have the lowest regional biases, owing to a combination of low snow cover (relative to winter) and milder radiation effects (as opposed to summer). Precipitation has a negative bias in most cases, regardless of the subregion analyzed, due to the physical mechanism employed and the topographic features of each region. Both the change in the number of days when the temperature exceeds 25 °C and the change in the number of days when precipitation exceeds 5 mm/day are captured by the model reasonably well, exhibiting similar characteristics with their counterpart means.