Search Results (10)

Seaplane operations connect remote areas, promote tourism, and provide unique transportation solutions. After many years of preparations, commercial seaplane operations on a network of 100 water airports and 200 waterways in Greece are about to commence. The network can serve the needs of 1.6 million permanent residents of the Greek islands, the inhabitants of the mainland, and over 35 million annual tourists. This paper aims to conduct a PESTLE (Political, Economic, Social, Technological, Legal, and Environmental) analysis to identify the factors that have delayed operations and those that will affect the success of future operations. As such, 26 factors are examined. It was found that the Greek debt crisis and the COVID-19 pandemic were impediments to operations. The potential of using electric seaplanes is discussed. Recent developments in using drone inspection capabilities for aviation safety are examined. Management strategies for the Etesian winds and other environmental issues are presented. Overall, seaplane operations have enormous potential, while the Greek economic recovery provides favorable conditions for completing the project. The critical issue determining success is executing a multi-faceted business model to ensure seaplane operations’ financial viability. The network can act in synergy with other modes of transportation to help achieve social cohesion, improve tourism services, and foster economic development. Full article

Sea surface temperature (SST) fronts were analyzed in the Levantine Basin of the Mediterranean Sea over a 20-year period (2003–2022) using a high-resolution (~1 km) satellite dataset. Frontal gradients were strongest in regions of freshwater influence and around the Ierapetra eddies and Rhodes Gyre. Seasonally, maximum frontal activity was observed in fall and summer. Empirical orthogonal function (EOF) analysis revealed both monthly-to-seasonal variability and interannual variability in frontal gradients. Seasonal frontal variability is partially explained by atmospheric forcing; that is, wind stress curl (WSC) and net air–sea heat flux. The maximum frontal activity was observed in 2006, coinciding with the strongest WSC magnitude. The minimum frontal activity was observed in 2017, which saw the largest winter heat loss to the atmosphere. The highest frontal activity was typically observed in years with mild winters followed by strong Etesian winds. Over the study period (2003–2022), frontal gradients declined in the Levantine Basin. Our results suggest that years with a strong frontal boundary current (Asia Minor Current; AMC) coincide with reduced cross-shelf transport. Subsequent studies are recommended to concentrate on the variability in the frontal intensity of the AMC and associated cross-shelf transports, which are important for the oligotrophic Levantine Basin. Full article

The Etesian winds characterize the summertime circulation in the Eastern Mediterranean. Etesians are modulated by the Indian summer monsoon (ISM), but their response to other external forcings is not understood. Here, we investigate the response of Etesians to the Novarupta/Katmai 1912 volcanic eruption with the aid of 20th Century reanalysis and station-based wind observations. We demonstrate a robust reduction in the total number of days with Etesian winds in July and August 1913. We also detect a strong cooling and weakened surface pressure gradients in the Eastern Mediterranean, which explains the decline in Etesian winds in the post-eruption summer. Full article

The Mediterranean is recognized as one of the most sensitive regions regarding climate change. The northern sector winds are a dominant feature of summer low-tropospheric circulation over the Aegean basin in the eastern Mediterranean (EMed). This study is an updated assessment that uses state-of-the-art tools in order to investigate the projected changes in the meridional wind speed and Etesian regime during summer period (June-July-August) over the 21st century. The analysis is based on 17 Global Climate Models simulations (GCMs) available from Coupled Model Intercomparison Project Phase 6 (CMIP6) covering the historical period (from 1971 to 2014) and the future period (from 2015 to 2100) under two Shared Socioeconomic Pathways (SSPs), an intermediate-, and a very high-emission scenario (SSP2-4.5 and SSP5-8.5). Additionally, the results from GCMs analysis are compared to ERA5 reanalysis for the historical period from 1971 to 2000. Our findings suggest that the majority of GCMs reproduce the spatial pattern of Etesians but underestimate the meridional wind speed by about 0.5 to 1.0 m/s, as compared to ERA5. During the future period, the meridional wind speed is projected to be increased over the Aegean basin, mainly during the last period of 21st century. Findings show that the majority of GCM simulations (12 out of 17) show an increase in meridional wind speed of about 0.2 to 1.4 m/s for SSP5-8.5 and 0.2 to 0.6 m/s for SSP2-4.5, as compared to historical period from 1971 to 2000. Full article

The predominant climatological wind regime in summer over the Greek Seas and especially over the Aegean Sea is undoubtedly the Etesian winds system, very well known since the time of the ancient Greeks, who first identified and described its main characteristics. The Etesian winds have been under continuous and intensive research since early 1900s, and numerous papers have been published, which have revealed all the secrets associated with the physical mechanisms responsible for their creation and maintenance. The ordinary synoptic situation, which is closely associated with the appearance of spells of Etesian winds outbreaks over the Aegean Sea, refers to cases in which the Subtropical Jet Stream (SJS) is situated over the Greek mainland. Then the frontal surfaces associated with the Polar Jet Stream (PJS), or a polar jet streak, passing through Greece from the north can cause severe weather in northern Greece as far south as Larisa (39.39° N, 22.26° E). Precipitation does not usually occur south of Larisa, because the SJS constitutes a barrier to the southward extension of the upper half of the frontal surface. In this case, cold advection occurs in the lower troposphere, resulting in a drop in temperatures even in southern Greece, due to the establishment of an Etesian winds outbreak. Thereafter, these north-easterly winds persist for a long time, weakening gradually, following the variation of the pressure gradient due to the combination of the mobile dynamic anticyclone positioned over the Balkans, after the passage of the cold front and the permanent Cyprus surface low. The main goal of this article is to investigate how much the case of a time period around 9 July 2022 differs from the conceptual model mentioned above, as deep convection occurred over all of Greece over three successive days, breaking the Etesian winds regime and defeating the low tropospheric stability usually accompanying this wind regime. Full article

In July 2022, strong and high-frequency northern sector winds blew over the Aegean Sea. The low tropospheric circulation in combination with air quality and human comfort is of great importance for the climate and human health. This study investigates the variation in pollutants’ concentrations (PM₁₀, NO₂, O₃ and SO₂), meteorological factors (temperature, relative humidity, wind speed and direction) and the discomfort index in the city of Rhodes during July 2022. Additionally, the impact of Etesians on pollution levels is studied. The strength of the Etesian flow is quantified by calculating a statistical index that takes the July pressure gradient (ΔP) over the Aegean Sea into consideration. For the analysis, pollutants’ concentration recordings from a mobile air-quality-monitoring system during July 2022 and mean sea level pressure (MSLP) data from ERA5 reanalysis during July for the period from 1980 to 2022 are analyzed. The results indicate that traffic affects the pollution level although the pollution limits, according to the European directive for air quality (2008/50/EC), are not exceeded. The findings also reveal an increase in ΔP, about 1.8 hPa, during 2022 compared to the period from 1980 to 2022 and the dipole of high (over Balkans) and low (over eastern Mediterranean) pressure centers also strengthens, leading to stronger winds over the Aegean Sea. The ΔP is strongly correlated (0.8) to the first principal component of MSLP over the eastern Mediterranean. Finally, this study shows that the Etesian flow tends to reduce the concentration of PM₁₀, NO₂ and O₃, and improving the air quality in the city of Rhodes. Full article

In this work, the ERA5 reanalysis dataset, with its fine spatial and temporal resolution, is used to study the wind speed and direction characteristics in the Mediterranean basin from 1979 to 2020. Their variability, trend and mean values, as well as their association, are examined in the monthly, annual and interannual/decadal time scales. The long-term variability of the wind direction is assessed using the angular variance, while the mean annual and interannual variability are used for the wind speed. The most characteristic and constant flow systems appear in the Gulf of Lion (Mistral) and the Aegean Sea during the summer (Etesian winds). The mean annual variability maximizes in the northern part of the basin, while the western part appears to have the most variable wind directions, while the fastest increasing wind speeds appear in the southwestern Levantine sub-basin. The long-term linear trend for the mean, the 95th and 99th quantiles of annual wind speed and the number of occurrences of extreme wind events have been also assessed. For particular areas, there is an increasing tendency in both intensity and frequency of occurrence of extreme wind events. Τhe linear-circular correlation coefficient has been implemented in order to quantify the linear association between the wind direction and the wind speed. This parameter demonstrates higher annual values for the Mistral wind in the Gulf of Lion and the Etesian winds in the Aegean Sea during the summer. Finally, the comparison of the results of ERA5 with the results of ERA-Interim highlighted significant differences in the Mediterranean wind speed and direction characteristics. Full article

The Mediterranean region is a densely populated and economically relevant area with complex orography including mountain ranges, islands, and straits. In combination with pressure gradients, this creates many mesoscale wind systems that cause, e.g., wind gusts and wildfire risk in the Mediterranean. This article reviews the recent state of the science of several mesoscale winds in the Mediterranean and associated processes. Previous work, including case studies on several time ranges and resolutions, as well as studies on these winds under future climate conditions, is discussed. Simulations with grid spacings of 25 to 50 km can reproduce winds driven by large-scale pressure patterns such as Mistral, Tramontane, and Etesians. However, these simulations struggle with the correct representation of winds channeled in straits and mountain gaps and around islands. Grid spacings of 1–3 km are certainly necessary to resolve these small-scale features. The smaller grid spacings are widely used in case studies, but not yet in simulations over large areas and long periods, which also could help to understand the interaction between small-scale phenomena in separate locations. Furthermore, by far not all Mediterranean straits, islands, and mountain gaps were studied in-depth and many interesting Mediterranean small-scale winds still need to be studied. Full article

Near surface turbulent momentum flux estimates are performed over the Aegean Sea, using two different approaches regarding the drag coefficient formulation, a wave boundary layer model (referred here as KCM) and the most commonly used Coupled Ocean–Atmosphere Response Experiment (COARE) algorithm. The KCM model incorporates modifications in the energy-containing wave spectrum to account for the wave conditions of the Aegean Sea, and surface similarity to account for the stratification effects. Airborne turbulence data during an Etesian outbreak over Aegean Sea, Greece are processed to evaluate the simulations. KCM estimates found up to 10% higher than COARE ones, indicating that the wave-induced momentum flux may be insufficiently parameterized in COARE. Turbulent fluxes measured at about 150 m, and reduced to their surface values accounting for the vertical flux divergence, are consistently lower than the estimates. Under unstable atmospheric stratification and low to moderate wind conditions, the residuals between estimates and measurements are less than 40%. On the other hand, under stable stratification and strong winds, the majority of the residuals are more than 40%. This discrepancy is associated with the relatively high measurement level, shallow boundary layer, and the presence of a low level jet. Full article

The Indian summer monsoon (ISM) is a prominent feature of the summer circulation in the Northern Hemisphere (NH) and has been found to modulate the weather and climate conditions in many remote regions. This study investigates the most recurrent patterns of summertime midlatitude circulation, over the eastern Mediterranean (EM) and also globally, that are most associated with the ISM. Monthly data of 44 summers from the ERA40 dataset are used and two multidimensional statistical methods, the Principal Component Analysis (PCA) and Canonical Correlation Analysis (CCA), are implemented. The ISM is found to be related to subsidence anomalies in the middle and more extendedly in the upper troposphere over the central and eastern Mediterranean and with an Etesian-like pattern regarding the field of the lower troposphere winds. An equatorial Rossby wave pattern, extending westward from an ISM heat source up to EM and N. Africa, was identified to be associated with the variability of ISM. The observed relationship between the ISM and the EM circulation features can be attributed to this equatorial Rossby wave response to the monsoon forcing. CCA implementation revealed the interconnection of the aforementioned PCA results with an ISM action center over the northern Arabian Sea and the monsoon trough region. Full article