Christina Oikonomou

Frederick University · Frederick Research Center

The relationship of prolonged dry spells in Eastern Mediterranean with large-scale surface and upper circulation is investigated on seasonal basis with the aid of the Singular-Value Decomposition Analysis (SVDA) for the period 1958–2000. The study was based on daily precipitation data of 56 stations, evenly distributed over Eastern Mediterranean re...

This study investigates the characteristics of the vertical component of the ionospheric F2 layer plasma drift over the mid-latitude station of Nicosia, Cyprus (\(\hbox {35}^{\circ }\hbox {N}\), \(\hbox {33}^{\circ }\hbox {E}\), at magnetic dip angle, \(\hbox {I}=\hbox {51.7}^{\circ }\)), during pre- and post-sunset hours using digisonde data from...

"Dunkle Materie" (DM) came from unexpected cosmological observations. Nowadays within our solar system, diverse observations also defy conventional explanations, like the main physical process(es) underlying the heating of the different solar atmospheric layers. Streaming DM offers a viable common scenario following gravitational focusing by the so...

Dark matter (DM) dominates our universe, while its nature remains unknown. To unravel its composition is of fundamental importance for all physics. The solid Earth, with its atmosphere, could be the new target and detector of “invisible matter”. Any not well-understood dynamical behavior is of potential interest, e.g., the anomalous annual temperat...

"Dunkle Materie" (DM) came from unexpected cosmological observations. Nowadays within our solar system, diverse observations also defy conventional explanations, like the main physical process(es) underlying the heating of the different solar atmospheric layers. Streaming DM offers a viable common scenario following gravitational focusing by the so...

Nine years of ionograms from a higher mid-latitude ionospheric station (Moscow) are analyzed, by applying the ‘height–time–intensity’ (HTI) technique along with Spectrum (Lomb periodogram) analysis with the aim to investigate the daily and seasonal variability of sporadic E (Es) and intermediate descending layers (IDLs). Es and IDL traces are obser...

Nine years of ionograms from a higher mid-latitude ionospheric station (Moscow) are analyzed, by applying the ‘height–time–intensity’ (HTI) technique along with Spectrum (Lomb periodogram) analysis with the aim to investigate the daily and seasonal variability of sporadic E (Es) and intermediate descending layers (IDLs). Es and IDL traces are obser...

The current study presents the first attempt to investigate the November 2019 catastrophic flash flood in Olympiada (North Greece) under an operational forecasting and monitoring context, based on the mesoscale weather and research forecasting (WRF) model and the integrated multi-satellite retrievals for global precipitation measurement (GPM-IMERG)...

In this study, we investigate the negative ionospheric response over the European sector during two storms that took place on 8 September 2017, primarily, by exploiting observations over ten European locations. The spatial and temporal variations of TEC, foF2 and hmF2 ionospheric characteristics are examined with the aim to explain the physical mec...

This manuscript presents the dawn characteristics of zonal plasma drift and the resultant plasma drift velocity vector (the resultant vector of vertical and zonal plasma velocity components) over the mid latitude station Nicosia, Cyprus (35°N, 33°E, and Dip angle, I= 51.7°), analyzed for a duration of one year from 2013 October to 2014 September. A...

The manifestation of the dark Universe begun with unexpected large-scale astronomical observations. We are investigating the possible origin of small-scale anomalies, like the annual stratospheri temperature anomalies. Unexpectedly within known physics, their observed planetary relationship, does not match concurrent solar activity (F10.7 and EUV e...

This paper investigates total electron content (TEC) observations obtained from a Global Positioning System (GPS) receiver station in Dhaka, Bangladesh (geographic latitude 23.8° N, longitude 90.4° E, geomagnetic latitude 14° N) under the northern crest of equatorial ionospheric anomaly (EIA) region. Eight years of TEC measurements from 2004-2011 c...

Long sequences of ionograms from three European mid-latitude ionospheric stations (Athens, Nicosia, and Pruhonice) are examined, by applying the ‘height–time–intensity’ (HTI) technique along with Spectrum (Lomb periodogram) analysis with the aim to investigate the daily and seasonal variability of sporadic E (Es) and intermediate descending layers...

This investigation aims to identify possible pre-earthquake ionospheric and atmospheric anomalies and observe their possible relationship, by employing various methodologies. Three large earthquakes in Greece are selected (6.9Mw, 6.6Mw and 6.3Mw, during 24 May 2014, 20 July and 12 June 2017 respectively). For this purpose, Total Electron Content (T...

The Southeast Mediterranean (SEM) is characterized by increased vulnerability to river/stream flooding. However, impact-oriented, operational fluvial flood forecasting is far away from maturity in the region. The current paper presents the first attempt at introducing an operational impact-based warning system in the area, which is founded on the c...

We examine systematic differences between topside electron density measurements and different topside model formulations including α‐Chapman, NeQuick, and an improved NeQuick (NeQuick‐corr) topside formulation, recently proposed. The global topside electron density data set used, was extracted from Radio Occultation (RO) topside electron density pr...

The series of X and M class flares and associated coronal mass ejections that occurred on the first days of September 2017 induced significant perturbations on the low‐latitude ionospheric electrodynamics. On 8 September in the Indian sector, the storm caused a severe modification of the equatorial electrojet (EEJ) with a consequent variation of th...

Multi-reflected echoes (MREs) and satellite traces (STs) are referred in literature as ionogram signatures of Travelling Ionospheric Disturbances (TIDs) which is a phenomenon that apparently drives spread F development mainly at nighttime mid-latitude ionosphere. A long-term statistical study has been undertaken to investigate the morphological asp...

The purpose of the present study is to investigate simultaneously pre-earthquake ionospheric and atmospheric disturbances by the application of different methodologies, with the ultimate aim to detect their possible link with the impending seismic event. Three large earthquakes in Mexico are selected (8.2 Mw, 7.1 Mw and 6.6 Mw during 8 and 19 Septe...

There is an increasing interest to study the interactions between atmospheric electrical parameters and living organisms at multiple scales. So far, relatively few studies have been published that focus on possible biological effects of atmospheric electric and magnetic fields. To foster future work in this area of multidisciplinary research, here...

The CyFFORS (Cyprus Flood Forecasting System) project aims at increasing flood risk awareness and promoting preparedness against flooding by developing and validating a pilot flood forecasting system targeted over three river/stream basins in the Larnaca region, Cyprus, and Attica region, Greece. The present study demonstrates the analysis of flood...

Travelling Ionospheric Disturbances (TIDs) are plasma density fuctuations that propagate as waves through the ionosphere. TIDs constitute a threat for operational systems using predictable ionospheric characteristics as they can impose signicant disturbances in the ambient electron density and Doppler frequency shift on HF signals. TIDs can have ef...

The warning system provides large-(LSTID) and medium-scale (MSTID) TID detection, TID activity indicators, and TID drivers to the user communities.

In an effort to explore the morphology of nighttime spread F at the lower mid-latitude European station of Nicosia, Cyprus (35°N, 33°E geographic; magnetic dip. 29.38°N), all ionograms recorded by the DPS-4D digisonde during the interval 2009–2016 have been analyzed. Subsequent detailed investigation was performed to establish the possible effect o...

TechTIDE project, funded by the European Commission Horizon 2020 research and innovation program [AD-1], will establish a pre-operational system to demonstrate reliability of a set of TID (Travelling Ionospheric Disturbances) detection methodologies to issue warnings of the occurrence of TIDs over the region extended from Europe to South Africa. Te...

As Nepal sits on the Indo-Eurasian plate boundary, it is highly susceptible to catastrophic earthquakes which have been posing a grave threat to the people of the country. Even though earthquake is one of the most destructive natural phenomena, its occurrence is still unpredictable. Advance warning of disastrous earthquakes is crucial so that the d...

Tropospheric delay comprises one of the most important error sources in satellite navigation and is caused when radio signals broadcasted by GPS satellites propagate into the atmosphere. It is usually projected onto zenith direction by using mapping functions named as Zenith Tropospheric Delay (ZTD). ZTD is described as the sum of the Zenith Hydros...

Spread F is an ionospheric phenomenon which has been reported and analyzed extensively over equatorial regions on the basis of the Rayleigh-Taylor (R-T) instability. It has also been investigated over midlatitude regions, mostly over the Southern Hemisphere with its generation attributed to the Perkins instability mechanism. Over midlatitudes it ha...

This paper reports the diurnal, seasonal, and long term variability of the E layer critical frequency (foE) and peak height (hmE) derived from Digisonde measurements from 2009 to 2016 at the low-middle latitude European station of Nicosia, Cyprus (geographical coordinates: 35°N, 33°E, geomagnetic lat. 29.38°N, I = 51.7°). Manually scaled monthly me...

The critical frequency of ionospheric F2 layer (foF2) is a measure of the highest frequency of radio signal that may be reflected back by the F2 layer, and it is associated with ionospheric peak electron density in the F2 layer. Accurate long-term foF2 variations are usually derived from ionosonde observations. In this paper, we propose a new metho...

This paper presents an investigation of F1 layer characteristics derived from manually scaled digital ionosonde measurements at the low-middle latitude European station in Nicosia, Cyprus (geographical coordinates: 35oN, 33oE, geomagnetic lat. 29.38oN, I = 51.7o) from low to high solar activity conditions (2009-2014) and their comparison with IRI-2...

The largest geomagnetic storm in solar cycle 24 occurred during 17–18 March 2015 where the main phase of the storm commenced from 07:00 UT of 17 March 2015 and reached the Dst negative minimum at 22:00 UT. The present paper reports observations of total electron content (TEC), amplitude, and phase scintillations from different GPS stations of India...

The characteristics of mid-latitude vertical plasma drift, with a focus on pre-sunrise hours for Nicosia station, Cyprus, based on digital ionosonde measurements, have been investigated and are reported for the first time. The pre-sunrise vertical plasma drift is defined by an uplift prior to sunrise, followed by a downward drift, which is referred...

Ionospheric TEC (Total Electron Content) variations prior to the deep (≈600 km) earthquake doublet close to magnetic equator in Peru (M=7.6) and to the intermediate (≈200 km) earthquake in Afghanistan (M=7.5) during 2015 were investigated using measurements from Global Navigation Satellite System (GNSS) network with the aim to detect possible ionos...

Ionospheric TEC (Total Electron Content) variations and Low Frequency (LF) signal amplitude data prior to three large earthquakes (M≥6) in Greece were analyzed using observations from the Global Navigation Satellite System (GNSS) and the European INFREP (International Network for Frontier Research on Earthquake Precursors) networks respectively, ai...

Ionospheric total electron content (TEC) variations prior to 2 large earthquakes in Nepal (M = 7.8) and Chile (M = 8.3) in 2015 were analyzed using measurements from global navigation satellite system network with the aim to detect possible ionospheric anomalies associated to these seismic events and describe their main features, by applying statis...

We examine the lithosphere-atmosphere-ionosphere interaction with respect to earthquake events using Total Electron Content (TEC) data deriving from the Romanian permanent GPS network by applying three different techniques: a) estimation of TEC deviations from the mean state, b) Cross-Correlation Analysis and c) Spectral Analysis. The analysis conc...

Occurrence of L band scintillations around midnight and postmidnight hours have not been well studied and reported from the higher equatorial latitudes in the transition region from the equatorial to midlatitudes over the Indian longitude sector. The present paper reports cases of postmidnight L band scintillation observations by COSMIC during Marc...

This study aims to evaluate the performance of the global model of ionospheric slab thickness (GMIST) in terms of F2 layer critical frequency (foF2) estimation during geomagnetic disturbed conditions. Hourly values of foF2 as obtained from ionosonde stations located at equatorial, low- and mid-latitude regions are compared with the corresponding GM...

We investigate first the climatology expressed by diurnal and seasonal variations of the critical frequency (foF2) and the peak height (hmF2) of the F2-layer derived from digital ionosonde measurements at the low-middle latitude European station in Nicosia, Cyprus (geographical coordinates: 35oN, 33oE, geomagnetic lat. 29.38°N, I=51.7°). Monthly me...

The determination of the atmospheric humidity profile has been traditionally conducted on a relatively local basis by ground-based radiosondes which are special types of instruments used for monitoring atmospheric parameters, such as temperature, humidity, wind and pressure at various altitudes in the atmosphere. An alternative modern technique for...

The determination of the ionospheric electron density profile below the electron density peak (bottomside) has been traditionally conducted by ground-based ionosondes, which probe the ionosphere up to the maximum electron density and define the profile above the peak (topside) using functions which extrapolate the profile above the peak. An alterna...

Although most past studies tend to agree that projected changes in average climatic conditions could impact negatively wheat production in countries of the Mediterranean basin, there still subsist large uncertainties concerning the magnitude of that projected negative impact. Our inability to infer reliable estimates of the response of crop product...

The objective of this study is to investigate the relationship of orography over Greece with prolonged dry spells, as represented by the maximum number consecutive dry days (CDD index) during an extremely dry summer. For this purpose a simulation experiment was conducted with the aid of the regional climate model RegCM3.1 using a spatial resolution...

This report is concentrated on the High-Resolution Regional Climate Model COSMO-CLM and the climatic and statistical analysis of the model’s results concerning the precipitation and temperature on the Alpine area and the Italian Peninsula. The study represents a first attempt aimed to investigate the impact of climate change in these areas. For thi...

The objective of this study is to investigate the linkage of large-scale upper air circulation over the greater European area with intense precipitation events over Eastern Mediterranean and then to estimate potential changes in the atmospheric patterns in the future, under global warming conditions. For this purpose, results from the regional clim...

Precipitation regime over Greece is controlled by the atmospheric circulation, orography sea surface temperature distribution and land/sea interaction. Previous studies have shown that the precipitation amounts are increased in Western Greece, which is located in the upstream side of the largest mountain range of the central mainland. Furthermore,...

The aim of this study is to estimate future potential changes in duration of extreme dry and wet spells and rainfall intensity in Eastern Mediterranean. For this purpose, daily precipitation amounts, deriving from the regional climate model of UK Hadley Centre HadRM3P have been used for the present (1960-1990) and the future period 2070-2100 on 0.4...