HELENA FLOCAS

Dr. HELENA FLOCAS

Department of Physics, National and Kapodistrian University of Athens, GR-157 84 Athens, Greece
orcid

Research Focus & Metrics

Academic Career Length

24Years (2003-Present)

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

Representative Publications

View All Publications
1 October 2010 in Journal of Climate
Verified
Journal Article
Open access
HELENA FLOCASHELENA FLOCAS
HELENA FLOCAS
ISIan Simmonds
Ian Simmonds
JKJohn Kouroutzoglou
John Kouroutzoglou
KKKevin Keay
Kevin Keay
MHMaria Hatzaki
Maria Hatzaki
DADemosthenes Asimakopoulos
Demosthenes Asimakopoulos
In this study, an updated and extended climatology of cyclonic tracks affecting the eastern Mediterranean region is presented, in order to better understand the Mediterranean climate and its changes. This climatology includes intermonthly variations, classification of tracks according to their origin domain, dynamic and kinematic characteristics, and trend analysis. The dataset used is the 1962–2001, 2.5° × 2.5°, 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40). The identification and tracking of the cyclones was performed with the aid of the Melbourne University algorithm. It was verified that considerable intermonthly variations of track density occur in the eastern Mediterranean, consistent with previous studies for the entire Mediterranean, while further interesting new features have been revealed. The classification of the tracks according to their origin domain reveals that the vast majority originate within the examined area itself, mainly in the Cyprus area and the southeastern Aegean Sea, while the tracks that originate elsewhere most frequently enter from the west. Deeper cyclones follow the southwest track originating from the area between Algeria and the Atlas Mountains. A greater size characterizes the westerly tracks (southwest, northwest, and west), while the northwest tracks propagate faster over the study area. A negative trend of the track frequency was found on an annual basis that can be mostly attributed to the winter months, being associated with variations in the baroclinicity. This negative trend is more prominent for the westerly and northeasterly tracks, as well as for those originating in the northern part of the examined area.

23 April 2019 in Atmosphere
Verified
Journal Article
Open access
PDF file
Platon PatlakasPlaton Patlakas
Platon Patlakas
CSChristos Stathopoulos
Christos Stathopoulos
HELENA FLOCASHELENA FLOCAS
HELENA FLOCAS
CKChristina Kalogeri
Christina Kalogeri
George KallosGeorge Kallos
George Kallos
The climate of the Arabian Peninsula is characterized by significant spatial and temporal variations, due to its complex topography and the large-scale atmospheric circulation. Furthermore, the role of dust in the formation of regional climate is considered to be crucial. In this work, the regional climatology for the Arabian Peninsula has been studied by employing a high resolution state of the art atmospheric model that included sophisticated physical parameterization schemes and online treatment of natural aerosol particles. The simulations covered a 30-year period (1986–2015) with a temporal resolution of 3 h and a spatial distance of 9 km. The main focus was given to the spatial and temporal variations of mean temperature and temperature extremes, wind speed and direction, and relative humidity. The results were evaluated using in situ measurements indicating a good agreement. An examination of possible climatic changes during the present climate was also performed through a comprehensive analysis of the trends of mean temperature and temperature extremes. The statistical significant trend values were overall positive and increased over the northwestern parts of the examined area. Similar spatial distributions were found for the daily minimum and maximum temperatures. Higher positive values emerged for the daily maxima.

28 September 2011 in International Journal of Climatology
Verified
Journal Article
Open access
PDF file
JKJ. Kouroutzoglou
J. Kouroutzoglou
HELENA FLOCASHELENA FLOCAS
HELENA FLOCAS
KKK. Keay
K. Keay
ISI. Simmonds
I. Simmonds
MHMaria Hatzaki
Maria Hatzaki
An objective climatology of explosive cyclones is performed over a 40‐year period (1962–2001), for the Mediterranean region with the aid of the Melbourne University automatic cyclone finding and tracking scheme. The major temporal and spatial characteristics of Mediterranean explosive cyclones are investigated, including frequency, movement, generation and dissipation, scale, depth, and intensity. It was verified that the explosive cyclogenesis in the Mediterranean is a rather rare phenomenon that occurs mainly from November to March. Explosive cyclones preferentially form along the northern Mediterranean coast, with maximum density in the Ligurian and Aegean Seas. The cyclogenesis mechanism that predominates in their development is characterized by an interaction of a short and an open long wave in a pre‐existing development (referred to as the KF mechanism). There are distinct differences between Western Mediterranean and Eastern Mediterranean explosive cyclones. Although explosive cyclones tend to form in the Western Mediterranean, their scale and depth is greater in the Eastern Mediterranean. Explosive cyclones more likely move from the main cyclogenetic areas in the Western Mediterranean along specific eastward paths over southern Italy and the Ionian Sea where they dissipate or they generate in Eastern Mediterranean and move north‐eastwards to the Black Sea or eastwards to Cyprus and Middle East. Copyright © 2010 Royal Meteorological Society

16 April 2008 in Theoretical and Applied Climatology
Verified
Journal Article
Closed access
PDF file
HELENA FLOCASHELENA FLOCAS
HELENA FLOCAS
AKA. Kelessis
A. Kelessis
CHConstantinos Helmis
Constantinos Helmis
MPM. Petrakakis
M. Petrakakis
MZM. Zoumakis
M. Zoumakis
KPK. Pappas
K. Pappas

10 October 2006 in International Journal of Climatology
Verified
Journal Article
Open access
PDF file
MHMaria Hatzaki
Maria Hatzaki
HELENA FLOCASHELENA FLOCAS
HELENA FLOCAS
DAD. N. Asimakopoulos
D. N. Asimakopoulos
PMP. Maheras
P. Maheras
In this study, an attempt is made to investigate possible teleconnection patterns of atmospheric circulation, centered over eastern Mediterranean (EM) with the aid of gridded NCEP/NCAR daily values of geopotential heights for the period 1958–2003. For this purpose, two approaches have been used: correlation analysis and rotated principal component analysis (PCA) on a seasonal and monthly basis. A teleconnection pattern between the EM and northeastern Atlantic was identified at 500 and 300 hPa in winter, which will be referred to as the Eastern Mediterranean Pattern (EMP), appearing as an independent mode of the upper circulation. The pattern also exists in autumn but is substantially weakened with its dipole centers being shifted eastwards. Significant monthly variations were found in the location, strength and structure of the pattern. The employment of a standardized index demonstrated that the negative phase of the EMP prevails throughout the year with the maximum frequency at wintertime. Copyright © 2006 Royal Meteorological Society

22 June 2021 in Climate
Verified
Journal Article
Open access
PDF file
Platon PatlakasPlaton Patlakas
Platon Patlakas
CSChristos Stathopoulos
Christos Stathopoulos
HELENA FLOCASHELENA FLOCAS
HELENA FLOCAS
NBNikolaos S. Bartsotas
Nikolaos S. Bartsotas
George KallosGeorge Kallos
George Kallos
The Arabian Peninsula is a region characterized by diverse climatic conditions due to its location and geomorphological characteristics. Its precipitation patterns are characterized by very low annual amounts with great seasonal and spatial variability. Moreover, extreme events often lead to flooding and pose threat to human life and activities. Towards a better understanding of the spatiotemporal features of precipitation in the region, a thirty-year (1986-2015) climatic analysis has been prepared with the aid of the state-of-the-art numerical modeling system RAMS/ICLAMS. Its two-way interactive nesting capabilities, explicit cloud microphysical schemes with seven categories of hydrometeors and the ability to handle dust aerosols as predictive quantities are significant advantages over an area where dust is a dominant factor. An extended evaluation based on in situ measurements and satellite records revealed a good model behavior. The analysis was performed in three main components; the mean climatic characteristics, the rainfall trends and the extreme cases. The extremes are analyzed under the principles of the extreme value theory, focusing not only on the duration but also on the intensity of the events. The annual and monthly rainfall patterns are investigated and discussed. The spatial distribution of the precipitation trends revealed insignificant percentage differences in the examined period. Furthermore, it was demonstrated that the eastern part and the top half of the western Arabian Peninsula presented the lowest risk associated with extreme events. Apart from the pure scientific interest, the present study provides useful information for different sectors of society and economy, such as civil protection, constructions and reinsurance.