Mediterranean Tropical Like Cyclones (Medicanes): Mean /Anomalies Meteorological Synoptic Conditions/Anomalies and Impacts

Postgraduate Thesis uoadl:1318190 533 Read counter

Unit:
Κατεύθυνση Γεωγραφία και Περιβάλλον
Library of the School of Science
Deposit date:
2016-02-03
Year:
2016
Author:
Καραβανά-Παπαδήμου Κωνσταντίνα
Supervisors info:
Νάστος Παναγιώτης Καθηγητής ΕΚΠΑ
Original Title:
Κυκλώνες με Τροπικά Χαρακτηριστικά στη Μεσόγειο (Medicanes): Μέσες /Ανώμαλες Συνοπτικές Μετεωρολογικές Συνθήκες και Επιπτώσεις
Languages:
Greek
Translated title:
Mediterranean Tropical Like Cyclones (Medicanes): Mean /Anomalies Meteorological Synoptic Conditions/Anomalies and Impacts
Summary:
Mediterrenean tropical-like cyclones, also known as Medicanes, are
meteorological phenomena that occur occasionally in the Mediterranean area
accompanied by gale winds and severe precipitation. They are characterized by a
low-pressure area in their center, around which a rotation of a dense cloud
mass can be observed. Their warm core, strong convection and surface flows, all
characteristics of tropical cyclones, make them differ from ordinary cyclones.
The detection of these systems becomes feasible by using visible and infrared
satellite images, which are also useful to monitor their total trajectory and
structure.
Cyclones of this type occur with low frequency in the Mediterranean region, due
to its size that does not favor the genesis of tropical systems. However, its
particular geography (presence of marginal orographic systems and intense
engulfment) offers favorable conditions to medicanes’ formation. These
conditions are mainly a strong convection and the contribution of warm and
moisture-rich air from the Mediterranean waters, a process mainly favored after
the summer season.
This study examines a number of medicane cases (64 events), that refers to the
period 1947-2014, in reference to the meteorological parameters connected to
their formation, as well as their impacts in the Mediterranean region. Medicane
events and a database, including the characteristics and the impacts of these
phenomena, are presented. Moreover, the events and their impacts are seasonally
and geographically studied, as well as the synoptic conditions and anomalies of
the meteorological parameters, regarding the days these phenomena occur.
The methodology includes bibliographical research regarding medicane events and
relevant data, followed by their combined study with the corresponding
satellite images and the organization of the database. Data processing
includes the construction of diagrams showing the seasonal and temporal
distribution of medicanes, and the use of GIS software to illustrate their
geographical distribution and to locate areas where most of them have been
developed. Their impacts have been classified in categories and studied
seasonally. Moreover, all impacts and records of wind speed and tornadoes
attributed to these phenomena have been presented geographically, using GIS
software.
To study the synoptic conditions and anomalies of the meteorological parameters
related to medicanes, NCEP/NCAR reanalysis data (Project of the National
Oceanic and Atmospheric Administration (NOAA)), regarding the days of medicane
occurrence during September, have been received, due to the fact that their
highest frequency appears in that month. Composite mean and anomalies diagrams
regarding a number of parameters (sea level pressure, sea surface temperature,
precipitation rate, lifted index (LI), air temperature at 500 hPa, geopotential
height at 500 hPa, surface wind shear and vector wind speed) have been
presented and commented. Also, the results have been combined in order to draw
conclusions concerning the examined month.
The results of this study were useful regarding the distribution of the
medicane events. Their seasonal pattern has shown that September and October
are the months with the highest occurrence frequency and that their mean annual
frequency is 1.79. Moreover, two areas which favor the genesis of medicanes
have been detected: the first extends south of Italy, between Sicily and the
Tunisian and Libyan coast, in central Mediterranean, while the second extends
from the Balearic sea to the west of Sardinia, in the west Mediterranean. These
areas present differences in their seasonal pattern, mainly regarding the high
number of medicane events in the central area during September, opposed to the
west area.
The study of the synoptic conditions and anomalies of the meteorological
parameters has shown that composite means appear to be higher in the area
between Sicily and the north African coasts in the central Mediterranean, which
spatially corresponds to the area where most of the medicanes’ genesis occurs.
Also, a second area with high composite mean values has been located around the
Balearic Islands. The respective anomalies of the meteorological parameters
also present high values in the same regions. These results agree with the high
number of medicanes taking place in the central and west-central area of the
Mediterranean during September, according the bibliography.
The geographical distribution of the medicane impacts has shown a number of
areas where those impacts occur (maximum in the area of Italy and Malta, in the
central Mediterranean). Also, the areas with the maximum occurrence of
categorized impacts have been presented. A percentage of 62.5% of the examined
events has caused high intensity impacts. This high percentage is mainly due to
the fact that the recording of low intensity and small extent impacts is
incomplete and that these have not been connected to medicane events.
Further study of the medicane events would be useful, especially regarding high
impact events and events that have affected Greece. Also, it would be important
to study the synoptic conditions and anomalies of the meteorological parameters
that correspond to the remaining months with medicane occurrence, as well as to
organize a complete database of their impacts.
Keywords:
Cyclones, Mediterranean , Meteorological Conditions, Impacts, Medicanes
Index:
Yes
Number of index pages:
2
Contains images:
Yes
Number of references:
94
Number of pages:
143
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