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Thunderstorm Activities over Turkey
Ceyhan Kahya, Mikdat Kadioglu
Istanbul Technical University, Department of Meteorology
Characteristics of Thunderstorms
Thunderstorms have a special importance among all
meteorological events, due to their occurance at any
time and anywhere in the world
Thunderstorms can lead to casualities and/or damage
to public properties
It is crucial to examine the thunderstorm activity and
warn both the government and public in order to
prevent possible losses
Thunderstorms
Dynamical characteristic of a thunderstorm is one of the
most difficult to predict meteorological event since its
locally occurance characteristic and mixed structure
The effect of mezo-scale events increase this difficulty
Thunderstorms -2
Thunderstorms usually occur at strong vertical wind
shear regions and at upper level divergence regions of
an approaching synoptical-scale cold fronts in relation
with the low pressure trough systems
Thunderstorms - 3
As a result of convectivity, thunderstorm occurance
depends on the warming of the lower level and
moisture
Absorbs the heat energy from the surface and
transforms to electrical energy by means of lightning
and to kinetic energy by means of winds
Occurance of Thunderstorms
In general the occurance of the thunderstorms depend
on;
„ Unstable air mass
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Lifting mechanism –Uplifting
Moisture at mid and low level of the atmosphere
Warm and dry air at upper levels
Occurance of Thunderstorms
Once uplifting has begun, the warm moist air is carried
upwards until the temperature surrounding the parcel of
air drops below the dew point for that parcel of air
At that time, the moisture inside of the parcel of air will
begin to condense out and form the fluffy cumulous
clouds especially forming on sunny afternoons
Occurance of Thunderstorms
As moisture condenses, it releases latent heat and
warms the air parcel more, causing more uplifting.
Thus, the thunderstorm, which began as a typical
cumulous cloud, continues to become larger and more
buoyant. This stage of formation is known as the
cumulous stage
Occurance of Thunderstorms
If conditions for growth remain favorable, the cumulous
stage of the thunderstorm will become even stronger
with a strengthening updraft drawing in more warm,
moist air and releasing more latent heat
About 15 to 30 minutes after cumulous stage is reached,
precipitation begins to fall from the base of the cloud,
marking the transition from cumulous stage to mature
stage
Occurance of Thunderstorms
The storm is now a full blown thunderstorm, complete
with thunder, lightning, heavy precipitation, and
turbulent winds
Occurance of Thunderstorms
As the precipitation falls, it cools the air in two ways: by
direct contact and by absorbing latent heat to cause
some precipitation evaporation into the surrounding air
Both of these result in a cooler, more dense airmass in
the downdraft of the storm, making it even stronger. The
presence of these vigorous updrafts and downdrafts is
very characteristic of mature stage thunderstorms
Occurance of Thunderstorms
About 15 to 30 minutes after entering the mature stage,
a typical thunderstorm enters the dissipating stage
This is caused by the cold downdraft air spreading out
far enough that it cuts off the storm's supply of warm
humid air
Once deprived of it's source of heat energy and
moisture, the storm weakens
Occurance of Thunderstorms
Thunder and lightning diminish and eventually cease
altogether and the storm consists of weak downdrafts
and light precipitation
Study Area
In this study;
Aimed:
Investigation of temporal and spatial distribution of
thunderstorm activities to discover the relationship
among convective instabilities and severe storms
Used:
Quality controlled radiosonde data of 7 stations in
Turkey; 1972-1997
Study Area
Radiosonde Stations
İstanbul
İzmir
Isparta
Ankara
Adana
Samsun
Diyarbakır
Radiosonde Data
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Pressure
Temperature
Humidity profiles
Geopotential height
Radiosonde Data
By using radisonde data;
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Lapse rate
Mixing ratio
Equivalent potential temperature
Dew point temperature and etc.
were calculated
Mid-Latitudes
During the end of spring and the beginning of summer
at mid-latitudes including Turkey, active cyclones and
wide stratiform clouds are replaced by small-scaled air
movements and convective rains caused by vertically
growing convective clouds
Instability Indices
In general small-scaled convective rains cannot be
predicted by models since they lay between numerical
weather prediction grids
Thus thermodynamically analyzed variables of the lower
troposphere were compared with instability indices in
order to predict the occurance mechanism of
thunderstorms
Instability Indices
Instability indices help us to predict the storms and
thunderstorms without using temp diagrams
The critical values of instability indices are calculated
according to the geographical and meteorological
characteristics of the region it is developed for
Instability indices
Instability indices;
„ Showalter index
„ K index
„ Rackliff index
„ Jefferson index
„ Vertical total index
„ Cross total index
„ Total total index
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Potential wet bulb index
SWEAT index
KO index
3D index
Humidity index
Energy instability index
Sari index and etc.
Annual Change
Monthly mean thunderstorm observation numbers
Annual change of thunderstorm occurance numbers
show a biomodal time distribution over Turkey
months
Thunderstorm Activity
The first maximum in thunderstorm numbers is reached
by May and the second by October
The distribution in both graphs is alike
In Turkey thunderstorms are mostly effective in
between May-October
Thunderstorm
observation
numbers for the
first maximum;
May
Thunderstorm Activity
Monthly occurance percents of thunderstorms
Monthly thunderstorm percents are calculated to
examine the months important for the occurance time
of thunderstorms
months
Seasonal Thunderstorm Activity
Spring and fall are the major seasons of thunderstorm
activity
Effective thunderstorms over Southeastern region
during mid-spring move to whole Anatolia by the
beginning of May
Differential heating is the major source
Fall and winter seem to be the major seasons on the
other sides of Meditterranean where the sea-air
temperature difference increases until January
Seasonal Thunderstorm Activity
During spring by;
„ The increase of daytime
„ Rare rain systems over Turkey
the temperature over the surface increases rapidly and
convective rains occur by means of the surface warming
As a result in April and June thunderstorm frequency
increases over the inner regions
Along Blacksea region strong winds blow from
sea to land, sea breeze and orographic lifting
cause strong thunderstorms during September
Seasonal Thunderstorm Activity
During summer frontal systems effecting the
thunderstorm activity originates from Meditterranean –
Aegean region and the Balkans
Most of these thunderstorms are a result of
temperature difference and the rest are related to
depressions
Sea-centered polar air climbs over the mountains and
emits the inactive warm air to the region of thermal low
and as a result strong thunderstorms occur
Results & Discussion
Thunderstorm formation in Turkey mostly depends on;
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Differential heating
Topography
Distance from the sea
Atmospheric front systems
Results & Discussion
Mid and Southeastern Anatolia are Turkey’s
thunderstorm regions whereas the Aegean region is the
least effected
Results & Discussion
Enlargement of the study area and validation of new
indices for the determination of Turkey’s general
specifications should be made