thunderstorm activities over turkey · an approaching synoptical-scale cold fronts in relation with...
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Thunderstorm Activities over Turkey
Ceyhan Kahya, Mikdat KadiogluIstanbul Technical University, Department of Meteorology
Characteristics of Thunderstorms
Thunderstorms have a special importance among allmeteorological events, due to their occurance at any
time and anywhere in the world
Thunderstorms can lead to casualities and/or damageto public properties
It is crucial to examine the thunderstorm activity andwarn both the government and public in order to
prevent possible losses
Thunderstorms
Dynamical characteristic of a thunderstorm is one of themost difficult to predict meteorological event since itslocally occurance characteristic and mixed structure
The effect of mezo-scale events increase this difficulty
Thunderstorms -2
Thunderstorms usually occur at strong vertical windshear 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 occurancedepends on the warming of the lower level and
moisture
Absorbs the heat energy from the surface andtransforms 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 dependon;
Unstable air mass
Lifting mechanism –UpliftingMoisture at mid and low level of the atmosphereWarm 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 airBoth 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 relationshipamong convective instabilities and severe stormsUsed:Quality controlled radiosonde data of 7 stations in Turkey; 1972-1997
Study Area
Radiosonde Stations
İstanbul
İzmir
Isparta
Ankara
Adana
Samsun
Diyarbakır
Radiosonde Data
PressureTemperatureHumidity profilesGeopotential height
Radiosonde Data
By using radisonde data;
Lapse rateMixing ratioEquivalent potential temperatureDew point temperature and etc.
were calculated
Mid-Latitudes
During the end of spring and the beginning of summerat mid-latitudes including Turkey, active cyclones andwide stratiform clouds are replaced by small-scaled airmovements 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 lowertroposphere were compared with instability indices in
order to predict the occurance mechanism of thunderstorms
Instability Indices
Instability indices help us to predict the storms andthunderstorms without using temp diagrams
The critical values of instability indices are calculatedaccording to the geographical and meteorological
characteristics of the region it is developed for
Instability indices
Instability indices;Showalter indexK indexRackliff indexJefferson indexVertical total indexCross total indexTotal total index
Potential wet bulb indexSWEAT indexKO index3D indexHumidity indexEnergy instability indexSari index and etc.
Annual Change
Annual change of thunderstorm occurance numbersshow a biomodal time distribution over Turkey
months
Mon
thly
mea
n th
unde
rsto
rm o
bser
vatio
n nu
mbe
rs
Thunderstorm Activity
The first maximum in thunderstorm numbers is reachedby May and the second by October
The distribution in both graphs is alikeIn Turkey thunderstorms are mostly effective in
between May-October
Thunderstorm observation
numbers for the first maximum;
May
Thunderstorm Activity
Monthly thunderstorm percents are calculated to examine the months important for the occurance time
of thunderstorms
months
Mon
thly
occ
uran
ce p
erce
nts
of t
hund
erst
orm
s
Seasonal Thunderstorm Activity
Spring and fall are the major seasons of thunderstormactivity
Effective thunderstorms over Southeastern regionduring mid-spring move to whole Anatolia by the
beginning of MayDifferential heating is the major source
Fall and winter seem to be the major seasons on theother sides of Meditterranean where the sea-airtemperature difference increases until January
Seasonal Thunderstorm Activity
During spring by;The increase of daytimeRare rain systems over Turkey
the temperature over the surface increases rapidly andconvective rains occur by means of the surface warming
As a result in April and June thunderstorm frequencyincreases 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 thethunderstorm activity originates from Meditterranean –
Aegean region and the BalkansMost of these thunderstorms are a result of
temperature difference and the rest are related todepressions
Sea-centered polar air climbs over the mountains andemits 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;
Differential heatingTopographyDistance from the seaAtmospheric front systems
Results & Discussion
Mid and Southeastern Anatolia are Turkey’sthunderstorm regions whereas the Aegean region is the
least effected
Results & Discussion
Enlargement of the study area and validation of newindices for the determination of Turkey’s general
specifications should be made