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