Thunderstorm Activities over Turkey

Transcription

1 Thunderstorm Activities over Turkey Ceyhan Kahya, Mikdat Kadioglu Istanbul Technical University, Department of Meteorology

2 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

3 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

4 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

5 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

6 Occurance of Thunderstorms In general the occurance of the thunderstorms depend on; Unstable air mass Lifting mechanism Uplifting Moisture at mid and low level of the atmosphere Warm and dry air at upper levels

7 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

8 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

9 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

10 Occurance of Thunderstorms The storm is now a full blown thunderstorm, complete with thunder, lightning, heavy precipitation, and turbulent winds

11 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

12 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

13 Occurance of Thunderstorms Thunder and lightning diminish and eventually cease altogether and the storm consists of weak downdrafts and light precipitation

14 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;

15 Study Area

16 Radiosonde Stations İstanbul İzmir Isparta Ankara Adana Samsun Diyarbakır

17 Radiosonde Data Pressure Temperature Humidity profiles Geopotential height

18 Radiosonde Data By using radisonde data; Lapse rate Mixing ratio Equivalent potential temperature Dew point temperature and etc. were calculated

19 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

20 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

21 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

22 Instability indices Instability indices; Showalter index K index Rackliff index Jefferson index Vertical total index Cross total index Total total index Potential wet bulb index SWEAT index KO index 3D index Humidity index Energy instability index Sari index and etc.

23 Annual Change Annual change of thunderstorm occurance numbers show a biomodal time distribution over Turkey Monthly mean thunderstorm observation numbers months

24 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

25 Thunderstorm Activity Monthly thunderstorm percents are calculated to examine the months important for the occurance time of thunderstorms Monthly occurance percents of thunderstorms months

26 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

27 Seasonal Thunderstorm Activity During spring by; Theincreaseof 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

28 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

29 Results & Discussion Thunderstorm formation in Turkey mostly depends on; Differential heating Topography Distance from the sea Atmospheric front systems

30 Results & Discussion Mid and Southeastern Anatolia are Turkey s thunderstorm regions whereas the Aegean region is the least effected

31 Results & Discussion Enlargement of the study area and validation of new indices for the determination of Turkey s general specifications should be made