Classification and temporal distribution of the fog events according to mechanism of trigger formation at the airports and obtained ataturk airport's ruyetograph

Air transportation is influenced directly from the weather conditions which are occurred in the atmosphere, making it important to study meteorological event affecting volatility at airports. In order to make regularly and safely the volatility activities at the airport, meteorological conditions must be within the specified criteria. If the meteorological conditions go the negative direction, this cause aircraft landing and departure times by airport operators, breaking up in the planning such as applied CAT category, delays in the flights, divert, cancellations and major crashes. It's known that many crashes and even fatal accidents occur negative weather events which are caused by meteorological phenomena. Such negative weather conditions are caused the loss of flight capacities at airports or negative situation such as crashes cause huge financial losses especially at the big airline companies, the negatives due to unplanned massive passengers on airport operation and the negatives are caused on the passengers due to temporal losses. Meteorological conditions such as strong wind, fog, thunderstorm, very low cloudiness which are the major negative weather evets cause difficulties in air transportation. Fog is the most important weather event that affects air transport negatively by restricting sight distance to a large extent locally. At the airport where it is observed the fog incident cause is more effective than the other negative meteorological events and the more frequent occurrence due to seasonality leads to more negative impacts of the flight. In addition, the predictability of local base occurrence due to the influence of environmental factors (sea, lake, river, hill, slope, etc.) is caused more complicated and more difficult than other meteorological events. Due to the fact that fog is the most difficult event to estimate, it cause a sudden unpredictable sight drop in the airports and the delays in all operations of the flights. Besides, with the sight drop fog causes important negatives both land and marine transportation. In this study, the fog weather events were examined that occurred at all airports in Turkey. The frequency analysis of the fog was carried out by examining the fog events in metar and speci observations made for aviation. In addition, fog events are classified according to their occurrence mechanisms. Fog events are also classified based on the types and examined temporal frequencies that characterizes with their duration and intensity. Classifying fog types; along with the objective criteria set out by using meteorological parameters (wind, cloud-base lowering) affecting the fog formation process, are taken into account in some geographical features of the airports. Geographical features are considered in classification. In addition, the parameters are examined such as temperature, wind, and pressure in the periods in which the fog came into existence. At the airport, the track CAT category was examined to show how narrow the visibility range of the observed fog line. With the frequency analysis of fog incident observed at airports, it is aimed to make it easier to predict when and how long the fog line is effective at each airport especially to airline companies and to estimate the fog line by classifying. In the study, the data of 2008-2016 years of Turkish State Meteorological Service metar-speci observations were used. Frequency analyzes of the fog events of the airports were obtained on an annual, monthly and daily basis. In addition, changes in meteorological parameters such as temperature, wind, and pressure were determined during the periods when the fog was observed. The other important topic in this study is frequency analyzes were carried out by using a simple objective algorithm classification based on the mechanism of occurrence of the fog line in each airport and by classifying 6 types of fog which are used extensively due to fog characteristic. If the observed fog line isn't included any class according to this algorithm, it is included to the classification which is called undefined fog type (UNK). In addition, the hydrological hydrograph approach to obtained as a ruyetograph for Atatürk (LTBA) airport is aimed to be evaluated the time interval from the fog formation period according to the visibility. According to the analysis carried out in the study, when it is considered regionally, it is seen that fog events occur more frequently in the airports established in Marmara region. When it is considered locally, it was presented that the fog event was observed mostly foggy days at Batman (LTCJ), Kocaeli Cengiz Topel (LTCQ), Balıkesir (LTBF), Bursa Yenişehir (LTBR), Ağrı (LTCO) airports and at least foggy days at Muğla Imsık (LTBV), Yalova (LTBP), Balıkesir Edremit (LTFD), İzmir Kalkıç (LTFA)airports. Atatürk (LTBA) airport average 5.6 days of year and 2015 year 9 foggy days and Sabiha Gökçen (LTFJ) airport; In 2015, the annual average was 30.8 daysof year and 47 days in total. There was a fog event in the Balıkesir (LTBF) airport that continued for 71 hours without interruption. It was concluded that airports fog events in Turkey are more frequent observed within the periods until at the end of autumn and the beginning of spring. In Erzurum (LTCE) airport, fog events accounted for %91.4 of cold fog, %4.8 of frost fog. When fog occurrences were observed at Atatürk (LTBA) airport, %39.6 of the wind was calm or variables directions and %25.1 was dominated by southwest SW. The fog events observed at Istanbul Atatürk Airport (LTBA) were classified as % 48.1 radiation (RAD), % 38.9 advection (ADV), % 11.1 cloud base lowering (CBL), % 1.0 precipitation (PCP) fog. According to the CAT category classification of the airports of Afyon (LTAF), Atatürk (LTBA), Bandırma (LTBG), Balıkesir (LTBF), Erzurum (LTCE), Konya (LTAN), Diyarbakir (LTCC), Bursa (LTBR) were performed in the category of CAT III according to the airport runway visibility when the fog rates were more than %53.4, %41.9, %55.2, %51.0, %59.0, %49.9, %55.5. Based on half hour (30 min) metar observations made at Ataturk airport, the onset fog, perpetuation and dissipation of fog events between 2008 and 2016 took an average of 5 hours and 03 minutes. It is natural that advection fog more occur than the airports that are left in the inland or in the city to the airports which are established near the sea, water structures and rivers.