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Investigations of a Southerly Non-Convective High Wind Event in Turkey and Effects on PM10 Values: A Case Study on April 18, 2012

  • Emrah Tuncay ÖzdemirEmail author
Article

Abstract

On 18 April 2012, a cyclone originating in the Central Mediterranean caused a southerly non-convective high wind event, gusts ≥ 50 kn and not associated with thunderstorms, in the western and interior regions of Turkey. Dust events occurred because of dust plumes that rose from the Sahara Desert and from the interior regions of Turkey. The particle matter profile (PM10) on 18 April 2012 was the result of dust transport that appeared in conjunction with a non-convective high wind event, which is investigated in this study. The main objective of this research is to describe the conditions that prevailed before or during the event that occurred over airports and the long-range (intercontinental) trans-boundary transport of PM10 in Turkey. The dust transport trajectories were adjusted to determine the trajectories of long-range dust particles and/or dust particles that moved from interior regions of Turkey using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and by calculating the backward trajectories of airports that experienced dust occurrences. Furthermore, dust RGB and MODIS satellite pictures, CALIPSO images, BSC-DREAM8b outputs, Global Forecast System analysis outputs, and surface chart analysis outputs were used for various analyses. On 18 April 2012, Turkey’s largest average hourly value of PM10 was observed to be 844 µg/m3 at Kayseri 1 Air Quality Observation Station. Consequently, it was concluded that the Sahara Desert is the main source of dust transport in Turkey.

Keywords

Non-convective high wind event PM10 CALIPSO HYSPLIT Sahara Desert 

1 Introduction

Particles from desert areas can be moved thousands or up to 10,000 km by the lift of strong winds under suitable meteorological conditions. Moreover, particles carried from the Sahara Desert can reach North America and South America after crossing the Atlantic Ocean (Prospero 1999; Goudie and Middleton 2001; Özdemir and Ertaş 2011; Bozlaker et al. 2013; Şengün and Kiranşan 2013). Meteorological cases involving dust and sand events disrupt air traffic and cause flight delays and cancellations (Özdemir et al. 2018).

Particulate matter of different sizes and shapes can consist of hundreds of different chemicals (EPA 2019). These particles spread to the atmosphere because of human activities (e.g., industrial sources, home heating sources, traffic) and natural sources (e.g., desert dust, wildfires). The PM10 has an aerodynamic diameter less than 10 μm and contains the entire range of inhalable atmospheric particulate matter (Vardoulakis and Kassomenos 2008). Wang et al. (2008) investigated changes in PM10 concentrations during dust storm events and found a strong correlation (r2 = 0.90) between PM10 and visibility. Subsequently, Leys et al. (2011) classified dust events into four major groups based on the effect of PM10 concentration on visibility, including severe dust storm: PM10 20.055 µg/m3, 0 ≤ visibility ≤ 0.2 km; moderate dust storm: PM10 3.252 µg/m3, 0.2 km < visibility ≤ 1 km; severe haze: PM10 527 µg/m3, 1 km < visibility ≤ 5 km; moderate haze: PM10 240 µg/m3, 5 km < visibility ≤ 10 km. Hence, PM10 concentration is a critical tool for analyzing meteorological events that limit visibility (Draxler et al. 2001; Escudero et al. 2006).

A cyclone that originated in the Central Mediterranean on 18 April 2012 caused a southerly non-convective (not related to thunderstorms) high wind event (i.e., gusts ≥ 50 kn) in the western and interior regions of Turkey. Dust events were observed over different areas, which decreased visibility down to and under 1 km. New extreme values were recorded at certain meteorological stations during the cyclone transition. A new extreme value of 81 kn (150 km/h) in Elmadağ/Ankara (capital of Turkey) was the highest observed value during this cyclone transition (TSMS 2018).

Anıl et al. (2009) found that in the year of 2008 in Istanbul, there were 96 days when the mean daily PM10 concentration exceeded 50 µg/m3 (the limit for human health), as measured at ten air quality observation stations. Based on seasonal periods, the authors used Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) modelling to examine the PM10 transport trajectories after calculating backward trajectories that belonged to each “mean daily 50 µg/m3 exceed” day. The authors concluded that the intercontinental transport of PM10 varies significant by season. In addition to this study, there are many national and international studies in the literature regarding dust storms, sand storms, PM10 transport, and utilization of models to determine backward trajectories to find the source areas (Karaca et al. 2005, 2009; Kındap et al. 2006; Chen et al. 2008; Kındap 2008; Wang et al. 2008; Leys et al. 2011; Kocak et al. 2011; Desouza et al. 2011; Incecik and Im 2012; Ghasem et al. 2012; Ozdemir et al. 2012; Wu et al. 2012; Fatemi et al. 2015; Tilev-Tanriover and Kahraman 2015; Singh et al. 2016; Çapraz et al. 2016; Baltaci 2017; Fatima et al. 2017; Modarres and Sadeghi 2018; Özdemir et al. 2018; Galabov and Chervenkov 2018).

In this study, the causes of dust events related to the southerly non-convective high wind event that occurred at airports located in the western and central parts of Turkey on 18 April 2012 were investigated. Long-range (intercontinental) PM10 transport routes and transport locations of dust particles from the inner regions of Turkey were investigated in detail. HYSPLIT back trajectory model was applied to the PM10 episode period to determine long-range dust transport to the airports in Turkey and also the transport locations of dust particles from the inner regions of Turkey.

2 Materials and Methods

2.1 METAR and SPECI Reports, AWOS, and PM10 Data

Aviation Routine Weather Report (METAR) and Aviation Selected Special Weather Report (SPECI) reports written by the Airport Meteorology Offices of Libya for the dates of 16 April and 18 April 2012 and by all Meteorology Offices of Turkey for the date of 18 April 2012 were examined (TSMS 2018; Ogimet 2018). For this research, the meteorological data sets of Benina (Benghazi) International Airport in Libya were interpreted (Table 1).
Table 1

Airport information

Airports

Coordinates

Elevation (m)

Libya

  

 Benina (Benghazi)

32°05′49″N 20°16′10″E

132

Turkey

  

 Afyonkarahisar

38°43′35″N 30°36′04″E

1009

 Atatürk (İstanbul)

40°58′34″N 28°48′50″E

50

 Çardak (Denizli)

37°47′16″N 29°42′18″E

852

 Dalaman (Muğla)

36°42′45″N 28°47′29″E

6

 Erkilet (Kayseri)

38°46′13″N 35°29′43″E

1069

 Esenboğa (Ankara)

40°07′41″N 32°59′42″E

953

 Eskişehir

39°47′02″N 30°34′55″E

787

 Eskişehir Anadolu

39°48′40″N 30°31′30″E

789

 Sivrihisar (Eskişehir)

39°27′01″N 31°21′56″E

968

 Güvercinlik (Ankara)

39°56′08″N 32°44′26″E

821

 Konya

37°58′50″N 32°33′45″E

1031

 Sabiha Gökçen (İstanbul)

40°53′54″N 29°18′33″E

95

 Süleyman Demirel (Isparta)

37°51′54″N 30°22′55″E

864

 Yalova

40°41′11″N 29°22′48″E

13

 Samandıra (İstanbul)

40°59′29″N 029°12′57″E

123

To illustrate the METAR and SPECI observations, Automated Weather Observing System (AWOS) surface observation data of the airports administered by the Turkish State Meteorological Service (TSMS) were used. In addition, mean hourly PM10 data sets measured by air quality observation stations of the Ministry of Environment and Urbanization (101 stations) and air quality observation stations managed by Istanbul Metropolitan Municipality (11 stations) were used in this study (Havaizleme 2018). There are 100 urban, five industrial, four traffic, and three rural (a total of 112) air quality observation stations. PM10 concentrations are measured at 3 m above ground level. During the study period, only six stations measured PM2.5 concentration in Turkey. These stations were in Ankara, the capital of Turkey. Hence, this study did not use PM2.5 data. Figure 1 shows the locations of the studied airports and air quality observation stations.
Fig. 1

Locations of air quality stations (blue points) and airports (aircraft shapes) in Turkey

In wind storm research of Turkey, the Beaufort scale is used to define storms. According to the Beaufort scale, wind speeds greater than or equal to 33.4 kn (17.2 m/s) are classified as storms (Engin 2004; Öztürk 2010). Saaroni et al. (1998) and Deniz et al. (2013) analyzed storm events in which the hourly wind speed exceeded 30.1 kn (15.5 m/s). The National Weather Service (NWS) of the United States describes the following criteria for a high wind event: wind speed that is effective for at least 1 h must be equal to or greater than 35 kn, wind gusts for any period of time must be equal to or greater than 50 kn (NOAA 2018). A wind gust value that is equal to or greater than 50 kn was used in this study. In addition, wind gusts of 50 kn or greater in combination with a thunderstorm was accepted as a criterion for a severe thunderstorm (Özdemir and Deniz 2016; Özdemir 2018). On April 18, 2012, there was no thunderstorm event in combination with a high wind event; hence, this study is evaluated as being a non-convective high wind event. There are many studies related to this subject (Lynch et al. 2003; Knox et al. 2008, 2011; Sirdas et al. 2017; Özdemir 2018). On the event day, measured wind gust values at the airports that were equal to or higher than 50 kn are shown in Table 1.

At the international airports of Turkey, METAR observations are issued at the 20th and 50th minute of every UTC hour. In contrast, at the civil and military airfields, METAR observations are issued only at the 50th min of every UTC hour. According to the International Civil Aviation Organization (ICAO) ANNEX-3 (Annex (3) ICAO 2016), a SPECI observation is issued any time between two METAR observations when SPECI conditions exist. Both METAR and SPECI observations provide the speed, direction, and gustiness of wind. Furthermore, meteorological cases and other meteorological parameters that are detected by meteorological engineers or officers have been reported on observations. All METAR and SPECI observations and recorded data sets of the 18 April 2012 meteorological case on were analyzed. All wind gust values of the airports in Turkey were examined (62 airports); significant weather events were included in this research. Wind speed and direction are measured at 10 m above the ground at the Turkish airports. In addition to METAR and SPECI, synoptic observations are also issued at the airports. Meteorology stations at the airports are not only well equipped by having AWOS, but also employ humans who are responsible for observing and reporting meteorological events. However, many synoptic and climatology stations are automated; hence, these stations are not capable of reporting meteorologic events. Furthermore, these 62 airports are homogeneously distributed within Turkey (Fig. 1). Therefore, only airport meteorology stations are used in this study. METAR and SPECI observations, which belong to Libyan airports in North Africa between the dates of 16–18 April 2012, were interpreted in order to search the source area of the dust.

2.2 Synoptic, Upper Level Maps, and GFS Model

A synoptic map shows surface weather observations. The spatial distribution of sea level pressure on a synoptic map is used to analyze the locations of fronts and air masses. At the surface point of observation, in addition to sea level pressure, other meteorological parameter elements and on-going meteorological events are shown on a synoptic map (NWS 2019). Upper level maps, obtained from radiosonde observations, are produced for different portions of the atmosphere above the lower troposphere, generally starting from 850 hPa. Isolines (i.e., equal pressure lines) on these maps show the heights of a constant pressure surface (NWS 2019). The Global Forecast System (GFS) is a global numerical weather forecast model produced by the National Centers for Environmental Prediction (NCEP). In this dataset, atmospheric variables are available for temperatures, winds, precipitation, and atmospheric ozone concentration. The spatial resolution of the GFS is 18 miles (28 km) and is used for weather forecasts for up to 16 days (GFS 2019). The surface chart prepared by Deutscher Wetterdienst and the 850 hPa, 700 hPa, 500 hPa, and 300 hPa upper level maps that are owned by GFS analysis products are published on the Wetter3 web page. All these maps were used for synoptic analyses on the dates of 16, 17, and 18 April 2012 (Wetter3 2018).

2.3 Satellite Images

First, to confirm transport, dust transport was analyzed using the dust product of Meteosat Second Generation (MSG) satellite pictures. The dust product is the combined red, green, blue (RGB) picture of MSG infrared (IR) channels. This product enables one to observe the development and movement of dust (pink color) during nighttime and daytime. Dust RGB satellite pictures are the combination of Spinning Enhanced Visible and Infrared Imager (SEVIRI) IR8.7, IR10.8 and IR12.0 channels (EUMETRAIN 2018). These dust RGB satellite picture are obtained from TSMS.

Moderate Resolution Imaging Spectroradiometer (MODIS) satellite pictures that had been recorded by Aqua and Terra satellites from the National Aeronautics and Space Administration (NASA) were utilised for the analysis of satellite pictures. The viewing swath of MODIS is 2330 km and MODIS sees every point on the earth in 36 spectral bands every 1–2 days. Hence, MODIS tracks the vital signs of the earth with a wider array than any other Terra sensor. The sensor measures cloud coverage nearly every day (MODIS 2019). MODIS satellite images are obtained from NASA (NASA 2018).

CALIPSO (Cloud—Aerosol LIDAR Infrared Pathfinder Satellite Observations) measures clouds and aerosol concentrations in the atmosphere. The spatial resolution of cloud products is 5 km, but cloud boundaries can be detected at higher spatial resolution. The aerosol profile products of CALIPSO at 532 nm has 40 km spatial resolution at all altitudes to account for weaker backscatter signals of aerosols (CALIPSO 2019). In this study, CALIPSO Level 2 at 5-km spatial resolution aerosol profile pictures were used, which were obtained from CALIPSO (CALIPSO 2019).

2.4 ArcGIS and BSC-DREAM8b

The ArcGIS 9.3 programme was used to show the temporal and spatial distribution of average hourly PM10 values over Turkey. In this study, the spatial distribution maps of PM10 concentrations are plotted using the inverse distance weighted (IDW) interpolation technique. The IDW technique gives more weight on the measurement points closer to the prediction point than those farther away. Hence, the influence of measurement on a prediction point is reduced by distance (ARCGIS 2019).

Pictures of the dust concentration at the surface level were used to display the spatiotemporal change in the concentrations during the analysis period. These pictures were obtained from the BSC (BSC-DREAM8b 2018), which utilizes the Barcelona Supercomputing Center—Dust Regional Atmospheric Model (BSC-DREAM8b), and has eight transport bin sizes ranging between 0.1 and 10 µm. This model solves the Euler-type partial differential non-linear equations for dust mass continuity for understanding and predicting dust (Basart et al. 2012; BSC 2019).

2.5 HYSPLIT Model and GDAS Meteorological Data

The HYSPLIT model was developed by NOAA and Australia’s Bureau of Meteorology and uses trajectories of air parcels to investigate the potential routes of particles. In this study, this model was used to determine the source of transported dust. The HYSPLIT model uses a hybrid approach that is a combination of Eulerian and Lagrangian approaches. While the Eulerian approach uses a fixed three-dimensional grid as a frame of reference to compute pollutant air concentrations, the Lagrangian approach uses a moving frame of reference for the advection and diffusion calculations as the trajectories move from their initial location (ARL 2019).

The Global Data Assimilation System (GDAS) meteorological data was run on the NOAA Air Resources Laboratory (ARL) HYSPLIT-WEB (Internet-based) trajectory model (HYSPLIT 2018). The GDAS collects all available meteorological data from different sources, including global satellite, conventional (rawinsonde, aircraft, and surface), and radar observations, within a ± 3-h window of the analysis time. A 9-h Global Spectral Model (GSM) forecast obtained from the previous GDAS analysis was used as the first guess for assimilation. The GDAS operates with the most comprehensive available dataset at a late data cutoff (06:00) to provide background for the next 6 hourly cycle forecasts. The GDAS is converted from a spectral coefficient to 1° spatial resolution grids in latitude and longitude and from sigma levels to a mandatory pressure level (ARL 2019; EMC 2019). In this study, 1° GDAS data were used in HYSPLIT runs. The HYSPLIT model was run at heights of 10 m, 1500 m, and 3000 (e.g., Escudero et al. 2006; Kaskaoutis et al. 2008; Meloni et al. 2008; Carmona and Alpert 2009; Nastos 2012; ARL 2019) to calculated the backward trajectories for 48 h. The lowest level is selected for two reasons. First, a 10-m height represents the boundary layer transport for near the surface. Second, the wind speed and direction are measured at 10 m above the ground level at the airports. The heights of 1500 m and 3000 m are selected because they represent the boundary layer transport free from topographic effect and free troposphere, respectively.

3 Analysis and Results

3.1 Source Region Analysis

METAR and SPECI observations made at the airports in Libya on 16 April to 18 April were interpreted. Table 2 displays the METAR and SPECI observations, which indicate that visibility values less than 1000 m were observed at the Benina International Airport in Benghazi, Libya (Fig. 2). According to the observations, widespread blowing dust events started rapidly and visibility decreased to 4 km at 08:40 UTC on 16 April. Then, a widespread blowing dust event turned into a storm event at 10:13 UTC. The most effective period of the dust storm event was between the hours of 11:50 UTC and 13:20 UTC. During this time range, the wind gust value reached 40 kn and meteorological and vertical visibility were 200 m and 300 ft, respectively. At 15:20 UTC, the dust storm event turned into a widespread dust event, which lasted until 20:55 UTC. A widespread blowing dust event restarted at 06:25 UTC on 17 April, which changed into a dust storm event at 08:20 UTC. The dust storm event lasted until 13.55 UTC. Moreover, meteorological and vertical visibility dropped to 100 m and 200 ft, respectively. The dust storm event turned into a widespread blowing dust event at 14:20 UTC that continued until 14:55 UTC.
Table 2

METAR and SPECI observations when the visibility dropped below 1000 m at Benina (Benghazi) International Airport for the period from 16 to 18 April 2012

Time (UTC)

Wind direction (°)

Mean wind speed (kn)

Gust speed (kn)

Weather phenomena

Visibility (m)

Vertical visibility (ft)

Cloud base (ft)

16 April 2012

 10:13

150

30

40

DS

500

 10:50

160

30

40

DS

300

300

 11:20

160

30

40

DS

300

300

 11:50

170

30

40

DS

200

300

 12:20

170

20

30

DS

200

300

 12:50

170

25

35

DS

200

300

 13:20

170

25

35

DS

200

300

 13:50

170

30

DS

500

300

 14:20

170

30

DS

500

300

 14:50

170

30

DS

500

300

17 April 2012

 08:20

160

25

DS

800

300

 08:50

160

25

DS

500

300

 09:20

160

20

DS

300

200

 09:55

170

15

DS

200

200

 10:20

180

15

DS

100

200

 10:50

180

10

DS

100

200

 11:20

230

10

DS

100

200

 11:50

240

10

DS

100

200

 12:30

250

10

DS

300

200

 12:55

270

10

DS

500

200

 13:30

310

25

DS

800

300

DS (dust storm)

Fig. 2

Locations of the study area

3.1.1 Synoptic, Satellite Images, CALIPSO, and BSC-DREAM8b Analyses on 16 April 2012

On 16 April 2012 at 12:00 UTC, a system in Southern Italy brimmed with a 1000 hPa low pressure center (Fig. 3a). The cold front over the Central Mediterranean, which was related to the low-pressure system, was united with the warm front over Libya, which had a low-pressure value or 1000 hPa. A 144 decametre (dam; 1 dam = 10 m) contour of 850 hPa that ranged to the Western Mediterranean by the way of Tunisia and Algeria and a 15 °C isotherm passed over Libya (Fig. 3b). Over Libya, steep gradients in contours and isotherms were observed. A 0 °C isotherm crossed over Libya in the 700 hPa map and there was a 292 dam low center that covered a large part of Italy (Fig. 3c). Moreover, there was contour congestion over the north of the Central Mediterranean and Libya. On the 500 hPa map, − 25 °C cold weather covered Algeria and Tunisia. A 552 dam contour formed a sharp trough by lying down to the southwest of Algeria (Fig. 3d). On the 300 hPa, two jets had a 120 kn core, which was located over North Libya (Fig. 3e). One of these jets was lying over Turkey, while the other was lying over Egypt. In Fig. 3f (dust storms (pink) during both day and night), an RGB satellite picture at 12:00 UTC shows the dust storm in Libya and dust concentrations over the Central Mediterranean.
Fig. 3

Weather maps and dust image at 12:00 UTC on 16 April 2012; a surface map (continuous black lines: average reduced sea level pressure, hPa = 100 Pa; cold front: black line with triangles; warm front: black line with semicircles; occluded front: black line with triangles and semicircles), b 850 hPa (continuous black lines: geopotential heights, dam = 10 m; continuous white lines: temperatures, degrees Celsius, white lines with 5 °C interval; colours: temperatures, degrees Celsius, colours with 2 °C interval), c 700 hPa (continuous black lines: geopotential heights, dam = 10 m; continuous white lines: temperatures, degrees Celsius, white lines with 5 °C interval; colours: temperatures, degrees Celsius, colours with 2 °C interval), d 500 hPa (continuous black lines: geopotential heights, dam = 10 m; continuous white lines: temperatures, degrees Celsius, white lines with 5 °C interval; colours: temperatures, degrees Celsius, colours with 2 °C interval), e 300 hPa (wind barb: indicates the wind direction and wind speed, long barb = 10 kn, short barb = 5 kn, pennant = 50 kn), and f MSG dust image (dust plume: bright magenta, pink; mid, thick clouds: tan shades; cold, thick clouds: red; high, thin ice clouds: black)

Dust transport over Khalij Surt and the Central Mediterranean resulting from a dust storm over Libya on 16 April 2012 can be detected on the MODIS natural-coloured satellite picture that was taken by the NASA Aqua satellite (Fig. 4a). The desert-based dust concentration increased from east of Benghazi towards the Central Mediterranean. West of the Gulf of Sidra, thin dust particles were carried to the Central Mediterranean (Ritter 2006; CIA 2018; NASA 2018). The dust storm over Libya could be easily seen in the 532 nm total attenuated backscatter pictures, which were taken between 12:05 UTC and 12:18 UTC from the CALIPSO at morning time (Fig. 4b). Dust concentration reached up to a height of approximately 5 km, from Northeast Chad to the Gulf of Sidra in Libya. The dust reached a height of nearly 7 km over the Central Mediterranean (Fig. 4c).
Fig. 4

On 16 April 2012; a dust storm over Libya (natural color image—MODIS Aqua satellite), b daytime orbit track and 532 nm total attenuated backscatter image between 12:05 UTC and 12:18 UTC, c aerosol subtype image between 12:05 UTC and 12:18 UTC, d dust surface concentration image at 12:00 UTC

As a result of the dust storm and the southern wind flow over Libya, the dust concentration increased over the Central Mediterranean. Based on the BSC-DREAM8b, dust surface concentration approached the maximum level of 320 µg/m3 over the Central Mediterranean, Peloponnese, İzmir (west of Turkey), and its vicinity (Fig. 4d) at 12:00 UTC on 16 April 2012.

3.1.2 Synoptic, Satellite Images, CALIPSO, and BSC-DREAM8b Analyses on 17 April 2012

On the 17 April 2012 12:00 UTC surface chart, two high pressure centers measuring 1015 hPa existed over Turkey (Fig. 5a). There were two 1005 hPa low pressure centers and frontal systems that were related to the pressure centers over northern Libya and Greece. On the 850 hPa map of the same day, contour and isotherm congestion remained over Libya (Fig. 5b). The 700 hPa and 500 hPa maps are shown in Fig. 5c, d, respectively. Both maps contain two sharp troughs that are positioned towards the northwest Sahara, including Algeria and Tunisia. On the 300 hPa map, two jets have a core of 120 kn (Fig. 5e). One of the two jets, which appears on the northern side, are positioned toward the northwest of Turkey. When the 12:00 UTC dust RGB satellite picture is examined, a dust storm over Benghazi, Libya and surroundings can be easily observed (Fig. 5f).
Fig. 5

Weather maps and dust image at 12:00 UTC on 17 April 2012; a surface map, b 850 hPa, c 700 hPa, d 500 hPa, e 300 hPa, and f MSG dust image (explanations are given in Fig. 3)

The dust storm, which occurred over Libya on 17 April 2012, is shown in the MODIS natural-coloured picture taken by the NASA Terra satellite in Fig. 6. The desert-based dust storm moved toward the Central Mediterranean by crossing over Benghazi and the Al-Berka highland, as on the previous day (CIA 2018; NASA 2018).
Fig. 6

Dust storm over Libya on 17 April 2012 (natural color image—MODIS Terra satellite)

Dust storms that occurred over Libya on the dates of 16 April and 17 April 2012 resulted in increased dust concentrations over the Central Mediterranean. The 532 nm total attenuated backscatter picture, which was taken by CALIPSO on 17 April 2012, shows that the dust concentration over Northeast Africa, Turkey, and the North Black Sea increased to approximately 5 km, 7 km, and 9 km height, respectively, between 00:02 and 00:16 UTC (Fig. 7a, b). In the aerosol subtype picture of CALIPSO, dated 17 April 2012 between the hours of 11:09–11:23 UTC, the dust concentration over the East Mediterranean was increased to 5.5 km height (Fig. 7c).
Fig. 7

On 17 April 2012; a night-time orbit track and total attenuated backscatter image between 00:02 UTC and 00:16 UTC, b aerosol subtype image between 00:02 UTC and 00:16 UTC on 17 April 2012, c daytime orbit track and aerosol subtype image between 11:09 UTC and 11:23 UTC, d dust surface concentration image at 12:00 UTC

Values that nearly reached approximately 80 µg/m3 that spread over the Central Mediterranean and Northwest-interior regions of Turkey are seen in the BSC-DREAM8b picture of dust surface concentration, dated 17 April 2012 at 12:00 UTC (Fig. 7d).

3.1.3 Synoptic and Satellite Image Analyses on 18 April 2012

The 985 hPa low-pressure center extended over the Aegean Sea deepening on 18 April 2012 at 06:00 UTC (Fig. 8a). The wind data at a height of 10 m revealed 30 kn westerly winds between southern Crete and Libya. Additionally, the system caused southerly and southeasterly winds to reach western Turkey by a cyclonic turn due to the 985 hPa low pressure center that was located over the Aegean Sea. Over the Aegean Sea, while there was a low center of 128 dam on 850 hPa (Fig. 8b), a 284 dam low center dominated on 700 hPa (Fig. 8c). On the 500 hPa map, a 546 dam contour ran from western Turkey to Crete Island (Fig. 8d). Two jet streams with southerly wind jet core values crossed over the Mediterranean from the northeast of Libya to western Turkey (Fig. 8e). These values are 120 and 130 kn on the 500-hPa and 300-hPa maps, respectively. Based on rawinsonde observations, the depth of jet over İzmir, in which winds of 60 kn or greater extend at that point, was between 2 and 16 km at 00:00 UTC on 18 April 2012 (data not shown). An RGB satellite picture taken at 06:00 UTC shows that the dust concentration was deep and dense over Turkey (Fig. 8f).
Fig. 8

Weather maps and dust image at 06:00 UTC on 18 April 2012; a surface map, b 850 hPa, c 700 hPa, d 500 hPa, e 300 hPa, and f MSG dust image (explanations are given in Fig. 3)

While the cold front of the low-pressure center reached Cairo, Egypt by crossing over the southeast regions of Turkey (from the Aegean Sea), the warm front of the system reached Russia by crossing over the Aegean Sea, Bulgaria, and northwest of the Black Sea (Fig. 9a). On 18 April 2012 at 12:00 UTC, the low-pressure center maintained its value of 985 hPa and it moved toward the North Aegean Sea. The system occluded during its movement, which resulted in formation of an occluded front. Three fronts were related to the 985 hPa low-pressure center: the occluded front that reached Bulgaria and west of the Black Sea by crossing over the North Aegean Sea; the cold front that arrived in Cyprus by way of the west of Black Sea; and the warm front that reached Russia from the northwest of Black Sea by way of the west of Black Sea. Following analysis of the wind data at a height of 10 m on 18 April 2012 at 12:00 UTC, westerly winds of 45 kn are seen. Two low-pressure centers developed because of a 995 hPa low-pressure center that was located over the Aegean Sea, which moved toward the northeast by preserving its value. The first of these low-pressure centers was located over the North Aegean Sea, while the second of these centers was located over the Eastern Marmara and Western Black Sea. While the 128 dam low center existed over the North Aegean Sea, Thrace, Bulgaria, and Greece at 850 hPa (Fig. 9b), the 284 dam low center was seen over these same areas at 700 hPa (Fig. 9c). As for the 500 hPa map, the 546 dam contour reached toward the South Aegean from the interior regions of Turkey (Fig. 9d). The jet stream, which had jetcore values of 110 kn and 120 kn at 500 hPa and 300 hPa, respectively (Fig. 9e), reached out from Northeast Libya to Western Turkey by crossing over the Mediterranean. Based on rawinsonde observations, the depth of jet over Ankara was between 3 and 14 km at 12:00 UTC on 18 April 2012 (figure not shown). The RGB satellite picture in Fig. 9f shows 12:00 UTC on 18 April 2012. In the satellite picture, an intense dust concentration is seen over the interior regions of Turkey.
Fig. 9

Weather maps and dust image at 12:00 UTC on 18 April 2012; a surface map, b 850 hPa, c 700 hPa, d 500 hPa, e 300 hPa, and f MSG dust image (explanations are given in Fig. 3)

3.2 Analysis of Airport Observations in Turkey on 18 April 2012

METAR, SPECI, daily maximum wind values, and recorded event values obtained from airports were analyzed. Table 3 shows wind gust values greater than or equal to 50 kn at airports, time, wind speeds, weather events, visibility, vertical visibility, and cloud base height values on 18 April 2012. The highest observed gust value was 65 kn at Afyonkarahisar Airport at 08:22 UTC and Sivrihisar Airport at 09:50 UTC. Based on Table 3, widespread dust, blowing widespread dust, light showers with rain, and blowing sand events were observed in various regions and places. The events with values and their regions are as follows: widespread dust in Afyonkarahisar City; blowing widespread dust at Esenboğa Airport (max. wind gust 56 kn), Eskişehir (max. wind gust 52 kn), Eskişehir Anadolu (max. wind gust 56 kn), and Sivrihisar and Güvercinlik Airports (Ankara) (max. wind gust 55 kn); blowing widespread dust (max. wind gust 63 kn) and light showers with rain at the airport in Konya; and a blowing sand event at Sabiha Gökçen Airport (max. wind gust 59 kn), and Samandıra Airport (max. wind gust 57 kn). Consequently, dust or sand events with a southerly storm were observed on 18 April 2012 over nine airports located in five different cities.
Table 3

Airports with gust values equal to 50 kn or more with time, wind speed, and weather events on 18 April 2012

Airport

Time (UTC)

Wind direction (°)

Maximum wind gust speed (kn)

Weather phenomena

Visibility (m)

Vertical visibility (ft)

Cloud base (ft)

Afyonkarahisar

07:50

150

56

8000

3500

Afyonkarahisar

08:03

150

60

DU

4500

3500

Afyonkarahisar

08:22

150

65

DU

Afyonkarahisar

08:32

150

61

DU

2500

3500

Afyonkarahisar

08:50

150

63

DU

1700

3000

Afyonkarahisar

09:28

150

53

DU

4000

3000

Atatürk

10:11

220

57

Atatürk

10:17

230

57

10,000

3500

Atatürk

10:20

230

57

10,000

3500

Çardak

03:50

140

50

10,000

3500

Çardak

08:37

190

54

Çardak

08:50

170

52

10,000

3500

Çardak

09:03

160

50

7000

3500

Dalaman

05:20

160

53

10,000

3000

Dalaman

05:23

160

57

Erkilet

14:33

140

54

Esenboğa

13:09

170

56

BLDU

Esenboğa

13:20

180

53

BLDU

1000

800

Eskişehir

09:04

180

52

BLDU

Eskişehir

09:08

180

52

BLDU

4200

4000

Esk. Anadolu

08:50

160

53

BLDU

5000

4000

Esk. Anadolu

09:10

210

56

BLDU

Güvercinlik

12:54

190

55

BLDU

Konya

08:20

180

50

BLDU

3500

4000

Konya

09:12

170

51

BLDU

1700

3000

Konya

09:50

180

51

BLDU

4000

3000

Konya

10:40

200

53

(–)SHRA

6000

3500

Konya

11:39

180

53

(–)SHRA/BLDU

1200

3000

Konya

11:50

180

53

(–)SHRA/BLDU

1100

3000

Konya

11:54

160

63

()SHRA/BLDU

Sabiha Gökçen

10:28

230

59

BLSA

2200

3500

Samandıra

10:32

160

57

BLSA

1000

1000

Sivrihisar

08:50

160

53

BLDU

2000

20,000

Sivrihisar

09:50

180

65

BLDU

1500

20,000

Sivrihisar

10:50

190

55

BLDU

4000

3500

Sivrihisar

11:50

160

55

BLDU

6000

3500

Süleyman Demirel

08:56

170

59

Süleyman Demirel

09:20

180

55

10,000

3500

Süleyman Demirel

09:50

170

54

10,000

3500

Yalova

10:25

250

56

Yalova

10:27

250

56

6000

1600

Bold characters represent the maximum wind speed and its time

DU widespread dust, BLDU blowing widespread dust, SHRA light shower with rain, BLSA blowing sand

3.3 PM10 Analysis of Turkey on 18 April 2012

On 18 April 2012, the maximum mean hourly PM10 concentration value for 2012 were observed at many air quality stations. The annual maximum mean hourly PM10 concentration and the average mean hourly PM10 concentration in 2012 at those stations are: Bilecik (max.: 472 µg/m3, avg.: 52 µg/m3), Burdur (max.: 786 µg/m3, avg.: 78 µg/m3), İstanbul (Sarıyer) (max.: 393 µg/m3, avg.: 38 µg/m3), Kayseri 1 (max.: 844 µg/m3, avg.: 67 µg/m3), Kocaeli (max.: 636 µg/m3, avg.: 54 µg/m3), Konya (Selçuklu) (max.: 788 µg/m3, avg.: 56 µg/m3), and Sakarya (max.: 618 µg/m3, avg.: 82 µg/m3) (Table 4).
Table 4

Maximum mean hourly PM10 concentration (µg/m3) and the time of observation on 18 April 2012 and the average mean hourly PM10 concentration (µg/m3) for 2012 at certain air quality stations

Air quality station

Coordinates

Episode time (UTC)

Max. and avg. PM10 (µg m−3)

Bilecik (urban)

40°08′28″N 29°58′40″E

10:00

472 and 52

Burdur (urban)

37°43′22″N 30°17′40″E

08:00

786 and 78

Isparta (urban)

37°46′37″N 30°32′49″E

09:00

522 and 86

Gaziantep (urban)

37°03′30″N 37°21′03″E

05:00

209 and 108

Batman (urban)

37°54′02″N 41°07′44″E

16:00

169 and 109

Afyon (urban)

38°45′06″N 30°32′34″E

05:00

296 and 98

Düzce (urban)

40°50′44″N 31°08′53″E

13:00

491 and 85

Kayseri 1 (rural)

38°44′24″N 35°22′31″E

14:00

844 and 67

Konya (Selçuklu) (urban)

37°56′40″N 32°30′29″E

11:00

788 and 56

Konya (Meram) (urban)

37°51′36″N 32°28′31″E

09:00

742 and 73

Uşak (urban)

38°40′21″N 29°24′20″E

10:00

332 and 69

Kütahya (urban)

39°25′07″N 29°59′09″E

11:00

220 and 77

Kocaeli (urban)

40°45′49″N 29°56′46″E

11:00

636 and 54

Sakarya (urban)

40°45′19″N 30°23′28″E

12:00

618 and 82

İstanbul (Kartal) (urban)

40°53′24″N 29°12′26″E

11:00

422 and 79

İstanbul (Kağıthane) (urban)

41°05′15″N 28°58′57″E

12:00

441 and 81

İstanbul (Sarıyer) (urban)

41°07′44″N 29°02′58″E

11:00

393 and 38

Bold text refers to measurement of the maximum annual value during this episode

The spatial distribution of mean hourly PM10 concentration values in Turkey between 00:00 UTC and 15:00 UTC on 18 April 2012 were plotted (Fig. 10a–p). A southerly, non-convective high wind event had started at 03:50 UTC at Çardak Airfield and ended at 14:33 UTC at Erkilet Airfield. Because of the duration of this event, the temporal distribution of PM10 concentrations until 15:00 UTC are plotted. Values of PM10 started to increase in the western-interior regions of Turkey between 00:00 UTC and 03:00 UTC. Beginning at 04:00 UTC, increments of PM10 spread toward the interior and northern regions of Turkey. PM10 increased to a maximum value over Istanbul at approximately 11:00 UTC. After 13:00 UTC, PM10 values started to decrease in the western and northwest regions of Turkey. After 15:00 UTC, a decrease was seen over the western regions and an increase was observed over the southeast regions.
Fig. 10

Temporal and spatial distribution of hourly mean PM10 concentration (µg/m3) values over Turkey from 00:00 UTC until 15:00 UTC on 18 April 2018 (the color represents the effect of PM10 concentration on human health; green: good; yellow: moderate; orange: unhealthy for sensitive groups; red: unhealthy; purple: very unhealthy; brown, black, and white: hazardous)

3.4 HYSPLIT Analysis

A HYSPLIT model was used to find the trajectories of dust events (episodic PM10), which occurred during a southerly non-convective high wind event over airports on 18 April 2012. The GDAS was run in the NOAA ARL HYSPLIT-WEB trajectory model for 48 hourly backward trajectories at 12 h intervals. The study focused on nine airports in five different cities with above ground levels heights of 10 m, 1500 m, and 3000 m and event times in the HYSPLIT model to determine the 48 hourly backward trajectories that were tracked by particles. The time at which wind strengths of dust events with the southerly non-convective high wind event were at their highest values is based on the UTC hour (Table 3). The highest wind speed recorded time observed with the southerly non-convective high wind event at the airports is considered to be the onset time of the dust events; the nearest exact UTC hour was selected (e.g., 03:00, 04:00 etc.) to execute the HYSPLIT model.

In the 48 hourly backward trajectory analysis for dust heights of 10 , 1500 , and 3000 m during the event that occurred over Afyonkarahisar Airport on 18 April 2012 at 09:00 UTC, it can be seen that transport at 10 m, 1500 m, and 3000 m came from the eastern Mediterranean, Aegean, and the Sahara Desert, respectively (Fig. 11a). Airfields of Eskişehir (Eskişehir, Eskişehir Anadolu, and Sivrihisar Airports) have similar levels of the same transport source at 10:00 UTC (Fig. 11b). For airports in Istanbul, the event appeared at 11:00 UTC and its source was the central and east Mediterranean on the 48 hourly-backward trajectories (Fig. 11c, d). For the Konya Airport, while the source is the Sahara Desert for the height of 3000 m, the east Mediterranean is the source for 1500 m (Fig. 11e). The source for the event that occurred at Güvercinlik and Esenboğa Airports at 13:00 UTC was in the Sahara Desert (Libya and Egypt) for both heights of 10 m and 3000 m, respectively (Fig. 11f).
Fig. 11

48-h back trajectories at 10 m (red line: backward trajectory; red triangle label interval: every 12 h backward trajectory location), 1500 m (blue line: backward trajectory; blue square label interval: every 12 h backward trajectory location) and 3000 m (green line: backward trajectory; green circle label interval: every 12 h backward trajectory location); a starting at 09:00 UTC for Afyonkarahisar Airport (black star), b starting at 10:00 UTC for the three airports in Eskişehir City (left upper black star: Eskişehir and Eskişehir Anadolu Airports (close to each other), right bottom black star: Sivrihisar Airport), c starting at 11:00 UTC for Samandıra (Istanbul) Airport (black star), d starting at 11:00 UTC for Sabiha Gökçen (Istanbul) Airport (black star), e starting at 12:00 UTC for Konya Airport (black star), f starting at 13:00 UTC Güvercinlik (Ankara) (left bottom black star) and Esenboğa (Ankara) (right upper black star) Airports

4 Discussions and Conclusions

In this study, wind gust speeds equal to or greater than 50 kn were detected at 15 different airports in Turkey. On 18 April 2012, the maximum wind gust value was measured to be 65 kn in the airports of Afyonkarahisar and Sivrihisar. Dust and sand events were reported at nine airports. According to the PM10 data sets generated at the air quality stations of the Ministry of Environment and Urbanization and Istanbul Metropolitan Municipality, episodes were encountered in all regions of Turkey on 18 April 2012 except for the east region. In the satellite and synoptic analyses that were performed to determine the sources of the episodes, a cyclone that was based in the central Mediterranean was observed to affect the interior and western regions of Turkey by getting deep on 18 April 2012. The cyclone that moved with the jetstreams collected dust blocks from the Sahara Desert and the central Mediterranean that resulted in increased particle matter profiles in Turkey. A series of 48 hourly-backward trajectories at 10 m, 1500 m, and 3000 m were calculated for nine selected airports using the HYSPLIT model. Modelling results determined that the source of the dust events that occurred on 18 April 2012 was partly the central Mediterranean and mainly the Sahara Desert.

In this cyclone transition, the new record of the highest wind speed value was measured to be 81 kn (150 km/h) in Elmadağ/ Ankara. The other observed extreme values were in Datça [Muğla, 74 kn (137 km/h)] and Cihanbeyli [Konya, 64.8 kn (120 km/h)]. According to the data of the TSMS, some failures in air traffic control appeared to be due to this southerly non-convective high wind event. Dust events occurred in certain counties and cities; dust transport caused a reduction in visibility and muddy rain in other regions. Also, a dust event occurred on the Konya-Ankara and Konya-Ereğli highways because of the southerly non-convective high wind event reaching a speed of 63.2 kn (117 km/h) over Konya. Thus, it was stated that visibility was partially reduced to under 1 km and many multiple-vehicle accidents occurred on various highways. Two people died and 20 people were injured in the accidents. According to the TSMS reports, the roofs of some buildings flew off, covers of greenhouses were damaged, trees and billboards fell over, traffic signs were dislodged, and branches of trees were broken in dramatic fashion. In certain settlements, communication and energy lines were ruined and, as a result of this situation, power blackouts occurred. Numerous people and animals were harmed as a result of the ripping off of roofs and billboards. The southerly non-convective high wind event caused interruptions to land, marine, and air traffic. Because of the southerly non-convective high wind event, a few airplanes had to pass over the airfield at Istanbul Atatürk International Airport. Because of this, the operations tower and General Directorate of State Airport Authority took essential precautions that included warning authorities. In addition, some of the signs in the airport were disassembled.

On 18 April 2012, the maximum mean hourly PM10 value was 844 µg/m3, which was observed at Kayseri 1 Air Quality Observation station among all stations in Turkey. The Kayseri 1 station is located in a rural area and contributes a significantly high value of PM10 concentration relative to other stations. The regional-average values of maximum hourly PM10 were 269.5 µg/m3 for the South region, 123.7 µg/m3 for the East region, 215.2 µg/m3 for the West region, 168.6 µg/m3 for the Southeast region, 340.6 µg/m3 for the interior and center region, 236.8 µg/m3 for the North region, and 314.9 µg/m3 for the Northwest region. Based on these values, the interior and central regions of Turkey were affected the most, while the east region of Turkey was minimally influenced. The average for all of these stations was 238.5 µg/m3. The lowest recorded meteorological visibility in Turkey’s airports was 1000 m (Esenboğa and Samandıra Airports). A PM10 value was not detected when wind speed was higher than 50 kn or when dust was witnessed. While the visibility at Esenboğa Airport (Ankara) was 1000 m, the average hourly PM10 value at the Dikmen Air Quality Observation Station was 443 µg/m3 (max. 643 µg/m3). The average hourly PM10 value observed at Bilecik Air Quality Station was 472 µg/m3 (max. 472 µg/m3), while visibility at Sivrihisar Airport (Eskişehir) was 1500 m. The average hourly PM10 value at the Kartal Air Quality Observation Station was 422 µg/m3 when visibility at Samandıra Airport (Istanbul) was 1000 m (max. 422 µg/m3). While visibility at Konya Airport was 1100 m, the average hourly PM10 value at Meram Station was 266 µg/m3 (max. 742 µg/m3). As described earlier, the highest mean hourly PM10 concentrations in 2012 in Bilecik, Burdur, İstanbul (Sarıyer), Kayseri 1, Kocaeli, Konya (Selçuklu), and Sakarya were measured on 18 April 2012.

A 995 hPa low-pressure center that was centered over the Al-Berka highland and south of the central Mediterranean on 17 April 2012 at 18:00 UTC reached a value of 985 hPa over the North Aegean on 18 April 2012 by getting deep. The dust concentration located over North Africa and the central Mediterranean moved to the north due to movement of the system.

In the MODIS satellite pictures, a dust storm was detected over Libya on the dates of 16 April and 17 April 2012. Dust concentration was identified over the central Mediterranean in the dust MSG satellite pictures of 17 April 2012. According to the 18 April 2012 MSG dust satellite pictures, the direction of transportation of the dust concentrations, which were carried to the airports of Sabiha Gökçen and Samandıra from the central Mediterranean, was toward the northeast along with the cold front that crossed over the Peloponnesos and Crete Island. According to the satellite pictures, dust concentrations that intensified over western Crete Island entered Turkey from the southwest and southern regions of Turkey by moving in the direction of the cold front.

A synoptic system was effective over Central Europe and all of Italy on 16 April 2012 at 00:00 UTC. Western and interior regions of Turkey faced southerly winds due to the low-pressure system. Furthermore, the jet stream flow that stirred the system moved toward the Southeast Mediterranean by crossing over the southern part of the system. On 16 April 2012 at 12:00 UTC, since the jet flow moved toward the northern latitudes, the system proceeded toward the east; i.e., it moved over Greece and Turkey.

The main reason for the dust storm over Libya can briefly be described as the following: the low-pressure system and the steep horizontal temperatures gradients raised dust plumes from the Sahara Desert with a southerly wind, which advanced with the jet flow. On 16 April 2012 at 18.00 UTC, the system kept moving by enhancing its strength. The high-pressure system that was affecting Turkey started to be supplanted by the low-pressure system, which was directed by jet flows. After the combination of two low-pressure systems, which occurred on 17 April 2012 at 18.00 UTC, the system intensified and the strength of the surface winds increased, depending on the pressure gradient. Thus, the transport of desert dust accelerated significantly. On 18 April 2012, jets increased their effect over Turkey. On 18 April 2012, One of the two jets located over North Africa crossed over northwest of Turkey (Thrace and the Marmara Sea), and another one crossed over south of Turkey. Based on RGB charts, the dust concentration at 00:00 UTC on 18 April 2012 over middle Mediterranean affected two regions. The portion between Crete and the Moreau Peninsula crossed over the Aegean Sea and reached Istanbul and its vicinity. The second portion extended between Crete and Cyprus, passed over southern Turkey, and reached interior regions of Turkey, Konya and its vicinity. The movement of these dust concentrations took approximately 11 h. There is a consistency between 11:00 UTC dust RGB charts and the spatial map of PM10 concentrations shown in Fig. 11l. In dust RGB charts, even though dust concentrations are blurred with cold and thick clouds (shown in red colour), the portion that is not overlaid by clouds can be easily analyzed.

On 18 April 2012, the wind direction in all upper level charts was from southerly directions. The steep pressure gradient on the surface chart and the steep gradients in contours and temperatures in upper level charts caused high wind events over western and interior parts of Turkey. The effectiveness of two jets over Turkey, from the ground to a height of 2 km and 3 km over the west and central parts of Turkey, respectively, caused fast transport of dust concentrations within 11 h from middle Mediterranean to these regions. On 18 April 2012, which is the day of the event, the system affected the interior and western regions of Turkey, and it deposited all the carried desert dust on the ground as wet and dry precipitation. Hence, dust events were reported at several airports.

The orbit after moving from the source region of the dust event, which is seen at the Istanbul airports, is seen as Istanbul over South Aegean Sea in RGB dust pictures. However, the 48 hourly backward trajectories for airports in Istanbul excluding Samandıra at heights of 10 m and 1500 m exited from a region extending from Crete to Cyprus, according to the HYSPLIT model output. For the Samandıra airport, the 48 hourly backward trajectories at a height of 10 m exited from the South Aegean Sea.

The 48 hourly backward trajectories for Afyonkarahisar and Eskişehir airports at a height of 10 m show the source region between Crete and Cyprus, but those at a height of 1500 m show as middle part of Aegean Sea.

The 48 hourly backward trajectories at a height of 10 m for Konya and airports in Ankara are northern Aegea and the Sahara Desert, respectively. The corresponding locations at a height of 1500 m are south of Cyprus for Konya and southeastern Mediterranean Sea and southeast of Crete for airports in Ankara.

The 48 hourly backward trajectories at a height of 3000 m for Afyonkarahisar, Eskişehir, Konya, and airports in Ankara show the Sahara Desert, but the region between Crete and Cyprus for Samandıra and southeast Mediterranean for Sabiha Gökçen Airport.

Based on the evaluated information, the Sahara Desert was the main source region of the dust event which was effective on 18 April 2018 in the west and interior part of Turkey.

Notes

Acknowledgements

The author is thankful to the Environmental Ministry of Turkey for providing air quality data and TSMS for meteorological data. In addition, the author thanks Ali Deniz, Y. Burak Öztaner, İsmail Sezen, Özkan Çapraz, Ömer Yetemen, and Bahtiyar Efe for their help. In addition, the author gives thanks to the Scientific and Technological Research Council of Turkey for support. Certain sections of this article were discussed at the Ostiv (International Scientific and Technical Soaring Organisation) Meteorology Panel and at the TSMS remote sensing workshop (Öztaner et al. 2013; Özdemir et al. 2013). The author thanks the editor and two anonymous reviewers for improving the manuscript.

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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Turkish State Meteorological ServiceAtatürk International Airport Meteorology OfficeIstanbulTurkey

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