Analysis of Surface Wind Speed at Minangkabau International Airport for the period 2011-2020 using the Windrose Method

Weather information is very much needed in flight operations because it is related to the smooth running of the aircraft from takeoff to landing. Weather information required by the runway surface wind data needs as important information in the landing process. Information on the surface wind components determines Minangkabau International Airport’s direction and average surface wind speed pattern. Analysis of changes in surface winds also determines the effect of wind on flight safety, especially in the process of taking off and landing aircraft. Wind direction and speed data obtained are from synoptic observations of the Minangkabau Meteorological Station for ten years (2011-2020). Surface wind data is processed using the windrose method with the WRPLOT (Wind Rose Plots for Meteorological Data) application which shows the direction and difference in wind speed and produces a wind pattern image in the form of a windrose diagram. The results of this study note that the dominant wind blows from the Southwest (203°-248°) with a percentage of 41.97%. The west direction (248°-293°) with a percentage of 27.93%. The south (158°-203°) with a percentage of 13.81%. The prevailing wind speed is 4.08 – 7 knots, with a percentage of 54.8%. The rate of 0.97 – 4.08 knots with a percentage of 38.1%, and the speed that occurs is 7-11.08 knots with a percentage of 6.1%. The condition of the overall average wind direction and speed that occurred from 2011-2022 at Minangkabau International Airport was still in the safe category for the takeoff and landing process.


Introduction
Indonesia is an area that stretches from the geographical latitude of 07° 20' North Latitude to 14° South Latitude and 92° East Longitude to 141° East Longitude is an archipelago country where the territorial waters are more significant than the land area.The islands in Indonesia are displayed by transportation, be it land, sea, or air.With a high population density, fast means of transportation and a high level of security to connect the islands.The air route is the primary and most dominant choice.
Minangkabau International Airport is the international standard airport in the province of West Sumatra and serves flights to the city of Padang.The airport is about 23 km from the center of Padang City and the region in Ketaping, Batang Anai District, Padang Pariaman Regency.The coordinates of Minangkabau International Airport are 00° 47' 12"S 100° 16' 50" E.
Aviation transportation has a very high level of safety.If there is a small mistake that will have an impact on passenger safety, that flight safety is regulated internationally by the International Civil Aviation Organization.One of the aviation safety standards in terms of meteorology (weather) is the influence of surface winds which affect the takeoff, landing, and cruising processes [1] [2].
The wind is moving air caused by the Earth's Rotation and also because of differences in air pressure [3] [4].Wind moves from areas of high pressure to areas of low pressure.The winds happen because of pressure or air temperature differences in the horizontal direction [2] [5].
Wind can move vertically and horizontally at various speeds and dynamic fluctuations.The difference in air pressure from one place to another can be a driving factor for the movement of air masses, the flow of air masses can be deflected due to the Coriolis force.Coriolis force that can affect the Earth's Rotation in the direction of the wind is called the Coriolis Effect.
The wind is a vector quantity expressed in a two-way frequency distribution, namely direction and speed.Wind direction is the direction from which the wind blows or from where the wind current comes and is expressed in degrees determined by the direction of rotation in a clockwise direction and starting from the compass point [8].Wind speed is the distance traveled by air or airflow expressed in kilometers per hour or meters per second (m/s) or knots [6].
The factors that affect the wind [7] are the first barometric gradient in the form of numbers that indicate the difference in air pressure of two isobars 111.322 km apart.The larger the barometric gradient, the faster the wind blows.The barometric gradient formula is as follows: Both locations are where the wind speed near the equator is faster than that far from the equator.Third, the higher the altitude, the wind blows faster; this is due to the influence of the frictional force that inhibits the air velocity.Wind speed changes with distance above ground level and rapidly at low elevations.Four times during the day, the wind will blow faster than at night Surface wind is one of the meteorological observations that quickly changes direction and speed.In addition, surface winds affect flight because at the time of doing and taking off from the foundation of life is influenced by the wind that is on the surface [8].Wind speed is measured using an anemometer installed at an elevation of 10 meters above ground level.The type of anemometer used is a bowl anemometer with a rotary type.The rotation speed of the bowl anemometer depends on the wind speed without considering the direction of the wind.Above ground level, the anemometer used is a bowl anemometer [9].
Surface wind at an airport takes effect and is taken into account for landing and taking off aircraft.Surface winds are found at an altitude of 6 to 10 meters from the runway surface, but for broadcasting surface wind data, it is the wind 10 meters above the runway surface [2].In addition to the surface wind speed, changes in the probability distribution of wind speed are also significant.Knowledge of the probability distribution of surface wind speeds is essential for surface flux estimation, wind risk assessment, and many applications in wind power climatology [10].
Analysis of variations in wind direction and speed near the surface is needed to know the dominant wind direction and speed of the surface wind at Minangkabau International Airport from 2011 -2020, so that wind direction and speed can predict to happen.It can also increase knowledge of weather observations in the field, especially at Minangkabau International Airport period January 2011 -December 2020.
Taking into account the data of direction and speed that changes quickly, a method is needed to predict the direction and speed of surface winds and their effects on flights during take-off, cruising, and landing.The technique used in solving the above problems is using the wind rose method.The wind chart shows the percentage of wind occurrences with speeds from various directions over a certain period.The wind rose image contains radial lines of wind direction, and each circle shows the percentage of wind events in the measurement period [11].
Research related to surface winds has been done by previous researchers such as: research [12] at the Douwaturure-Nabire Airport Runway regarding surface winds which were still in the safe category to support flight safety, especially the take-off and landing process of aircraft.Several approaches obtained the results of the analysis of the average wind classified as very safe with speeds.Further, research [9] using surface wind direction and speed parameters shows that the wind direction and speed conditions at the Sultan Syarif Kasim II airport in Pekanbaru are still in the direction of the aircraft runway and can be determined using wind direction analysis.Determination of the direction of the runway required by ICAO (International Civil Aviation Organization) is the direction of the runway of an airport that must be oriented so that aircraft can land and take off at least 95% of all wind components blowing.
There are three wind patterns on flights at the airport: headwind, tailwind and crosswind as seen in Figure 1.Based on figure1, headwind is the effect of wind originating from the front of the aircraft; this headwind is very beneficial because it can help the aircraft increase lift when taking off and can also increase friction with the fuselage when landing.This wind can maintain the balance of the fuselage.The pilot often chooses the headwind wind pattern during landing and takeoff.
Tailwind is the wind that comes from the rear (tail) of the aircraft, where this tailwind can inhibit the plane's lift.The aircraft will avoid landing and taking off if there is a tailwind.However, the tailwind will be selected if the aircraft is cruising.Tailwinds can increase the aircraft's speed by factoring in the wind from the plane's rear.
Crosswind is the wind that blows from the sides of the fuselage.Pilots avoid this wind pattern for flight because it can have a negative impact during the flight, which can cause the plane to deviate from the runway or even slip [1].The allowable crosswind speed limit is 10 knots for airports with a runway length of 1200-1500 m and a speed of 20 knots for airports with a runway length of more than or equal to 1500 m [13].If the plane gets a crosswind, a pilot must have a strategy to balance the crosswind so that the aircraft does not sway and the plane can survive the dangers of the crosswind effect on the runway.

Research Methods
This type of research is descriptive research using secondary data from wind direction and speed data obtained from the Minangkabau International Airport Meteorological Station sourced from BMKG in the 2011-2020 period.In this study, the independent variable is the direction and speed of the wind and the dependent variable is the flight at the Minangkabau International Airport.
Wind direction and speed data were obtained from an anemometer installed in the Minangkabau Meteorological Station tool park.The software used to process and analysis wind direction and speed data is Microsoft Excel and the WRPLOT view application (Wind Rose Plot for Meteorological Data), which is open source software.The wind state data used in this paper is the direction and speed of the daily surface wind on synoptic observations of the Minangkabau Meteorological Station for the period January 2011 to December 2020 with hourly synoptic data.
Systematically, the flow diagram for surface wind analysis at the Minangkabau International Airport for the period 2011-2020 using the wind rose method can see in Figure 2.

Figure 2. Flowchart
Based on the figure2, the framework of thinking begins with determining the problem to be analyzed.Based on these problems can be determined the purpose of the research conducted.
Minangkabau International Airport is a means of air transportation strongly influenced by weather factors, mainly surface winds.Daily wind direction and speed data for 2011 to 2020 were obtained from BMKG data.The data are grouped by the same month within ten years for processing surface wind data using the windrose method.The first is grouped based on the monthly average wind direction to get the pattern of the wind direction that blows, and the second is based on the average speed to get the wind speed pattern.From the two ways of direction and average wind speed, the influence of the wind on the seasons is obtained, as well as providing information about the surface wind speed at Minangkabau International Airport.

Results and Discussion
The analysis of surface winds from January, 2010 to December, 2020 using WRPLOT (Wind Rose Plot for Meteorological Data) to produce images of the dominant wind every month.The results of the analysis in January-December can see in Figure 3.
Based on figure 3, the results of data processing that has been carried out, as shown in Figure 3 on the average wind direction that occurs at Minangkabau International Airport, it is found that the origin of the wind direction varies from the period 2011 -2020.The processed wind data is obtained from the Minangkabau Meteorological Station.Wind direction is measured using a cup anemometer on the wind vane sensor.
The average wind direction at Minangkabau International Airport in January comes from the Southwest direction with 22.9%.In February, the wind comes from the Southwest at 18.79%.In March, the wind comes from the Southwest at 41.93%.In April, the wind from the Southwest was at 52.84%.In May, the average wind comes from the Southwest with 41.74%.In June, the wind from the Southwest was at 39%.In July, the wind comes from the Southwest with 45.3%.In August, the wind comes from the Southwest at 35.16%.In September, the wind comes from the Southwest at 33.55%.In October, the wind comes from the Southwest with 41.29%.In November, the wind comes from the Southwest with 32.33%.In December, the wind comes from the Southwest with 42.58%.
Wind speed is measured using a cup anemometer on the wind speed sensor.The average wind speed that occurs at Minangkabau International Airport is 4.08 -7 knots, with a percentage in January of 62.6%, in February 69.9%, in March 69.7%, in April 64.3%, in May 67.3%, June 56.7%, in July 53.4%, in August 53.9%, in September 56.7%, in October 60.6%, in November 55.3%, and in December 54.8%.Based on figure 4, The Minangkabau International Airport area is an area that has a tropical climate and is greatly influenced by the dominant wind coming from the west westerly wind.
West Sumatra has an equatorial climate type, an area where the rainy and dry seasons are not much different, so it has two peaks of the rainy season or is said to have no dry season [15].Wind direction is influenced by general wind patterns and is also influenced by local wind patterns generated by topography and location.
The Minangkabau International Airport area is an area around the coast.The wind in the coastal area is influenced by local wind factors, namely sea breezes and land breezes.The Padang area, located near the Indian Ocean, makes the weather in Padang greatly influenced by the Indian Ocean.Sea breezes that carry water vapor from the Indian Ocean are the primary source of weather processes in the Padang area.
The influence of wind on the flight is very influential is the crosswind wind pattern that can impact the takeoff and landing process.If the value of the crosswind wind that occurs is significant, it will be able to cause the plane to slip off the runway, and it can even cause an airplane to crash on the runway.The calculation results show that the crosswind event can be seen in the appendix.
Sea breezes are a response to variations in meso scale atmospheric surface warming.Sea breezes occur limited to layers of 1-2 km.Therefore sea breezes are greatly influenced by the viscosity and conduction of the boundary layer [16].Sea breezes are usually stronger than land breezes, reaching speeds of 4 -8 ms-1 and the thickness of the air layer covering an altitude of 1000 m.Sea breezes in the tropics can enter the land as far as 100 km.In some locations, sea breezes may be able to push against a topographical barrier (barrier) on the coast and penetrate ashore.
The influence of wind on the flight is very influential in the crosswind wind pattern that can impact the takeoff and landing process.If the crosswind wind value is significant, it will cause the plane to slip off the runway, and it can even cause an airplane to crash on the runway.The crosswind value is shown in Figure 6.

Figure 5. Crosswind Wind Class Frequency Distribution
Based on Figure 5, the wind events that often cut the runway are winds with a speed of 4 to 7 knots.The maximum wind speed on the runway of Minangkabau International Airport is 18 knots, while almost all of the wind speed is calm with a rate of 0 knots.Based on ICAO provisions, the wind direction intersects the runway with a track length of more than 1500 m. proves that the runway at Minangkabau International Airport during the ten years from 2011-2020 is generally safe for flight operations.
Especially in aviation, in addition to the level or intensity of weather elements, the type of aircraft, the aircraft's condition, and the flight's position are also factor that determine its sensitivity to weather.The effect of crosswind on the runway at a speed of 20 knots may pose a danger to small aircraft making landings, but it does not affect large and modern aircraft [13].However, because every airplane has the same three activities, namely taking off, flying, and landing, the use of the meaning of danger in flight, is generally applied to each of these activities [8].
Like an accident that slipped and left the runway for Citilink Flight Number QG 970 to Jakarta-Padang at Minangkabau International Airport on Sunday, August 2, 2015, 19.30WIB, the slip of the plane was caused by weather factors, one of which was the influence of strong winds, mainly crosswind winds with a speed of 10-14 knots coming from the side of the fuselage.This accident was the first plane crash at Minangkabau International Airport, which was affected by crosswind winds.Weather analysis on the day of the accident had a maximum air temperature of 31.4 and a minimum of 23.4,33 mm of rainfall, 1011 Hp air pressure, and 3.7 hours of sunshine.
According to ICAO [17], the crosswind component that can hinder the takeoff and landing of aircraft, in general, is when the speed exceeds 37 km/hour (20 knots) for aircraft with ARFL (Aeroplane Reference Field Length) of 1,500 meters or more.Unless braking action on the runway is poor (due to insufficient longitudinal coefficient of friction), a crosswind component of more than 24 km/h (13 knots) may hinder the aircraft's takeoff and landing.If the crosswind speed exceeds 20 knots, it can cause the aircraft to slip to the side of the runway.If the crosswind is strong enough and occurs suddenly, the plane may sway so that the plane's wings will break and cause a more significant crash.Several International Civil Aviation Organization (ICAO) and Federal Aviation Administration (FAA) references state that the maximum allowable crosswind depends on the aircraft operating, size, wing arrangement, and runway surface conditions.Crosswind does not always blow from the side perpendicular.Crosswind can also blow from the front side to the direction of the plane's bow.Pilots need to know which component is more significant between the head and tailwind to overcome this crosswind.

Conclusion
The paper results show that in the wind pattern at Minangkabau International Airport, the dominant wind direction blew from the southwest by 41.97% and the west by 27.93%, which almost occurred throughout the year from 2011-2020.The average wind speed is 4.08 -7 knots with a percentage of 54.8% and only 0.1% with wind speeds of 17.11 -21.58 knots.Predicting the state of the wind direction and speed can help minimize the potential for aircraft accidents.Judging from wind direction and speed frequency during the last ten years (2011-2020).The hazard criteria in the flight process at Minangkabau International Airport are still minimal because the average surface wind condition is below 20 knots.The magnitude of the surface wind speed affecting the flight, especially crosswind, is generally still in the safe category, with a value of 18 knots for an airport runway length of more than 1500 meters.