Volcanic Ash Advisory Center

A Volcanic Ash Advisory Center (VAAC) is a group of experts responsible for coordinating and disseminating information on atmospheric volcanic ash

Volcanic ash

Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...

 clouds that may endanger aviation

Aviation

Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...

. As of 2010, there are nine Volcanic Ash Advisory Centers located around the world, each one focusing on a particular geographical region. Their analyses are made public in the form of Volcanic Ash Advisories (VAA) and often incorporate the results of computer simulation models called Volcanic Ash Transport and Dispersion (VATD).

The worldwide network of Volcanic Ash Advisory Centers was set up by the International Civil Aviation Organisation (ICAO), an agency of the United Nations

United Nations

The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...

, as part of the International Airways Volcano Watch (IAVW), an international monitoring system managed by the International Airways Volcano Watch Operations Group (IAVWOPSG) which replaced the Volcanic Ash Warnings Study Group (VAWSG). The individual VAACs are run as part of national weather forecasting organisations of the country where they are based, e.g. the US NOAA or the British Met Office

Met Office

The Met Office , is the United Kingdom's national weather service, and a trading fund of the Department for Business, Innovation and Skills...

.

The centers were set up in the 1990s to improve forecasts of the locations of ash clouds from volcanic eruptions following incidents where commercial aircraft had flown through volcanic ash resulting in the loss of engine power. British Airways Flight 9, a Boeing 747, lost power to all four engines in 1982 over Indonesia after an eruption of Mount Galunggung. KLM Flight 867

KLM Flight 867

On 15 December 1989, KLM Flight 867 en route to Narita International Airport, Tokyo from Amsterdam was descending into Anchorage International Airport, Alaska when all four engines failed...

, another Boeing 747, again lost power to all engines in 1989 over Alaska after Mount Redoubt

Mount Redoubt

Mount Redoubt is the name of three mountains:* Mount Redoubt in Alaska, United States* Mount Redoubt in Washington, United States* Redoubt Mountain in Banff National Park, Canada...

 erupted. It was recognised following these and other incidents that volcanic ash was a danger to commercial aviation and that the only way to ensure that there would be no loss of an aircraft was to alert pilots in a timely manner to divert their flight around the cloud.

Danger of volcanic ash to aviation

Volcanic ash

Volcanic ash

Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...

 consists of small tephra

Tephra

200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....

, which are bits of pulverized rock and glass created by volcanic

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 eruptions, less than 2 millimetres in diameter. The ash enters the atmosphere from the force of the eruption and convection currents from the heated air and is then carried away from the volcano by winds. The ash with the smallest size can remain in the atmosphere for a considerable period of time and be carried well away from the eruption point. The ash cloud can be dangerous to aviation if it reaches the heights and enters the paths used by aircraft.

It was recognised that there was an issue following the incident in 1982 with the British Airways Flight 9 and therefore the ICAO established the Volcanic Ash Warning Study Group in 1982. Due to the difficulty in forecasting accurate information out to 12 hours and beyond the VAAC were set up by the ICAO as part of IAVW.

Purpose

The purpose of the VAAC is to gather information from volcano observatories, satellite images, pilot reports on ash clouds released by volcanoes, these are then analysed and forecasts made on future movements. This alert and forecast is then issued to interested parties in the aviation industry including Meteorological Watch Offices and Area Control Centers for aircraft and adjacent VAAC where an ash cloud may move from one area to another.

To be able to perform this function each VAAC develop models on the dispersion of volcanic ash. Using the reports available from satellites, volcanic observatories and pilot reports they identify ash clouds and then use the models to forecast where they likely to be a danger to aviation.

Locations

There are nine VAAC locations each with a defined area to monitor. The centers coordinate with adjacent VAAC, flight control centers within and adjacent to their area as well as meteorological offices within and adjacent to their area of operation.

The areas covered by the VAAC are set either by coordinates or by Flight Information Region

Flight Information Region

In aviation a flight information region is a region of airspace with specific dimensions, in which a flight information service and an alerting service are provided. It is the largest regular division of airspace in use in the world today....

s (FIR) that are internationally agreed as part of the IAVW program of the ICAO and the areas that each has responsibility is set out in the IAVW handbook.

Name	Area of Responsibility	Part of National Organisation
Anchorage	FIR: Anchorage Oceanic; Anchorage continental; Anchorage Arctic and west to 150 east north of 60 north	NOAA
Buenos Aires Buenos Aires Buenos Aires is the capital and largest city of Argentina, and the second-largest metropolitan area in South America, after São Paulo. It is located on the western shore of the estuary of the Río de la Plata, on the southeastern coast of the South American continent...	South of 10 south between 10 west and 90 west
Darwin Darwin, Northern Territory Darwin is the capital city of the Northern Territory, Australia. Situated on the Timor Sea, Darwin has a population of 127,500, making it by far the largest and most populated city in the sparsely populated Northern Territory, but the least populous of all Australia's capital cities...	Southward from 10 north and from 100 east to 160 east, and the Perth FIR between 100 east and 75 east, Colombo FIR, and those parts of the Kuala Lumpur, Bangkok, Chennai, Yangon and Calcutta FIRs lying within 10 north 100 east to 20 north 100 east to 20 north, 82 east to 10 north, 82 east to 6 north, 78 east to 2 south, 78 east to 6 south 75 east	Bureau of Meteorology
London London London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...	FIR: Bodø Oceanic, Reykjavik, Shanwick Oceanic, London, Scottish, Shannon	Met Office Met Office The Met Office , is the United Kingdom's national weather service, and a trading fund of the Department for Business, Innovation and Skills...
Montreal Montreal Montreal is a city in Canada. It is the largest city in the province of Quebec, the second-largest city in Canada and the seventh largest in North America...	FIR: Gander Oceanic Canadian Continental FIRs (including the Arctic Ocean), Reykjavik Søndre Strømfjord	Meteorological Service of Canada Meteorological Service of Canada The Meteorological Service of Canada , also known as "The Canadian Weather Service", is a division of Environment Canada, which primarily provides public meteorological information and weather forecasts and warnings of severe weather and other environmental hazards...
Tokyo Tokyo , ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...	60 north to 10 north– and from 90 east to Oakland Oceanic and Anchorage Oceanic and Continental FIR boundaries	Japan Meteorological Agency Japan Meteorological Agency The or JMA, is the Japanese government's weather service. Charged with gathering and reporting weather data and forecasts in Japan, it is a semi-autonomous part of the Ministry of Land, Infrastructure and Transport...
Toulouse Toulouse Toulouse is a city in the Haute-Garonne department in southwestern FranceIt lies on the banks of the River Garonne, 590 km away from Paris and half-way between the Atlantic Ocean and the Mediterranean Sea...	Santa Maria Oceanic, AFI Region to 60 south, EUR Region west of 90 east (except for London, Scottish and Shannon FIRs) and MID Region: south of 71 north, west of 90 east	Météo-France Météo-France Météo-France is the French national meteorological service.The organisation was established by decree in June 1993 and is a department of the Ministry of Transportation. It is headquartered in Paris but many domestic operations have been decentralised to Toulouse...
Washington Washington, D.C. Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....	New York Oceanic, Oakland Oceanic and United States continental FIRs, North of 10 south 140 west	NOAA
Wellington Wellington Wellington is the capital city and third most populous urban area of New Zealand, although it is likely to have surpassed Christchurch due to the exodus following the Canterbury Earthquake. It is at the southwestern tip of the North Island, between Cook Strait and the Rimutaka Range...	Southward from the Equator and from 160 east to 140 west	Meteorological Service of New Zealand Limited Meteorological Service of New Zealand Limited Meteorological Service of New Zealand Limited was established as a State-Owned Enterprise in 1992. It employs about 215 staff and its headquarters are in Wellington, New Zealand...

The areas of responsibility for VAAC cover most of the world, with the exception of part of northern Russia and the Arctic; part of the South Pacific and the Antarctic, the areas that are not covered are shown by the hatched areas on the map.

Detection

Satellite data is the main source of information on ash clouds; it can provide the timeliest information. The remote nature of many volcanoes, and that only a few have permanent monitoring from volcanic observatories mean that onsite reports will often not arrive quickly. Though they are remote in terms of population, aircraft may still fly over them regularly. For example the Aleutian Islands are on the great circle

Great circle

A great circle, also known as a Riemannian circle, of a sphere is the intersection of the sphere and a plane which passes through the center point of the sphere, as opposed to a general circle of a sphere where the plane is not required to pass through the center...

 route between Asia and North America which has a number of volcanoes. Over 50,000 aircraft a year fly through the area which has 40 volcanoes that have been active in historic time. Pilot reports if present will only be available for flights during daylight hours as they cannot observe ash clouds during the night.

Even satellites will have issues as cloud cover of the volcano can limit the detection capability. Volcanoes in high latitudes are not covered as well by weather satellites as those in lower latitudes due to the curvature of the Earth from the position of a geosynchronous orbit. The details of the ash erupted (concentration and size of particles) are often not available to the forecasters, but with this data a better forecast can be made.

Alerts

When an ash cloud is detected the VAAC will gather all the available information on this and then make use their computer models to predict the path of the ash cloud at different flight levels used by aircraft. They will then issue an alert to aviation and meteorological offices as stated within the IAVW procedure manual. This alert will be in the format of an alert stating that it is a Volcanic Ash Advisory.

Within the alert the following information will be provided: the name of the volcano, the country, location and crater elevation of the volcano, the source of the information, e.g. satellite or pilot observation, details of the eruption including time of day in UTC and date of the eruption, details of the ash cloud including the flight level and size, detail on the current movement of the ash cloud, forecast movement for 6, 12 and 18 hours ahead following the time of the advisory and finally the next update time.

External links

• International Airways Volcano Watch Operations Group (IAVWOPSG)
• Anchorage VAAC
• Buenos Aires VAAC
• Darwin VAAC
• London VAAC
• Montreal VAAC
• Tokyo VAAC
• Toulouse VAAC
• Washington VAAC
• Wellington VAAC