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QVA information provides users with a high-resolution four-dimensional representation of a volcanic ash cloud, providing a more realistic depiction of the ash cloud.
Grid point forecasts of quantitative volcanic ash concentration shall be in a regular grid with a horizontal resolution of 0.25° of latitude and longitude and vertical height ranges:
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relative frequency of exceedance probabilities for the volcanic ash concentration thresholds of 10, 5, 2 and 0.2 mg/m3
Forecasts of QVA concentration information shall be valid for fixed times of 0, 3, 6, 9, 12, 15, 18, 21 and 24 hours after the time (0000, 0600, 1200 and 1800 UTC) of the synoptic data on which the forecasts were based.
Updated forecasts of quantitative volcanic ash concentration information shall be issued as necessary but at least every six hours until the volcanic ash “cloud” is no longer considered to be significant.
Gridded data will be provided in a GRIB file format
Additionally, QVA concentration information shall be made available as objects in IWXXM form for the very high, high, medium and low quantitative volcanic ash concentration ranges:
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QVA information offers operators the opportunity to move away from traditional discernible/visible ash criteria and instead use certified engine susceptibility for flight route planning and inflight replanning. Visible ash is what an observer or flight crew member sees with their eyes. Discernible ash is what a satellite or other remote sensing instrument detects. Discernible ash from satellites has been used by the VAACs to define the observed area in the volcanic ash advisories (VAA) in both text and graphic form (VAG) over the past two decades.
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The QVA information service(s) are designed to provide situational awareness of volcanic ash in the atmosphere which may have implications for the safety of aircraft in flight.
Pilots will use QVA information for flight planning purposes to avoid hazardous environmental conditions.
Flight operators will use QVA information to develop safety cases for any planned activities in affected airspace. Operators with approval and procedures/practices, e.g., maintenance for planned flight into select thresholds of ash concentration, will be able to use QVA information to fly more efficient routes in accordance with their safety management program. Probabilistic QVA information is intended for use in operator’s flight planning and decision support systems. Operators will use probabilistic QVA information in conjunction with their safety management program to optimise airspace and plan more efficient routes during significant volcanic ash cloud events.
Air Traffic providers and network manager will use QVA information to anticipate capacity and demand associate with rerouting of aircraft avoiding particular ash concentration thresholds. They also issue the appropriate ASHTAM which will be based on QVA information, as well as VONA and VAAs.
MET providers use the information for inclusion in other dependant MET information services, such as SIGWX charts and SIGMETs.