The impact the weather can have on the efficiency and safety of commercial flights is enormous, and the accuracy of the UK's Met Office is of paramount importance in planning and operating flights across Europe and the Atlantic. Servicing the aviation industry is one of the highest priorities to which the Met Office turns its sophisticated technology and wealth of experience.
Over the years, it has constantly striven to improve the accuracy of its forecasts, and to make its products more relevant to the industry's needs.
"We are making great strides in helping the aviation industry to reduce weather-related delays. We are regulated by targets and performance indices for accuracy, including visibility and cloud-base readings, measuring wind over the Atlantic at cruising altitude, and the timeliness of delivery. We always meet our targets and we have done for many years," says Doug Johnson, the Met Office's head of transport.
"Over many decades, our models have greatly improved accuracy. For instance, the average error for wind accuracy is 62 seconds for a flight from Los Angeles to London Heathrow, which is over 11 hours. Pilots recognise the value of our forecasts, and they would be very surprised if the weather differs from our prediction," he adds.
As a monopoly provider, the Met Office is bound by many regulations covering the aviation industry, most notably stipulations from the ICAO on meteorological services for international flights. Beyond its obligatory services to the industry, it provides other products to commercial airlines, including a ground-based de-icing service, which enables airlines to have resources in place on snowy days.
A relationship built on accuracy
Blending huge super computing power and highly sophisticated data models with the vast experience of its skilled meteorologists, the Met Office is one of only two world area forecast centres (WAFC) that can provide global wind, temperature and weather information above 24,000ft.
The resolution of its weather analysis models is constantly improving, and is currently 40km per grid square on a global scale for all 70 vertical layers. Regional resolution across Europe is 12km, while local UK resolution is 1.5km for each grid square, which yields impressive levels of accuracy and consistency. It is not surprising, therefore, that the Met Office has enjoyed good relations with the aviation industry.
That relationship was sternly tested, however, by the recent Icelandic volcano eruption, which spawned an ash cloud that severely disrupted flights.
Through the ash cloud
One of the world's nine volcanic ash advisory centres (VAAC), the Met Office's operation in Exeter is known as the London VAAC, which covers the Icelandic volcanoes. It plays a major role in maintaining safety and efficiency during an eruption, helping airlines to determine routes and fuel requirements.
Yet, negative perceptions of the Met Office's performance surfaced among airlines during the recent eruption, partly through a misunderstanding. It is not, as some thought, within the Met Office's remit to tell aviation authorities to cancel flights or close airspace.
While the ash cloud persisted, the Met Office gave accurate reports on its development in line with regulatory requirements. In doing so, it faced many challenges, not only from the regulatory environment, but also from the physical parameters of the eruption.
"Our wind forecasts are very accurate and are available for all to see, as the regulator requires, but volcanic ash is a unique problem. The ICAO tasks the world's VAACs to advise on ash clouds with a 'no tolerance' policy, which means showing where there is any ash.
"But VAACs have no guidance on what is a safe level of ash. VAACs have sought advice from engine manufacturers about safe levels, but that advice has not always been forthcoming," says Johnson.
"We use the wind model from the WAFC, which is quantitatively proven to be the world's most accurate, and the numerical atmospheric dispersion modelling environment (NAME) for particulate matter in the atmosphere. But we must know the source strength of the volcano and how much matter it emits over time, which can change very fast. I can't praise the Icelandic Met Office highly enough. It worked very hard to monitor the volcano's source strength. We also did a fantastic job. Wherever we saw a red zone and research aircraft were in the vicinity, they verified that we were right. Any inaccuracy in our model was due to not knowing the source strength. Knowing how much ejected rock and silica can be borne away is very difficult," he adds.
The Met Office classified different zones within the ash cloud according to the concentration of ash. Red zones represent the standard threshold of 200 micrograms per cubic metre, as used in the official VAAC product. Grey zones represent ash concentration of ten to 20 times the red zone threshold. Black zones represent concentrations 20 times or more higher than the red threshold, which exceed tolerances stipulated by engine manufacturers, and could prompt the closure of airspace.
"The main advancement since the ash cloud is that the CAA now has engine manufacturers to advise on safe levels of ash mass concentration. We have worked with them, and with regulators, on new products to assist with opening up airspace, which is purely a CAA issue. We did not advise on the opening or closing of airspace," Johnson stresses.
Building bridges with airlines
The ash cloud yielded many lessons for airlines and meteorologists alike. Yet the Met Office is dedicated to improving its services to the aviation industry – not because of the ash cloud but as a general principle.
"We are working across Europe to prepare for the next volcanic event and there is a great effort to improve performance. Our numerical models improve anyway, almost on a weekly basis. That is part of our daily job here. We are working on the sources of error, which in this case was the source strength of the volcano. Iceland had only one radar monitoring the volcano, and the plume can be hidden by the mountains.
"Now, another is being installed, paid for by the ICAO, and the UK is purchasing civil contingency aircraft, which will be on 24-hour callout from January," explains Johnson.
He notes that some airlines, including Flybe, worked very closely with the Met Office throughout the ash cloud event, helping to define black zones along with some engine manufacturers.
"So, we will be better prepared for the next event. Some airlines were very critical of us in the beginning, but they understand our role better now, as does the rest of the aviation industry. Engine manufacturers' input on safe levels of ash would have made the biggest difference, but now we are working with companies like Rolls Royce, which has shown us eight cases where engines were affected by ash, and the NAME model has shown why each of those would have had a problem. That gives us confidence in the model's ability to predict," Johnson remarks.
"We have had long discussions with airlines like BA, and we have created a better understanding now, although some airlines are still critical and hard to engage with. Now, we need to consult with the industry more, as part of the Single European Sky, and meet all of their requirements. The aviation industry is our highest priority."