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F
LYING MEANS TAKING
an aeroplane into the air - the air
is an environment with very specific characteristics that
has to be treated with respect. Many natural disasters are
weather related. Be it a thunderstorm, a hurricane, heavy or
freezing rain, all these events can have serious consequences if
not handled properly.
Aviation and weather are intimately related. In between 15
and 20 per cent of all aviation accidents, weather is a factor. This
highlights the importance of correct weather information for a
safe flight.
Over the years, weather information has improved dramati-
cally. Accurate weather forecasts are extremely important for a
safe and efficient flight. Both National Meteorological Services
(NMS) and private weather service providers, whether these are
private companies or airline meteorological departments,
continue to work towards improving the performance of their
prediction models and services. The implications of these
improvements are not limited to airlines and air travel – indeed,
the aviation industry is itself involved in providing vital meteo-
rological data, and the benefits stretch far and wide.
Airlines as end users
Airlines need accurate weather information and predictions in
order to plan flight schedules efficiently and ensure passenger
safety. Both the safety and operating efficiency of aircraft are
greatly affected by the accuracy of meteorological forecasting.
But weather services also have a significant environmental
impact – as airlines strive to limit emissions and minimize the
environmental effects of air travel, better flight planning can
help keep fuel usage, as well as costs, to a minimum.
The World Area Forecast System (WAFS) is responsible for
providing basic, essential meteorological products to the avia-
tion community in a cost-effective manner, through a
comprehensive, integrated and consistent worldwide system.
There are two World Area Forecast Centres (WAFC), one
based at the UK Met Office and one at the US National
Oceanic and Atmospheric Administration in Washington and
Kansas City (the National Weather Service’s Aviation Weather
Center). The WAFCs provide global significant weather, wind
and temperature forecasts, and a suite of OPMET data. Each
works to support and back up the other in providing real-
time meteorological information broadcasts for aviation
purposes. Both the London and Washington WAFCs have
studied possible failure scenarios in their WAFS operations,
and each centre is able to replace the other in the event of a
failure, ensuring that there is no break in the provision of
these crucial services.
Each WAFC operates its own satellite-based broadcast system
to distribute data to airports across the world for pilot briefings.
The UK Met Office’s Satellite Distribution System (SADIS)
primarily covers Europe, Asia, the Indian Ocean and Africa,
while NOAA’s International Satellite Communications System
(ISCS) mainly covers America, the Atlantic and the Pacific
Oceans. WAFC broadcasts are supervised by the International
Civil Aviation Organization (ICAO) under the requirements of
ICAO Annex 3, which concerns meteorological information for
international air navigation.
Both WAFCs continually strive to improve the performance of
their numerical prediction models of upper air wind and temper-
atures. The graph below shows WAFC London forecasts of
winds at 250 hectopascals (hPa), flight level (FL) 340. It indi-
cates that forecasts of winds at 250hPa (FL340) have improved
in accuracy by around 20 per cent over the northern hemisphere
in the past six years.
This can be attributed to higher resolution models (WAFC
London’s global model now has a horizontal resolution of 40
kilometres); better model physics, and an increased density of
observations both from aircraft and satellites.
The net result is that forecasts of flight durations for long-haul
flights are typically within a few minutes accuracy. Adverse
weather can lead to much greater delays en route (for example
thunderstorms and turbulence) and within the terminal area. It
is the aspects of weather forecasting of the latter where the great-
est environmental benefits can be made in the coming years. By
working more closely with Air Traffic Management authorities,
National Meteorological Services can provide timelier, more
accurate and more detailed weather information up to 24 hours
in advance, and this will provide the greatest gains in terms of
improved capacity and fuel savings in the future.
While aviation meteorology focuses on mitigating the effect
of hazardous weather on passengers and operations, the envi-
ronmental record of the aviation industry is coming under
increasing scrutiny. Air transport represents 2 per cent of
global carbon emissions, but airlines are working hard to limit
this. Airlines are continuously modernizing their fleets, and
one of the effects of this is a reduction in fuel burn for the
same payload. For example, at one US air carrier, a switch
from DC10 to A330 aircraft has reduced fuel burn for the same
payload by over 30 per cent – in other words, 30 per cent less
carbon dioxide is being left in the atmosphere for the same
number of passengers. Overall fuel efficiency has improved
10 per cent over the past five years. The new generation of
aircraft such as the Airbus A380 will have a fuel consumption
of less than three litres per 100 passenger kilometres, lower
even than a hybrid car.
Airlines as information providers
However, limiting emissions is not the only benefit from
improvements in aircraft technology. While the role of satellite
technology in weather monitoring is fairly well-known (satel-
Airlines and weather
Adriaan Meijer, International Air Transport Association