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serious stress on pilots in severe weather has contributed to
fatal pilot errors.
Advance warnings of serious weather hazards are provided
during flight planning, in the form of charts of significant
weather, depicting critical areas to warn crews in good time of
expected turbulence or convection. Proper estimation of both
the required flight time and the conditions expected at the
terminal aerodrome are used to enable calculation of the
required amount of fuel, including a safety margin in case of
unexpected problems.
New challenges to aviation weather provision arise from the
non-linear dependence of acceptance rates at major hub
airports on extreme forms of weather. Here, passing thresholds
that are difficult to define a priori lead to a breakdown of air
traffic in areas around the aerodrome affected by severe, wide-
spread convection or massive snowfalls. New products for
advanced planning are currently being developed by individ-
ual aviation weather service providers, but international
coherence and coordination of such procedures will be neces-
sary to avoid economic losses and delays to the travelling
public.
Aircrews in flight are alerted by significant meteorological
information (SIGMET) and airmen’s meteorological informa-
tion (AIRMET) messages transmitted to the aircraft by
uplinking or voice communication. In addition, new forms of
digital communication such as automatic dependent surveil-
lance broadcast (ADS-B) permit rapid, unambiguous and
targeted information on critical situations. These systems
contribute to making airline flights the safest way of travelling
in terms of passenger deaths per mile travelled. The procedures
to be adhered to by all stakeholders are defined very precisely
by the International Civil Aviation Organization (ICAO) in
close cooperation with the World Meteorological Organization
(WMO), with safety and security taking first priority.
Economy and regularity of aviation operations under
ICAO and national aviation authorities
Aviation, in terms of passenger miles flown per year, has
shown a robust growth of an average five to seven per cent
over the past 30 years. Short downturns following world
crises such as oil shortages, terrorist attacks and epidemics
such as severe acute respiratory syndrome (SARS) and Avian
Influenza have typically been compensated for by increased
growth during subsequent years. Growth rates of aviation are
typically linked to the speed and strength of economic
growth, as can be currently seen in East Asia, where growth
rates in double figures are now common, and aircraft are
purchased at the rate of around one per day. Despite these
healthy growth rates, the economics of scheduled aviation
are far from easy, with capacity often running ahead of
demand, leading to a serious price war. This fierce competi-
tion leads to a very detailed scrutiny of all external costs to
the airlines. Service providers, from airports and air naviga-
tion services to aeronautical meteorologists, are asked to
prove a positive cost-to-benefit ratio.
The growth of aviation in many areas of the world is now
limited by the acceptance capacity of airports, which is strongly
linked to prevailing weather conditions. These acceptance rates
may be reduced to less than half in conditions of low visibil-
ity, cloud-ceiling height, thunderstorms, or with snowfall and
icing. Several studies undertaken in the US and Europe have
shown a direct link between weather and air traffic delays,
leading to costs of millions of US dollars or euros for a single
large airport on a day affected by severe weather conditions.
Although it is difficult to specify exactly what percentage of
theses losses could be avoided with the aid of accurate and reli-
able weather information, it is safe to say that the potential
benefits far outweigh the costs for the provision of these
services.
All services to the aviation industry have to be provided
under the regulations given in the annexes of the ICAO
convention, and are subject to approval and directions by the
national or, as in the case of the emerging Single European Sky,
trans-national aviation authorities. These regulations are begin-
ning to have an impact on the nature of service delivery –
enforcing, for example, the implementation of quality manage-
ment systems, accountability and regional harmonization of
procedures. It is expected that these regulations will further
contribute to a restructuring of service provisions on the
national and international level.
Aviation and the environment
Increasing concern about the effects of aviation on global
climate change is becoming apparent from Intergovernmental
Panel on Climate Change (IPCC) assessment reports. Concerns
regarding local air quality are also beginning to affect planning
permission for extensions of existing hub airports in the vicin-
ity of megacities. Not only is the contribution of aviation to
levels of carbon dioxide and nitrous oxides considered, but
also the radiative forcing from aviation contrails and cirrus
clouds, particularly at night, where they have a clear warming
impact. It is expected that the inclusion of aviation in national
inventories will be debated in future meetings of the United
Nations Framework Convention on Climate Change
(UNFCCC), Conference of Parties, and other relevant bodies.
Aviation meteorology may be able to contribute to mitigating
measures, for example by identifying dry layers unlikely to
produce contrails and cirrus clouds, and to issues of local air
quality by determining and forecasting episodes of high
concentrations of pollutants that could be used in advance
traffic planning.
User-provider cooperation and information transfer
Though it is clear that the potential savings based on accurate
weather information are very large, the devil is, as always, in
the detail. Even a perfect weather forecast has no economic
value if it is not used properly in the decision-making process.
The formal requirements established by regulatory authorities
(national and international) were designed with safety as the
first priority, and their universal application in all states, inde-
pendent of technological development, makes them a very
slowly reacting tool for economic decisions. The lack of precise
statistical data on the reliability of the forecasts, which is in
part due to antiquated code forms and product specifications,
makes it difficult to use the information in an optimal statisti-
cal manner. Decision making in a typical cost-loss situation
requires the full spectrum of probabilities for all event cate-
gories, and full knowledge of the verification characteristics of
all forecast and warning products. In the context of its
Aeronautical Meteorology Programme, WMO in close coop-
eration with ICAO, will address this issue over the coming
years as a matter of priority to ensure that services to aviation
continue to be a good investment and are viewed by the indus-
try as such.