Elements for Life

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The meteorological requirements for international air navigation

are laid out in Annex 3 – ‘Meteorological service for international

air navigation to the Convention on International Civil Aviation’.

The various chapters of Annex 3/Technical Regulations

[C.3.1] outline the overall responsibilities of the designated

meteorological authority for the provision of services and facil-

ities for international air navigation. The associated appendices

provide detailed specifications for use by those actually provid-

ing these services. The areas covered include aerodrome

observations and forecasts; warnings (both in the terminal area

and en route); forecasts for en route issued by the World Area

Forecast Centres (WAFC) in London and Washington; advi-

sories for volcanic ash and tropical cyclones; air reporting;

needs for meteorological information by air traffic service units

and communications requirements.

A number of other documents are issued as guidance mate-

rial by ICAO and WMO in order to provide ICAO Contracting

States and WMO members with additional information to assist

them in implementing the provisions contained in Annex 3.

In accordance with the working arrangements between the

two organizations, major amendments to Annex 3 are developed

by conjoint ICAO/WMO meetings. Between meetings, most of

the proposed amendments are developed by the ICAO Secretariat

with the assistance of ICAO operations and study groups. These

are composed of experts nominated by states and international

organizations, including WMO. Currently, there are six such

groups working on the World Area Forecast System, satellite

distribution system for information relating to air navigation

(SADIS), international airways volcano watch, wind shear, auto-

matic meteorological observing systems and the use of data link

for the uplink and downlink of meteorological information. All

draft amendments developed by these groups are sent for consul-

tation to ICAO Contracting States and WMO Members before

being submitted for adoption by the ICAO Council and approval

by the WMO Executive Council.

In accordance with the working arrangements, through the

WMO Commission for Aeronautical Meteorology (CAeM)

which is responsible for implementing the WMO Aeronautical

Meteorology Programme (AeMP), WMO is responsible for

training meteorological personnel and for specifying the tech-

nical methods and practices to be used for the provision of

meteorological services to international air navigation.

CAeM has established expert teams to deal with training,

improvements to forecasts in the terminal area, quality manage-

ment, customer focus and cost recovery. The Commission is

also involved in the Aircraft Meteorological Data Relay

(AMDAR) programme and in studies related to the impact of

aviation on the global atmospheric environment. In order to

ensure that the needs of aviation users are fully addressed, repre-

sentatives of ICAO, the International Air Transport Association

(IATA) and the International Federation of Air Line Pilots

Associations are invited to participate in meetings of CAeM.

Furthermore, in 2004, WMO and IATA established focal points

between the two organizations to facilitate frequent contacts

followed by similar arrangements with EUROCONTROL in

2005. This was prompted by the increased involvement of that

organization in activities related to the newly established Single

European Sky.

In addition, the WMO Commission for Basic Systems (CBS) is

actively involved in ensuring the timely availability of basic mete-

orological data on which aviation weather forecasts are based. In

this regard, the contribution of the AMDAR programme to the

when assessing whether the prevailing conditions are above

the landing and take-off minima and whether the pilot is in

a position to establish the required visual reference at the

decision altitude.

With regard to hazardous weather phenomena for take-off or

landing, pilots need to be warned of the existence or forecast of

fog, snowstorms, wind shear, tropical cyclones, etc. During the

flight, pilots need to know whether they are likely to encounter

severe thunderstorms involving hail, severe turbulence, icing

or volcanic ash to enable them to avoid these hazardous

phenomena. Thunderstorms are notorious for extreme up- and

downdraughts, and the associated turbulence can easily exceed

the structural limits of the aircraft. Moreover, thunderstorms

are particularly dangerous in the vicinity of aerodromes as the

associated downdraughts can cause aircraft to sink below the

glide path. This may mean that the aircraft could strike an obsta-

cle or the ground before it can regain its flight path.

Explosive volcanic eruptions produce clouds of dense ash

that can reach into the stratosphere. When the ash is ingested

into aircraft jet engines, these are severely damaged and may

flame out completely, as has happened on at least three occa-

sions. This is a serious hazard to aviation and has been

addressed over the last few years by the International Civil

Aviation Organization (ICAO), in coordination with WMO.

WMO and ICAO working arrangements

In order to meet the needs of international civil aviation in an

efficient manner, it is important that ICAO and WMO work

closely together and ensure that stated aviation requirements

can be met without any unnecessary overlap of activities. This

has been recognized from the early days of aviation, and

working arrangements between WMO and ICAO were estab-

lished as early as 1953.

These arrangements can be

summarized as follows:

• ICAO is responsible for defining aeronautical meteoro-

logical requirements

• WMO is responsible for defining the most appropriate

methods for fulfilling the requirements, including the

training of aeronautical meteorological personnel.

It is important to note that the dissemination of operational

meteorological (OPMET) data is the prerogative of ICAO and

that the planning for such dissemination is undertaken by it.

Furthermore, the provisions in Annex 3/Technical Regulations

[C.3.1] stipulate that the ICAO aeronautical fixed service should

be used for the dissemination of such information.

One constant challenge is to ensure that the work is carried

out in an efficient and cost-effective manner. To this end,

proper coordination between the two organizations has to be

constantly maintained with full consultation and cooperation

at every stage of the process. This coordination is also achieved

by the systematic participation of WMO in the work of ICAO

operations and study groups, and of ICAO in the work of the

relevant WMO technical commissions. This ensures that:

• No aviation requirement is generated that is impossible

to fulfil

• No methodology is developed for a requirement that is

not foreseen to exist

• Both organizations continue to operate according to the

working arrangements, to avoid the duplication of effort

and redundancy of services and facilities established for

international civil aviation by their respective members.