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DEFINITIONS The terms defined below have the meanings given for the purpose of this Annex only:

Electronic Observations. The use of electro-magnetic and/or electrostatic principles for obtaining meteorological observations.

Forecast. A statement of future meteorological conditions that are expected to exist in given areas at specified times at the earth's surface or in the free air. The statement may be presented in plain language or in code, or by means of charts, forms or diagrams.

Forecaster. A meteorologist qualified to prepare forecasts.

Initial Meteorological Office. The meteorological office responsible for providing meteorological information to an aircraft prior to its departure on a flight.

Meteorological Information. All classes of meteorological reports, analyses, forecasts, warnings, advices, and revisions or amendments thereto, which may be required in connection with air route technical services and procedures.

Meteorological Minima. The minimum values of meteorological elements prescribed for specified types of flight operation.

Meteorological Observation. The measurement by instrumental means or estimation of the values of one or more meteorological elements.

Meteorological Office. An office staffed and equipped to provide meteorological information for aircraft operations.

Meteorological Reconnaissance Flights. The flights of aircraft carrying trained meteorological observers and special meteorological equipment for the purpose of taking and recording meteorological observations.

Meteorological Report. A statement of past and/or present meteorological conditions observed at a given place on the earth's surface, or in the free air. The statement may be presented in plain language or in code, or by means of charts, forms or diagrams.

Meteorological Service. A state agency charged with the collection and dissemination of meteorological information.

Meteorological Station. A station equipped to take meteorological observations.

Observer. Anyone qualified to take meteorological observations.

Route Meteorological Chart. A meteorological chart showing fronts and pressure distribution-along and for a limited distance to each side of an air route.



Classification of Meteorological Information The meteorological information necessary for meteorological protection of aeronautics may be divided, in a general way, into three categories, viz:

1. Current Information, which is based upon reports of surface and upper air observations transmitted to local, regional, or national meteorological centers. This information may be divided into two classes:

(a) Information necessary for the preparation of synoptic and upper air charts.

(b) Information necessary for the operation of air routes. 2. Forecasts, which are statements of future meteorological conditions expected to exist in a given area for specified periods of time at the earth's surface or in the free air.

3. Climatological Information, which is based upon past meteorological records analyzėd and summarized to show the meteorological conditions which are experienced in the long run at a given place or in a given area.

It is required:
(a) In connection with the selection of air routes.

(b) For indicating the diurnal and annual variations according to place and altitude of the meteorological conditions affecting flights.

(c) For indicating the places at which stations should be established for furnishing current information.


General Organization for Meteorological Protection of International


4. Object of Protection. The object of the meteorological protection of aeronautics as set forth herein shall be to assure the safety of the aircraft, the economic and regular operation of aircraft along air routes, and the comfort of passengers, as far as they are affected by the meteorological elements.

5. Those Concerned With Protection. Meteorological information shall be supplied according to its various categories, to persons in command of aircraft, to personnel charged with the operation and control of aircraft and of airports, and to the administrations of aeronautics.

6. Responsibility for Protection. The provisions prescribed hereunder shall be international in application. They shall necessitate the participation of a contracting State even when the air route does not cross that State. They are also applicable to the oceans, the interior seas, and the uninhabited areas of continents.

7. Universality of the Provisions. Meteorological protection of aeronautics shall be provided in conformity with the standards and procedures defined hereunder in the territory of a contracting State, over the oceans, the interior seas, and the uninhabited areas of continents.

8. Services and Personnel Charged With Protection. Meteorological protection of aeronautics shall be arranged by an official meteorological service in each contracting State.

9. Procedure to Follow for Requests for Meteorological Protection. The contracting States concerned shall arrange to notify the interested meteorological services of the creation of an air route sufficiently. beforehand to permit the organization of meteorological protection for the regions covered. The notice shall contain detailed information concerning the air route and the proposed schedules.

All alterations to the schedules for an air route shall be notified to the meteorological services concerned sufficiently in advance to permit the necessary reorganization involved.

All notices shall be transmitted through the channels prescribed by the Convention.


Networks of Meteorological Stations 10. Object of the Networks. The operation of official meteorological services of the contracting States requires the establishment of networks of meteorological stations for the purpose of taking surface and upper air observations and also requires the collection and distribution of these observations.

11. Universal Provisions Concerning Observations. The observations shall be taken by meteorological observers with the aid of equipment whose quality and dependability are such that they would be endorsed by the International Meteorological Organization. The observations shall be taken at hours fixed by international agreement and shall be collected at regional or national centers. The reports shall be drawn up in the forms and according to the code tables specified by the International Meteorological Organization.

12. Classification of Observations and Requirements. Observations shall be provided in the following categories, which show the requirements for frequency of observations for the meteorological protection of aeronautics:

(a) Surface Synoptic Observations. These observations are for the purpose of recording the meteorological elements and showing their distribution over large areas. They provide the basic material for forecasts. Requirements are four complete surface synoptic observations per station daily at the internationally agreed synoptic times; this number shall be increased to eight as required.

(b) Supplemental Surface Observations. These observations shall complete the preceding category by filling in its gaps, either in time or in space. They may include only a selection of the elements which form a complete surface synoptic observation. They are taken either at fixed times or at the request of a meteorological office, or at times of marked changes in weather, or to cover the appearance or disappearance of important phenomena. Requirements are a sufficient number of supplemental surface observations to provide meteorological offices with complete and continuous information on the progress and development of meteorological conditions observed in the surface synoptic observations.

(c) Upper Wind Observations. These observations shall provide information of the wind direction and speed at various altitudes above the surface. They are used in conjunction with surface observations as basic material for forecasts. Requirements are four soundings made at starting times as close as possible to the principal synoptic hours. Additional soundings may be required to meet the needs of aeronautics.

(d) Upper Level Pressure, Temperature, and Humidity Observations. These observations shall provide pressure, temperature, and humidity data of the atmosphere for use in forecasting. Requirements are soundings at regular intervals, several times daily, synchronous, so far as possible, with the principal surface synoptic observations. Observations shall be made by radiosonde or by aircraft. When soundings are made by aircraft, observations of elements in addition to pressure, temperature, and humidity shall be taken to provide information of direct use to pilots.

(e) Observations of Special Phenomena Pertinent to Aeronautics. These observations shall cover meteorological phenomena which have a particular importance for aeronautics (such as turbulence, icing conditions, et cetera) due either to their nature or because of their rapid appearance or disappearance. Requirements are observations of these special phenomena sufficient to insure protection from the results of their occurrence to all aircraft operating in their vicinity.

(f) Observations Made by Electronic Means. These observations shall provide electronic and meteorological information useful in forecasting. Requirements are a sufficient number of observations to provide knowledge of electronic and meteorological conditions not obtainable by observations of other classifications.

(g) Observations Made by Meteorological Reconnaissance Aircraft. These observations shall be taken from aircraft especially assigned to routine or special flights mainly over oceans. These observations are for the purpose of obtaining information of surface and upper level meteorological conditions mainly in areas where there is no permanent network of meteorological stations. Requirements are regular and special observations to supply sufficient meteorological information to aid in the determination of current meteorological conditions and in forecasting their evolution and progress.

13. Distribution of Meteorological Stations. The contracting States shall arrange to establish and maintain sufficient meteorological stations to assure meteorological protection for international air routes in accordance with the provisions of the Convention.

Requirements for this protection are twofold:

(a) Stations to provide the general over-all picture of surface and upper air conditions.

(b) Stations to provide the detailed picture of surface and upper air conditions along the international air routes.

14. Ocean Observations. The contracting States shall provide for the development of ocean networks, including adequate networks of stationary meteorological ships maintained under international agreement, to these ends:

(a) A sufficient minimum regular distribution for the analysis of. the meteorological situation.

(b) A frequency of at least four complete surface synoptic observations daily.

(c) A reasonable distribution of upper wind soundings and radiosonde observations taken from a selection of ships.

(d) The participation of islands in these observations and these soundings.

(e) A reasonable frequency and distribution of meteorological reconnaissance flights.

15. Observations in the Interior Seas. Whenever the meteorological conditions over interior seas are of importance in forecasting for an air route, the contracting States shall provide for the development of networks for observations on ships, islands, and lightships in accordance with the following considerations:

(a) Frequency of the observations shall be the same as that of the neighboring land areas. In case this frequency is not necessary or practicable, choice shall be made, by the appropriate meteorological service, of the times for which the geographical position of the ship will be of the greatest importance from the meteorological point of view.

(b) These observations shall be taken at internationally agreed times.

(c) Selections of the meteorological reports from ships shall be incorportated by the meteorological services in the messages broadcast for aeronautics.

16. Observations in the Uninhabited Areas of Continents. Whenever the meteorological conditions over uninhabited areas of continents are of importance in forecasting for an air route, the contracting States shall provide for the establishment of adequate networks of meteorological stations throughout those areas. These networks shall be established and maintained by international agreement when necessary.

Observations shall include: (a) Complete surface observations at the principal synoptic hours.

(b) Upper wind soundings and radiosonde observations from selected stations at standard times.

(c) Meteorological reconnaissance flights when necessary.

17. Observations on Board Aircraft. Meteorological observations shall be made on board aircraft in accordance with the procedure set forth in Section V of this Annex. The observations shall be recorded on forms and reported in codes in conformity with the specifications of the International Meteorological Organization. A selection of the meteorological reports received from aircraft in flight, or secured from observation forms received by meteorological offices after flight, shall be included in international exchanges.

18. Modifications. The meteorological services shall notify the International Meteorological Organization of all changes made regarding the establishment or closing of meteorological stations, identification numbers or letters and in the use of approved codes, for promulgation to all the contracting States. This information shall also be exchanged mutually between the meteorological services concerned with the operation of air routes involved.

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