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.

SECTION IV

Telecommunications Requirements for the Meteorological Protection of International Aeronautics

19. Introduction. It is recognized that the telecommunications requirements for the protection of international aeronautics are closely associated with the requirements of other fields of meteorological protection. This Section details the requirements of international aeronautics only. The coordination of these requirements with the requirements of other fields is the responsibility of the national meteorological services, working through the International Meteorological Organization.

20. Responsibility. The contracting States shall arrange for dependable telecommunication facilities for the transmission of the meteorological information required for the protection of aeronautics on international air routes. These facilities shall provide for point-topoint transmissions and general broadcast transmissions by radio, land lines, cable, or any combination of these methods, in order to meet efficiently the requirements of meteorological protection. 21. Requirements. Requirements are:

(a) Rapid collection and dissemination of current meteorological information, with the highest possible priority, by dependable telecommunication facilities are essential in providing meteorological protection for aeronautics on international air routes.

(b) Schedules and contents of these transmissions shall be arranged so as to simplify the reception by those concerned of all essential meteorological information with a minimum of repetition.

(c) Details of methods, schedules and contents of these transmissions, and, in addition, frequencies and power of the radio transmissions are published by the International Meteorological Organization. These details shall also be mutually exchanged between the meteorological services concerned.

22. Types of Telecommunications. The meteorological information shall be exchanged by broadcast, point-to-point and ground/air telecommunications. The proportions of the information transmitted by each means shall depend on the telecommunication facilities at the disposal of the contracting States concerned and the nature of the traffic.

23. Categories of Meteorological Broadcasts. Meteorological broadcasts shall normally be provided in the following categories:

Continental

National or Multinational
Regional
Local
Marine

(a) Continental. The purpose of continental collective broadcasts is to exchange meteorological information between one continent and another, mainly for the construction of generalized charts, and shall contain information from one or more continents.

(b) National or Multinational. The purpose of national or multinational collective broadcasts is to exchange meteorological informa

tion between neighboring nations, mainly for the construction of detailed charts. These broadcasts shall contain information from one or several nations.

(c) Regional. The purpose of regional collective broadcasts is to exchange detailed meteorological information between adjacent geographical areas.

(d) Local. The purposes of local broadcasts are:

(i) To provide meteorological reports and forecasts for aircraft. (ii) To provide local meteorological reports for inclusion in regional, national, or continental collectives or for the detailed. analysis of local meteorological conditions.

(e) Marine. The purpose of marine collective broadcasts is to exchange meteorological information obtained from ocean areas. The exchanges may take place between regions, nations, or continents

24. Point-to-Point Telecommunications. Point-to-point telecommunications shall be made of all required current meteorological information which is not satisfactorily provided by broadcasts.

25. Ground/Air Telecommunications. Ground/air telecommunications shall provide all meteorological information, required for the meteorological protection of aircraft in flight, that is not satisfactorily provided by broadcasts.

SECTION V

Procedures for Meteorological Protection of Flights on International Air Routes

26. Responsibilities. Meteorological services concerned shall name the meteorological offices responsible for protecting each air route and airport in accordance with the procedures outlined below, with due regard to the location of air traffic control centers and international airports.

27. Exchange of Meteorological Information Between Meteorological Offices. Meteorological services involved shall, by agreement, arrange exchanges of information between the responsible meteorological offices. This information shall consist of the following:

(a) Basic meteorological information.

(b) Analyses.

(c) Forecasts for route-sections.

(d) Forecasts for airports and alternate airports.

(e) Amendments to the forecasts listed in (c) and (d).

(f) In-flight and post-flight aircraft meteorological reports.

The frequency and content of the exchanges shall be arranged to permit meteorological offices to provide protection for routine, nonroutine and special flights.

28. Notification and Initial Action

(a) Routine Flights

(1) Operating agencies shall provide, to the meteorological offices concerned, copies of operating schedules and amendments thereto for flights over the air routes for which meteorological protection bas been requested.

(2) The responsible meteorological offices along the air route shall furnish forecasts for their route-sections, airports, and alternate airports. These forecasts shall be transmitted to the initial meteorological office either on a routine basis or a sufficient time before ETD to allow preparation of the flight forecasts. On routes where it is practicable to exchange complete meteorological information, the exchange of forecasts for route-sections may be suspended in favor of the exchange of prognostic or composite analyses.

(b) Non-Routine and Special Flights

(1) The initial meteorological office shall notify the other responsible meteorological offices of impending non-routine and special flights, in the standard form for forecast request, as soon as notice is received from the operating agency or the air traffic control center, unless the necessary notice has been forwarded to all concerned by the operating agency or the air traffic control center.

(2) Meteorological offices receiving this notice shall furnish, for transmission to the initial meteorological office, the necessary forecasts a sufficient time before ETD to allow the preparation of the flight forecasts.

29. Flight Watch. A flight watch is maintained at all air traffic control centers. The forecaster of the meteorological office concerned performs an essential part of this flight watch. The detailed responsibilities of the forecaster are outlined in paragraphs 30, 31, and 32 of this Annex.

30. Pre-Flight Procedure

(a) Liaison. The closest liaison shall be maintained between the forecaster and the operations officer. The operations officer shall visit the meteorological office prior to taking over watch and at such other times as he may consider necessary to satisfy himself regarding meteorological conditions for the flights for which he is responsible. The forecaster shall discuss with the operations officer the route and landing forecasts prepared for the person in command of the aircraft. He shall also advise the operations officer without delay of any amendments to these forecasts and changes in other meteorological information provided. The latter shall include conditions for cruising altitudes, off-course areas, and alternate airports not included in the flight plan, where conditions are more favorable than those forecast for the flight as planned.

(b) Basis of Information. Meteorological offices furnishing protection for flights shall base their forecasts and advices on all available meteorological information, including consideration of the analyses and forecasts provided by other responsible meteorological offices. (c) Action

(1) The initial meteorological office shall have available for the person in command of the aircraft, in sufficient time before the departure, a flight forecast prepared on the standard forms.

(2) A forecaster shall brief the person in command of the aircraft on the flight forecast and on the relevant off-course weather expected. (3) If any amendment to the flight forecast becomes necessary between the briefing and the departure of the aircraft, it shall be com