AMOSSG/5-SN No. 8

9/3/05

AERODROME METEOROLOGICAL OBSERVING SYSTEMS STUDY GROUP (AMOSSG)

FIFTH MEETING

Montreal, 11 to 14 April 2005

Agenda Item	5:	Aerodrome observation requirements
5.2:	Capability of automatic observing equipment to meet aeronautical requirements and the use of automated equipment during operational hours

REPORT OF THE AD HOC WORKING GROUP ON AUTOMATED OBSERVING SYSTEMS TO SUPPORT OPERATIONS

(Presented by S. Albersheim)

SUMMARY
Present and recent weather reporting criteria are evaluated in consideration of current capabilities of meteorological observing systems. A proposal is provided on what constitutes an automated observation during operational hours at aerodromes.

1.	INTRODUCTION

1.1	At the MET Divisional Meeting (2002), Recommendation 2/3 d) invited ICAO, in consultation with WMO, to re-evaluate the requirements for present weather and recent weather taking into account the ability of automatic systems to perform this function. This is an ongoing task of the AMOSSG.

1.2	States adopted Amendment 73 to Annex 3 with an effective date of 25 November 2004 where a recommendation was included in the annex under 4.7 that stated METAR and SPECI reports from automatic observing systems should only be used during non-operational hours of the aerodrome. METAR and SPECI issued from an automatic observing system should be identified with the word "AUTO".

1.3	During the fourth meeting of the AMOSSG, it was agreed that, in order to facilitate the use of fully automatic observing systems during operational hours, a review for the requirements for the reporting of present weather and recent weather would be necessary. Further, it was agreed that a working group would consider these issues with the following guidance:

a)	to consider whether any changes should be made to the requirements for the reporting of present and/or recent weather,bearing in mind the METAR is required to support flight-planning; and

b)	to establish a framework for the use of fully automatic observing systems during operational hours based on criteria such as runway categories.

1.4	This paper provides a proposal from the working group on the use of automatic observing systems during operational hours.

2.	DISCUSSION

2.1	Reporting Standards and Recommended Practices

2.1.1	In accordance with of Annex 3, paragraph 4.5 METAR and SPECI reports shall contain the following elements: identification of type of report; location indicator; time of the observation; identification of an automated or missing report, when applicable; surface wind direction and speed; visibility, runway visual range, when applicable; present weather; cloud amount; cloud type and height of cloud base or where measured vertical visibility; air temperature and dew-point temperature; and QNH.

2.1.2	Annex 3, Appendix 3, paragraph 4.4.2.3 lists the recommended present weather elements that should be reported. For precipitation they include DZ, RA, SN, SG, PL, IC, GR and GS. For obscurations categorized as hydrometeors, the recommended practice for the present weather is FG and BR and for obscuration classified as lithometeors the present weather is SA, DU, HZ, FU, VA. In addition to these elements, other phenomena are recommended to be reported when observed that include: PO, SQ, FC, DS and SS.

2.1.3	Characteristics of present weather phenomena are reported as TS, SH, FZ, BL, DR, MI, BC, and PR. Where appropriate the relevant intensity of selected present weather elements are reported (DZ, GR, GS, PL, RA, SG, SN, DS and SS).

2.1.4	For present weather not at the aerodrome but not further away than approximately 8 km from the aerodrome perimeter present weather observed can be reported as in the vicinity of the aerodrome for DS, SS, FG, FC, SH, PO, BLDU, BLSA, BLSN, TS and VA.

2.1.5	Wind speed/direction, temperature, pressure, sky cover, visibility, runway visual range and some present weather elements can be observed with remote sensors and do not require a human to make a direct observation. Even though some present weather elements and their associated characteristics can be observed through automation not all the elements can be observed. The issue on hand is whether there is a requirement to report present weather elements that cannot be observed through remote sensing in the METAR, necessitating the need to have a human augment a report for automated observing systems. In past practice there was no added cost for the observation as the human could observe all the recommended elements. But with the movement towards automation, there is now a re-evaluation of the need to report all of these present weather elements if they are not required for flight planning.

2.2	An alternative approach for present weather reporting criteria

2.2.1	Recent advances in technology allows with confidence the automated reporting of DZ, RA, SN and FG. Furthermore, technology allows for the reporting of intensity for these elements and identifying if the precipitation is in a frozen state. Several States that include Canada, France and United States have adopted this technology and are using it to provide observations at international landing right airports and non-international landing right airports.

2.2.2	Annex 3, Chapter 4 states that Contracting States shall establish at aerodromes or other points of significance to international air navigation aeronautical meteorological stations. An aeronautical meteorological station may be combined with a synoptic station. By definition, an aeronautical meteorological station makes observations and meteorological reports for use in international air navigation. The METAR is a meteorological report for dissemination beyond the aerodrome of origin mainly intended to support flight planning. On the other hand, a local routine report is for dissemination at the origin of the aerodrome intended for arriving and departing aircraft. Both the local and METAR support the requirements of an aeronautical meteorological station but their purposes and functions are very different.

2.2.3	The annex also states that at aerodromes with runways intended for Category II and III instrument approach and landing operations there is a requirement for surface wind, visibility, runway visual range, height of cloud base, air and dew-point temperature, and atmospheric pressure. No reference is made to a need for present weather.

2.2.4	Even though the annex makes reference that the present weather field is a required reportable element in the body of the METAR/SPECI, the reporting of the listed present weather elements is a recommended practice. For the most parts, States report all the recommended elements listed in the annex as a customary practice. In other words, if observed, the human will report the information.

2.2.5	If it is agreed that the essential information in the METAR, which is used for flight planning, is surface wind, visibility, runway visual range, height of cloud base, air and dew-point temperature and atmospheric pressure then automation of these elements can be attained with today's technology. The provision of present weather elements would still continue to be a recommended practice and that an automated observation by definition would require only those core elements.

2.2.6	Users of weather observations from an aerodrome including aviation meteorologist, dispatchers, and pilots can obtain present weather from the SYNOP code if a State were to elect to use the SYNOP code as the primary means to provide present weather. The State could also use the METAR but that would be an elective decision.

2.2.7	States are still required to forecast weather in the TAF, but that information could be gathered from other sources not solely dependent on the METAR.

3.	RECOMMENDATION

3.1	The group is invited to note the information presented in this working paper to formulate whether there is a requirement to report all present weather in the METAR/SPECI during operational hours of the aerodrome.

3.2	As an initial proposal, an automated observation would require at a minimum: surface wind, visibility, runway visual range, height of cloud base, air and dew-point temperature and atmospheric pressure. Automated observations would also include the following present weather elements: DZ, RA, and SN for precipitation and FG and BR for hydrometeors. The intensity of those elements is also to be reported. Characteristics of present weather including TS and FZ would also be reported in an automated observing system.

3.3	Other present weather elements would continue to be a Recommended Practice but are not deemed essential to support flight planning decisions. Thus when a pilot or dispatcher sees a METAR with "AUTO" they would know the core present weather elements available for flight planning. States that adopt automated observing systems during operational hours of the aerodrome would also be encouraged to file differences to indicate those elements that would not be supported by remote sensing as part of the recommended practices.

4.	ACTION BY THE GROUP

4.1	The ad hoc working group recommends that Annex 3 be amended to allow for the provision to:

a)	fully use automated observations to support aerodromes during operational hours;

b)	identify the core elements and those present weather elements referenced above for the METAR/SPECI that supports aerodromes during operational hours and the METAR/SPECI would be coded as "AUTO"; and

c)	identify a list of recommended practices that lists present elements that can be augmented but the METAR/SPECI would not be coded as an "AUTO" observation when disseminated for flight planning purposes.

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