AMOSSG/3-SN No. 3

31/12/01

AERODROME METEOROLOGICAL OBSERVING SYSTEMS STUDY GROUP (AMOSSG)

THIRD MEETING

Miami, 22 to 25 January 2002

Agenda Item	6:	Assessment of the current capability of automatic weather observing systems to meet the expected future requirements

(Presented by the Secretary)

SUMMARY
The group is expected to re-assess the current capability of automatic weather observing systems to meet the draft future requirements as specified under Agenda Item 5 and to be included in Annex 3 — Meteorological Service for International Air Navigation. Particular attention should be paid to the observation of visibility, present weather, cloud amount and type, and recent weather.

1.	INTRODUCTION

1.1	The group will recall that initial assessments of the capability of automatic weather observing systems to meet the expected future requirements have been undertaken at the previous two meetings. In these assessments, attention was paid to five parameters which, according to Annex 3, cannot be measured using fully automated systems, i.e. visibility, present weather, cloud amount and type, and recent weather. These assessments were carried out in two phases:

a)	first, the scope of expected changes in the requirements had to be estimated;

b)	second, the capability of modern equipment to meet these requirements, at the present time or in the near future, had to be assessed.

1.2	With regard to the first phase, the group concluded that the operational requirements concerning the critical parameters, i.e. visibility, present weather, cloud type and amount, and recent weather had not substantially changed and that similar information to that available currently would continue to be required in the future. Therefore, the task for the group consisted essentially of the assessment of automated weather systems to meet the current requirements.

1.3	As a result of discussions at the previous meetings, the group concluded that the visibility was the only one of the five critical parameters which could be currently observed with fully automated systems. It was recognized that substantial progress had also been made in other areas but some more work was still required before fully automated systems could be used in lieu of human observers.

2.	DISCUSSION

2.1	No new developments have been brought to the attention of the Secretary. A short note on the United States practice was provided to the Secretary and is attached to this study note for information.

2.2	If no major developments in this area are reported at the AMOSSG/3 Meeting, Annex 3 will have to continue to reflect the fact that input from human observers will continue to be required for the observations of present weather, cloud amount and type, and recent weather.

3.	ACTION BY THE GROUP

3.1	The group is invited to agree that the expected future requirements in Annex 3 concerning the observation of present weather, cloud amount and type and recent weather cannot yet be observed by fully automated systems without human intervention.

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AMOSSG/3-SN No. 3

Appendix

APPENDIX

GENERAL DISCUSSION OF AUTOMATED SURFACE OBSERVING FOR AVIATION

The United States (U.S.) has been working with automated surface observing systems for many years. There are over 1 500 aviation reporting locations using various forms of automated surface observing systems. Based on the Air Transport Association (ATA) operational requirements, we concluded that available automated systems did not have all the capabilities necessary to replace the human observer. This resulted in the need to identify airports that could be supported by a stand-alone ASOS, which we call Service Standards for Automated Surface Observing Systems (ASOS). The Automated Weather Observing System (AWOS) is designed for very low-density air traffic activity airports and is generally operated in a fully automated mode. With a few exceptions, AWOS is found at airports with no previous history of aviation weather reporting. Since 1994 we have added automated thunderstorm and freezing precipitation reporting. With these additions it was determined that fully automated reporting would be capable of replacing observers at low air traffic density locations that provided aviation weather reports generated by ASOS.

Even with the addition of thunderstorm and freezing precipitation reporting capabilities, we continue to require a human observer at locations that have an operating control tower. This is done to enhance capacity at the airport. The U.S. requires that, with the proper equipment, any automated surface observing system be capable of accepting manually generated reports or elements of reports that conform to approved observing practices. Capacity becomes an issue when the automated observing system generated report does not accurately reflect operationally significant weather elements. This can occur when weather is changing rapidly and the algorithms do not allow a rapid enough change in the observation. The algorithms are designed to favour a conservative approach to weather reporting so safety is not compromised.

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