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AMOSSG/2 — SN No.3
23/01/01
AERODROME METEOROLOGICAL OBSERVING SYSTEMS STUDY GROUP (AMOSSG)
SECOND MEETING
De Bilt , 20 to 23 February 2001
Agenda Item 6. Assessment of the current capability of automatic weather observing stations to
meet the expected future requirements
a)
b)
monitoring of results from research on the automatic detection of cloud types: Cb
and TCU
intensity thresholds for weather phenomena
(Presented by the Secretary)
SUMMARY
Under this agenda item, the group should undertake an
assessment of the current capability of automatic weather
observing stations to meet the expected future requirements to be
included in Annex 3. Particular attention should be paid to two
specific issues listed under a) and b) above.
1.
INTRODUCTION
1.1
The group will recall that during the AMOSSG/1 Meeting, an initial assessment of the
capability of automatic weather observing systems to meet the current requirements as stated in ICAO
Annexes. During this review, four critical parameters were identified: visibility, cloud (amount and type),
present weather and recent weather which, according to the provisions in Annex 3 — Meteorological
Service for International Air Navigation, could not be fully observed by automated systems without human
intervention. The group concluded that while substantial progress had been made in this area, out of these
critical parameters, only visibility could now be observed with instrumented systems; fully automatic
systems still fell short of detecting a) present weather; b) cloud amount; c) cloud type; and d) recent
weather (included in the supplementary information).
2.
DISCUSSION
2.1
The group is invited to review the situation against the expected future requirements,
most of which are reproduced in Appendix A to AMOSSG/2-Study Note No. 2. As agreed during the
AMOSSG/1 Meeting those requirements which are not directly associated with provisions in Annex 2 —
Rules of the Air, Annex 6 — Operation of Aircraft or Annex 11 — Air Traffic Services have been subject
to a revision. In this regard, the following simplifications are being proposed:
a)
the elimination of the use of towering cumulus (“TCU”) as a cloud type (the
justification is provided in Study Note No. 2);
a)
a simplification of the list of present and recent weather phenomena are proposed in
Study Note No. 9 prepared by Earle with the assistance of some study group
members.
2.2
It may be noted that information on cloud amount is required for operational decisions
(e.g. the ceiling depends on the cloud amount) and therefore, no simplifications in this area are considered
appropriate. Likewise, the occurrence of cumulonimbus clouds are of operational significance and could
not therefore be proposed for deletion.
3.
SPECIFIC TASKS
3.1
The group is also invited to review progress made in two specific tasks identified by the
AMOSSG/1 Meeting.
3.2
Monitoring of results from research on the automatic detection of cloud types: Cb
and TCU
3.2.1
Progress on this sub-task depends on the input by the AMOSSG Members. Since the
“TCU” clouds are proposed for deletion, all the efforts could perhaps be concentrated on the detection of
Cb-clouds.
3.3
Intensity thresholds for weather phenomena
3.3.1
The group will be aware that, in accordance with the working arrangements between
ICAO and WMO, the WMO is the organization responsible for defining the quantitative intensity
thresholds for weather phenomena. Work has been undertaken by WMO Commissions; in particular, the
PROMET sub-group of the WMO Commission for Aeronautical Meteorology (CAeM) developed a
number of proposals concerning precipitation intensities which have since been endorsed by the
appropriate WMO bodies. The salient results from the work undertaken by WMO are expected to be
highlighted by Saad (AMOSSG/2 — IP No. 2 refers).
4.
ACTION BY THE GROUP
4.1
The group is invited to undertake an assessment of the current capability of automatic
weather observing stations to meet the expected future requirements to be included in Annex 3, taking
account of :
the proposed elimination of the requirement to report “TCU” as a cloud type;
a)
and
a)
the simplification of the list of present and past weather phenomena presented
in Study Note No. 9.
— END —