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As advised by Tim Hailes (@tahailes), for those who are interested in the Area QNH and also winds and temps across Australia provided by BoM, they can visit: Brochures on these products are available here: |
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At the ICAO APAC MET/ATM Seminar 2024 on 22 Apr 2024, Kenrick Taylor of IFATCA delivered a presentation on Cold Temperature Altitude Correction, stating the need and ongoing efforts to introduce additional clarity to existing provisions. This is an interesting use case where SWIM Information Services could demonstrate its potential in supporting its needs. Rick has kindly provided the following elaboration regarding some ATS authorities' operational concept for cold temperature altitude corrections, including their meteorological needs:
With regard to cold temperature altitude correction, the ATS authorities and flight crew have a need for forecast and current air temperature. The current PANS-ATM and PANS-OPS procedures relating to cold temperature altitude correction (and indeed the procedures envisaged for applicability in 2028) refer to the 'altimeter setting source', which is the location on the Earth's surface at which air temperature and pressure is measured and promulgated, and then used by ATS and flight crew. What exactly is the 'altimeter setting source' is not defined in the PANS, but in practice it is assumed that the aerodrome is the altimeter setting source because currently that is where air temperature and pressure is measured and promulgated by METAR/SPECI. This leads to the first area of concern that we have: In the procedures it is assumed that flights operate near terrain only during arrival and departure, but what about long-range, low-level IFR flight? These flights need to know the temperature at the departure and arrival aerodrome, but also along their route. As discussed during the ATM/MET Seminar, it may be possible for meteorological authorities to provide air temperature at an almost unlimited number of locations, but this information still needs to be able to be interpreted by human pilots and ATS personnel for the foreseeable future (although it should probably also be obtainable by on-board and ground-based systems to automatically compute the necessary corrections). Currently operational personnel in these circumstances use the temperature from the nearest altimeter setting source but is this really the best method? Could it be better to measure temperature and pressure at published waypoints or other significant points? This is probably for the local authorities to determine. Those States which allow vertical position to be described as altitude away from the aerodrome already have to deal with this need for data over a wide area (although in this case it is concerned with air pressure) and Australia provides an example of 'area QNH' and a local procedure which allows an aircraft to use data from any altimeter setting source within 100 NM of the aircraft's position. Is this suitable for air temperature as well? Or is temperature more variable and therefore does it need alternative arrangements?
Pilots and their ground systems will need access to actual and forecast air temperature during the pre-flight planning stage, which will allow them to determine the minimum safe altitude for their planned route. During the flight, pilots and their airborne systems will need to receive updates to the air temperature and a person or system will need to identify if that temperature is colder than what was forecast. How will this temperature be shared with air and ground systems? Shared directly from the meteorological authority to the operator or aircraft as well as the ATS unit?
ATS units will need access to historic minimum temperatures, seasonal forecasts and short-term forecasts in order to determine how they participate in the cold temperature correction process. Currently, ATS units either base their decision on historic seasonal lows or they use METAR/SPECI to monitor temperatures. Where ATS units participate more actively in the process, they will need timely notifications of temperature changes, particularly colder temperatures, at the altimeter setting source. It will be ideal if this temperature can be fed directly into the ATM automation systems, which can then calculate changes to the lowest assignable levels given the temperature. Currently there are only thresholds defined in ICAO documentation for publication of increased temperatures in SPECI, but in reality the system needs to know about both increases (reduced aircraft performance) and decreases (possible need to change lowest assignable/usable level).
Any further views are most welcomed.
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