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Volume 3, July 2012

Message from the AMDAR Panel Chairman

Dear Reader,

It is my pleasure to welcome you to the third edition of the AMDAR Newsletter issued by the WMO AMDAR Panel.
The Summer holiday period (northern hemisphere) is always a difficult time for an editor to get enough input for publication. That is not the case for the AMDAR Newsletter. Again, with thanks to the contributors, you will find a number of very interesting articles informing you about the status of the various components of AMDAR and the Global AMDAR Programme.

In this edition, you will read about the China AMDAR Programme, an example describing how AMDAR is used in Marine Forecasting and two articles related to the Water Vapour Sensing System WVSS-II. This system, currently widely operationally implemented in the US AMDAR programme and under extensive quality testing in the European E-AMDAR programme, can be considered as a very important addition to the AMDAR system.

You will further read about the performance of the Global AMDAR Programme under Aircraft Observations Output and Coverage and a more technical article provides some insight into a known, small measurement bias in AMDAR temperature observations.

On the governance side, you will be informed about the Workshop on Aircraft Observing System Data Management, recently organised by the AMDAR Panel and the upcoming 15th Session of the AMDAR Panel to be held 6 to 9 November 2012 in Boulder, Colorado, in conjunction with a Technical Workshop on Turbulence.

The AMDAR Panel Chairman, Vice Chairman and Technical Coordinator welcome any questions or comments on the Global AMDAR Program. The names and contact details can be found at the end of this Newsletter.

Frank Grooters, AMDAR Panel Chairman

Aircraft Observations Output and Coverage

The graphic at left shows the smoothed, monthly average of daily observations (single point measurements made by an aircraft in space and time) transmitted on the World Meteorological Organization (WMO) Global Telecommunications System since 2003 up to June 2012, as contributed by all aircraft and all systems (blue): 

- From the AMDAR Programme with reports submitted in binary format (BUFR, red);
- From the AMDAR Programme with reports submitted in text format (FM42, green); and,
- From ICAO data sources (AIREP and ADS, magenta).

Over the last few months, the global aircraft observations output has continued to recover and is once again above 300,000 observations per day after a decline over 2011 that appears to have been associated mainly with economic and operational fluctuations in the airline industry.

WMO and the AMDAR Panel express gratitude to our aviation industry and airline partners for their continued contribution to the Aircraft Observing System and the AMDAR Programme, even in times of economic hardship and can be assured that these data are utilised within meteorological applications and forecasts that benefit aviation operations and safety. 

WMO AMDAR Panel and Technical Workshop on Turbulence 2012

AMDAR Panel Fifteen Session, Boulder, Colorado, USA, November 2012

Since its formation in 1998, the AMDAR Panel has been responsible for the development and management of the AMDAR Programme and is comprised of WMO Member National Meteorological and Hydrological Services operating under the Terms of Reference of the AMDAR Panel. For more information visit the WMO Aircraft Observations site.

The Panel has since met on an annual basis, often in countries and locations that have expressed an interest in developing an AMDAR Programme and might benefit from the interaction of local experts and aviation representatives with Panel Members. On several occasions, Panel meetings have also been held conjointly with technical workshops on AMDAR related systems and science.

In 2012, the Fifteenth Session of the AMDAR Panel will be held over the 6th to 9th of November 2012 in Boulder, Colorado, USA.

Technical Workshop on Turbulence

In conjunction with the AMDAR Panel meeting on the 5th of November, the AMDAR Panel, in cooperation with theFederal Aviation Administration (FAA) and the National Center for Atmospheric Research (NCAR) will hold a technical workshop on turbulence, with a particular focus on the monitoring and reporting of turbulence from the AMDAR system. More details will be available shortly from the WMO Aircraft Observations Meeting site.

The Workshop on Aircraft Observing System Data Management

At its 15th Session in 2007, WMO Congress recognised the work of the AMDAR Panel in its management of the AMDAR Programme and the progression of the AMDAR observing system as an operational component of the WMO Integrated Global Observing System (WIGOS). However, it was also recognised that, for AMDAR to be considered fully integrated into WIGOS, standards for data quality and data management would require consolidation and integration into WMO's technical regulatory framework. For that purpose the WIGOS Pilot Project for AMDAR was implemented. 

Among other objectives this Project focused on policies and practices impacting on AMDAR data collection, processing, archiving and dissemination. The standard practices used in observing the atmosphere need to be well documented to ensure sufficient detail accompany the observations so that users can interpret measurements correctly. The aims and objectives under the Pilot Project were defined as follows:

for the short-term:

(1) Development of a standardised AMDAR data format for transmission on the WMO Global Telecommunications System (GTS);
(2) Application of WMO Metadata relevant to AMDAR;
(3) Development of a standardised Quality Management Framework for AMDAR data; and
(4) Validation and preparation for inter-comparison of available Water Vapour sensor performance.

for the longer-term:

(5) Update of the AMDAR Reference Manual WMO-No.958; and
(6) Development of the framework for generic software specification for AMDAR

With the aim of furthering the progress of objectives 2 and 3 in particular and also to consider other aspects related to the development and maintenance of a Quality Management Framework for the aircraft observing system, the AMDAR Panel and WMO made plans for a Workshop on Aircraft Observing System Data Management, which was held over 5-8 June 2012 at the WMO Secretariat.

The Workshop was attended by ten experts from various Regions, Numerical Weather Prediction Centres, National Meteorological Centres and the Secretariat, all having skills and expertise in the areas associated either directly with Aircraft Observations (AO) data management or else from a data user background. Prior to the Workshop, the participants produced a set of documents that summarized the relevant information and issues related to a range of aspects and areas associated with the development of the AO Data Management Framework. These documents were presented and discussed by the participants during the first part of the Workshop. Breakout Sessions were conducted at which the participants discussed in more detail the issues and ideas that had been formulated, began work on identifying and defining strategies for solutions for some areas and developed a set of recommendations to be further considered and taken up by the AMDAR Panel and WMO.

Significant outcomes from the Workshop include: 
  • a proposal for the definition of a new or updated Data Management Framework for the Aircraft Observing System, including the management of AMDAR and other AO data sources; 
  • the further review and refinement of the metadata requirements; and, 
  • recommendations for improvements to the Quality Management System for aircraft observing system data, including Quality Control, Quality Monitoring and Quality Assurance procedures and processes.
The Workshop was considered by participants to have been successful, beneficial and to have achieved the prescribed aims and objectives.

The Aims and Objectives of the workshop and the Final Report can be found on the WMO AMDAR website.

The China AMDAR Programme

The China AMDAR Programme has been operational since 2002 under a cooperative arrangement between the Civil Aviation Administration of China (CAAC) and the China Meteorological Administration (CMA).

From an initial beginning with 1 airline and 9 aircraft producing around 2500 reports per day, the progamme has now grown to 3 airlines, 22 aircraft producing around 7000 reports per day, which are disseminated on the WMO Global Telecommunications System (GTS) after being evaluated by the Quality Control System.

Quality Control and Monitoring of China AMDAR Programme

The AMDAR Quality Control System (AQCS) was built by CAAC to ensure that the quality of AMDAR Data is monitored and checked before being distributed to data users. After the raw downlink data is received on the ground it is decoded and then passed to the AQCS where the data passes through a series of checks which include, a time calibration check, a flight phase check, meteorological parameter range checks and a meteorological parameter consistency check.

In 2011, the CAAC began testing an AMDAR report distribution control system, the AMDAR-WXM system, which was developed to improve the efficiency and reduce the running costs of the AMDAR programme.The system enables the switching of AMDAR on or off according to various parameters including, airspace position, flight number, observational time intervals, as well as other functions. The results of the trial have demonstrated that the system is 97.5% efficient in providing the required reporting functionality.

Use of AMDAR Data by CMA

In addition to producing AMDAR data as a contribution to the global AMDAR programme, CMA uses global AMDAR data received via the GTS, of which over 300,000 observations per day are now available.

Aviation and Public Weather Forecasting

AMDAR data have been used operationally in the meteorological service at airports such as Beijing Capital, Chengduand and Guangzhou international airport for several years. The main warning or forecast products provide assistance in the forecast and monitoring of phenomena such as:
  • Frontal weather systems;
  • Trough and shear-lines;
  • Low-level jets;
  • Inversion and stability;
  • Temperature advection;
  • Low level wind shear; and,
  • Upper and surface-level winds (see figure at right).
The figure at right shows a wind profile chart January 24, 2010 0710-1120UTC, Beijing Capital Airport

AMDAR data are also used to monitor and/or forecast other weather phenomena such as fog, precipitation type, turbulence and freezing level.

CMA has also developed an AMDAR display capability within its Meteorological Information Comprehensive Analysis and Process System (MICAPS), a processing, display, and telecommunication network which is the standard operational platform of the national-wide weather service. It is used by CMA to analyze AMDAR data more conveniently and efficiently.

On MICAPS, en-route AMDAR data, including wind, temperature and turbulence can be displayed horizontally by level as the figure at left shows.

Numerical Weather Prediction

CMA has worked on integrating AMDAR data into its various Numerical Weather Prediction (NWP) models. Assimilation of AMDAR Data to CMA Global/Regional Assimilation and PrEdiction System (GRAPES) NWP model has been conducted and results have shown  for the first time that AMDAR data has a significant positive impact on NWP forecast skill over the China region.

The Early Days of WVSS at UPS

United Parcel Service (UPS) first became interested in water vapor sensing by aircraft because in the mid 1990s, fog forecasting was important to the company’s operations.

Not only were flights arriving at a number of airports around sunrise (when fog is most likely), but also when only a few aircraft were able to land with Category III minimums {Runway Visual Range (RVR) of 600 feet}.  At the time, UPSB-747 and B-727 aircraft were Category I (RVR 1800 feet, or 1/2 statute mile) equipped, and the DC8s were Category II (RVR 1000 feet to -1600 feet) compliant.  Only the UPS B-757s were Category III ready.  Aircraft were swapped whenever a Category I plane was to be flown to an airport where Category III weather (fog) was expected.

Figure 1: One of the first aircraft soundings with water vapor data; ascent sounding from Jacksonville, FL May 30, 1997

The UPS fog forecasting method recognized the need for moisture data just above the surface, which was instrumental in UPS's involvement in the Water Vapor Sensing System (WVSS) program.  A WVSS presentation by Dr. Rex Fleming at an AMS annual meeting in the early 1990s led to high-rate ascent and descent reporting by UPS aircraft.  Those winds and temperature reports began during the summer of 1994 at UPS.  The WVSS took more time to implement, but the first flew in 1997 (see figure). 

The first generation of WVSS instruments (WVSS-I) employed thin-film capacitor technology.Thirty of these units were installed on UPS aircraft. Soon it was discovered that these sensors gradually lost sensitivity over about a 6 month period and eventually became non-responsive.  This, in large part, led to the move toward laser diode technology, the cornerstone of WVSS-II.

WVSS-II STC for the 737-700 Complete

A team effort, led by SpectraSensors, Inc., ARINC, and Southwest Airlines (SWA) has completed the project to achieve a Supplemental Type Certification (STC) for the Water Vapor Sensing System (WVSS-II) on the 737-700 aircraft.
This expands the WVSS-II STCs now held by SpectraSensors to include the 757-200PF, 737-300, and 737-700 aircraft types.  The first WVSS-II installation on a 737-700 took place in March at Southwest Airlines in Dallas, Texas as part of the STC process.  The STC was issued to SpectraSensors by the U.S. Federal Aviation Administration (FAA) on June 12th, 2012.  The FAA Parts Manufacturer Approval (PMA) was subsequently issued to SpectraSensors on June 20th.   With this STC approval ARINC’s proud partnership with SWA will enable an additional 36 WVSS-II units to go into operation on SWA 737-700 aircraft over the coming months, in support of ARINC contracts to the U.S. National Weather Service.  It also opens the door for further global WVSS-II implementations on the 737-700 aircraft, and the extension to 737-800 aircraft.

Bryce Ford, VP of Atmospheric Programs at SpectraSensors, states “SpectraSensors is proud to take this next step forward for WVSS-II so that we may better serve the AMDAR community.  We are confident this STC will enable WVSS-II to expand its service to AMDAR participants with air carrier partners operating this popular aircraft type.  We understand the role that high quality upper air observations of water vapor have in all forms of operational forecasting and we are committed to ensure that WVSS-II fills that role for our partners.  We look forward to supporting the AMDAR community in expanding the use of WVSS-II throughout the globe as part of the continuous evolution of the World Meteorological Organization Global Observing System.”

AMDAR Data Usage - Marine Forecast Example

U.S. National Weather Service (NWS) Forecast Offices near coastal locations have the responsibility to forecast winds for marine operations. This case shows how AMDAR data were used in forecasting strong winds. On the evening of October 3, 2004, NWS forecasters at the Chicago office were faced with the question of whether the gale force winds being experienced on Lake Michigan would persist overnight and if so, to continue the gale warning (winds of 34 knots to 47 knots) which was in effect.
The Skew-T Log-P diagram at left from a descending flight into O’Hare airport at 2230UTC shows west to northwest winds of at least 30 knots up to 300 hPa. The thermal profile was sufficiently unstable to allow the mixing of these winds down to the surface.

This evidence helped to give the forecasters confidence to continue the gale warnings for Lake Michigan through the night.



715 PM CDT SUN OCT 3 2004



Some Program-Scale Statistics Derived from Monthly Monitoring Reports

At the end of each calendar month there are two AMDAR data quality monitoring reports that are made available from international data monitoring centres. Each provides analysis of the AMDAR observations broadcast on the WMO Global Telecommunications System in the preceding month, with particular reference to the output of a NWP (numerical weather prediction) model. They are:

(a) the Meteo-France report (‘Monthly monitoring statistics for aircraft observations between 300 hPa and 150 hPa’); and,

(b) the two US-NWS NCEP (National Weather Service, National Centers for Environmental Prediction) reports ‘Monthly AMDAR Statistics Report’ and ‘Monthly ACARS Statistics Report’. 

Each of these reports, for all AMDAR reporting aircraft, takes the ensemble of observations by a particular aircraft and aggregates them to a range of summary statistics which serve to characterise the overall data contribution and quality of that aircraft for the month. The study undertaken and summarised in this artcle, takes this process one cycle further and aggregates the statistics for the many aircraft in a national or regional AMDAR program to yield a small set of statistics that might serve to characterise the overall data contribution and quality of that program for the month.

The full description of this process and its results, comprise an internal data QC study we have recently completed. Here we have extracted a few figures from that study concerning systematic bias of AMDAR observations data with respect to NWP data, a topic of current interest to both the NWP and AMDAR communities [e.g., Ballish and Kumar, Bull.Am.Met.Soc., November 2008]. The following text will introduce the figures only briefly.

Figures 1 and 2 illustrate, for the nine regional programs, estimates of measurement bias in AMDAR T (temperature) observations, with reference to Meteo-France NWP data and US-NWS NWP data, respectively. Note that Figure 1 pertains only to T observations in the pressure altitude range 300 hPa to 150 hPa; (the Meteo-France report constrains its analysis to observations acquired in this pressure altitude range). Figure 2 however, from US-NWS monthly reports, effectively covers T observations acquired through the entire pressure altitude range, and furthermore resolves it into the following categories: High (p < 300 hPa); Mid (300 hPa < p < 700 hPa) and Low (p >700 hPa). The two figures are consistent in indicating a systematic T measurement bias of almost +0.5 °C for Japan and Hong Kong, and somewhat less for the other regional programs. Figure 2 does not appear to suggest any systematic relationship between T bias and altitude.

Figure 1. Estimate of the overall bias, and its dispersion, in AMDAR T (temperature) observations at high altitude (150 hPa < p < 300 hPa). Record of the Mean and ±2Std.Dev. of the aircraft Bias (w.r.t. Meteo-France NWP) of T observations, on average, over the period July 2011-June 2012, for nine regional/national AMDAR programs.

Figure 2. Estimate of the overall bias, and its dispersion, in AMDAR T observations. Record of the Mean and ±2Std.Dev. of the aircraft Bias (w.r.t. US-NWS NWP) of T observations, on average, over the period July 2011-June 2012, for nine regional AMDAR programs. Resolved by altitude range: High (p < 300 hPa); Mid (300 hPa < p < 700 hPa) and Low (p >700 hPa).

Similarly, Figures 3 and 4 illustrate the estimated bias in WS (wind speed) observations. Again, the two figures are consistent and suggest the existence of a small systematic WS bias, ranging from -0.5 m.s-1 (at low altitudes in Canada) to +0.6 m.s-1 (at high altitudes in USA, Japan, Canada, South Africa and New Zealand). Figure 4 suggests some systematic relationship between the WS bias and altitude, with larger positive biases occurring at higher altitude.

Figure 3. Estimate of the overall bias, and its dispersion, in AMDAR WS (wind speed) observations at high altitude. Record of the Mean and ±2Std.Dev. of the aircraft Bias (w.r.t. Meteo-France NWP) of WS observations, on average, over the period July 2011-June 2012, for nine AMDAR programs.

Figure 4. Estimate of the overall bias, and its dispersion, in AMDAR WS observations. Record of the Mean and ±2Std.Dev.of the aircraft Bias (w.r.t. US-NWS NWP) of WS observations, on average, over the period July 2011-June 2012, for nine AMDAR programs. Resolved by altitude range.

While the results of this study indicates that all AMDAR programmes produce data of high quality, it appears that there are systematic biases in both air temperature and wind speed that are able to be consistently resolved across AMDAR programmes and, in the case of wind speed, with altitude, possibly indicating differences in onboard or ground-based data processing practices. This will be something that the AMDAR and NWP communities will investigate further in the future.

WMO AMDAR Panel Chairman

Mr Frank Grooters
Prunuslaan 17
NL-3723 WC Bilthoven
The Netherlands
Tel : +31 30 229 3250
Mob : +31 6 1122 5867
Email : fgrooters@gmail.com
WMO AMDAR Panel Vice-chair

Mr Carl Weiss
NOAA/NWS National Weather Service
1325 East, West Highway
SILVER SPRING 20910-3283
United States of America
Tel: +1-301-7131726-149
Email: carl.weiss@noaa.gov
WMO Scientific Officer, Aircraft Observations

Mr Dean Lockett
World Meteorological Organization
7 bis, avenue de la Paix Case postale No. 2300
CH-1211 GENEVA 2
Tel: +41-22-7308323
Email: dlockett@wmo.int