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Volume 2, April 2012

Message from the AMDAR Panel Newsletter Editor

Dear Reader,

Welcome to the second edition of AMDAR Newsletter issued by the World Meteorological Organization AMDAR Panel.  I hope you find the following articles both interesting and informative.

The goal of the newsletter is to inform the reader as to the status of AMDAR, how the data are used and what new capabilities are on the horizon.  Also, by keeping AMDAR in the forefront, we hope to stimulate NMHSs to consider beginning their own national/regional programs.

In this edition, you will read about:

  • Increases in overall data volume
  • Plans for an AMDAR data management workshop
  • AMDAR's role in South Africa's upper-air observations program;
  • EUMETNET WVSS-II flight testing
  • Value of WVSS-II data in a tornado situation
  • Status of airborne turbulence measurements, and
  • Australian data optimization efforts

The AMDAR Panel, its Chairman, Vice Chairman and Technical Coordinator welcome any questions or comments on the global AMDAR program and, in particular, any interest in the development and coordination of new national programs.  The names and contact details can be found at the end of this Newsletter.

Carl Weiss, AMDAR Panel Vice-Chairman and Newsletter Editor

Aircraft Observations Data Output Recovers

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 GTS since 2003 up to March 2012, as contributed by all aircraft and all systems (blue): By the AMDAR Programme with reports submitted in binary format (BUFR, red), by the AMDAR Programme with reports submitted in text format (FM42, green) and by ICAO data sources (AIREP and ADS, magenta).

AMDAR Data levels have been gradually increasing over the past 3-4 months, so that Aircraft Observations are once again up around 300K observations per day.

The increase appears to be generally associated with variation in airline activity associated with economic fluctuations, rather than with aircraft observations program changes. So, it is therefore mainly a reflection of more aircraft and hence more AMDAR aircraft being in the air more often. This trend is reflected in most AMDAR programs.

For further information see: http://www.wmo.int/amdar/AMDARStatistics.html

AMDAR Data Management Workshop

Currently, the AMDAR program is in the process of being integrated into the WMO Integrated Global Observing System (WIGOS) and the World Weather Watch Program (WWW).  Many governance activities for finalizing this process have been completed in the new structure. 

On the technical level, the AMDAR Pilot Project for WIGOS was established with the objective “To improve practices impacting AMDAR data collection, processing, archiving and dissemination”.  This general purpose includes the management of all aspects of AMDAR data: data origin, data quality, data archival, data access and display and metadata.  Some of these points have been touched on by some experts as a task under the AMDAR Pilot Project, but the integrated data management aspects are still to be developed.

At the recent joint meeting of the AMDAR Panel and the CBS Expert Team on Aircraft-Based Observations (ET-AIR) (November 2011), the members agreed to include in the 2012 AMDAR Work Plan the organization of an AMDAR Data Management Workshop.  At the workshop, it is expected that invited experts will recommend how to organize and operate an efficient AMDAR data management system, in line with WIGOS and the WMO Information System (WIS) requirements.  Having strong ties with WIGOS and WIS development would offer opportunities to make some important contributions to various data and product sources and platforms, including data provision to developing countries and programs.  Also, it would aid to centralize and standardize many data management practices for the AMDAR program.

The 3rd meeting of the AMDAR Panel Management Group (February 2012) agreed on the Terms of Reference (ToR) for the Workshop on Aircraft Observing System Data Management, which will take place 5-8 June 2012 at the WMO Secretariat in Geneva.  Significant contributions are expected from the invited experts, leading to a considerable step forward towards the integration of AMDAR into the WIGOS and the WWW.

For more information on the Data Management Workshop and the ToR, see the reports in  http://www.wmo.int/amdar/AMDARMeetings_000.html

AMDAR Contribution to Upper Air Data Coverage for Africa

The coverage of the upper-air data over Africa is described in several research papers as poor and sparse (ECA report, 2011; Parker et al., 2011; the Institute of Water for Africa, 2011; Washington et al., 2006). The sporadic nature of the upper-air data in the Africa region is reflected in Figure 1, which displays results of monitoring (October 2010) of the performance of the Regional Basic Synoptic Network upper-air stations. 

The global upper-air radiosonde network is made up of about 790 upper air stations. Based on an expectation of 2 soundings per day from each station, around two thirds meet the target of 90% or more (blue dots), around 17% submit between 45 and 90% of expected soundings (green dots), about 7% submit less than 45% of expected soundings (orange dots), whilst around 14% of stations fail to report at all (red dots).

Figure1. Results of WMO Annual Global Monitoring, Integrated WWW Monitoring of the Upper-air (TEMP) Regional Basic Synoptic Network, October 2010.

Unfortunately, as can be seen from Figure 1, much of the upper-air data from the African continent falls into the latter two categories. The reasons for the sporadic nature and inconsistency of the upper-air data over the Africa continent are the high costs involved in acquiring the data and the technical difficulties in maintaining the necessary systems and infrastructure to support both measurement and communications. WMO has offered an alternative, cost effective way for alleviating the upper air data problem through the Global AMDAR Programme.

South Africa (SA) is one of the few Member (sixteen in total) states that attended to the WMO’s call for the establishment of AMDAR Programmes at regional scale. SA recognized the advantage of this upper-air project to improve upper-air collection in Sub-Sahara Africa and supports WMO’s call for more Members within the region to initiate and manage their own programmes. Currently the South African Weather Service (SAWS) manages its SA-AMDAR Programme in partnership with South African Airways (SAA) and the European AMDAR Programme (E-AMDAR). To date the SA-AMDAR Programme  has employed thirty-two (32) aircraft, which provide valuable vertical profiles of upper air data for the following airports: Johannesburg (FAJS), Cape Town (FACT), Port Elizabeth (FAPE), East London (FAEL), George (FAGG), Sodwana (FAWW), Gaborone (FBSK), Nairobi (HKNA), Harare (FVHA), Entebbe (HUEN), Dar-es-salaam (HTDA), Lusaka (FLLS), Maputo (FQMA), Lilongwe (FWKI), Dakar (GOOY), Sal  Cape Verde (GVAC), Mauritius (FIMP), Luanda (FNLU).

The SA-AMDAR Program contributes about 3200 ascents per month to the Global AMDAR Program, providing a daily average of 106 ascents. These data play an important role in improving the coverage of upper air monitoring over Africa, thus benefiting the aviation industry, meteorological applications and other users of this high-quality data.

FAAM Flight Testing of WVSS-II Humidity Sensor

On behalf of EUMETNET-AMDAR, two WVSS-II version 3 humidity sensors have been flown in a "piggy-back" mode since the beginning of 2011 on the FAAM research aircraft type BAe 146 (see Figure 1).

Both instruments have been working well and providing valuable data and information about the performance of the sensors in a range of different conditions.

Figure 1 - The WVSS-II sensors are installed on the backside of two window plates (between right front door and wing). Copyright: FAAM

An example of a descent profile (Figure 2) demonstrates the correct operation of the WVSS-II units and close agreement with the on-board standard humidity instruments.The parallel use of two systems is required to test two different intake and outlet configurations, the conventional “Air Sampler” and a Rosemount TAT housing. An alternate solution for the conventional flow system may lead to a better performance and an extended sensitivity of the WVSS-II.

Figure 2 - Example of a descent profile. The mixing ratio results of the two WVSS-II units are plotted together with the results of chilled mirrors, Buck and General Eastern (GE), as well as a system for the total water content (TWC) based on a Lyman-Alpha absorption principle. Copyright: FAAM

In the range from 10 g/kg down to 0.5 g/kg the two sensors show a good congruence with the reference values based on the chilled mirror system General Eastern 1011 B (GE) and the aircraft’s static temperature and static pressure (see Figure 3).

Below that range, a systematic tendency can be seen in the relative deviation of the conventionally equipped WVSS-II unit, with absolute differences increasing to up to +20 %.

At mixing ratios below 0.02 g/kg the number of samples is too small for a reliable evaluation.

In order to test for a possible physical tendency  from individual sensor biases, the two WVSS-II sensing units are planned to be swapped.

Further flight tests will provide more opportunity to establish the statistical consistency of the results, which is especially required for the low humidity values at higher altitudes around 200 hPa.

Figure 3 - The relative deviations in the mixing ratio between the WVSS-II units and the General Eastern chilled mirror system are showing a noticeable difference at humidity values below 0.5 g/kg. The unit connected to the Air Sampler tends to higher values (red dots), whereas the unit driven by the TAT housing remains within ± 10 % of deviations. This diagram is based on measurements under clear conditions without water or ice particles. Copyright: FAAM

A WVSS-II Perspective of the Henryville, Kansas Tornado

A short-lived but devastating tornado struck Harveyville, Kansas on the evening of February 28, 2012, killing one person and destroying half of the small town. A Tornado Watch was in effect hours before the storm hit, and the National Weather Service in Topeka, Kansas issued a Severe Thunderstorm Warning that mentioned the possibility of tornadoes about 20 minutes before the storm arrived. Because the tornado lasted only several minutes, radar  gave meteorologists little opportunity to upgrade the severe thunderstorm warning to a tornado warning.
Several WVSS-II soundings from Kansas City, Missouri were available that evening, before and after the tornado. They all showed strong wind shear (helicity) within a kilometer of the ground,indicating the potential for rotating thunderstorms and tornadoes. A sounding from 0155 UTC (Fig. 1) has a computed SWEAT (Severe Weather Threat) Index of 431, which is well above the usual threshold of 400 for tornado potential.

Figure 1: WVSS-II sounding from Kansas City at 0155 UTC

The 0000 UTC radiosonde (Figure 2) at Topeka, Kansas (released at 2300 UTC) had a SWEAT index of 381, indicating that the atmosphere had become more unstable and developed more shear in the low levels as the evening went on.

Figure 2: Radiosonde from Topeka, Kansas

While most National Weather Service meteorologists are aware of the availability of AMDAR data in general, there has yet to be an educational effort about the WVSS-II data, so it is likely that these soundings were not utilized during the event. If they were, would the increasing instability and shear evident in the soundings have resulted in meteorologists issuing a tornado warning for this event? This was an extremely challenging warning decision given how rapidly the tornado formed, so it’s difficult to speculate.

 The purpose of presenting these soundings is to demonstrate how much valuable data they can provide to meteorologists making difficult warning decisions during severe weather.

Turbulence Measurement

Before in situ measurements of turbulence (e.g., Vertical g and Derived Equivalent Vertical Gust) became available, the only routine observations were (subjective) pilot reports (PIREPs).  These reports, however, show that their measurement is nonuniform in time and space, generally seem to appear with a low occurrence and are aircraft dependent. Pilots flying different sized airplanes generally sense different turbulence intensity levels. Research demonstrates the well-known fact that there are far fewer Null reports made than pilots experience, meaning that the data downlinked were not very representative of the state of the atmosphere.

Under the sponsorship of the US Federal Aviation Administration’s (FAA) Weather Research Program and Reduced Weather Impacts Program, work began in the early 1990s at the National Center for Atmospheric Research (NCAR) in Boulder Colorado to develop an in situ turbulence measurement and reporting system for commercial aircraft.  The concept was to use existing sensors, avionics and communication systems to produce and disseminate a state-of-the-atmosphere turbulence metric, called Eddy Dissipation Rate (EDR).  Using EDR as an aircraft independent solution, turbulence locations, intensities, distribution and the resolution of the intensities should be reported more accurately than those by PIREPs.

Over the past years, NCAR has developed improved versions of the EDR algorithm.  Under the project leadership of the FAA, EDR is being implemented in several hundred aircraft in the United Airlines, Delta Airlines and Southwest Airlines fleets.  The data are under a data quality program and are not yet available routinely.

Since AMDAR is capable of reporting turbulence information, the AMDAR Panel considers EDR as the next parameter to be added to the AMDAR suite of data.  At the joint meeting of the AMDAR Panel and ET-AIR (November 2011) and at the 3rd meeting of the AMDAR Panel Management Group (February 2012), the members were informed by FAA about the progress made regarding the implementation of EDR.  The AMDAR Panel agreed that more detailed information about EDR was needed and that more AMDAR related effort regarding EDR should be included into the AMDAR Panel work plan.

The members also agreed that “an international approach to turbulence monitoring and reporting was an important aspect of the AMDAR work programme and that the work done in the USA to provide observations for both model assimilation and verification should be built upon and extended to the global AMDAR programme. The AMDAR Panel should work together with the USA NWS, FAA and the relevant research bodies to ensure that the turbulence algorithms and metrics become standardized within AMDAR software specifications so that the next generation of AMDAR software incorporates them.”

In this regard, the members agreed that the AMDAR Panel should consider requirements for the implementation of EDR as a metric of turbulence within the AMDAR system.  An action was started to request the AMDAR focal points to survey within their respective NMHSs the intent to possibly use EDR in relation to both Numerical Weather Prediction and Aviation Services.

It also was agreed that a one day workshop on turbulence would be held on Monday 5 November 2012, prior to the next AMDAR Panel Meeting, with the content to be agreed upon between the Panel and the presenters, who would come mainly from representative experts from the FAA and NCAR.  Key topics currently under consideration include: 

History of EDR: motivation for its use and technical/theoretical description. 
Refresh and update on the FAA/UCAR EDR monitoring and prediction (M&P) program. 
Plans for extension of the EDR M&P program. 
The EDR index/categorization system and its use. 
Modelling application of EDR (both for aviation and meteorology). 
Benefits and impacts of the M&P program. 
Airline involvement and testimony of benefits and impacts. 
Scientific work on turbulence elsewhere. 
Possibilities and potential for internationalization of the EDR M&P program 

Australian AMDAR Data Optimisation System (ADOS)

The Australian AMDAR fleet, as of March 2012, comprises 112 aircraft, as set out in the table below:

Airframe Software #Planes Comment 
AAA Version 3
58Uplinking control of reporting enabled 
A320AAA Version 3
Uplinking control of reporting not yet enabled, but planned for 2012-13 
747-400 AAA Version 1 18  No uplinking possible 
767   AAA Version 1 7  No uplinking possible 
A319 AFIRS 1  No uplinking possible with AFIRS 

The major use of AMDAR data within the Australian Bureau of Meteorology is for assimilation into Numerical Weather Prediction models.  For this application, little additional benefit is derived from acquiring more than one AMDAR vertical profile (ascent or descent) per hour at any given airport.  (All Australian AMDAR aircraft are configured to be always reporting at seven minute intervals during level flight.)

With seven airports potentially producing more than 24 profiles a day, and three airports with more than 100 potential profiles per day, (namely Melbourne, Sydney and Brisbane), there is a need to optimise the system as much as is possible to reduce redundant data and minimize program costs.

The AMDAR Data Optimisation System (ADOS), is a ground-based system that analyses flight notification information from AMDAR aircraft and then, if possible, automatically configures the onboard software to enable or disable reporting according to preset requirements for vertical profiles at airport terminals.

As an example, on 22 November 2011, there were 385 potential vertical profiles from the 58 737-800 aircraft that have uplink command response capability. Of these 385 profiles, only 164 (~42%) were actually required and activated by ADOS.  This means that, for this day, data transmission costs were reduced by ~58%.

Currently, ADOS manages only those aircraft for which it can control the data production via VHF uplink command to the onboard AMDAR software. An upgrade to the ADOS system is under development and expected to be operational in May 2012 that will allow ADOS to eventually control the data output of the JetStar Airbus fleet, which will lead to an additional significant reduction in data transmission costs.

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