Meeting of 5th Session of Expert Team (ET) on Requirements for Data from Automatic Weather Stations (AWS)
Geneva, Switzerland, 5-9 May 2008

The AMS meeting group photo (thanks to CBS). Click to enlarge.

For the agenda and links to the documents please go to the link at: http://www.wmo.int/pages/prog/www/BAS/CBS-meetings.html 

The HMEI attendees of this meeting were: Bruce Sumner, HMEI Executive Secretary and Christine Charstone, HMEI Administrator. The full list of participants is available in annex 1 of the final report. The final WMO report of the meeting will be interesting for AWS manufacturers, it is available at: http://www.wmo.int/pages/prog/www/OSY/Reports/ET-AWS-5_Geneva_2008.pdf 

This HMEI report is not intended to be definitive, but highlights items considered of interest for HMEI Members.

Opening of the Meeting
The meeting was opened with a welcome from the WMO Secretary General given by Dr Miroslav Ondráš the Chief WMO Observing Systems Division.

Report of the Chairman of ET-AWS (Doc. 2) by Dr Igor Zahumenský
Dr Zahumenský's presentation gave the background  of the development of the work of the ET to the current point of the recommendation to the previous CBS in Seoul in 2006 (CBS-Ext 2006), where 7 recommendations from ET-AWS-4 were approved. The CBS-Ext 2006 also made further recommendations for the future work of the ET-AWS.

Item 5 of the report listed the proposal for the activities of ET AWS for the next intersessional period, as follows:

1. Further development of a basic set of variables (standard and additional) measured by a standard AWS and regular update of AWS Functional Specifications. This development and further standardisation will be important for the success of the WIGOS policy;

2. Further development of AWS metadata catalogues; cooperation with CBS-OPAG/ISS in the development of tools for incorporating the metadata into the WIS environment as well as for metadata transmission from AWS into data processing centres (e.g. further development of BUFR descriptors);

3. Development of the requirements for new sensors, integration and interoperability of sensors;

4. Development of guidelines and procedures for the further transition from manual to automatic observation, for integration of point measurements with area measurements;

5. Involvement in the process of standardisation to meet WIGOS requirements for building up an integrated, sustained and interoperable system of observing systems.

Dr Zahumenský's report also looked at the draft of the "Vision of the GOS in 2025", developed by the CBS/OPAG ET-EGOS-3rd session. This document has been out for comment to the  various interested parties and experts, including HMEI members. Amongst the responses, one HMEI member has made comments, whose viewpoints have been incorporated into the current draft of that document.

Standard and optional variables to be reported by AWS (ad hoc report)
Etienne Charpentier, from JCOMM, gave this report, which outlined the requirements for AWS from the marine community viewpoint. He gave a limited list of recommended extra marine observations for AWSs to be used by the marine community. These can be seen in red in the BASIC SET OF VARIABLES TO BE REPORTED BY THE STANDARD AWS FOR MULTIPLE USERS, Annex 9 of the WMO final report.

"Vision of the GOS in 2025" - Surfaced based Measurements
The comments on this item will be included in the considerations of the final revision to be prepared by the ET-EGOS in July 2008.

The "Vision" will need to have a balance between requirements for data and observations, and the science and technology developments, including traceability. See Doc. 14 for the current revised draft version of the Surface and Climate sections of the "Vision".

Etienne Charpentier talked about JCOMM's developments for the future for the "Vision", which includes developments that the ARGOS, VSOP and DBCP are working to implement, not only in ship Surface measurements, but also in measurements for Sub-surface and Deep Ocean.

Wolfgang Grabs from the Hydrology and Water Resources Programme, made some comments regarding the "Vision". In particular that, in regard to data communication, the importance of the WMO Information System (WIS) should be noted in the data "vision" for GOS, also that the importance of data archiving should be addressed in the "Vision". Dr Grabs wished to have the importance of working towards integrated systems for hydrology. He also noted the importance of stating consideration for the needs and capabilities of the Least Developed Countries (LDCs), especially when looking at cost issues and the necessity of capacity building in these regions. Dr Grabs further mentioned the need to have a paragraph on the integration between space-based and surface based components of the "Vision".

Liisa Jalkanen, Chief of the the Research Division of the AREP (Atmospheric Environment Research Programme) noted that the Global Atmospheric Watch (GAW), is currently compiling their input for the "Vision" and will be directly sending their comments to Chair of ET-EGOS for their next meeting. GAW believes that the "Vision" should be general overview "key" statements rather than detailed action items. Dr Ondráš requested that the GAW statements be sent to the CBS secretariat for compilation into a Surface Measurements document to be submitted to the Chair of ET-EGOS for the July meeting.

The meeting went on to look at the items in the "Vision" concerned with surface-based observations and networks. They refined various points in the draft to provide a concise documentation of the future expectations for surface networks. The amended draft of this document is available as Annex 10 in the WMO final report. Points of interest regarding the future trends the surface-based GOS is looking towards are:

The "Vision" is seen as a balance between requirements for data and observations by different WMO Programmes, various applications and users on one hand and science and technology developments on the other hand.

Regarding the requirements for data and observation, it should be considered that:

• Observational needs for future models that will be used for different time-range forecasts;
• Deficiencies of today’s models that show that current observations are not sufficient for most mesoscale applications;
• Critical atmospheric observations that are not adequately met by current and planned observing systems but are required for more accurate and timely Earth monitoring and decision-making.

Regarding the observing technologies and techniques, it should be considered that:

• Better understanding of the processes that govern weather requires advances in sensors and observing networks;
• All observational data should be traceable to international standards;
• Instruments should be interoperable as far as possible;
• Integrated observing systems may overcome gaps in existing observations.

The availability of test-beds for a successful transition from R&D to operations may be a critical aspect.

AWS Functional Specifications (Doc. 3) by J.P. van der Meulen
Dr van der Meulen reviewed the AWS functional specifications. Several points in this report were able to be updated by the ET-AWS members present.

The resulting revisions will eventually be included in the Functional Specifications for Automatic Weather Stations and related BUFR descriptors on the WMO website after their final endorsement by CBS in March 2009.

• HMEI was invited to send the information as revised by the meeting to the HMEI membership, for validation that the suggested functional specification ranges are feasible. Please see the document, Annex 2, in the WMO final report here
  Responses to this document by HMEI members, should be sent to the HMEI Secretariat at hmei@wmo.int. HMEI will then pass the HMEI comments to Dr van der Meulen.

Requirements and Implementation Plan for a robust, low power, continuous communications platform for all AWS, particularly those in remote locations (Doc. 4.1) by R Nitu
This presentation brought up some particular points/issues in regard to this topic:

• Communications to be by satellite;
• Question as to whether there should be one or two way communications;
• Challenges to access satellite communications services, particularly in smaller countries;
• Problem with power failure, need to ensure longer lasting power supply in remote locations.

Requirements and Subsequent Implementation Plan for AWS Hosted Sensors to Contribute Directly to the Calibration and Ground Truth of Space-based Observations (Doc. 5) by by Karl Monnik
Mr Monnik's presentation emphasised that there is an increasing number of remotely sensed measurements such as total water vapour column, rainfall, soil moisture, surface emissivity, albedo and evapotranspiration, that can benefit from ground-truth measurements from AWSs.

Requirements for new sensors or the integration of sensors to meet the deficiencies of AWS following the migration from manual observations (Doc. 6) by R Nitu
This document is a particularly useful one from the manufacturers point of view. It is recommended reading for AWS manufacturers. This report is available here.

In the General Requirements session of the document the points covered (see the document for details) are:

• Measuring performance;
• Sensor requirements for maintaining the traceability of measurements;
• Requirements regarding operational reliability.

Addressing the need for integration of point measurements with area measurements (Doc. 7) by J.P. van der Meulen
Jitze van der Meulen described in this presentation a technique to integrate point measurements, from AWS data, with area measurements, from satellite networks. This technique has to possibility to be used for optimizing meteorological networks, such as RBSN (Reference Baseline Surface Network).

Review of BUFR descriptors related to AWS measurements (Doc. 13.1) by I. Zahumenský
See the document here.
This report looks at the BUFR descriptors. There is a lack of homogeneity in the use of BUFR and descriptions of the coding between different WMO Commissions. Therefore the code needs to be traceable to the International Meteorological Vocabulary (IMV).

Also following the CBS and WIS recommendations there is to be a minimum necessary transmission of metadata and that it be sent separately form the observational data.

There is a need for 5 new metadata descriptors for:

• Classification of roughness;
• Siting and exposure – Siting classification;
• Expected performance of the instrument;
• QC flag for each parameter;
• Method of measurement / observation OR type of detection system for each variable measured by AWS (and transmitted in AWS BUFR template now or in a future).

The difficulty of standardizing descriptions, given that they are often created at short notice to follow new developments in real time, was noted. The references for tractability would come from regulator material i.e. WMO, ISO, and IMV.

The SYNOP code (FM-12), translated to a BUFR template, does note satisfy all the requirements of AWS data transmission needs. Work will need to be done on this.

National and WMO station identification (Doc. 13.2) by Eva Cervená
This document reports the developments made on a BUFR template for surface observations from one-hour and n-minute period for AWSs. These developments have been made in response to the lack of the existing international system of station numbers to be able to deal with AWSs.

The new descriptors and BUFR template were developed by the ET on Data Representation and Codes (ET-DR&C) and the Coordination Team on Migration to Table Driven Code Forms (CT-MTDCF). Michal Weis from IBL Engineering, a HMEI member, was one of the key people, from these teams, involved in the work resulting in this document.

Development of guidelines for the implementation of new data types from either new sensors or following the successful integration of sensors (Doc. 9) by H. Zhou
See this document here.
Dr Zhou gave a presentation outlining the development of Guidelines for implementation of new data types for new sensors or following successful integration of sensors.

China is looking at development of new types of multi-functional AWS, to enable the widest possible selection and integration of sensors; often these additional information sensors to the more usual array; cameras; or new sensors measuring parameters not previously included in weather AWSs, including climate and geophysical information. The need for this type of new AWS is driven by extended user requirements.

Although the requirements from users can be highly diverse, the conventional meteorological elements such as air temperature, air relative humidity, air pressure and wind are usually included. In addition certain other characteristics are universally required, these are:

• Reliability and of high quality;
• Timely dissemination – latest data available to users in minutes;
• Available in a variety of communication channels – including radio, TV, PCs, mobile phones and computing devices;
• User friendly for easy digestion;
• Location specific – high spatial resolution;
• Time specific – high temporal resolution; and
• Environmentally friendly.

AWS Development of the recommended four catalogues of AWS Metadata (Doc.10.1) by Karl Monnik
The final decisions regarding this document are in Item 13.8 of the the WMO final report

Development of guidelines and procedures to assist in the transition from manual to automatic surface observing stations (Doc. 8) by Karl Monnik
This document is available as Annex 7 in the WMO final report.

The document gives a very concise and useful set of guidelines for transition from manual observations to AWS.

Difficulties and differences were noted in how AWS observations can fully replace the observations made by humans. These differences need to be defined and also resolved where human "subjective" observations may need to be translated into measurements that can be made automatically by sensors.

Bruce Sumner commented that guidelines and information such as this were not necessarily used by all countries, particularly LDCs in the case where a donation is used to purchase a network of automatic stations. From this comment a suggestion was made that this document should be developed and published as a WMO Technical Document (WMO TD), in order that the useful information it contains can reach all members of WMO.

It was further noted that whilst a donation was often given for a LDC to purchase AWSs, there was often no thought given, nor money provided, for the ongoing maintenance and calibration necessary for long-term usefulness of such a AWS network. Although this document addresses these issues, it was suggested that a stronger statement, emphasising this critical nature of ongoing maintenance, could be needed.

The meeting agreed to the revision of the document, to include the issues raised above, be done for presentation of the document to International Cooperation Team on Information Systems and Services (ICT-ISS) in September this year, for endorsement and subsequent publication as a WMO TD.

Development of guidelines for siting classification of AWS (Doc. 11) by M. Leroy
This report looked at the needs for good siting and good metadata about the sites. Currently much data is used with no or limited knowledge of the siting conditions. Meteo-France has developed a classification for various parameters with 5 levels, ranging from the optimum WMO recommendations, to conditions of a site, which make it totally unsuitable to be used as a site for measurements. This document offers this development of classifications as a starting point for WMO classification, not only for AWS but also for any surface observing station.

It was also noted that a standard for siting is also being looked at by ISO. The Sub Committee SC5 (Meteorology) of the ISO Technical Committee, TC146 (Air Quality), are considering the creation of a new Working Group (WG) for the standardization of siting.

Comments:
Karl Monnik relayed a comment from Bill Wright, the Chairman of the WMO ET on Observing Requirements and Standards for Climate, that the siting for an AWS for climate observations, needs to reflect the climatological conditions as appropriate, in addition to general good siting.

Presentation on WIGOS and WIS by Don Hinsman
This was an excellent presentation explaining the concept, background, aims, and current status of WIGOS and WIS, with great clarity. The presentation is available here.

• Telecommunication:
  - There is now a wide range of solutions available for this. However as these vary widely form country to country, there is a need for standardization in this area.
• Data Acquisition:
  - Advances have made calibration of the acquisition part of AWS stable and well integrated, however there still remains a need for calibration of sensors. Sensors:
  - Advances in sensors are slower than other developments. Certain sensors for performance in harsh conditions and remote situations have high power requirements that cannot be met by a solar panel.
  - In many countries (i.e. in Europe), new sensor development is slow due to NMS budget limitations. There was a suggestion by Bruce Sumner from HMEI, that perhaps NMS could consider working with private manufactures.
  - Costs of maintenance and calibration continue to be high.
  - Reliable sensors for visibility, precipitation (both detection and density), present weather and state of ground, are available.
• Network;
  - In dense network areas, response to a users needs for extra variables can often be achieved by merging observations from the existing stations, rather than needing to create new stations.
• Cost;
  - The costs of AWSs is decreasing, however this is only marginal considering the total, initial and running, costs of a network.

Comments on this report, by various meeting participants, noted  that:

• Security issues for AWS still need to be further addressed;
• The combining of information from various sensors can produce additional parameters;
• Sensor changes are a challenge for the Climate community and their archiving;
• Considering the above statement, it would be very useful if manufactures were to inter-compare their own different models and upgrades, and subsequently publish these results, to help resolve this challenge;
• There can be a problem with Rain Gauges (RGs) in arid conditions, where lack of functionality (rather than lack of rain) cannot be picked up. There is thus seen a need to have ongoing self verification of functionality by the RG;
• Data storage in AWSs need to be sufficient (which is not always the case) for delayed recovery of data and archiving;
• Particularly for Climate purposes, networks are foreseen to need a good mix of AWSs and Manual Stations, rather than all AWSs;
• An advantage with the lower costs now of AWSs was noted, that now denser networks can be achieved at less cost;
• The advances with Smart Sensors that have better metadata, were seen as a very good;
• AWS self-monitoring of problems occurring would be highly useful (although the potential cost increase was recognised);
• It was also noted that users have a responsibility to have regular maintenance of AWSs;
• The need for lightening protection for AWSs in certain situations was noted;
• AWS modularity was very much appreciated. This approach was seen as essential for future developments to achieve the desired flexible, multi-purpose, AWS use.

Implementation Plan for Evolution of Space and Surface-based Sub-Systems of the GOS (EGOSIP) (Doc. 16.1) by Igor Zahumenský
As AWS are becoming widespread and of such importance for measurements, that planning should include:

• appropriate codes and reporting standards;
• global standard for quality management and the collection / sharing of metadata; and
• expanded range of measured parameters;
• ensuring recommended practices are complied with.

Close of  Meeting
The meeting closed at  2pm on Friday, 9 May 2008.