Part II: Individual Session of AOPC

A 6. Organization of the Individual Session of AOPC

The Chairman of the AOPC proposed a modified agenda for the individual session, which was accepted by the Panel (Annex II).

A 7. Development of an Atmospheric Observation Plan

A 7.1 The Chairman informed the AOPC participants of the progress on the GCOS Plan for Atmospheric Climate Observations since the last meeting. The Panel proposed that the Plan should take into consideration the role of satellite data, the monitoring of extreme local events (i.e., El NiZo), volcanoes, solar variability and data assimilation. The participants agreed that future issues to be incorporated should include radiative transfer, aerosols, precipitation, sea surface temperature and ice analyses, and the link to GOSIC. Furthermore, a discussion on the percentage of global radiosonde coverage should be integrated. The outline of the Plan, the lead authors of the respective chapters and an elaboration on each component of the Plan, was discussed and approved by the Panel (Annex A-III).

A 8. Current Activities and Developments

A 8.1 GCOS Upper-Air Network (GUAN)

Mr Parker discussed the temporal changes in radiosonde coverage in the UK Meteorological Office Hadley Centre data set. He showed that the Northern Hemisphere has a greater coverage in radiosondes than the Southern Hemisphere, and that there is a recent overall decline. Additional GUAN stations in India and Africa will be necessary to complete the global coverage. The GUAN reserve list, to be reviewed by CBS, should be short and well justified. The Panel recommended including new stations in the GUAN list. Mr Parker then discussed the purpose of the GUAN in its present state, considering it as a very valuable calibration tool. The combination of GUAN and the emerging technology of the Global Positioning System (GPS) should benefit the global observing systems.

Dr V. Barros gave a presentation on the radiosonde coverage and its performance in South America. He demonstrated that there are various possibilities to up-grade existing radiosonde stations to GUAN stations. Most of the non-silent GUAN stations were fully operational. Nevertheless, GUAN stations have a problem in following the 'best practice'. He noted that only very few stations reach 10hPa and only about 30% of the soundings reach 20hPa. He made it clear that developing countries have priorities in obtaining new instruments rather than maintaining long-term commitments for operational systems. Therefore, some funding should be made available to support developing countries, e.g., through the Voluntary Co-operation Programme of WMO. To avoid future poor GUAN performance in South America, Dr Barros suggested the Panel should consider integrating radiosondes which will be established for regional projects, e.g., the proposed radiosonde network for the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA). These are initially research networks, which will exist on a permanent basis, and which will become operational after the project ends.

Dr R. Okoola reported on the African upper-air network. There has been a decline in the network since 1979 when the First GARP^[8] Global Experiment (FGGE) took place. The radiosonde stations did not increase to make up for the decline in the pilot balloon observations. More conventional sounding data (radiosondes, etc) have now declined further due to the phasing out of the Omega and Loran-C navigation systems and the narrowing of the radio frequencies available for use. Dr Okoola showed a typical upper air chart used in operational forecasting at the National Meteorological Centre, Nairobi, which showed the lack of stations over equatorial Africa. He stressed the fact that the GUAN has large gaps over Africa, for example over the Congo Basin, and over the Sudan. The Congo Basin has been shown to be part of the rising branch of the East-West circulation (Walker Circulation). The displacement of this circulation leads to socio-economic hardships for many African countries whose economy is largely dependent on rainfed agriculture. Relationships have been found between ENSO and African seasonal rainfall, and between the Southern Oscillation (SO) and rainfall over the East African coast/Lake Victoria basin. The study of the variability in the SO over Africa demands for at least one upper-air Station within the African Convective Centre that sits in the mean over the Congo Basin. Dr Okoola recommended that two additional GUAN stations (one station over the Congo Basin, either Mbandaka or Kinshasa; and one station over Sudan preferably at Khartoum) would improve the description of the general circulation of the atmosphere over tropical Africa.

A 8.2 GCOS Surface Network (GSN)

This agenda item was tabled jointly with a JDIMP Ad Hoc working group 1 (see D 9.2.1). The discussion was focused on the adequacy of the network for (i) temperature, (ii) pressure, and (iii) precipitation measurements.

Dr P. Jones gave some background information on the selection process of the GSN. In March 1996, an expert meeting in Norwich, UK, designed a procedure to select components of the GSN. The procedure included a review of primary data sources to assess the most appropriate stations, a scoring algorithm for recording quality measures of candidate stations into one value, and requirements with regard to the geographical coverage and spacing of selected stations. A second expert meeting in June 1997 reviewed the final GSN station selection. The network includes a basic list together with a "stand-by" list of stations. The stand-by list includes stations of very high quality, but which are closed and stations which are well located geographically, but are either of lower quality (e.g., a rather short record) or lack sufficient quality information. Dr Jones pointed out that the network is adequate to capture large regional to global phenomena, but it is not for regional climate. GSN is sufficient for analysing temperature trends, but is insufficient for precipitation measurements, which require a denser network.

It was mentioned that transmission problems influence the performance of the network. In the following discussion the Panel recommended that it is necessary that all stations in the GSN should report CLIMAT measurements, and should serve as reference and baseline stations for regional and national climate purposes. The importance of a responsible data centre was stressed again. The Panel discussed as well the value of collecting daily rather than monthly data, since extreme events cannot be captured using only monthly information. There was some concern that with respect to historical data, daily data records do not go back as long as the monthly data record. The Panel noted that a meeting will be organised by the German Weather Service (DWD), where invited experts will discuss GSN data quality/control issues.

A 8.3 Atmospheric Constituents and Radiative Transfer

Dr D. Whelpdale reminded participants that at the third session of AOPC an agreement was reached on the list of atmospheric constitutents needed for climate. A chapter for the Plan has been drafted which integrates radiative transfer and clouds as well. The draft chapter discusses the contribution of atmospheric constituents measurements to: (i) an improved knowledge of biogeochemical cycles, particularly the sources and sinks of greenhouse gases, carbon and sulphur; (ii) understanding climate change and variability through improved knowledge of radiative forcing; (iii) improved capability to predict climate change by providing information to simulate the climate system and to initialise models; (iv) the capability to monitor the effectiveness of controls imposed on emissions of radiatively active substances by nations and under international agreements; and (v) understanding the effects of climate variability and change by enhancing knowledge of the feedback of climate on sources, sinks and ambient levels of atmospheric constituents and harmful radiation. The measurements of constituents should follow agreed guidelines. The draft chapter then gives examples of the main users of atmospheric constituents observations (i.e., scientists from International Geosphere-Biosphere Programme (IGBP)/International Global Atmospheric Chemistry (IGAC) and WCRP/SPARC, modellers, synthesis groups, IPCC Working Group I and others on assessing the state of the ozone layer, policy community and industry. The observing system products relate to the long-term observations of high-priority variables such as greenhouse gases, water vapour, tropospheric and stratospheric ozone and aerosols. The necessary information should be provided by combined surface and satellite measurements. The draft chapter also describes requirements on geographical coverage, spatial and temporal resolution. Dr Whelpdale pointed out that these requirements depend as well on the end-use of the products. Specifications are still needed for each observation and need to be solicited. To assign priority to the variables is difficult and depends on GCOS objectives, urgency and feasibility (i.e., if instruments are available). The current status of networks such as Global Atmosphere Watch (GAW), the Network for the Detection of Stratospheric Change (NDSC), the Atmospheric Lifetime Experiment-Global Atmospheric Gases Experiment (ALE-GAGE) and NOAA's Climate Monitoring and Diagnostics Laboratory (CMDL), needs to be updated. Information on spaced-observations of atmospheric constituents is available.

Dr Whelpdale discussed the next steps in completing the first version of the Plan: (i) to acquire a more complete understanding of what actions are required (i.e., specify requirements), (ii) identify gaps, (iii) propose actions to identify deficiencies, (iv) review status of observations, (v) discuss the GAW aerosol project and the CEOS SIT ozone projects. Further, short-term actions needed to address water vapour, ozone and aerosol measurements, which should be assigned to a task team. Overarching issues include the integration of observing systems which combine surface, satellite and other observations, the maintenance of observations for the long-term and the role of new observational platforms (e.g., aircraft).

In the following discussion about additional requirements, participants considered whether or not to include emissions. Existing projects, in which emissions are being studied were noted (e.g., the Global Analysis, Interpretation and Modelling Program (GAIM)). Flux measurements may be considered by GTOS. The Panel concluded that the Global Hierarchical Observing Strategy (GHOST) may not be relevant to atmospheric constituents measurements, because they are dependent on height and distributions differ considerably.

A 8.4 Air-Sea / Air-Ice Interface

Dr Harrison gave some examples of how surface data are successfully assimilated, and suggested improvements that are needed. With respect to SST, the analyses show differences (i.e., global trends of NCEP and of UK Meteorological Office differ from each other). Additionally, SST information will be missing if the NOAA Geostationary Operational Environmental Satellite (GOES) loses SST channels. Sea surface level pressure is one of the priority parameters, and small observational errors in the tropics have large impact on the simulation of equatorial Pacific winds. With respect to surface winds, scatterometer missions need better coverage to observe energetic scales. Re-analyses have not captured wind fields in the tropical Pacific, as may be demonstrated by using the TAO array observations. Precipitation measurements agree better with model results due to new technologies. Sea surface salinity observations, especially using sensors for long-term observations, are progressing. He noted that coupled models will face the same problems in analysing climate signals due to unsatisfactory observations of the ice-edge.

A 8.5 Emerging Technologies

Dr R. Fleming elaborated on new technologies to complement climate observations. Commercial airlines can provide water vapour, ozone, wind profiles and aerosol measurements and the very-high frequency (VHF) data links are improving continuously. Aircraft in future may be equipped with a variety of aerosol sensors and will be able to observe atmospheric species. He noted that the second generation of ultraviolet radiation and ozone sondes are already available. Light Detection and Ranging (Lidar) systems may provide wind profiles over the ocean. The GPS occultation technique may be of benefit for temperature observations in the upper troposphere, but water vapour may be difficult. Other new technologies will be interferometric techniques on satellites. Data provided by projects like MOZAIC (Measurement of Ozone and Water Vapour by Airbus in-service aircraft) could be discussed if appropriate. Dr Fleming pointed out that composite systems will be necessary to have a complete picture of the atmosphere, but stressed as well that there are still restrictions due to large errors in some fields.

A 8.6 Extreme Events

This agenda item was jointly discussed with the JDIMP Ad Hoc Working Group 1 (see D 9.2.1). Mr Karl informed the panel about the meeting on extreme events in Asheville 1997, which was focused on precipitation, temperature, wind and storms. A follow-up workshop will be held in 1999, engaging insurance and energy companies representing a broader community. The joint CCl/CLIVAR Working Group on Climate Change Detection would convene its second meeting in Bracknell, UK, in September 1998, to discuss precipitation and temperature indices, focussing on available data sets.

Several presentations were given on long-term analyses of climate data. Dr Heino informed the participants about the REWARD project (Relating Extreme Weather to Atmospheric circulation using a Regionalised Dataset). The REWARD data sets of climatic extremes include monthly data for all Nordic countries and contain climatic data for more than 50 stations for temperature, precipitation, pressure, snow cover and cloudiness. The data have been recorded mainly between the years 1890 to 1996. Dr Jones reported on daily temperature record comparison and trend analyses over several decades. Several European cities (Uppsala, St Petersburg, Padua, Milano, Brussels, Cadiz) and Central England have over 200 years of records of daily temperature and will be used to perform climate analyses. Prof P. Zhai reported that China has updated its climate data between 1951 to 1996, and that minimum and maximum temperatures are being recorded and analysed. Furthermore, the Chinese precipitation network is providing daily measurements. Dr V. Razuvaev informed the panel that Russia is using data sets of exteme air temperatures, daily precipitation and pluviograph data to detect extreme events. He mentioned that not only scientists are interested in this data set, but the building companies and atomic power plants as well. Mr Z. Atheru informed the group on the activities in Africa on extreme events, stressing the importance of the drought severity index, rainfall anomalies and flood indicators.

A 8.7 Monitoring of GCOS Data

Mr Karl discussed the possibility of assisting the IPCC to gain access to data archives, material and documentation. The SPARC data archive of upper-troposphere and lower-stratosphere ozone, water vapour and temperature data would be an invaluable contribution. With respect to historic data and data rehabilitation, Dr Manton recommended that CCl obtain historical data and metadata to support GSN and GUAN. Letters should be sent to Members requesting digitised daily data from historical records. Full records of historical GUAN data for wind, temperature and humidity should be made available for all standard levels and significant levels. Full records of historical GSN data should be made available for temperature, minimum and maximum temperature, pressure, wind speed and precipitation. The participants recommended that rehabilitated data should be archived and distributed on a CD-ROM, when available.

Dr Manton proposed a scheme of processing GCOS data. The first stream of monthly data would be distributed via GTS in near real-time to the national weather services, and collected in the GCOS monitoring centres. These centres would provide statistics and quality review on the data sets, as well as historical ones. The second stream of daily data would go via the national weather services, after a certain delay time, to the archives of the WDC.

A 8.8 GCOS Requirements

Dr C. Richter provided a background document on requirements and invited the panel participants to review and approve the variables and the respective requirements already in the WMO Affiliate Database, and to suggest variables whose requirements still need to be identified. The panel recommended to enter the variables into the Affiliate Database and to review the requirements before its next session.

A 8.9 Satellite data

The panel noted that the Microwave Sounding Unit (MSU) and GPS data become more and more significant with respect to GUAN. It was decided that a working group should look into the issue of how to integrate these data.

A 9. Recommendations and Final Report

A 9.1 Data flow for GCOS

The AOPC decided that it should consider the overall process for the collection, processing, archiving, analysis and distribution of the atmospheric component of GCOS. Such consideration is necessary to ensure that the observed data are of appropriate quality and value, and that the research and operational communities have timely access to these data. In this context, the contribution of CBS to GCOS is seen as vital in providing continuing advice and expertise to NMHSs operating sites in GCOS networks and in supporting real-time quality control. [Action 1]

Using GSN and GUAN as models, AOPC decided that it was necessary to have specific centres to ensure the overall quality of data and to produce basic products from GCOS data, in addition to the real-time centres that monitor initial data flow and validation. The data and basic products from GCOS networks should be finally available to the research community through the World Data Centres. [Action 2]

The generation of GCOS products, such as CD-ROMs of quality-controlled data, would serve the broad community and demonstrate direct outputs from GCOS. These outputs should encourage participants, such as NMHSs, in the overall GCOS process. The AOPC decided that it would be appropriate for the Chair of the JSTC to contact each year the NMHSs that contribute to networks such as GSN and GUAN. This contact would complement the continuing interaction through CBS, provide positive feedback on the appreciation of the broad community for contributions to GCOS, and inform NMHSs directly of the outcomes and outputs of their efforts. [Recommendation 1]

In discussion of GSN and GUAN, there was some uncertainty about whether there are some data transmission problems with the GTS. The Panel requested CBS to provide some statistics on the performance of the GTS, especially as it relates to the operation of GSN and GUAN stations. [Action 3]

A 9.2 GUAN

A review of GUAN observation statistics provided by CBS showed that there are a large number of silent or suspect stations. Moreover, not all the old Omega stations have yet been replaced. Given the closure of GUAN polar stations, the Panel also requested CBS to work with NMHSs to identify replacement stations at high latitudes. [Action 4]

GUAN is the minimal network needed to capture synoptic scale features for global monitoring; e.g., monsoons. It should also provide the baseline for regional networks to analyse regional climate features. The Panel also noted that the development of basic GUAN products, such as global heat budgets, is one means of justifying continuing support. [Recommendation 2]

The AOPC decided that GUAN needs to provide the long-term consistent backbone of upper-air observations to support GCOS. Thus at the outset GUAN needs to consist of existing core stations that can provide the required measurements. The effort must then be placed on maintaining those core stations. [Recommendation 3]

In order to achieve the required global coverage, the Panel recommended that new stations should be added to the GUAN list. The new stations would comprise 4 sites in India and 1 site in each of Diego Garcia, Sudan, Democratic Republic of Congo, and Angola. The Panel also requested USA to re-activate the TOGA radiosonde stations for GUAN at Wake Island and Canton Island. [Recommendation 4]

The Panel recommended that the Chair of JSTC should write annually to the NMHSs contributing to GUAN to thank them for their contribution and to inform them of outcomes of GUAN. A particular outcome should be the generation of a CD-ROM of global quality-controlled historic GUAN data. In order to develop that product, the Panel will request CBS to approach NMHSs for their historic GUAN data not already available through the CARDS programme. (This approach will be made after the GSN data issues are resolved.) [Action 5]

The quality control and assembly of GUAN data sets need to be carried out through a formal institutional arrangement. The Panel recommended that the Hadley Centre and NOAA/NCDC, who are collaborating on the CARDS project, should be requested to take the lead in this activity. [See Recommendation 1, Recommendation 5]

The AOPC recommended to CBS that GUAN data should be deemed essential under WMO Resolution 40 and to be exchanged free of charge in real time. [Recommendation 6]

The Panel considered and generally endorsed the best-practice procedures for GUAN developed by CBS. However, it was recognised that most of the stations are not reaching the best-practice altitude of 5 hPa, and that for broad GCOS purposes of monitoring the general circulation an upper altitude of 30 hPa should be discussed. [After confirmation from Dr Chanin, the Panel recommended that the best practice altitude of 5hPa should be maintained . ] [Endorsement 1]

The AOPC recommended that, where the performance of GUAN stations is consistently poor, GCOS should work with CBS and the NMHSs to identify the cause of any problem and to assist with the development of appropriate solutions. In particular, specific training may be helpful at some stations under overall capacity-building programs. [Recommendation 7]

The Panel recognised that there is a problem for developing countries in funding continuing operations; i.e. while one-off grants to establish activities can be found, external organisations are reluctant to offer continuing funds. This is a critical issue for GCOS that should be noted in the submission to SBSTA on climate observations. [Recommendation 8]

In reviewing the status of GUAN, the AOPC noted that an analysis of South American GUAN data showed that their quality was no better than that from neighbouring (non-GUAN) sites. The Panel recognised the value of these analyses of observation statistics, and encouraged members to continue to provide them. [Recommendation 9]

A 9.3 GSN

The AOPC noted that 65% of GSN stations are reporting over the CLIMAT network, and requested CBS to encourage all GSN operators to move to the correct CLIMAT format. [Recommendation 10]

The AOPC endorsed the revised list of GSN stations proposed by the Group of Experts and recommended that CBS should approve the list. However, it was noted that there are gaps in central and western France, and AOPC requested the Group of Experts to identify additional stations to fill the data gaps. [Endorsement 2, Action 6]

The Panel thanked the NMHSs of Germany and Japan for offering to monitor the real-time performance of the GSN. It was also noted that Germany will host an expert meeting later this year on real-time monitoring and quality control of GSN data. This meeting will involve participants from Germany, Japan, UK and invited experts. The Panel thanked Germany for the initiative and decided that it should have representation at the meeting. Mr M. Werschek and Mr Hasegawa will develop an agenda for the meeting. [Recommendation 11, Endorsement 3]

The detection and analysis of extreme events is a key requirement from GSN, and this means that daily data must be collected. In fact, although GSN CLIMAT reports are based on monthly summaries, those summaries depend upon daily data. The strategic sensitivity of some daily data is recognised by AOPC, and so it is proposed that the daily and monthly data be provided through different processes. The monthly data will be processed in real time using CLIMAT format from the GTS through the GSN real-time centres in Germany and Japan. The daily data will be sought directly from NMHSs in delayed-mode time through nominated GCOS data centres for research purposes. [Recommendation 12]

It is apparent that the GSN was initially designed on requirements for monitoring the global surface temperature distribution. Having established GSN and recognising that NMHSs almost invariably observe other parameters at GSN sites, the AOPC decided that GCOS should seek a more comprehensive data set from the GSN. [Action 7]

In particular, the GSN data should consist of:

• Mean daily temperature (calculated using current national practice)

• Maximum daily temperature

• Minimum daily temperature

• Total daily precipitation

• Daily mean sea level and station pressure (calculated using current national practice)

• Daily mean wind speed.

While AOPC expect the GSN to be appropriate for these additional variables, some basic analysis should be carried out to ensure that the data are available and that the distribution is adequate. With data-coverage information from NCDC, Dr Jones will consider these issues. [Action 8]

The AOPC stressed the importance of meta-data to complement the routine GSN observations. Analysis of both monthly and daily climate data for changes and trends requires detailed information on the station history so that spurious effects can be identified and corrected. The decisions of AOPC on the scope of GSN data need to be considered with WMO. The first issue to resolve is the availability of historical daily data and meta-data at GSN stations. A task group^[9] was asked to prepare a letter from WMO to NMHSs seeking these data, which would be sent to the World Data Centres A and B. [Action 9]

In order to ensure that the daily GSN data are appropriately quality-controlled and analysed, AOPC will seek a commitment from an organisation (which may involve more than one institute) to become the formal GCOS data centre for GSN data. The Panel recommended that NCDC should be requested to take the lead in this activity and entrain other qualified institutes. The activities of the GCOS data centre would include the rehabilitation of the global climate record. [Recommendation 13]

The best-practice criteria developed by CBS were endorsed by AOPC with amendments to cover the suggested changes in GSN to include daily data. [Endorsement 4]

As with GUAN, the Panel recommended that the Chair of JSTC should write to participating NMHSs each year to thank them for their contribution to GCOS and to inform them of outcomes from GSN activities. [see Recommendation 1]

A 9.4 Atmospheric constituents

Dr Whelpdale will continue to co-ordinate with the broader community on the development of the constituents chapter of the AOPC plan. Dr Chanin will provide comment particularly on the need for observations above the stratosphere.

The Panel agreed that the atmospheric component of GCOS generally will not involve the estimation of the sources of most atmospheric constituents. This function is being carried out internationally through the IPCC and Organisation for Economic Co-operation and Development (OECD) under obligations for the UNFCCC and the Kyoto Protocol. However, analysis of GCOS atmospheric data will draw on the emission data, and so each will provide a consistency check on the other.

It was noted that, while the Panel is developing a data-flow process for GUAN and GSN, the requirements for atmospheric constituents are not clear at present. It is assumed that the data collection, quality control, archive and access are all being handled by GAW. There was some question about the consistency of all the archived constituent data from different sites. An issue for future consideration is the need for specific GCOS products on constituents generated at identified GCOS data centres.

Many of the constituent observations are carried out at research sites, such as those of the NDSC. It was agreed that AOPC must develop a process for handling links with these groups. [Action 10]

The constituents section of the AOPC plan will include radiative transfer, clouds and aerosols. It was noted that the current global observations on aerosols are limited to satellite-based measurements in the stratosphere, but the research community is moving towards a more comprehensive programme for the tropospheric aerosol. This issue is a vital component of GCOS.

The most comprehensive programme for measuring global cloud is the ISCCP, which is a project in WCRP. The consistency and longevity of the programme should be investigated by AOPC, and the links between ISCCP and in situ cloud observations determined. [Recommendation 14]

A 9.5 Air-sea interface

The AOPC endorsed the proposal of OOPC to develop a number of reference sites around the world oceans to provide baseline data on air-sea properties related to surface fluxes. [Endorsement 5]

The AOPC noted that SST data are vital to the IPCC process and to the climate community in general. However, there are substantial differences in the analyses produced by different groups around the world. Difficulties arise especially at high latitudes where data are sparse and where uncertainties in the treatment of the marginal ice zone tend to magnify differences in SST analyses. The Panel recognised the importance of the Comprehensive Ocean-Atmosphere Data Set (COADS) and the continuing activity associated with it. However, it was seen that there are issues for GCOS that are not being covered by other groups. It was decided that AOPC should organise a workshop on SST analysis. A primary objective of the workshop is to determine criteria for best practice, so that specific GCOS products can be identified. The workshop^[10] could also consider the scope for enhancing the observational network in data-sparse areas. [Action 11]

It was noted that there are also large differences in the analysis of sea level pressure (SLP) from different centres. As with SST, the major differences occur at high latitudes where there are few observations. However, the highest priority needs to be on SST and so the workshop will not cover SLP.

A 9.6 Emerging technologies

The AOPC noted the rapid evolution of aircraft-based technology which will provide global-scale data on parameters such as water vapour, ozone and aerosol. These measurements, which are important for GCOS, will be supplemented by surface-based remote sensing, which is also developing quickly. In particular, the GPS-based technique for estimation of total water in the atmosphere is moving towards operational use in some countries. It is also appropriate for AOPC to monitor progress with the satellite-based GPS-Met system, which will provide global-scale temperature measurements, especially in the upper troposphere and higher.

A 9.7 AOPC plan

Dr Manton will co-ordinate the overall structure and editing. An initial draft should be available for the Director by June. The plan will be developed iteratively after that time. It would be desirable to have a good draft by September for CBS to consider at their next meeting (see Annex A-III). [Action 12]

A 9.8 WMO Affiliates Database

The AOPC noted the need to continue to specify the detailed measurement criteria for all the variables listed in the GCOS plan. It is seen that these specifications will be best developed in conjunction with the AOPC measurement programme. Thus the initial priority is on temperature, precipitation, pressure and wind, associated with AOPC measurement projects. In particular, it will be important for the AOPC plan to account for the needs of satellite measurements to complement the in situ observations from GUAN and GSN. [Recommendation 15]

A 9.9 IPCC linkages

It was recognised that AOPC should be able to assist the IPCC with several data issues. One initiative, arising from JDIMP, has been the joint project on the analysis of historical climate records for the detection of changes and trends in extreme events. The Panel endorsed the proposal to have a workshop in 1999 to follow on from the Asheville workshop in June 1997, and it also endorsed the proposal for APN to sponsor a similar meeting focused on the Asia Pacific region. [Endorsement 6, Endorsement 7]

Dr Jones and Mr Karl agreed to seek advice on whether AOPC could further assist IPCC with the provision of other data sets, diagrams and documentation to support the IPCC Third Assessment Report process. In particular, the JDIMP data centre may be able to assist. [Action 13]

During the discussion on extreme events, the AOPC noted the work being carried out in Europe in the REWARD project, which involves analysis of temperature and rainfall data. Other national activities in China, Russia and Kenya were also noted.

A 9.10 Satellite data

It is recognised that satellite data contribute to GCOS in three ways. There are satellite data, such as the Normalised Difference Vegetation Index (NDVI), that directly provide global data-sets of climate variables. There are satellite data that are combined with in situ data to yield composite estimates of climate variables, such as SST. There are also satellite data that are used in validation of in situ data, such as the use of TIROS^[11] Operational Vertical Sounder (TOVS) in GUAN. These differences are not always clear cut, but it is useful to recognise the scope of the application of satellite data. The use of satellite data in GUAN and GSN both to assist validation and to develop composite products should be considered further by AOPC. [Recommendation 16]

It is appropriate for AOPC to consider the endorsement or certification of satellite-based climate products. The planned workshop on SST analysis is a step towards the development of a policy on this issue. The handling of satellite-based estimates of precipitation, particularly the GPCP products, should be considered at the next meeting of AOPC. [Recommendation 17]

The Panel noted that two of the six CEOS SIT projects are of direct interest to AOPC. The ozone project, for which Dr Whelpdale is the GCOS contact, has received little feedback at this stage. The second project is on upper-air measurements, but it has been firmly focused on the needs for weather analysis and prediction, rather than climate needs. The Panel noted that the purpose of the CEOS IGOS, to which the SIT projects contribute, is to ensure that the overall needs of the community are accounted for in the development of satellite projects.

A 9.11 JDIMP links

Following discussion of the responsibilities of each GCOS Panel, it was agreed that AOPC would focus on planning and implementation issues related to the atmospheric component of GCOS. The role of JDIMP will include cross-cutting issues, such as the GOSIC at the University of Delaware which was seen as very important in improving access to GCOS data. It was seen that JDIMP would also take the lead on the international issues of data availability and intellectual property rights on data.

A 9.12 Terms of reference of AOPC

On the basis of decisions on AOPC activities, it is appropriate for the AOPC terms of reference to include explicitly data quality control issues and the generation of GCOS products.

A 9.13 Format of AOPC meetings

There was some discussion on the need to have a balance of science and planning/organisational issues in AOPC meetings. The schedule as outlined in Annex A-II was suggested for the format of future meetings. It may be possible to complete the tasks in three full days. If feasible, participants should bring personal computers so that reporting and writing assignments can be done efficiently.

A 10. Closure of the AOPC Individual Session

The individual session of AOPC was closed at 10:45 hrs, 1 May, 1998. As there will be a change in Director and Chair of JSTC over the next few months, it was suggested that AOPC could delay its next meeting until autumn 1999. On the other hand, there are several issues on GUAN and GSN that need consideration, as well as finalisation of the AOPC plan, and so a meeting in spring 1999 may be necessary.