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GCOS Atmospheric Surface Domain ECVs
Observations at the surface of the Earth are vitally important as they characterise the climate of the layer of the atmosphere in which we live, and where many impacts of climate change will be felt and necessitate adaptation. Climate analysis has traditionally placed emphasis on surface temperature, precipitation and pressure data. Temperature and precipitation have the greatest impact on natural systems and human activities, with pressure allowing a perspective on the meteorological systems that drive the weather. More recently, wind speed, wind direction and sunshine data have become increasingly important as Parties consider measures to adapt to future climate change, as these data are also essential for the design of renewable energy systems, which include wind and solar farms as well as hydroelectric systems. Wind, water vapour, sunshine and surface radiation are also associated with a range of direct impacts.
There is an increasing need for local, high-frequency surface atmospheric data on climate, to characterise extremes for the purposes of monitoring and research, and more generally to meet needs relating to impacts, vulnerabilities and adaptive responses. This Plan identifies a number of Actions to improve the availability of the required observations and data products for precipitation. It also identifies Actions to enhance the frequency of reporting and general operation of the WWW/GOS surface synoptic network, so that its data more fully meet climate needs. Several Actions that will improve observation of extremes over sea are also specified.
Notwithstanding the improvements in observation that are called for, and the scope for recovery of past observations, there will inevitably be limitations in the spatial and temporal coverage of in situ near-surface observations over land that cannot be compensated by observations from space, and limitations in observational coverage of the past will remain. Atmospheric reanalysis provides a complete coverage in space and time within the constraints of model resolution. Use of the products of reanalysis to develop links between meteorological conditions and socio-economic impacts is viewed as a key approach to develop the relationships needed to interpret the output of climate projection models for the purpose of assessing needs and options for adaptation. This brings with it requirements for reanalysis regarding the resolution in space and time of its products, in addition to general requirements for accuracy and homogeneity.
As networks evolve, it is important to note that the usefulness of all the ECVs in the atmospheric domain is enhanced through collocated measurements of terrestrial and ecosystem properties. Greater efforts should be made to establish key sites in selected areas where many of the ECVs for both the atmospheric and terrestrial domains are observed.
Although not reflected in an explicit Action in this Plan, specific attention needs to be paid to the measurement of the ECVs in the urban environment where an increasing proportion of the world’s population resides and where specific impacts and issues of adaptation arise.
The primary networks contributing to climate observations at the Earth’s surface include:
- Over land, the WMO WWW/GOS surface synoptic observing network (~10 000 stations) provides the major in situ observations of the following ECVs: Temperature, Air Pressure, Precipitation, Water Vapour, Surface Radiation (e.g., sunshine duration, solar irradiance) and Wind Speed and Direction. Included in this network is the global baseline GSN. The GSN comprises about 1000 stations that have been selected from the full available network based on past performance and their contribution towards a global representation of the climate system. The operators of GSN stations, in particular, are encouraged to fully meet the GCMPs for observation and for data exchange, where possible for all surface ECVs.The GSN data can be analysed to yield basic indicators of the global climate system, and also provide benchmark locations for higher-density regional and national networks. Important contributions to such regional networks are the WMO WWW Regional Basic Climatological Networks (RBCN, total ~3000 station subset of the WWW/GOS surface synoptic network), established in all regions of the world including Antarctica to support regional representations of the climate system. The GSN is implemented through cooperation among NMSs and the international community; through the AOPC working with the WMO Commission for Basic Systems (CBS) and WMO Regional Associations (RA); and through capacity-building initiatives such as those of the WMO Voluntary Cooperation Programme and the GCOS Cooperation Mechanism. The AOPC, in cooperation with the WMO CBS, carries out detailed analysis of the problems in the receipt of GSN observations and works with national services to resolve them. Figure 3 below shows the availability of GSN data at the NCDC World Data Centre for Meteorology, Asheville (WDC Asheville).
- Over the oceans, the in situ surface meteorological observations are provided by the Voluntary Observing Ships (VOS), including the higher-quality VOS Climate Project (VOSClim) subset, and by moored and drifting buoys. The implementation of these observing systems is covered in detail under the oceanic domain. Some specific issues on observing the marine meteorological fields (temperature, pressure, wind speed and direction, and water vapour) are addressed here. Satellite measurements are critical to the observing strategies addressing the global distribution of the essential atmospheric surface variables over the ocean. The combination of both land and marine data is vital for the true assessment of climate change over the planet.
Length of historical climate time series for GSN stations available at the GSN Archive Centre, NCDC (Source: NCDC).
While the WWW/GOS surface synoptic observing networks have been developed primarily to support weather prediction, their high spatial density and frequent sampling means that they are of increasing importance to the climate community, especially for the studies of extremes and of impacts, vulnerabilities and adaptation. The GCOS Steering Committee, through the WMO CBS, WMO CCl and WMO RAs, and WMO WWW encourages more frequent reporting for the Regional Basic Synoptic Network (RBSN) of the WWW/GOS (cf. Figure below).
Number of stations in the Regional Basic Synoptic Network reporting every 3 hours, as received by the World Data Centre for Meteorology, Asheville (Source: NCDC).
National vulnerability and adaptation to climate change, especially changes in extreme events, require national and regional climate observing networks at a much finer spatial scale than the international network cascade GSN-RBCN-RBSN-Full WWW/GOS surface synoptic observing network. The design and operational details of such fine-scale networks depend on both climate variability and change, and vulnerability in each specific case (region, province, city) and need to be determined by appropriate observing system studies. Using network density on land in the most economically advanced countries as rough guidance for desirable network density globally, data from around 3000 additional stations measuring standard meteorological parameters (ECV Temperature, Precipitation, Surface Pressure, Water Vapour, Wind Speed and Direction) are needed, mainly in developing countries. Some of those stations may already exist, but are not part of the WMO networks and do not exchange data internationally. Equally, some stations which are listed as functioning may no longer be functioning and are in need of renovation.
To realize the full potential value of the existing networks for application to climate, network operators should follow the GCMPs. Focused action by the National Services in cooperation/coordination with WMO CBS, WMO CCl and their RAs will be needed to attain the goal of complete network implementation. Good station metadata such as accurate station heights and location coordinates are required.
Many observing facilities (over both land and ocean) are being changed from the traditional manual operation to automatic or quasi-automatic operation. These changes have been demonstrated to insert potential inconsistencies and inhomogeneities into the climate record, and are addressed as one element of the GCMPs. Additional guidance on the ways and means to ensure compatible transition has been provided by the WMO Commission for Instruments and Methods of Observation (CIMO), in cooperation with WMO CCl and WMO CBS. Implementation of those guidelines, adherence to the GCMPs and further assessment of the consequences of transition through national and international studies would allay many of those concerns.
(Source: WMO/IOC Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) GCOS-138/GOOS-184/GTOS-76/WMO-TD/No. 1523)
References:
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