Purpose of the GCOS Surface Network (GSN)

The GCOS Surface Network (GSN) is a global network of  over 1000 stations (GSN Station Maps (2011)) (GSN Station List (2011)) selected from the network of many thousands of existing meteorological stations. The GSN is intended to comprise the best possible set of land stations with a spacing of 2.5 to 5 degrees of latitude, thereby allowing coarse-mesh horizontal analyses for some basic parameters (primarily Temperature and Precipitation). The criteria for selection include:

• The commitments National Meteorological Hydrological Services (NMHS) can accept with regard to continuity;
• Geographical representativeness of observations;
• Length and quality of historical time series;
• Available parameters.

It is recognized that the coarse network density limits the applicability for some applications. For parameters having smaller-scale horizontal variability (e.g., precipitation), it is accepted that the network data generally should be supplemented by those from networks with a finer mesh.

Monitoring Climate Variability

Observations of climate parameters at or near the earth’s surface comprise a crucial part of GCOS. It is at the earth’s surface that human beings live. It is the interface between the atmosphere and the underlying components of the climate system: land, ocean, cryosphere and biosphere. The climate at the earth’s surface, the surface temperature in particular, is considered to be essential for monitoring climate variability and detecting anthropogenic climate change. It is therefore essential that GCOS provide the data sets to support the scientific and operational aspects of the climate at the earth’s surface.

The GCOS surface climate data are a component of the overall Global Climate Observing System, and, as such, serve the overall GCOS purposes and users.

Purposes of the GSN

Specifically the purposes of the GSN are:

• To establish national commitments for the preservation of a set of valuable climate stations for the foreseeable future;
• To build a collection of validated data from these stations in standardized formats;
• To provide this information to the global climate community with no formal restrictions;
• To create a baseline and benchmark data set for more enhanced regional and sub regional climate networks and for newly-developed observing systems, including remote-sensing systems.

The User Community

The GSN data set will permit users to do such things as:

• monitor global hemispheric and regional climate and variability and address the subject of anthropogenic climate change
• understand spatial and temporal patterns of surface variables for climate monitoring and model validation
• observe and compute the exchange of relevant physical quantities through the interface between the atmosphere and the underlying components (not including the exchange of chemical constituents)
• conduct real-time analyses and re-analyses
• calibrate and validate of satellite data
• provide benchmarks for regional surface climate networks

In particular, GCOS and its surface component serve to support the work of Intergovernmental Panel on Climate Change (IPCC), and the implementation of the UN Framework Convention on Climate Change (FCCC).