World Meteorological Organization

The Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN) is an international reference observing network, designed to meet climate requirements and to fill a major void in the current global observing system. GRUAN observations will provide long-term, high-quality climate records from the surface, through the troposphere, and into the stratosphere. These will be used to determine trends, constrain and validate data from space-based remote sensors and to provide accurate data for the study of atmospheric processes.

GRUAN is envisaged as a global network of 30-40 stations, where possible, building on existing observational networks and capabilities.

GRUAN goals

• Provide long-term high-quality upper-air climate records
• Constrain and calibrate data from more spatially-comprehensive global observing systems
• Fully characterize the properties of the atmospheric column and their changes
• Measure co-related climate variables with deliberate measurement redundancy
• Focus efforts on characterizing observational biases, including complete estimates of measurement uncertainty
• Ensure traceability of measurements by extended metadata collection and comprehensive documentation of observational methods;
• Tie measurements to SI units or internationally accepted standards
• Ensure long-term stability by managing instrumental changes
• Further the understanding of climate variability and change