ENAGNSS

GRUAN, GCOS Reference Upper Air Network, is an international reference observing network of sites measuring essential climate variables above Earth's surface, designed to fill an important gap in the current global observing system. See more details on the GRUAN website.

GRUAN’s objectives are to:

• Provide long-term, high-quality climate records
• Constrain and calibrate data from more spatially comprehensive global observing systems, (including satellites and current radiosonde networks
• Fully characterize the properties of the atmospheric column.

In support of these goals GNSS precipitable water (GNSS-PW) measurement has been included as a high-priority measurement of the essential climate variable, water vapor. In addition, a minimum of twice-daily measurements (ideally hourly measurement) of PW is required for entrance to the GRUAN program. GNSS-PW is the primary means to accomplish this entrance requirement. The GNSS-PW program produces a nearly continuous reference measurement of PW and is therefore a substantial part of GRUAN.

The GFZ German Research Centre for Geosciences (GFZ) contributes to GRUAN with its expertise in processing of the ground-based GNSS network data to generate highly accurate PW products. Since 2013 GFZ has hosted a GRUAN central processing facility for GNSS-PW. GFZ is responsible for the installation of GNSS hardware, raw data transfer, processing and archiving, derivation of GNSS-PW products according GRUAN requirements including PW uncertainty estimation, and quality checks and archiving of GNSS-PW products.

The GRUAN sites, the GNSS-PW Task Team, GFZ, and the GRUAN Lead Center all work together to deliver the best-quality GRUAN GNSS-PW data product.

GFZ is highly interested in cooperation with ARM for GRUAN.

Timeline