This paper documents the next chapter in the story of how the GRUAN community has progressed in achieving the goal of constructing an observing network that, ultimately, will meet the challenges of climate science in the twenty-first century.
Key aspects of the GRUAN chronicle, summarized here, are the organization and management of GRUAN; the establishment and certification of network sites; the current and planned data products; the scientific basis for GRUAN operations; and GRUAN's contributions to the broader GOS.
The manual describes mandatory operating protocols that are expected of participating sites, the GRUAN Lead Centre, and the WG-GRUAN to achieve GRUAN's goals.
WHAT OBSERVATIONAL DATA PRODUCTS AND SERVICES IS GRUAN PROVIDING?
To fulfill the requirements for reference observations, each GRUAN product emanates from a tailored raw data and metadata collection tool, deployed at each measurement site, to collate, screen, verify, and transmit to a centralized processing facility the data and metadata required to generate the product.
The corrections for radiation-related biases, and their uncertainties, are based on outcomes of experiments made at the GRUAN Lead Centre.
The time-lag correction and other minor corrections applied in the GRUAN processing of humidity measurements are discussed in Dirksen et al.
GRUAN sites are required to measure at least one high-quality water vapor profile in the UT/LS each month using the best instrumentation possible, typically a balloonborne frost point hygrometer (WMO 2013a).
TCWV measurements at hourly resolution, or better, will be derived from ground-based GNSS measurements at all participating GRUAN sites.
The GRUAN lidar program provides a complete framework for all aspects of the planned lidar activities, covering temperature, ozone, and water vapor profiles from near the ground into the stratosphere.
GRUAN data products from Fourier transform spectroscopy (FTS) will initially include total columns of water vapor, methane, carbon dioxide, and ozone retrieved from high-resolution spectra acquired in the midinfrared to near-infrared using solar-viewing geometry that maximizes the signal-to-noise ratio.