NIWA establishes first Antarctic GRUAN site
A NIWA-led collaboration with the United States Antarctic Programme, Antarctica NZ and Land Information New Zealand is seeing atmospheric measurements taken from Antarctica’s Ross Island added to a highly respected international climate data reference network. It’s only the second place in the Southern Hemisphere (after Lauder New Zealand) and 13th worldwide to achieve GRUAN certification.
Short for Global Climate Observing System Reference Upper-Air Network, GRUAN is a state-of-the-art global network of high-quality measurements of climate variables in the upper atmosphere.
GRUAN-certified measurements are now being taken from radiosondes launched from United States-run McMurdo Station at the southern tip of Ross Island. NIWA has provided a standard humidity chamber to help calibrate their radiosondes.
Strung beneath helium-filled balloons, McMurdo’s radiosondes measure atmospheric pressure, temperature, humidity, wind speed and direction.
Global navigation satellite system (GNSS) data from a LINZ receiver at nearby New Zealand-run Scott Base are being collected and fed into the GRUAN network to determine atmospheric water vapor abundances. Over the coming months and years, measurements from a range of NIWA’s instruments on Ross Island will also be included as more measurement techniques gain GRUAN-certification and those new data streams come online.
NIWA atmospheric scientist Dr Richard Querel initiated the Ross Island GRUAN certification process and was instrumental in getting it over the line. It involved an exhaustive two-year application process, which was thoroughly scrutinised and ultimately voted on for approval by an expert working group.
He says while standard radiosonde flights are an important part of weather forecasting, they are challenging to use in long-term global climate trend studies, because changes in instrumentation, data processing methods and retrievals can lead to observational biases and uncertainties over time.
“The GRUAN network aims to express all of the uncertainties of these observational measurements in a fully traceable way. GRUAN’s high-quality measurements are important because they can be used to help calibrate and validate measurements taken by satellites and to improve models used for numerical weather prediction.”
More Southern Hemisphere atmospheric measurement sites are expected to be added to the GRUAN network, including Reunion Island off the east coast of Madagascar and several around Australia.