Hong Kong Observatory's Observing Station officially certified as a Global Climate Observing System Reference Upper-Air Observing Station

The Hong Kong Observatory’s upper-air observing station at King's Park has recently been officially certified as a member of the World Meteorological Organization (WMO) Global Climate Observing System Reference Upper-Air Network (GRUAN), which is dedicated to providing high-quality upper-air data for climate change monitoring and research.

GRUAN is a global network established by the WMO that provides long-term, high-quality upper-air climate data for studying trends and variations in upper-air meteorological elements. The data is also useful in numerical weather model analysis, as well as calibration and validation of satellite observations. Currently, GRUAN consists of over thirty members, seventeen of which have been certified, with Hong Kong among them. The Observatory’s upper-air observing station is China’s second GRUAN certified station, following the first in Xilinhot, Inner Mongolia, which was certified in 2025. Together, these two stations cover the southern and northern regions of China respectively.

The Observatory’s upper-air observing station has a distinguished history, having been recognized by the WMO in 2021 as the world's first centennial upper-air observing station. The station conducts measurements by adhering to strict operational procedures that ensure data quality, traceability and long-term consistency essential for reliable climate monitoring. Receiving the GRUAN certification confirms the high standard of the Observatory’s measurement capabilities and positions Hong Kong as a key contributor to global climate science. With this certification, the Observatory exchanges comprehensive upper-air observation data with the GRUAN community. This includes the use of a dedicated cryogenic frostpoint hygrometer for monthly measurements of water vapour content. Water vapour is a natural greenhouse gas that acts as a major amplifier of climate change, making the precise measurements particularly valuable for climate research.

The GRUAN site certificate awarded to the Hong Kong Observatory’s upper-air observing station

Observatory staff launching a weather balloon with a cryogenic frostpoint hygrometer to precisely measure upper-air water vapour content