New ISO standard advances accuracy of global climate observations

The Korea Research Institute of Standards and Science (KRISS, President Lee Ho Seong) has succeeded in having its radiosonde performance evaluation technology—used for one of the key instruments in weather and climate observation—adopted as an international standard.

* A radiosonde is an atmospheric observation instrument suspended from a large balloon and launched to altitudes of approximately 35 km to measure meteorological parameters such as temperature, humidity, and pressure. It consists of temperature and humidity sensors and a radio transmitter.

The radiosonde temperature sensor calibration test method, jointly developed by the Thermometry and Fluid Flow Metrology Group at KRISS in collaboration with Weathex Co., Ltd., the Korea Meteorological Administration (KMA), and the Korea Meteorological Institute (KMI), has been adopted as an international standard in meteorology (ISO 8932-1). This marks the first establishment of an international benchmark for accurately evaluating and calibrating radiosonde temperature sensors and is expected to significantly enhance the accuracy of weather forecasting and global climate prediction worldwide.

 Air temperature is a primary indicator that most directly reflects climate change. Short-term weather forecasts, which people encounter in daily life, primarily rely on temperature data from the troposphere, where air circulation is highly active. In contrast, long-term climate change observations depend on temperature measurements in the stratosphere, a region characterized by relatively stable air and limited atmospheric motion. To improve the accuracy of climate change predictions, it is therefore essential to continuously and precisely measure subtle temperature variations in the stratosphere.

Radiosondes are the primary instruments used to measure temperatures in the stratosphere. Today, meteorological agencies around the world rely on radiosondes for upper-air weather and climate observations. In particular, the sensors of a radiosonde—which directly interact with the surrounding atmosphere—are critical components that determine overall measurement performance. Because the upper atmosphere is strongly influenced by solar radiation and high-altitude winds, regular calibration of these sensors is essential to maintain measurement accuracy.

However, until now, there had been no internationally recognized standards or procedures for objectively evaluating the performance of radiosonde sensors. As a result, radiosonde users were forced to rely on performance specifications provided by manufacturers, making it difficult to independently verify sensor performance and limiting the reliability of upper-air meteorological observation data.

The ISO 8932-1 test method, newly approved as an international standard, defines detailed criteria and procedures for calibrating the measurement errors of radiosonde temperature sensors under upper-atmospheric conditions. Using this method, calibration errors can be maintained within 0.1 °C even in environments reaching altitudes of up to 40 km and temperatures as low as –85 °C.

The international standard is based on KRISS’s proprietary calibration technology for radiosonde temperature sensors and was finalized following a comprehensive review by an ISO working group (ISO WG) comprising meteorological and climate experts as well as manufacturers from multiple countries. In 2019, KRISS independently developed an Upper Air Simulator (UAS) capable of reproducing key atmospheric parameters—including temperature, humidity, pressure, solar radiation, and wind speed—under controlled laboratory conditions. Leveraging this system, KRISS has since established advanced techniques for high-precision calibration of radiosonde temperature sensors across a wide range of atmospheric environments.

With the establishment of an internationally recognized test method, the accuracy of upper-air meteorological observation data is expected to improve significantly. Radiosonde manufacturers will be able to evaluate and refine product performance at the development stage, while national meteorological agencies can verify radiosonde performance against objective criteria, ensuring more accurate and reliable weather information.

Dr. Kim Yong-Gyoo stated,

“The establishment of this international standard will enable countries worldwide to secure more reliable meteorological observation data, and is expected to contribute to the development of more sophisticated global climate prediction models.”

This research was supported by the KRISS Basic Research Program and the National Standards Technology Advancement Program funded by the Ministry of Trade, Industry and Resources (MOTIR).