Evaluation of radiosonde humidity sensors at low temperature using ultralow-temperature humidity chamber

Abstract

Abstract. Accurate measurements of temperature and water vapor in the upper-air are of great interest in relation to weather prediction and climate change. Those measurements are mostly conducted using radiosondes equipped with a variety of sensors that are flown by a balloon up to lower stratosphere. Reference Upper Air Network (GRUAN) has identified water vapor pressure as one of the most important measurands and has set an accuracy requirement of 2 % in terms of the mixing ratio. In order to achieve the requirement, many errors in the humidity measurement such as a temperature dependency in sensing characteristics including measurement values and response time need to be corrected because humidity sensors of radiosondes pass through low-pressure (1 kPa) and low-temperature (−80 ∘C) environments in the upper-air. In this paper, the humidity sensing characteristics of Jinyang radiosonde sensors in relation to temperature dependencies were evaluated at low temperature using a newly developed ultralow-temperature humidity chamber. The sensitivity characteristic curve of the radiosonde sensors was evaluated down to −80 ∘C, and the calibration curves of the humidity sensor and the temperature sensor were obtained. The response time of humidity sensor slowly increased from 52 to 116 s at the temperature from 20 to −40 ∘C, respectively, and then rapidly increased to almost one hour at −80 ∘C. Those results will help to improve the reliability of the upper-air observation data.

Comprehensive Analysis and Validation of the Atmospheric Weighted Mean Temperature Models in China

“…where z 1 and z 2 are the altitude values of the upper and lower observation layers, e and T are the water vapor pressure and temperature over the observation layers, respectively. Although the T m calculated by RS has relatively good accuracy and can be used as a reference to evaluate the accuracy of the T m model, there is uncertainty in the calculation of T m due to the uncertainty in the humidity measurement and this approach has low spatial and temporal resolutions [43,44].…”

Drone-based meteorological observations up to the tropopause

“…Above 500 hPa, an increasing deviation between radiosonde and UAS measurements can be observed in relative humidity. This is likely caused by the dramatically increasing response time of the humidity sensor at lower temperatures (Choi et al, 2018) in addition to the delaying effect of the implemented closed path sensor setup. Moisture is known as a critical parameter to measure in the upper troposphere (Nash et al, 2011;Dupont et al, 2020).…”

Calibration of RS41 humidity sensors by using an upper‐air simulator

“…The slow response of humidity sensors, especially at low temperatures, induces a time lag in the measurement (Miloshevich et al, 2004). To evaluate the calibration uncertainty, several groups have reported the development of low-temperature low-pressure humidity chambers, including KRISS (Lee et al, 2019a), the Istituto Nazionale di Ricerca Metrologica (INRiM) in Italy (Cuccaro et al, 2018), and the VTT in Finland (Sairanen et al, 2014(Sairanen et al, , 2015. According to the GRUAN, the required accuracy of the water vapour measurement in the upper air is 2% in terms of the mixing ratio (GCOS, 2007).…”

“…In the humidity chambers developed at KRISS, the thin‐film humidity sensors measure lower values of relative humidity than the reference values at low temperatures when these sensors are calibrated only at the room temperature (Choi et al, 2018; Lee et al, 2019b). This aspect highlights the importance of the calibration of radiosonde humidity sensors at low temperatures as in the free atmosphere.…”