Compensation of solar radiation and ventilation effects on the temperature measurement of radiosondes using dual thermistors

Abstract

The temperature measurement in the upper air by radiosondes is affected by various environmental factors such as solar irradiation, ventilation and air pressure. Among them, solar irradiation induces radiative heating of sensors whereas ventilation causes convective cooling. Here, the effect of these opposite factors on air temperature measurement is studied to obtain a correction formula using an experimental set-up consisting of a wind tunnel, a solar simulator and dual thermistors with different emissivities. The relationship between the temperature difference between the dual thermistors, irradiance and ventilation speed is first established in order to calculate irradiance in-situ by solely using the temperature difference. The temperature difference between dual thermistors is linearly proportional to the irradiance up to 1500 W m−2 and the slope of the linear function is decreased as the wind speed is increased up to 10 m s−1 at a fixed pressure level (about 1000 hPa). The uncertainty of the calculated irradiance using dual thermistors is 12.2% at the coverage factor k = 2. The calculated irradiance is then used for the correction of temperature of thermistors relative to the reference temperature in the shade inside the wind tunnel. The combined uncertainty of corrected temperature including uncertainty factors due to the compensation of wind and irradiance as well as the reference temperature is 0.19 K (k = 2). The dual thermistor-based technique can provide the traceability of the temperature measurement in upper air through in-situ compensation of the solar radiation effect.