Numerical Analysis And Optimization Design Of The Sounding Temperature Sensor

Bead thermistor is currently the mainstream radiosonde temperature sensor which is used to observe upper atmospheric temperature. Meteorologists are able to retrieve temperature profile of the atmosphere from the sea level through troposphere to lower stratosphere by using this type of sensors. It will provide the observational data for weather analysis and forecast, climate diagnostics and prediction, and atmospheric environmental monitoring and so on. It can provide calibration data for the measurement results of satellite remote sensing as well.Bead thermistor has the advantages of small size, light weight and fast response. However, it is susceptible to the solar radiation when sensing the high altitude vertical temperature in the daytime, resulting in a positive radiation error induced by solar heating. In order to obtain the true atmospheric temperature, it is necessary to modify the data set of bead thermistor measurement results, so that the solar radiation error can be minimized.At present, wind tunnel experiment and empirical estimation are the methods used to study the correction of solar radiation heating error. However, because of the environmental constraints of upper air sounding, there are still some limitations on these two methods. Based on existing research and theory, this paper propose a new method of numerical simulation to improve the measurement accuracy of the bead thermistor and make up for the shortages of the traditional solutions. In this study, by employing the computational fluid dynamics (CFD) software simulation radiation heat transfer and fluid-structure interaction, radiation errors that occur within the range from0km to32km altitude can be obtained numerically. The reflectivity of the surface coating, the body dimension of the ceramics thermistors, the lead angle, and the irradiate status of the sun play critical roles. All of the four factors are studied in this work. According to simulation results, the relation between the altitude and the error caused by solar radiation heating is not a simple linear relation but a parabolic relation, with the slop increasing as the altitude increases. The correction values of the radiosonde temperature measurement result vary with respect to the altitude. According to the modeling results, and based on the state-of-the-art thermistors, the improvement of surface reflectivitiy and the shrinkage of the dimensions of the thermistors offer an effective way to minimize solar radiation error under high barometric pressure. Nevertheless, under low barometric pressure the solar radiation has considerable impacts on the accuracy of temperature measurement, where the numerical method presented in this paper may find its applications. Further found that based on the numerical results, the bead thermistor of30°lead angle is found to be the optimal design of the lead angle, regardless of barometric pressure or radiation angle of the sun.This paper uses a software of computational fluid dynamics to simulate a matrix of bead thermistors in the radiation heat transfer and fluid-structure interaction. It can be used to improve radiosonde temperature sensor design, and provide the data and algorithm to optimize of the correction of the radiation error. In addition, it will improve the measurement accuracy of the sounding temperature sensor, and provide potential contribute to improve climate change research, the accuracy of numerical weather forecast, and satellite remote sensing accuracy of the atmospheric vertical temperature distribution.