探空湿度测量太阳辐射误差修正流体动力学研究

针对太阳辐射加热导致的误差显著限制了相对湿度测量的准确度,提出一种新颖的相对湿度误差修正方法—–基于流体动力学的数值分析法.在流体-固体耦合传热数值模拟分析中考虑探空湿度传感器的外部热环境情况,施加对流-太阳辐射耦合热边界条件,建立了地面到32 km高空不同气压和温度条件下探空湿度传感器的温度误差分析模型.结合Goff-Gratch饱和水汽压逼近公式,进而提出了相应的相对湿度误差流体动力学数值分析模型,并且着重研究了太阳辐射方向、传感器尺寸、反射率和衬底材料热导率等物理参数对相对湿度误差的影响.分析数值仿真结果表明:随着海拨的升高,其与太阳辐射加热引起的相对湿度误差之间存在非线性的单调递增关系;太阳辐射方向对于湿度测量精度的影响显著,当太阳辐射方向垂直于传感器正面时误差最大、传感器顶部时次之、侧面时误差最小;虽然通过减小探空湿度传感器的尺寸、降低衬底材料的热导率以及提高反射率均可以一定程度地降低太阳辐射加热引起的相对湿度误差,但是在低气压高空条件下,太阳辐射加热误差对于湿度准确性的影响仍然十分明显,需加以修正.与实验结果对比表明,基于流体动力学模拟仿真的相对湿度误差数值分析法为辐射误差修正提供了一种新的途径.

Fluid dynamic analysis on solar heating error of radiosonde humidity measurement

The error of humidity sensor induced by solar radiation seriously affects the accuracy of the relative humidity measurement. To solve this problem, this paper presents a novel numerical analysis method of correcting the error of relative humidity based on computational fluid dynamics. In view of the external thermal environmental conditions of radiosonde humidity sensors, the convection-solar radiation coupled thermal boundary conditions are adopted in the numerical simulation with analysis method of fluid-solid coupled heat transfer. The temperature error analysis model is first established from the ground to 32 km altitude with different pressures and temperatures. Combined with Goff-Gratch approximation formulas of saturation vapor pressure, the corresponding fluid dynamic numerical analysis model of relative humidity is put forward for error correction. Moreover, the relative humidity errors are reported in the different physical parameters such as the direction of the solar radiation, the reflectivity of sensor, thermal conductivity of the substrate material, the size of sensor, etc. The data analysis shows that the error of relative humidity, caused by solar radiation nonlinearly increases with altitude. The humidity measurement accuracy is affected notably by the direction of solar radiation. Among the errors caused by solar radiation, the error in the direction perpendicular to the front of the sensor is biggest, the error in the direction of the top of the sensor is the next, and the error in the direction of the side of the sensor is smallest. The data analysis also indicates that the solar heating error of the relative humidity can be reduced by reducing the size of the sensor, reducing the thermal conductivity of the substrate material, or improving the reflectivity of sensor. However, the solar heating error can not be neglected under low air pressure at high altitude. A comparison with experimental results shows that the numerical analysis method of the relative humidity error based on fluid dynamics simulation provides a new way to enhance the radiation error correction.
Keywords： humidity sensor solar radiation error correction computational fluid dynamics