基于固体腔扫描法布里-珀罗干涉仪的大气温度绝对探测方法研究

大气温度是描述大气状态的重要基本特征参量之一.目前,基于Rayleigh散射的大气温度探测方法多应用于大气温度的相对探测,即温度反演时需要响应函数和校准程序.本文提出了利用固体腔扫描式法布里-珀罗干涉仪进行大气Rayleigh散射谱型的精细探测方法和残余米散射信号的抑制方法.根据Rayleigh散射谱特点,针对固体腔扫描式法布里-珀罗干涉仪的自由光谱区、固体腔几何长度、腔体介质类型、半高全宽、腔体反射率、扫描间隔等参数进行了优化设计.利用优化参数的固体腔扫描式法布里-珀罗干涉仪获取Rayleigh散射谱上离散点信息,并采用多项式插值方法获得拟合谱型,与根据标准大气模型和S6模型获得的理论谱型进行比对,大气温度探测不确定度小于0.8 K.当信噪比为10时,白天与夜晚的探测距离分别为4.5和7.9 km.该方法可实现大气温度廓线的全天时和高精度绝对探测,并对同类高光谱激光雷达分光系统研究具有借鉴意义,为我国高光谱激光雷达陆基及星载应用提供了一套可行的分光系统解决方案.

Investigation of the absolute detection method of atmospheric temperature based on solid cavity scanning Fabry-Perot interferometer

measurement methods based on Rayleigh scattering are employed to relatively detect atmospheric temperature profiles. That is to say, the definition of response functions and calibration procedures is required for temperature retrieval. Because the thermal motion rate of gas molecule complies with Maxwell distribution, and gas molecule is always in motion state, the frequency of scattering return signal generates Doppler spectral broadening. There is a positive correlation between the full width at half maximum of widened Doppler spectrum and T^1/2, atmospheric absolute temperature can be obtained by measuring the Doppler spectrum shape. In this paper, the fine detection method of the spectrum shape of Rayleigh scattering and residuary Mie-scattering correction method based on solid cavity scanning Fabry-Perot (F-P) interferometer are investigated. According to the characteristics of Rayleigh scattering spectrum, the free spectral range, the geometric length of solid cavity, the type of cavity media, the full width at half maximum, the reflectivity of cavity, and the scanning step are designed. When the electro-optical crystal of KD*P with the length of 8.5 mm acts as solid cavity medium of scanning F-P interferometer, the designed free spectral region and 3 dB bandwidth are 11.5 GHz and 60 MHz at the central wavelength of 354.7 nm, respectively. The energy datum of 185 discrete points at Rayleigh scattering spectrum are obtained by using an optimized solid cavity scanning F-P interferometer with the scanning voltage of 23.5 V. A fitting spectrum is generated by employing polynomial interpolation method at the atmospheric temperature of 300 K. The maximum absolute error and full width at half maximum error of Rayleigh scattering spectrum are 22 MHz and 337 kHz, respectively. In order to verify the results, a numerical simulation of Rayleigh scattering spectrum based on standard atmosphere model and S6 model is performed. The detection uncertainty of atmospheric temperature is up to 0.8 K. As SNR (signal to noise ratio) is 10, the detection distance is 4.5 and 7.9 km at day-time and night-time, respectively. The research provides a new solution of filter system for the achievement of all-time, high-precision, and absolute detection of atmospheric temperature in the future. In meteorology, in order to investigate the temporal and spatial characteristics, the change rules and physical mechanism of weather processes, the temperature in the boundary layer of urban atmosphere is absolutely detected, where human activities are frequent and the changes of weather elements are obviously at day and night. In addition, the absolute detection method of atmospheric temperature can provide the valid means to research urban heat island, weather forecast for urban environment, and high temperature alert. In environmental studies, the absolute detection of atmospheric temperature can provide the big amount of scientific data for establishment of numerical model and research on air pollution diffusion. There is reference significance for the investigation of filter system of similar lidar. Simultaneously, the scanning filter method provides a feasible solution for the filter system with the characteristics of miniaturization, high anti-interference and high stability in the space-based platform.