Perturbative solution to the two-component atmosphere DIAL equation for improving the accuracy of the retrieved absorption coefficient

Bunn Catharine E.; Repasky Kevin S.; Hayman Matthew; Stillwell Robert A.; Spuler Scott M.

摘要

Thermodynamic profiling using ground-based remote sensing instruments such as differential absorption lidar (DIAL) has the potential to fill observational needs for climate and weather-related research and improve weather forecasting. The DIAL technique uses the return signal resulting from atmospherically scattered light at two closely spaced wavelengths to determine the range-resolved absorption coefficient for a molecule of interest. Temperature profiles can be retrieved using a temperature-sensitive absorption feature of a molecule with a known mixing ratio such as oxygen. In order to obtain accuracies of less than 1 K, the narrowband DIAL equation must be expanded to account for Doppler broadening of molecular backscatter, and its relative contribution to the total signal, the backscatter ratio, must be known. While newly developed low-cost high spectral resolution lidar (HSRL) can measure backscatter ratio with sufficient accuracy, the frequency-resolved DIAL equation, even with this information, remains transcendental, and solving it for temperature can be computationally expensive. In this paper, we present a perturbative solution to the frequency-resolved DIAL equation when we have an HSRL providing the required ancillary measurements. This technique leverages perturbative techniques commonly employed in quantum mechanics and has the ability to obtain accurate temperature profiles (better than 1 K) with low computational cost. The perturbative solution is applied to a modeled atmosphere as an initial demonstration of this retrieval technique. An initial estimate of the error in the temperature retrieval for a diode-laser-based O-2 DIAL is presented, indicating that temperature retrievals with an error of less than +/- 1 K can be achieved in the lower troposphere. While this paper focuses on temperature measurements, the perturbative solution to the DIAL equation can also be used to improve the accuracy of retrieved number density profiles. (C) 2018 Optical Society of America

机译：热力学分析采用差动吸收利达（拨号）等地基遥感仪器有可能填补气候和与天气相关研究的观测需求，并改善天气预报。拨号技术使用由两个紧密间隔波长的大气散射光产生的返回信号，以确定感兴趣分子的范围分辨的吸收系数。可以使用具有已知混合比如氧的分子的温度敏感的吸收特征来检索温度曲线。为了获得小于1 k的精度，必须扩展窄带表盘方程以考虑分子反向散射的多普勒扩大，并且其对总信号的相对贡献必须已知。虽然新开发的低成本高光谱分辨率LIDAR（HSRL）可以测量具有足够精度的反向散射比，即使有这些信息，频率分辨的拨号方程也仍然是超凡的，并且解决温度可以计算昂贵。在本文中，当我们有一个HSRL提供所需的辅助测量时，我们向频率分辨的拨号方程呈现扰动解决方案。该技术利用通常用于量子力学中的扰动技术，具有能够以低计算成本获得精确的温度曲线（优于1 k）。作为这种检索技术的初步示范，将扰动溶液应用于建模的气氛。呈现了基于二极管激光的O-2转盘的温度检索误差的初始估计，表明在较低的对流层中可以实现具有小于+/- 1k的误差的温度检索。虽然本文重点介绍温度测量，但也可以使用对表盘方程的扰动解决方案来提高所检索的数量密度配置文件的精度。（c）2018年光学学会

Perturbative solution to the two-component atmosphere DIAL equation for improving the accuracy of the retrieved absorption coefficient

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