Pure rotational Raman scattering lidar is an important remote sensing tool for atmospheric temperature measurement. However, traditional backward pure rotational Raman scattering lidar has limitations in achieving effective atmospheric temperature detection in the lower atmosphere due to the overlap function effect of lidar systems. We present a novel technique of lateral scanning pure rotational Raman scattering lidar for accurate measurement of atmospheric temperature without the influence of blind zones and transition zones, which employs the bistatic structure of lidar systems. The atmospheric temperature profiling is realized by the detection of high- and low-quantum-number transitions of lateral pure rotational Raman scattering spectra at different heights, which is performed by elevation angle scanning of the lateral receiver system. The biggest advantage of this technique is the utilization of continuous-wave lasers as the excitation source, which not only significantly reduces equipment costs but also facilitates convenient mobility for outdoor observations.

The lateral pure rotational Raman scattering lidar technique is studied in the accurate measurement applications of atmospheric temperature from the ground to the height of interest. First, a novel lateral scanning pure rotational Raman scattering lidar technique is proposed and systematically designed. Each telescope combined with a narrow-band interferometric filter is adopted to detect the lateral scattering signals of the low- and high-quantum-number transitions of pure rotational Raman scattering spectra. Then, the atmospheric temperature inversion algorithm for lateral scanning pure rotational Raman scattering lidar is established and the calibration function is optimized to improve the inversion accuracy of atmospheric temperature. Finally, the experimental system is constructed, and the preliminary experiments are conducted using the lateral scanning pure rotational Raman scattering lidar. Two different rotation schemes including the continuous equidistant resolution and segmented equidistant resolution are employed during the experimental observations.

The detection principle of the proposed Raman scattering lidar is innovatively presented. It breaks through the traditional backward pure rotational Raman scattering lidar using a monostatic transceiver system structure, which produces blind and transition zones that cannot realize effective detection of near-surface atmospheric temperature. Meanwhile, this technology can leverage a continuous-wave laser, which features light weight, portability, mobility, and low cost (Fig. 1). By analyzing the eight newly expanded calibration functions, the calibration function that introduces the smallest error is selected as the expression for atmospheric temperature detection by a lateral pure rotational Raman scattering lidar (Fig. 2). Based on completing the lateral pure rotational Raman scattering lidar system design, the lateral Raman scattering lidar system is constructed (Fig. 3). Preliminary experimental observational studies of a lateral scanning pure rotational Raman scattering lidar are performed by two different rotation schemes of the continuous equidistant resolution and segmented equidistant resolution, which are employed during the experimental observations. The experimental results show that the lateral scanning pure rotational Raman scattering lidar has precise detection capability of atmospheric temperature up to a height of 1400 m. Furthermore, the segmented equidistant resolution rotation scheme provides a finer spatial distribution of temperature within the height interval of 0-312 m (Figs. 4-7),compared with the continuous equidistant resolution rotation scheme.

We propose a novel lateral pure rotational Raman scattering lidar technique to realize non-blind detection of the temperature profile distribution in the lower atmosphere. The profiling of lidar returns in the lateral pure rotational Raman scattering lidar is performed by elevation angle scanning of the lateral receiving system. Meanwhile, the intensities of the lateral Raman scattering signals at each setting of elevation angles are sampled and analyzed, and the biggest advantage of this technique is that a low-cost continuous laser can be employed as the excitation light source to simplify the system and reduce costs. Additionally, the pulsed laser in the backward pure rotational Raman scattering lidar can be adopted as the transmitter to construct a lateral + backward pure rotational Raman scattering lidar for finely detecting the atmospheric temperature from the ground to the height of interest. The preliminary experimental results show that the atmospheric temperature below the height of 1400 m can be detected finely with the 60 m distance between the transmitter and receiver. The segmented equidistant resolution rotational scheme can realize a more refined temperature profile than the whole continuous equidistant resolution rotation scheme.