This paper reports the open path measurement of atmospheric transmission in the spectral region of 3000–3450 nm using a mid infrared tunable lidar in New Delhi (28.7^oN, 77.1^oE), India. Results on the measurement of atmospheric transmission in New Delhi are reported for the first time, to the best of our knowledge. A tunable infrared lidar system has been developed in-house, which transmits laser radiation with the wavelength interval of 1 nm in the above spectral band into the atmosphere. A 200-mm-diameter Cassegrain receiver telescope with mercury cadmium telluride (MCT) detector is used to collect the backscattered radiation from the atmosphere. The reflected laser radiation received from the tower located at a distance of 400 m is used to generate the transmission spectrum. Data recorded during the daytime measurements have been considered in this paper. Transmission spectra measured over several days showed a similar pattern, which confirmed the repeatability of the system performance. The measured spectra are also compared with the SkyCalc transmission model generated using the online database. Preliminary analysis indicated that these spectra had good agreement in general with a small shift in wavelength region. We have also analyzed the HITRAN database line-by-line and identified the possible major absorbing molecules in this band. The sources of air pollutants that absorb in this band and also discussed.

中文翻译：

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使用可调中红外激光雷达在3000-3450 nm范围内测量大气透射光谱的开放路径

本文报告了在新德里（28.7 ^o N，77.1 ^o N）使用中红外可调谐激光雷达在3000-3450 nm光谱区域中大气传输的开放路径测量E），印度。据我们所知，这是首次报告新德里大气传输的测量结果。内部已开发出可调谐的红外激光雷达系统，该系统将上述光谱带中波长间隔为1 nm的激光辐射传输到大气中。直径为200毫米的Cassegrain接收器望远镜配有碲化汞镉（MCT）检测器，用于收集来自大气的反向散射辐射。从位于400 m处的塔接收到的反射激光辐射用于生成透射光谱。本文考虑了白天测量期间记录的数据。几天内测得的透射光谱显示出相似的模式，这证实了系统性能的可重复性。还将测得的光谱与使用在线数据库生成的SkyCalc传输模型进行比较。初步分析表明，这些光谱总体上具有良好的一致性，并且波长范围的变化很小。我们还逐行分析了HITRAN数据库，并确定了该谱带中可能存在的主要吸收分子。并在此频段吸收了空气污染物的来源。