基于球载激光衰荡光谱技术的青藏高原水汽稳定同位素垂直廓线高精度探测方法研究

The Tibetan Plateau is the third pole of the earth and the Asian water tower. The Second Tibetan Plateau Scientific Expedition and Research (STEP) project pointed out that the Asian water tower was becoming unbalanced, and the water cycle research was urgently needed. Observations of stable isotopes in water in the vertical dimension, which become one of the key problems to be solved urgently in the study of water cycle. Picarro l2130-i, a foreign imported equipment currently used in the mainstream, is designed for the conventional atmospheric environment, with problems such as narrow range, high sampling pressure, and stringent requirements for cavity temperature and pressure control, which cannot fully meet the requirements for the vertical profile detection of water and vapor stable isotopes. This project aims to optimize the existing CRDS spectral technology and solve the key scientific problems in its application in the vertical profile detection of the Tibetan Plateau. Development of new wavelength division multiplex -CRDS technology, to achieve water vapor isotope (delta 18O) wide detection range (2~3 orders of magnitude) high precision (1‰) measurement, the accurate spectral line strength correction model is established to reduce the need of the temperature control and improve the long-term observation ability, and the high-precision detection needs of water vapor isotope (delta 18O) in the range of 3~10km above sea level is satisfied.

青藏高原是地球第三极、亚洲水塔。2017年启动的第二次青藏高原科学考察首期成果指出，亚洲水塔正走向失衡，迫切需要开展水循环研究，垂直维度上的水汽稳定同位素的精确原位测量成为青藏高原水循环研究迫切需要解决的关键问题之一。目前主流使用的国外进口设备Picarro L2130-i是针对常规大气环境设计的，存在量程窄、测量下限高、取样压力大、腔体温度压力控制要求苛刻等问题，不能充分满足水汽稳定同位素的垂直廓线探测需求。本项目旨在优化已有的CRDS光谱技术，解决其在青藏高原垂直廓线探测应用中的关键科学问题。发展新型波分复用-CRDS技术，实现水汽同位素（δ18O）的宽检测范围（2~3个量级）高精度（1‰）测量；建立精确的谱线强度修正模型，降低对腔体温度控制精度要求，提升CRDS光谱的长时间观测能力，满足海拔高度3~10km范围内的水汽同位素（δ18O）高精度探测需求。

青藏高原是地球第三极、亚洲水塔。2017年启动的第二次青藏高原科学考察首期成果指出，亚洲水塔正走向失衡，迫切需要开展水循环研究，垂直维度上的水汽稳定同位素的精确原位测量和温室气体尤其是CH4浓度变化成为青藏高原水循环研究迫切需要解决的关键问题之一。针对H2O同位素及CH4在青藏高原的气体特征，本项目选择了合适的吸收谱线，分析了温度、流速和气压对观测结果的影响，开展了适应于青藏高原环境的电路、机械机构等设计，研发了高性能的CRDS观测仪。在实验室对观测仪的性能进行了充分的分析论证（如温度控制、气压控制、检测范围、检测精度和漂移等）。研发的球载CH4原位在线监测样机参与了多次青藏高原科考（如2022巅峰使命-珠峰科考等），获得了林芝、纳木错、珠峰等地区的高空CH4垂直廓线原位观测数据，CH4的检测范围达到0.1ppb~10ppm，跨度5个数量级，时间分辨20s。基于CH4的垂直廓线观测，为球载H2O同位素样机积累了丰富的经验，H2O同位素原位在线观测样机拟定于2023年参与珠峰科考。