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DOI:

10.11834/jrs.20210095

收稿日期:

2020-04-20

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激光掩星探测大气UTLS温度和水汽的方法及仿真
李虎1,2,王建宇1,2,洪光烈1
1.中国科学院空间主动光电技术重点实验室 中国科学院上海技术物理研究所, 上海 200083;2.中国科学院大学, 北京 100049
摘要:

以高精度和高垂直分辨率探测大气区间对流层顶—平流层底UTLS(Upper Troposphere/Lower Stratosphere,5—35 km)的温度和水汽廓线是提高大气条件变化监测水平的关键,而利用激光掩星方法同时探测温度和水汽则是对现有探测技术的重要补充。本文研究了激光掩星协同探测和反演温度和水汽分子数密度的方法,其中重点研究了双吸收波长近红外激光反演温度的方法,具体为从近红外波段氧气吸收光谱中,选择2个不同跃迁能级对应的特征吸收峰,在每个吸收峰附近各选出1个吸收线,利用2个吸收线对应的双吸收波长激光以及参考线对应波长激光进行掩星探测,进而由探测数据反演出温度。整个温度和水汽协同反演步骤是先反演温度廓线,然后由温度廓线以及5 km参考高度处的压强先验值计算得到压强廓线,最后在温度和压强廓线基础上,结合水汽单吸收波长和参考波长激光掩星数据,反演得到水汽分子数密度廓线。此外,本文对探测和反演过程进行了模拟仿真,通过在近红外波段选择合适的氧气吸收波长和水汽吸收波长,模拟得到掩星透过率数据,以此反演得到温度和水汽分子数密度廓线。并通过对整个过程的分析,明确了反演过程中的误差项及其传递关系,结合数值仿真结果,说明了各个误差项的影响大小。结果显示,在UTLS区间内,温度反演误差总体小于1.05 K,水汽分子数密度反演误差总体小于4%,该误差范围说明了温度和水汽协同反演方法的可行性。

Retrieval method and simulation of UTLS temperature and water vapor by laser occultation
Abstract:

Measuring temperature and water vapor profiles with high accuracy and vertical resolution in the upper troposphere and lower stratosphere (UTLS, 5—35 km in height) is significant for improved monitoring of condition changes in the free atmosphere, and simultaneously measuring with laser occultation method is a significant supplement to the existing exploration technology. Here we introduce an algorithm to retrieve temperature and water vapor profiles from laser occultation data, and thoroughly describe the temperature retrieval method from dual oxygen absorption wavelength laser occultation data.In this paper, the method of laser occultation cooperative measuring and retrieval of temperature and water vapor molecular number density is studied and the emphasis is on the method of deriving temperature from detected data. The method is selecting two characteristic absorption peaks corresponding to different transition energy levels from the near-infrared band oxygen absorption spectrum, choosing one absorption line near each absorption peak, using the double absorption wavelength laser corresponding to the two absorption lines and the wavelength laser corresponding to the reference line for occultation measuring.The algorithm steps of cooperative retrieval of temperature and water vapor are retrieving temperature profile from occultation data and deriving pressure profile from temperature profile and the pressure prior value at the reference height of 5 km, then as a second step, retrieving water vapor molecular number density from single water vapor absorption wavelength and reference wavelength laser occultation data.We furthermore simulate the occultation process with selected oxygen absorption wavelength and water vapor absorption wavelength laser signals, and retrieve from the simulated transmittance data. The error term and its transfer relationship in the retrieval process are analyzed and the influence of each error term is presented by the simulation results. This results show that the temperature retrieval errors are generally smaller than 1.05 K, and the water vapor molecular number density retrieval errors are generally smaller 4%, which shows the feasibility of the temperature and water vapor collaborative retrieval method.

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