太赫兹临边探测O3与HCl敏感性分析

臭氧(O_3)是平流层大气最重要的成分之一,而随着人类活动增加的影响,平流层O_3不断减少。在O_3的衰减循环中,Cl化合物是最主要的介质,而氯化氢(HCl)是活性氯的储存库,因此同时探测O_3与HCl对进一步认清平流层O_3的源与汇具有重要意义。本文基于太赫兹临边探测辐射传输软件包ARTS(Atmospheric Radiative Transfer Simulator),模拟研究太赫兹临边探测O_3与HCl的敏感因子量化大气辐射传输及其他大气成分对O_3和HCl的影响。结果表明:(1)在太赫兹波段,O_3与HCl分别在切高大于8 km与大于10 km处,具有很高的敏感性,可以探测O_3与HCl垂直廓线;(2)太赫兹临边探测对于探测目标O_3和HCl,在10 km及以下高度,对目标的浓度变化不敏感,而在中高空则很敏感;温度与水汽的变化对O_3与HCl的探测影响不大,而传感器的天线半带宽及光谱分辨率对于O_3与HCl的探测有一定的影响。

Simulating sensitivity of O3 and HCl with THz limb sounding

O₃ is the key composition of stratosphere. The problem on ozone and the effect on ozone by anthropogenic actions have always been the hot issue in the world. During attenuation circle of ozone, Chlorine composition is the most important medium. HCl is the storage of active chlorine. Therefore, monitoring HCl is significant. The development of limb sounding can supply three-dimensional information of O₃ and HCl. Simulation interface of THz limb sounding is developed based on the THz limb sounding radiative transfer software ARTS. This study analyzes the low-limit height within the limb sounding in THz bands between 100 GHz and 1000 GHz. The frequencies, 235.7098 GHz and 625.9188 GHz, were selected as the central frequencies for O₃ and HCl, respectively, based on the frequency of international available THz sensor radiometer. Then, the brightness temperature of limb sounding was simulated under different atmospheric backgrounds (standard atmospheric background and enhanced concentration of O₃ and HCl at 5%, 10%, and 15%, respectively), different temperatures and moistures (standard background temperature at 0.5 K, 1 K, and 1.5 K increase, standard water vapor concentration increased by 5%, 10%, and 15%), and different bands and different sensor characteristics (different HPBW and different spectral resolution). The sensitivity analysis module of the simulation interface shows that O₃ and HCl sensitive factors are further studied by limb sounding. The results are as follows: (1) Measuring O₃above the tangent height of 8 km at frequency of 235.7098 GHz is highly possible, whereas to measure O₃ below 8 km is difficult. For the measurement of HCl, the threshold height is 10 km, above which profiles of HCl can be available and below which profiles is difficult to measure. (2) At THz bands, the variety of temperature and moisture has little effect on the measurements of O₃ and HCl. Therefore, THz bands are superior to infrared bands, which are influenced greatly by temperature. (3) Half power beam width and spectral resolution have a certain effect on the measurements of O₃ and HCl.