Accuracy Improvement and Uncertainty Reduction of Spectroscopic Parameters of Water Vapor Lines in the HITRAN Database

本项目的主要目的是为HITRAN数据库中水蒸气分子参数的更新和改进提供理论支持。HITRAN中水蒸气主要氧同位素物的压力加宽半宽、诱导线位移和温度指数的最新变化主要来自于依赖Robert-Bonamy形式的理论计算，该形式是三十多年前发展起来的，包含几个近似。从第一性原理直接计算这些光谱参数具有理论复杂性和数值困难的特点。所提出的方法提供了几个新的特性和优点。首先，重新表述Robert-Bonamy的形式表明，去掉一个使人衰弱的近似实际上减少了计算负担。其次，在Hilbert空间中引入坐标表示，可以使用足够高的截止点来保证所有计算的完全收敛。第三，对不同碰撞过程的贡献分析为潜在模型优化中基准线的选择提供了新的指导。此外，采用信号处理中的因果函数概念来获得希尔伯特变换，这对计算线移至关重要，允许计算甚至不必执行柯西主积分。有了这些强大的工具，我们将重新计算纯旋转带中吸收谱线的加宽半宽、谱线位移和温度指数。所有这些都是完全收敛的，并且来自“精确”的轨迹模型。这些结果将显著降低数值的不确定性，因此比现有的HITRAN 2008计算值更可靠。利用空间和地面仪器进行可靠的信息检索以及可靠的气候和大气模拟直接依赖于HITRAN提供的精确的水汽光谱参数。许多不同学科的研究科学家已经开始期望高质量的HITRAN作为他们必不可少的数据资源，必须是正确的。HITRAN水蒸气光谱参数的更新将提高辐射传输建模的准确性，例如控制寒冷和干燥极地大气中局部能量平衡的20微米“脏窗”光谱区域。本文的计算方法不仅适用于纯旋转波段的水汽谱线，也适用于其他波段。此外，它还可以用于预测HITEMP开发中涉及非常高j态的线参数，HITEMP是一个旨在解决天体物理学，行星和恒星大气以及工业，环境和监视应用所需的分子气体光谱的高温建模的项目。

The primary objective of this project is to provide theoretical support for updating and improving parameters for the water vapor molecule in the HITRAN database. The latest changes made to the pressure broadened half-width, induced line shift, and temperature exponent for the principal oxygen isotopologue of water vapor in HITRAN come mostly from theoretical calculations that rely on the Robert-Bonamy formalism, which was developed more than three decades ago and contains several approximations. Direct calculation of these spectroscopic parameters from first principles is characterized by theoretical complexity as well as numerical difficulty. The proposed approach offers several new features and advantages. First, re-formulating the Robert-Bonamy formalism shows that the removal of one debilitating approximation actually reduces the computational burden. Second, introducing the coordinate representation in Hilbert space enables the use of sufficiently high cut-offs to guarantee full convergence for all the calculations. Third, contribution analysis from different collisional processes establishes a new guideline for selecting benchmark lines in optimizing the potential model. Furthermore, the adoption of the causal function concept from signal processing to obtain the Hilbert transforms, crucial in calculating line shifts, allows the calculations to go forward without even having to perform the Cauchy principal integrations. With these powerful tools in hand, the broadened half-widths, line shifts, and temperature exponents for the absorption lines in the pure rotational band will be recalculated ? all with full convergence and from the "exact" trajectory model. These results will significantly reduce the numerical uncertainties, and are thus more reliable than the existing calculated values in HITRAN 2008.Reliable information retrieval using space and ground-based instruments, and reliable climate and atmospheric modeling are directly dependent on accurate water vapor spectroscopic parameters provided by HITRAN. Research scientists in many different disciplines have come to expect the high quality of HITRAN as their indispensable data resource that simply must be correct. The updating of the HITRAN water vapor spectroscopic parameters will improve the accuracy of radiative transfer modeling, such as the 20 micrometer 'dirty window' spectral region that controls the local energy balance in the cold and dry polar atmospheres. The computational approach described herein is applicable not only to the water vapor lines in the pure rotation band, but to other bands as well. Moreover, it can also be used to predict line parameters that involve very high j states in the development of HITEMP, a project designed to address high-temperature modeling of the spectra of molecular gases needed for astrophysics, planetary and stellar atmospheres, as well as industrial, environmental, and surveillance applications.