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New Non-LTE Model of OH and CO2 Emission in the Mesosphere-Lower Thermosphere and its Application to Retrieving Nighttime Parameters

机译：中层低层热圈中OH和CO2排放的新非LTE模型及其在夜间参数反演中的应用

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摘要

The hydroxyl, OH, and carbon dioxide, CO2, molecules and oxygen atoms, O(3P), are important parameters that characterize the chemistry, energetics, and dynamics of the nighttime mesosphere and lower thermosphere (MLT) region. Hence, there is much interest in obtaining high quality observations of these parameters in order to study the short-term variability as well as the long-term trends in characteristics of the MLT region. The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on board the Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics (TIMED) satellite has been taking global, simultaneous measurements of limb infrared radiance in 10 spectral channels, including the OH 2.0 and 1.6-micron and CO2 4.3-micron emissions channels, continuously since late January 2002. These measurements can be interpreted using sophisticated non-Local Thermodynamic Equilibrium (non-LTE) models of OH and CO2 infrared emissions which can then be applied to obtain densities of these parameters (2.0 and 1.6-micron channel for O(3P)/OH and 4.3-micron channel for CO2). The latest non-LTE models of these molecules, however, do not fully represent all the dominant energy transfer mechanisms which influence their vibrational level distributions and infrared emissions. In particular, non-LTE models of CO2 4.3-micron emissions currently under-predict SABER measurements by up to 80%, and its application for the retrieval of CO2 will result in unrealistic densities. Additionally, current O(3P) retrievals from SABER OH emissions have been reported to be at least 30% higher compared to studies using other instruments. Methods to obtain OH total densities from SABER measurements have yet to be developed. Recent studies, however, have discovered a new energy transfer mechanism which influences both OH and CO2 infrared emissions, OH(v) → O(1D) → N2( v) → CO2(v3). This study focuses on the impact of this new mechanism on OH and CO2 infrared emissions as well as model applications for the retrieval of nighttime O( 3P), OH, and CO2 densities.;We first study in detail the impact of the new mechanism on OH( v) vibrational level populations and emissions. We compared our calculations with the SABER/TIMED OH 1.6 and 2.0-micron limb radiances of the MLT and with ground and space observations of OH(v) densities in the nighttime mesosphere. We find that the new mechanism produces OH(v) density distributions which are in good agreement with both SABER limb OH emission observations and ground and space measurements.;We then couple our OH non-LTE model with CO2 to study the impact of the new mechanism on CO2(v3) vibrational level populations and emissions. We compare our calculations with the SABER/TIMED 4.3-micron CO2 limb radiances and find that the new mechanism provides a strong enhancement of the 4.3-micron CO2 emissions, agreeing to within a 10-30% range.;Further, a two-channel retrieval algorithm is developed to self-consistently invert the SABER measured radiances in the OH 2.0 and 1.6-micron channel to obtain vertical profiles of OH and O(3P) Volume Mixing Ratio (VMR). Studies of the inversion algorithm made with synthetic radiances indicate that a stable solution of the inverse problem can be obtained that is nearly independent of the starting conditions.;The results presented from the two-channel algorithm to the SABER v2.0 data include comparisons of retrieved O(3P) with current SABER O(3P), in addition to O(3P) retrievals measured by the SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) instrument, as well as those calculated by the WACCM (Whole Atmosphere Community Climate Model) model for four different days. The O( 3P) density retrieved between 90-95 km are, on average, lower than current SABER O(3P) by 10-50%. OH retrievals are performed over the same days and are compared with OH WACCM calculations as well as other studies.;Finally, a similar self-consistent algorithm used for the retrieval of daytime CO2 densities is adopted for nighttime. The situation, however, is more complex for nighttime CO2, where lack of solar irradiation excitation greatly reduce 4.3-micron emission sensitivity to CO 2 density and, therefore, produces unrealistic retrievals. Alternative retrieval methods will be required to overcome these obstacles. For daytime, retrieval of temperature and CO2 are performed simultaneously due to strong coupling between these two parameters. Consideration of this effect will be crucial to obtain accurate nighttime CO2 densities.
机译：羟基（OH）和二氧化碳（CO2）分子和氧原子O（3P）是表征夜间中层和低热层（MLT）区域的化学，能量和动力学的重要参数。因此，人们非常希望获得这些参数的高质量观​​测值，以便研究MLT地区特征的短期变化以及长期趋势。在热层，电离层，中层层，能量学和动力学（TIMED）卫星上使用宽带辐射辐射（SABER）仪器进行的大气探测已在全球范围内同时测量了包括OH 2.0在内的10个光谱通道中的肢体红外辐射以及自2002年1月下旬以来连续1.6微米和CO2 4.3微米的排放通道。可以使用复杂的OH和CO2红外辐射的非局部热力学平衡（non-LTE）模型解释这些测量结果，然后可以将其用于获得密度这些参数（O（3P）/ OH为2.0和1.6微米通道，而CO2为4.3微米通道）。但是，这些分子的最新非LTE模型不能完全代表影响其振动能级分布和红外发射的所有主要能量传递机制。特别是，目前，CO2 4.3微米排放量的非LTE模型低估了SABER测量高达80％，并且其在CO2检索中的应用将导致不切实际的密度。此外，据报道，与使用其他仪器进行的研究相比，目前从SABRE OH排放物中回收的O（3P）至少高出30％。从SABRE测量获得OH总密度的方法尚待开发。但是，最近的研究发现了一种新的能量转移机制，该机制同时影响OH和CO2的红外发射，即OH（v）→O（1D）→N2（v）→CO2（v3）。这项研究的重点是这种新机制对OH和CO2红外辐射的影响以及夜间O（3P），OH和CO2密度的反演模型应用。 OH（v）的振动能级和排放量。我们将计算结果与MLT的SABER / TIMED OH 1.6和2.0微米肢体辐射度以及夜间中层OH（v）密度的地面和空间观测值进行了比较。我们发现新机制产生的OH（v）密度分布与SABER肢体OH发射观测以及地面和空间测量都非常吻合;然后我们将OH non-LTE模型与CO2耦合以研究新OH的影响CO2（v3）振动能级人口和排放的机理。我们将计算结果与SABRE / TIMED的4.3微米CO2肢体辐射进行了比较，发现新机制大大增强了4.3微米CO2排放量，同意在10％至30％的范围内。此外，还有两个通道开发了检索算法，以自洽地反转OH 2.0和1.6微米通道中SABER测得的辐射度，以获得OH和O（3P）体积混合比（VMR）的垂直轮廓。对合成辐射度反演算法的研究表明，可以获得反问题的稳定解，而该解几乎与起始条件无关。；从两通道算法到SABER v2.0数据的结果包括：除了使用SCIAMACHY（大气层制图成像成像吸收光谱仪）测量的O（3P）以及WACCM（整个大气社区气候模型）计算出的O（3P）检索值外，还可以使用当前的SABRE O（3P）检索到O（3P）。 ）模型进行四个不同的工作日。平均而言，在90-95 km之间检索到的O（3P）密度比当前的SABRE O（3P）低10-50％。 OH的检索在同一天进行，并与OH WACCM计算和其他研究进行比较。最后，在夜间采用了类似的自洽算法来白天白天CO2密度的检索。但是，对于夜间CO2，情况更为复杂，因为缺少太阳辐射激发会大大降低对CO 2密度的4.3微米发射敏感度，因此产生了不切实际的检索。将需要替代的检索方法来克服这些障碍。在白天，由于这两个参数之间的强耦合，因此同时进行温度和CO2的获取。考虑此影响对于获得准确的夜间CO2浓度至关重要。

著录项

  • 作者

    Panka, Peter A.;

  • 作者单位

    George Mason University.;

  • 授予单位 George Mason University.;
  • 学科 Aeronomy.;Atmospheric sciences.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 192 p.
  • 总页数 192
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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