TES/Aura L2 Carbon Monoxide Nadir V008

TL2CON_8 is the Tropospheric Emission Spectrometer (TES)/Aura Level 2 Carbon Monoxide Nadir Version 8 data product. TES was an instrument aboard NASA's Aura satellite and was launched from California on July 15, 2004. Data collection for TES is complete. TES Level 2 data contains retrieved species (or temperature) profiles at the observation targets and the estimated errors. The geolocation, quality, and other data (e.g., surface characteristics for nadir observations) were also provided. L2 modeled spectra were evaluated using radiative transfer modeling algorithms. The process, referred to as retrieval, compared observed spectra to the modeled spectra and iteratively updated the atmospheric parameters. L2 standard product files included information for one molecular species (or temperature) for an entire global survey or special observation run. A global survey consisted of a maximum of 16 consecutive orbits.

A nadir sequence within the TES Global Survey was a fixed number of observations within an orbit for a Global Survey. Prior to April 24, 2005, it consisted of two low resolution scans over the same ground locations. After April 24, 2005, Global Survey data consisted of three low resolution scans. The Nadir standard product consists of four files, where each file is composed of the Global Survey Nadir observations from one of four focal planes for a single orbit, i.e. 72 orbit sequences. The Global Survey Nadir observations only used a single set of filter mix. A Global Survey consists of observations along 16 consecutive orbits at the start of a two day cycle, over which 3,200 retrievals were performed. Each observation was the input for retrievals of species volume mixing ratios (VMRs), temperature profiles, surface temperature and other data parameters with associated pressure levels, precision, total error, vertical resolution, total column density and other diagnostic quantities. Each TES Level 2 standard product reported information in a swath format conforming to the HDF-EOS Aura File Format Guidelines. Each Swath object wa bounded by the number of observations in a global survey and a predefined set of pressure levels representing slices through the atmosphere. Each standard product could have had a variable number of observations depending upon the Global Survey configuration and whether averaging is employed. Also, missing or bad retrievals were not reported.

The organization of data within the Swath object was based on a superset of the Upper Atmosphere Research Satellite (UARS) pressure levels that was used to report concentrations of trace atmospheric gases. The reporting grid was the same pressure grid used for modeling. There were 67 reporting levels from 1211.53 hPa, which allowed for very high surface pressure conditions, to 0.1 hPa, about 65 km. In addition, the products reported values directly at the surface when possible or at the observed cloud top level. Thus in the Standard Product files each observation could potentially contain estimates for the concentration of a particular molecule at 67 different pressure levels within the atmosphere. However, for most retrieved profiles, the highest pressure levels were not observed due to a surface at lower pressure or cloud obscuration. For pressure levels corresponding to altitudes below the cloud top or surface, where measurements were not possible, a fill value was applied.

To minimize the duplication of information between the individual species standard products, data fields common to each species (such as spacecraft coordinates, emissivities, and other data fields) have been collected into a separate standard product, termed the TES L2 Ancillary Data product (ESDT short name: TL2ANC). Users of this product should also obtain the Ancillary Data product.

TL2CON_8 是对流层发射光谱仪（Tropospheric Emission Spectrometer, TES）/光环（Aura）卫星二级一氧化碳天底观测版本8数据产品。TES是搭载于美国国家航空航天局（National Aeronautics and Space Administration, NASA）光环卫星的仪器，于2004年7月15日从加利福尼亚州发射升空。TES的数据采集任务已全部完成。TES二级数据包含观测目标处的反演物种（或温度）廓线及其估算误差，同时还提供了地理定位信息、质量评估数据以及其他相关数据（例如天底观测对应的地表特征）。二级模拟光谱通过辐射传输建模算法开展评估。这一被称为反演的过程，将观测光谱与模拟光谱进行比对，并迭代更新大气参数。二级标准产品文件为单次全球巡天或特殊观测任务中的单一种类分子（或温度）提供相关信息。一次全球巡天最多包含16个连续轨道。

TES全球巡天中的天底序列，指单次全球巡天轨道内的固定数量观测任务。2005年4月24日之前，该序列包含对同一地面位置的两次低分辨率扫描；2005年4月24日之后，全球巡天数据则包含三次低分辨率扫描。天底标准产品包含4个文件，每个文件对应单个轨道的4个焦平面之一的全球巡天天底观测数据，共计72个轨道序列。全球巡天天底观测仅使用单一组滤光片组合。全球巡天涵盖两天周期起始阶段的16个连续轨道的观测任务，在此期间共完成3200次反演。每次观测作为输入，用于反演物种体积混合比（Volume Mixing Ratios, VMRs）、温度廓线、地表温度及其他关联压力层级、精度、总误差、垂直分辨率、总柱密度和其他诊断量的数据参数。

每个TES二级标准产品以条带（swath）格式组织数据，符合HDF-EOS光环卫星文件格式指南。每个条带对象的边界由全球巡天中的观测数量以及代表大气分层的预定义压力层级集合确定。标准产品的观测数量可随全球巡天配置及是否采用平均处理而变化。此外，缺失或无效的反演结果不会被记录。条带对象内的数据组织基于上层大气研究卫星（Upper Atmosphere Research Satellite）压力层级超集，该层级集曾用于痕量大气气体浓度的报告。其报告网格与建模所用的压力网格一致，共包含67个报告层级，覆盖范围从适用于极高地表压力条件的1211.53百帕，到约65千米高度处的0.1百帕。此外，若条件允许，产品还会直接报告地表或观测到的云顶处的数值。因此，在标准产品文件中，每次观测理论上可包含大气中67个不同压力层级处的特定分子浓度估算值。但对于多数反演廓线而言，由于地表压力更低或云层遮蔽，最高压力层级的观测无法完成。对于云顶或地表以下高度对应的压力层级（无法开展测量），将使用填充值。

为减少各物种标准产品间的信息重复，各物种共有的数据字段（如航天器坐标、发射率及其他数据字段）已被整合至单独的标准产品，即TES L2辅助数据产品（ESDT简称：TL2ANC）。使用该数据产品的用户需同时获取辅助数据产品。