Köehler Philipp, Frankenberg Christian, Magney Troy S, Guanter Luis, Joiner Joanna, Landgraf Jochen
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
Geophys Res Lett. 2018 Oct 16;45(19):10456-10463. doi: 10.1029/2018GL079031. Epub 2018 Oct 2.
In recent years, solar-induced chlorophyll fluorescence (SIF) retrieved from space borne spectrometers has been extensively used as a proxy for terrestrial photosynthesis at relatively sparse temporal and spatial scales. The near-infrared band of the recently launched TROPOspheric Monitoring Instrument (TROPOMI) features the required spectral resolution and signal-to-noise ratio to retrieve SIF in a spectral range devoid of atmospheric absorption features. We find that initial TROPOMI spectra meet high expectations for a substantially improved spatio-temporal resolution (up to 7 km × 3.5 km pixels with daily revisit), representing a step change in SIF remote sensing capabilities. However, interpretation requires caution, as the broad range of viewing-illumination geometries covered by TROPOMI's 2600 km wide swath needs to be taken into account. A first inter-sensor comparison with OCO-2 (Orbiting Carbon Observatory-2) SIF shows excellent agreement, underscoring the high quality of TROPOMI's SIF retrievals and the notable radiometric performance of the instrument.
Photosynthesis is the most essential process for life on Earth, but gradually changing environmental conditions such as increasing concentrations of atmospheric trace gases, rising temperatures or reduced water availability could adversely affect the photosynthetic productivity. The recently launched TROPOspheric Monitoring Instrument (TROPOMI) is designed to monitor atmospheric trace gases and air pollutants with an unprecedented resolution in space and time, while its radiometric performance also permits us to see a weak electromagnetic signal emitted by photosynthetically active vegetation - solar induced chlorophyll fluorescence (SIF). Mounting evidence suggests that SIF observations from satellite instruments augment our abilities to track the photosynthetic performance and carbon uptake of terrestrial vegetation. In this study, we present the first TROPOMI SIF retrievals, largely outperforming previous and existing capabilities for a spatial continuous monitoring of SIF from space.
近年来，从星载光谱仪获取的太阳诱导叶绿素荧光（SIF）已在相对稀疏的时空尺度上被广泛用作陆地光合作用的替代指标。最近发射的对流层监测仪器（TROPOMI）的近红外波段具有所需的光谱分辨率和信噪比，能够在没有大气吸收特征的光谱范围内获取SIF。我们发现，最初的TROPOMI光谱符合人们对大幅提高时空分辨率（高达7千米×3.5千米像素，每日重访）的高度期望，代表了SIF遥感能力的一个飞跃。然而，由于需要考虑TROPOMI 2600千米宽的观测带所覆盖的广泛的观测-照明几何形状范围，所以在解释时需要谨慎。与轨道碳观测站-2（OCO-2）的SIF进行的首次传感器间比较显示出极佳的一致性，突出了TROPOMI的SIF反演的高质量以及该仪器显著的辐射测量性能。
光合作用是地球上生命最重要的过程，但诸如大气微量气体浓度增加、气温上升或水资源可用性降低等逐渐变化的环境条件可能会对光合生产力产生不利影响。最近发射的对流层监测仪器（TROPOMI）旨在以前所未有的时空分辨率监测大气微量气体和空气污染物，同时其辐射测量性能还使我们能够看到光合活性植被发出的微弱电磁信号——太阳诱导叶绿素荧光（SIF）。越来越多的证据表明，卫星仪器对SIF的观测增强了我们追踪陆地植被光合性能和碳吸收的能力。在这项研究中，我们展示了首次TROPOMI SIF反演结果，在从太空对SIF进行空间连续监测方面大大超越了以往和现有的能力。
