FORUM Earth Explorer 9: Characteristics of Level 2 Products and Synergies with IASI-NG
FORUM Earth Explorer 9: Characteristics of Level 2 Products and Synergies with IASI-NG
复制标题
FORUM Earth Explorer 9：2 级产品的特性以及与 IASI-NG 的协同作用
作者：
M. Ridolfi;S. D. Bianco;Alessio Di Roma;E. Castelli;C. Belotti;Paolo Dandini;G. D. Natale;B. Dinelli;L. C.;L. Palchetti
论坛(远红外辐射理解和监测)已被批准为欧洲航天局的第九次地球探测器任务。这项任务计划在2025-2026年间搭载极地卫星发射。核心仪器是傅里叶变换光谱仪，以非常高的精度测量上升的光谱辐射，从100到1600厘米−1(波长从100到6.25微米)，从而覆盖远红外(FIR)和地球发射的中红外(MIR)光谱的一部分。论坛将与MetOp-SG-1A卫星一起以松散的编队飞行，托管新一代红外大气探测干涉仪(IASI-NG)。IAIS-NG将只测量上升大气光谱中的和平红外部分，从645厘米到2760厘米−1(波长从15.5微米到3.62微米)，因此，匹配的论坛测量将补充缺失的FIR补充。这两次飞行任务将首次提供对地球发射的全部热谱的光谱分辨率测量。经校准的光谱辐射率本身将是论坛飞行任务的主要产品，但是，辐射率也将被处理到2级，以确定水蒸气的垂直轮廓、地表光谱发射率和在多云大气情况下的云参数。在本文中，我们评估了基于晴空模拟检索的论坛2级产品的性能，并研究了如何将论坛和IASI-NG匹配测量融合到协同检索方案中，以提供改进的2级产品。仅考虑测量噪声和系统校准误差分量，我们发现协同论坛和IASI-NG反演产品的数据如下。在对流层上部/平流层下部，垂直采样1公里即可反演水汽廓线，误差在10%~15%之间。在300~600 cm−1的范围内，在干燥的极地大气中，地表光谱发射率的绝对误差可达0.001。当冰水路径值在0.2~60g/m2范围内时，可以反演冰水路径和云顶高度等冰云参数，误差分别小于10%和1 km。
FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) has been approved to be the ninth Earth Explorer mission of the European Space Agency. The mission is scheduled for launch on a Polar satellite in the 2025–2026 time frame. The core FORUM instrument is a Fourier Transform Spectrometer measuring, with very high accuracy, the upwelling spectral radiance, from 100 to 1600 cm−1 (from 100 to 6.25 microns in wavelength), thus covering the Far-Infrared (FIR), and a Mid-Infrared (MIR) portion of the spectrum emitted by the Earth. FORUM will fly in loose formation with the MetOp-SG-1A satellite, hosting the Infrared Atmospheric Sounding Interferometer – New Generation (IASI-NG). IASI-NG will measure only the MIR part of the upwelling atmospheric spectrum, from 645 to 2760 cm−1 (from 15.5 to 3.62 microns in wavelength), thus, the matching FORUM measurements will supply the missing FIR complement. Together, the two missions will provide, for the first time, a spectrally resolved measurement of the full Earth emitted thermal spectrum. The calibrated spectral radiance will be, on its own, the main product of the FORUM mission, however, the radiances will also be processed up to Level 2, to determine the vertical profile of water vapour, surface spectral emissivity and cloud parameters in the case of cloudy atmospheres. In this paper we assess the performance of the FORUM Level 2 products based on clear-sky simulated retrievals and we study how the FORUM and IASI-NG matching measurements can be fused in a synergistic retrieval scheme, to provide improved Level 2 products. Considering only the measurement noise and the systematic calibration error components, we find the following figures for the synergistic FORUM and IASI-NG retrieval products. In the upper troposphere/lower stratosphere region, individual water vapour profiles can be retrieved with 1 km vertical sampling and an error ranging from 10% to 15%. In the range from 300 to 600 cm−1, surface spectral emissivity can be retrieved with an absolute error as small as 0.001 in dry Polar atmospheres. Ice cloud parameters such as ice water path and cloud top height can be retrieved with errors smaller than 10% and 1 km, respectively, for ice water path values ranging from 0.2 to 60 g/m2.