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首页> 外文期刊>Atmospheric chemistry and physics >Restoring the top-of-atmosphere reflectance during solar eclipses: a?proof of concept with the UV absorbing aerosol index measured by TROPOMI
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Restoring the top-of-atmosphere reflectance during solar eclipses: a?proof of concept with the UV absorbing aerosol index measured by TROPOMI

机译：在太阳日食期间恢复大气层的反射率：a？概念证明与rootomi测量的uv吸收气溶胶指数

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During a solar eclipse the solar irradiance reaching the top of the atmosphere (TOA) is reduced in the Moon shadow. The solar irradiance is commonly measured by Earth observation satellites before the start of the solar eclipse and is not corrected for this reduction, which results in a decrease in the computed TOA reflectances. Consequently, air quality products that are derived from TOA reflectance spectra, such as the ultraviolet (UV) absorbing aerosol index (AAI), are distorted or undefined in the shadow of the Moon. The availability of air quality satellite data in the penumbral and antumbral shadow during solar eclipses, however, is of particular interest to users studying the atmospheric response to solar eclipses. Given the time and location of a point on the Earth's surface, we explain how to compute the obscuration during a solar eclipse, taking into account wavelength-dependent solar limb darkening. With the calculated obscuration fractions, we restore the TOA reflectances and the AAI in the penumbral shadow during the annular solar eclipses on 26?December 2019 and 21?June 2020 measured by the TROPOMI/S5P instrument. We compare the calculated obscuration to the estimated obscuration using an uneclipsed orbit. In the corrected products, the signature of the Moon shadow disappeared, but only if wavelength-dependent solar limb darkening is taken into account. We find that the Moon shadow anomaly in the uncorrected AAI is caused by a reduction of the measured reflectance at 380? nm , rather than a colour change of the measured light. We restore common AAI features such as the sunglint and desert dust, and we confirm the restored AAI feature on 21?June 2020 at the Taklamakan Desert by measurements of the GOME-2C satellite instrument on the same day but outside the Moon shadow. No indication of local absorbing aerosol changes caused by the eclipses was found. We conclude that the correction method of this paper can be used to detect real AAI rising phenomena during a solar eclipse and has the potential to restore any other product that is derived from TOA reflectance spectra. This would resolve the solar eclipse anomalies in satellite air quality measurements in the penumbra and antumbra and would allow for studying the effect of the eclipse obscuration on the composition of the Earth's atmosphere from space.
机译：在日落时，在月亮阴影中降低了到达大气层（TOA）顶部的太阳辐照度。在太阳日食开始之前，太阳辐照度通常通过地球观察卫星测量，并且不会纠正这种降低，这导致计算的TOA反射的减少。因此，衍生自TOA反射光谱的空气质量产品，例如吸收气溶胶指数（AAI）的紫外线（UV），在月球的阴影中扭曲或未确定。然而，在太阳日食中的Penumbral和抑郁症阴影中的空气质量卫星数据的可用性对于对太阳日食的大气反应的用户来说是特别感兴趣的。鉴于地球表面上的点的时间和位置，我们解释了如何计算日食期间的遮蔽，考虑到波长依赖的太阳肢体变暗。随着计算的遮蔽分数，我们在26岁的环形日食期间恢复到Penumbral阴影中的ToA反射和Aai？2019年12月和21日的21岁及21六月由Tropomi / S5P仪器测量。我们使用未折叠的轨道将计算的遮蔽与估计的遮蔽。在校正的产品中，月亮影子的签名消失了，但仅考虑波长依赖的太阳肢体变暗。我们发现未经校正的AAI中的月亮暗影异常是由380的测量反射率降低引起的？ NM，而不是测量光的颜色变化。我们恢复常见的AAI功能，如Sugglint和Desert Dust，我们确认了21岁的恢复AAI功能？6月2020年6月在Taklamakan沙漠的同一天测量，但在月球阴影之外。没有发现由Eclipses引起的局部吸收气雾剂的局部变化。我们得出结论，本文的校正方法可用于在日食期间检测真正的AAI上升现象，并且有可能恢复来自TOA反射光谱的任何其他产品。这将在Penumbra和antumbra中解决卫星空气质量测量中的太阳日食异常，并允许在从空间中研究Eclipse遮蔽对地球大气组成的影响。

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