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首页> 外文期刊>Atmospheric Measurement Techniques >Retrieval of tropospheric CO column from hyperspectral infrared sounders – application to four years of Aqua/AIRS and MetOp-A/IASI
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Retrieval of tropospheric CO column from hyperspectral infrared sounders – application to four years of Aqua/AIRS and MetOp-A/IASI

机译：从高光谱红外测深仪中提取对流层CO柱-适用于Aqua / AIRS和MetOp-A / IASI的四年

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Four years of tropospheric integrated content of CO were retrieved from infrared hyperspectral observations of AIRS onboard Aqua and IASI onboard MetOp-A, for the period July 2007–June 2011. The retrieval method is based on a double differential approach that relies on the difference between brightness temperatures observed by the sounder and BT simulated by the Automatised Atmospheric Absorption Atlas (4A) radiative transfer model on colocated ECMWF reanalyses, for several couples of channels located in the 4.67 μm CO band. AIRS and IASI give access to similar integrated contents of CO with a maximum sensitivity near 450 hPa and a half-height width of the weighting function between 200 and 750 hPa depending on the thermal contrast (i.e., the difference between the surface temperature and the temperature of the first pressure level). However, differences in their spectral and radiometric characteristics yield differences in the retrieval characteristics with AIRS selected couples of channels being more sensitive to surface characteristics. Moreover, IASI covers the whole CO absorption band, with a 3 times better spectral resolution, giving access to channels presenting a 3 times higher signal to noise ratio. This results in a better precision and lower standard deviation of the IASI retrievals. Conservatively, comparisons with CARIBIC aircraft measurements yield an averaged relative difference of 3.4% for IASI and 4.9% for AIRS. On average, AIRS and IASI retrievals are in very good agreement, showing the same seasonality, seasonal amplitudes, interannual variability and spatial distribution. The analysis of the monthly evolution of CO particularly highlights the expected strong influence of biomass burning on the evolution of CO in several tropical regions. In particular, a sharp increase in CO in 2010 in the southern tropics, especially over South America and South Africa, is observed, and is shown to be related to El Ni?o and to the Atlantic Multidecadal Oscillation.
机译：从2007年7月至2011年6月期间从Aqua上的AIRS和MetOp-A上的IASI的红外高光谱观测中检索了对流层CO的四年总含量。该检索方法基于一种双微分方法，该方法依赖于在共存的ECMWF重新分析中，对位于4.67μmCO波段中的几个通道进行了测深仪观测到的亮度温度和自动大气吸收图集（4A）辐射传输模型模拟的BT。 AIRS和IASI可以访问相似的一氧化碳含量，其最大灵敏度接近450 hPa，加权函数的半高宽度介于200和750 hPa之间，具体取决于热对比度（即，表面温度与温度之间的差异）。的第一压力水平）。然而，它们的光谱和辐射特征的差异导致了检索特征的差异，其中AIRS选择的通道对对表面特征更为敏感。此外，IASI覆盖了整个CO吸收带，具有3倍的光谱分辨率，从而可以访问具有3倍高信噪比的通道。这样可以提高IASI检索的精度，降低标准偏差。保守地，与CARIBIC飞机的测量结果相比，IASI的平均相对差异为3.4％，AIRS的平均相对差异为4.9％。平均而言，AIRS和IASI的检索结果非常吻合，显示出相同的季节性，季节振幅，年际变化和空间分布。对CO每月演变的分析特别突出了一些热带地区生物质燃烧对CO演变的预期强烈影响。尤其是，观察到2010年南热带地区，尤其是南美和南非地区的二氧化碳排放量急剧增加，这与厄尔尼诺现象和大西洋多年代际涛动有关。

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