Assessing the near surface sensitivity of SCIAMACHY atmospheric CO 2 retrieved using (FSI) WFM-DOAS
Assessing the near surface sensitivity of SCIAMACHY atmospheric CO 2 retrieved using (FSI) WFM-DOAS
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DOI：
10.5194/acp-7-3597-2007
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发表时间：
2007-07
影响因子：
6.3
通讯作者：
M. Barkley;P. Monks;Alan J. Hewitt;T. Machida;Ankur R. Desai;N. Vinnichenko;T. Nakazawa;M. Arshinov;N. Fedoseev;T. Watai
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文献类型：
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作者：
M. Barkley;P. Monks;Alan J. Hewitt;T. Machida;Ankur R. Desai;N. Vinnichenko;T. Nakazawa;M. Arshinov;N. Fedoseev;T. Watai
对大气中二氧化碳的卫星观测为确定区域碳源和碳汇以及研究碳循环过程提供了可能。然而，卫星测量的有用程度取决于所选传感器的近表面灵敏度。本文考察了ENVISAT上的SCIAMACHY仪器对低对流层和地面CO2变率的观测能力。为此，使用全光谱起始(FSI)WFM-DOAS算法从SCIAMACHY近红外(NIR)光谱测量中反演大气CO2，并将其与西伯利亚上空的现场飞机观测以及蒙古、欧洲和北美上空的塔台和地面CO2数据进行比较。根据公园瀑布的地面傅里叶变换光谱仪(FTS)柱测量的日平均SCIAMACHY/FSICO2初步验证，在站点的±1°范围内的配置测量的负偏差约为−2.0%。然而，在这个空间阈值下，SCIAMACHY只能捕捉月时间尺度上FTS观测的可变性。为了观察FTS观测的每日可变性，必须增加配置限制。此外，与现场二氧化碳观测的比较表明，SCIAMACHY能够在(至少)月的时间尺度上观测到代表对流层低变率的季节信号。在17个时间序列比较中，有11个时间序列的相关系数在0.7或更高，且具有相似的季节性周期幅度。通过FSI得到的二氧化碳与美国20多个选定地点的MODIS植被指数的显著相关性，提供了SCIAMACHY近地表敏感性的额外证据。SCIAMACHY/MODIS的比较表明，在许多地点，CO2变化量与植被活动量是一致的。目前的分析表明，SCIAMACHY有可能探测到由陆地生物圈活动引起的对流层最低层内的二氧化碳变率。
Satellite observations of atmospheric CO 2 offer the potential to identify regional carbon surface sources and sinks and to investigate carbon cycle processes. The extent to which satellite measurements are useful however, depends on the near surface sensitivity of the chosen sensor. In this paper, the capability of the SCIAMACHY instrument on board ENVISAT, to observe lower tropospheric and surface CO 2 variability is examined. To achieve this, atmospheric CO 2 retrieved from SCIAMACHY near infrared (NIR) spectral measurements, using the Full Spectral Initiation (FSI) WFM-DOAS algorithm, is compared to in-situ aircraft observations over Siberia and additionally to tower and surface CO 2 data over Mongolia, Europe and North America. Preliminary validation of daily averaged SCIAMACHY/FSI CO 2 against ground based Fourier Transform Spectrometer (FTS) column measurements made at Park Falls, reveal a negative bias of about −2.0% for collocated measurements within ±1.0° of the site. However, at this spatial threshold SCIAMACHY can only capture the variability of the FTS observations at monthly timescales. To observe day to day variability of the FTS observations, the collocation limits must be increased. Furthermore, comparisons to in-situ CO 2 observations demonstrate that SCIAMACHY is capable of observing a seasonal signal that is representative of lower tropospheric variability on (at least) monthly timescales. Out of seventeen time series comparisons, eleven have correlation coefficients of 0.7 or more, and have similar seasonal cycle amplitudes. Additional evidence of the near surface sensitivity of SCIAMACHY, is provided through the significant correlation of FSI derived CO 2 with MODIS vegetation indices at over twenty selected locations in the United States. The SCIAMACHY/MODIS comparison reveals that at many of the sites, the amount of CO 2 variability is coincident with the amount of vegetation activity. The presented analysis suggests that SCIAMACHY has the potential to detect CO 2 variability within the lowermost troposphere arising from the activity of the terrestrial biosphere.