HCOOH measurements from space: TES retrieval algorithm and observed global distribution
HCOOH measurements from space: TES retrieval algorithm and observed global distribution
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DOI：
10.5194/amt-7-2297-2014
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发表时间：
2014-01-01
影响因子：
3.8
通讯作者：
Wells, K. C.
中科院分区：
文献类型：
--
作者：
Cady-Pereira, K. E.;Chaliyakunnel, S.;Wells, K. C.
详细介绍了TES（对流层发射光谱仪）-Aura卫星甲酸（HCOOH）检索算法和量化对流层HCOOH全球分布的初步结果。给出了包括最优估计方法、光谱微窗、先验约束和初始猜测信息在内的反演策略。为了描述检索性能、信号自由度、垂直分辨率和检测极限，进行了全面的误差和灵敏度分析。这些结果表明，TES HCOOH检索(i)通常最多提供1.0条信息；（ii）在900至600 hPa范围内具有最高的垂直灵敏度，垂直分辨率接近2公里；（iii）如果热对比度大于5 K，则需要至少0.5 ppbv（十亿分之一体积）的HCOOH进行检测，并且随着热对比度的降低，浓度会更高；（iv）基于模拟检索的集合，标准差为+/-0.4 ppbv，无偏。从TES得到的对流层HCOOH的相对空间分布及其相关的季节性与最先进的化学输运模型（GEOS-Chem CTM）的预测广泛相关。然而，TES的HCOOH通常高于GEOS-Chem的预测，这与最近的工作一致，指出大气HCOOH的大量缺失来源。模式偏差在夏季和生物质燃烧地区尤为明显，这意味着生物源排放和火灾是模型中缺失的大气HCOOH的主要来源。
Presented is a detailed description of the TES (Tropospheric Emission Spectrometer)-Aura satellite formic acid (HCOOH) retrieval algorithm and initial results quantifying the global distribution of tropospheric HCOOH. The retrieval strategy, including the optimal estimation methodology, spectral microwindows, a priori constraints, and initial guess information, are provided. A comprehensive error and sensitivity analysis is performed in order to characterize the retrieval performance, degrees of freedom for signal, vertical resolution, and limits of detection. These results show that the TES HCOOH retrievals (i) typically provide at best 1.0 pieces of information; (ii) have the most vertical sensitivity in the range from 900 to 600 hPa with similar to 2 km vertical resolution; (iii) require at least 0.5 ppbv (parts per billion by volume) of HCOOH for detection if thermal contrast is greater than 5 K, and higher concentrations as thermal contrast decreases; and (iv) based on an ensemble of simulated retrievals, are unbiased with a standard deviation of +/-0.4 ppbv. The relative spatial distribution of tropospheric HCOOH derived from TES and its associated seasonality are broadly correlated with predictions from a state-of-the-science chemical transport model (GEOS-Chem CTM). However, TES HCOOH is generally higher than is predicted by GEOS-Chem, and this is in agreement with recent work pointing to a large missing source of atmospheric HCOOH. The model bias is especially pronounced in summertime and over biomass burning regions, implicating biogenic emissions and fires as key sources of the missing atmospheric HCOOH in the model.