Characterisation of dust aerosols in the infrared from IASI and comparison with PARASOL, MODIS, MISR, CALIOP, and AERONET observations
Characterisation of dust aerosols in the infrared from IASI and comparison with PARASOL, MODIS, MISR, CALIOP, and AERONET observations
复制标题
IASI 红外粉尘气溶胶的表征以及与 PARASOL、MODIS、MISR、CALIOP 和 AERONET 观测结果的比较
DOI：
10.5194/acp-13-6065-2013
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发表时间：
2012
影响因子：
6.3
通讯作者：
N. Scott
中科院分区：
文献类型：
--
作者：
S. Peyridieu;A. Chédin;V. Capelle;C. Tsamalis;C. Pierangelo;R. Armante;C. Crevoisier;L. Crépeau;M. Siméon;F. Ducos;N. Scott
抽象的。 2007年7月至2011年12月期间的红外大气探测仪干涉仪（IASI）观测数据以月平均值、1°×1°、10μm尘埃气溶胶光学深度（AOD）、平均高度和粗模有效半径进行解释。地理研究区域包括北部热带大西洋和西北部阿拉伯海，这两个地区都有强烈、定期的沙尘事件。所开发的方法依赖于针对大量大气情况和观测条件计算的查找表的构建。在区域尺度上，IASI 检索的 10 μm AOD 与中分辨率成像光谱辐射计（MODIS/Aqua 或 Terra）或多角度成像光谱辐射计 (MISR) 或大气科学反射率偏振和各向异性与激光雷达观测相结合 (PARASOL) 的 550 nm 处总可见光深度之间存在良好的一致性。考虑到红外和可见光 AOD 之间存在的比率，不同 550 nm AOD 之间的多样性类似于这些 AOD 与 IASI AOD 之间的差异。红外 AOD 与可见光 AOD 的比率部分反映了 IASI 观察到的灰尘粗模式颗粒与其他仪器观察到的精细模式之间灰尘层的变化分布，发现该比率随观察区域的变化而变化，其值接近已公布的值。 10 μm IASI AOD 和 PARASOL 非球形粗模式 AOD 在 865 nm 处的气候学之间的比较（两者都预计代表灰尘粗模式）根据所考虑的区域得出不同的结论。这些差异根据 MODIS Angstrom 指数（865-550 nm）进行讨论。在局部范围内，大约六个气溶胶机器人网络 (AERONET) 站点，无论距离尘源远近，IASI 和可见 AOD 之间都存在类似的令人满意的一致性，并且显示和分析了这些产品之间的差异。 IASI 反演的尘埃层平均高度也与正交偏振云气溶胶激光雷达 (CALIOP/CALIPSO) 气溶胶平均层高度相比较，无论是在气候学方面还是在整个大西洋的纬向演化方面。将 IASI 检索的尘埃粗模有效半径与 AERONET 在六个站点检索的结果进行比较，发现存在约 +0.35 μm 的几乎系统偏差（IASI-AERONET）。消除这种偏差可以使这两种产品的气候学达到令人满意的一致性。总体而言，这些结果说明了沙尘向西输送的特点是沙尘光学深度快速下降、高度下降稍慢、有效半径在夏季整个北热带大西洋几乎保持不变。它们还展示了高分辨率红外探测器的能力，有助于提高我们对气溶胶相关过程（运输、来源、循环、气溶胶对地面辐射的影响等）的理解。
Abstract. Infrared Atmospheric Sounder Interferometer (IASI) observations covering the period from July 2007 to December 2011 are interpreted in terms of monthly mean, 1°×1°, 10 μm dust Aerosol Optical Depth (AOD), mean altitude and coarse mode effective radius. The geographical study area includes the northern tropical Atlantic and the northwest Arabian Sea, both characterised by strong, regular dust events. The method developed relies on the construction of Look-Up-Tables computed for a large selection of atmospheric situations and observing conditions. At a regional scale, a good agreement is found between IASI-retrieved 10 μm AOD and total visible optical depth at 550 nm from either the Moderate resolution Imaging Spectroradiometer (MODIS/Aqua or Terra), or the Multi-angle Imaging SpectroRadiometer (MISR), or the Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a Lidar (PARASOL). Taking into account the ratio existing between infrared and visible AODs, the diversity between the different 550 nm AODs is similar to the difference between these and the IASI AODs. The infrared AOD to visible AOD ratio, partly reflecting the varying distribution of the dust layer between the dust coarse mode particles seen by IASI, and the fine mode seen by the other instruments, is found to vary with the region observed with values close to already published values. Comparisons between the climatologies of the 10 μm IASI AOD and of the PARASOL non-spherical coarse mode AOD at 865 nm, both expected to be representative of the dust coarse mode, lead to conclusions differing according to the region considered. These differences are discussed in the light of the MODIS Angstrom exponent (865–550 nm). At local scale, around six Aerosol Robotic Network (AERONET) sites, close or far from the dust sources, a similar satisfactory agreement is found between IASI and the visible AODs and the differences between these products are shown and analysed. IASI-retrieved dust layer mean altitudes also compare well with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP/CALIPSO) aerosol mean layer altitude, both in terms of climatology and of zonal evolution throughout the Atlantic. Comparisons between the IASI-retrieved dust coarse mode effective radius and retrievals from AERONET at the six sites brings into evidence an almost systematic bias of about +0.35 μm (IASI-AERONET). Removing this bias leads to a satisfactory agreement between the climatologies of these two products. Overall, these results illustrate the dust westward transport characterised by a fast decrease of the dust optical depth, a somewhat slower decrease of the altitude, and an effective radius remaining almost constant during summer throughout the northern tropical Atlantic. They also demonstrate the capability of high resolution infrared sounders to contribute improving our understanding of processes related to the aerosols (transport, sources, cycles, effect of aerosols on the terrestrial radiation, etc.).