Impact of ship emissions on the microphysical, optical and radiative properties of marine stratus: a case study
Impact of ship emissions on the microphysical, optical and radiative properties of marine stratus: a case study
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DOI：
10.5194/acp-6-4925-2006
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发表时间：
2006-10
影响因子：
6.3
通讯作者：
M. Schreier;A. Kokhanovsky;V. Eyring;L. Bugliaro;H. Mannstein;B. Mayer;H. Bovensmann;J. Burrows
中科院分区：
文献类型：
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作者：
M. Schreier;A. Kokhanovsky;V. Eyring;L. Bugliaro;H. Mannstein;B. Mayer;H. Bovensmann;J. Burrows
船舶废气对现有云层的改变是众所周知的，但没有充分量化的影响，这可能会导致气候变化。船舶产生的气溶胶对云层的扰动改变了云的反射率，并通过卫星图像中的长曲线（称为船舶轨迹）来识别。由于船舶航迹表明污染了非常干净的海洋环境，并且还影响云下和云上的辐射收支，因此研究其辐射和气候效应非常重要。卫星数据从中分辨率成像分光仪在地球上被用来检查现场从2003年2月10日，船舶轨迹被发现接近北美西海岸。云的光学和微物理性质是用半解析检索技术结合查表法得到的。提出了一种算法，以区分船舶轨迹像素从未受干扰的云像素在场景中，并从这个前者的光学特性进行了比较，后者。在船舶跟踪液滴数浓度的显着变化，有效半径和光学厚度相比，未受影响的云。由此产生的云属性用于计算云下方和上方的辐射收支。假设所选场景的平均太阳天顶角为63 °，船舶航迹下方的平均太阳表面辐射减少了43.2Wm2，大气顶部的平均反射率（TOA）增加了40.8Wm2。对于整个分析场景的船舶排放减少了太阳辐射在表面由2.1 Wm 2，并增加了后向散射的太阳辐射在TOA由2.0 Wm 2，而没有显着的热辐射的影响被检测到。
Modifications of existing clouds by the exhaust of ships are well-known but inadequately quantified impacts, which could contribute to climate change. The perturbation of a cloud layer by ship-generated aerosol changes the cloud reflectivity and is identified by long curves in satellite im- ages, known as ship tracks. As ship tracks indicate a pollu- tion of a very clean marine environment and also affect the radiation budget below and above the cloud, it is important to investigate their radiative and climatic effects. Satellite- data from MODIS on Terra are used to examine a scene from 10 February 2003 where ship tracks were detected close to the North American West-Coast. The cloud optical and mi- crophysical properties are derived using a semi-analytical re- trieval technique combined with a look-up-table approach. An algorithm is presented to distinguish ship-track-pixels from the unperturbed cloud pixels in the scene and from this the optical properties of the former are compared to those of the latter. Within the ship tracks a significant change in the droplet number concentration, the effective radius and the optical thickness are found compared to the unaffected cloud. The resulting cloud properties are used to calculate the radiation budget below and above the cloud. Assuming a mean solar zenith angle of 63 for the selected scene, the mean solar surface radiation below the ship track is decreased by 43.2 Wm 2 and the mean reflectance at top of atmosphere (TOA) is increased by 40.8 Wm 2 . For the entire analyzed scene the ship emission decreases the solar radiation at the surface by 2.1 Wm 2 and increases the backscattered solar radiation at TOA by 2.0 Wm 2 , whereas no significant effect on thermal radiation was detected.