Tropical stratospheric aerosol layer from CALIPSO lidar observations
Tropical stratospheric aerosol layer from CALIPSO lidar observations
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DOI：
10.1029/2009jd011946
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发表时间：
2009-02
影响因子：
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通讯作者：
J. Vernier;J. Pommereau;A. Garnier;J. Pelon;N. Larsen;J. K. Nielsen;T. Christensen;F. Cairo;L. Thomason;T. Leblanc;I. McDermid
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文献类型：
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作者：
J. Vernier;J. Pommereau;A. Garnier;J. Pelon;N. Larsen;J. K. Nielsen;T. Christensen;F. Cairo;L. Thomason;T. Leblanc;I. McDermid
利用正交极化云-气溶胶激光雷达（CALIOP）激光雷达数据，研究了自2006年6月云-气溶胶激光雷达和红外探路者卫星观测（CALIPSO）任务开始以来热带平流层中气溶胶的演变。结果表明，当前的业务校准在热带地区需要调整。实际上，基于30至34千米之间为纯瑞利散射的假设，由于热带地区直至35千米高度存在大量气溶胶，与中纬度地区形成对比，当前校准导致散射比平均低估6%。通过将校准调整到更高海拔（36 - 39千米）可获得更好的结果，过去的平流层气溶胶和气体实验（SAGE）II消光测量显示在该高度几乎完全没有气溶胶。重新校准后，CALIOP在任务前两年提供的热带平流层气溶胶图像揭示了与不同输送过程相关的气溶胶浓度的显著变化。在平流层中，若干火山层的缓慢上升及其向副热带的经向输送与 Brewer - Dobson环流非常吻合。北半球夏季在20千米左右观测到的近乎零的垂直速度与辐射加热计算结果非常吻合。在热带对流层顶层（TTL），在陆地对流期间观测到弱的退偏粒子，在南亚季风季节期间尤为强烈。最后，北半球冬季TTL中明显清洁空气的季节性快速出现需要更多研究以了解其来源。
[1] The evolution of the aerosols in the tropical stratosphere since the beginning of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission in June 2006 is investigated using Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar data. It is shown that the current operational calibration requires adjustment in the tropics. Indeed, on the basis of the assumption of pure Rayleigh scattering between 30 and 34 km the current calibration leads to an average underestimation of the scattering ratio by 6% because of the significant amount of aerosols up to 35 km altitude in the tropics, in contrast to midlatitudes. A better result is obtained by adjusting the calibration to higher altitudes, 36–39 km, where past Stratospheric Aerosol and Gas Experiment (SAGE) II extinction measurements showed an almost complete absence of aerosols. After recalibration the tropical stratospheric aerosol picture provided by CALIOP during the first 2 years of the mission reveals significant changes in the aerosol concentration associated with different transport processes. In the stratosphere the slow ascent of several volcanic layers and their meridional transport toward the subtropics are very consistent with the Brewer-Dobson circulation. The near-zero vertical velocity observed around 20 km during the Northern Hemisphere (NH) summer is in good agreement with radiative heating calculation. In the Tropical Tropopause Layer (TTL), weak depolarizing particles are observed during land convective periods, particularly intense over South Asia during the monsoon season. Finally, seasonal fast occurrence of apparent clean air in the TTL during the NH winter requires more investigations to understand its origin.