Long-term evolution of stratospheric aerosol extinction and particle sizes at northern mid and high latitudes

平流层硫酸盐气溶胶对气候系统非常重要，因为它们散射太阳辐射，增强地球的行星反照率，并导致表面冷却。它们对平流层化学很重要，因为它们即使在极地涡旋之外也能促进氯的活化，而且众所周知，它们在极地平流层云的形成中发挥着重要作用。根据政府间气候变化刑法(IPCC)的第五次评估报告，平流层气溶胶是目前全球变暖中断的原因之一。遥感平流层气溶胶最准确的方法之一是基于地面激光雷达观测。在这里提出的研究项目中，将使用不同地点的高质量激光雷达数据集--迄今尚未用于研究平流层气溶胶--来实现这一目的。激光雷达系统由德国库伦斯伯恩罗斯托克大学莱布尼茨大气物理研究所(IAP)操作，位于挪威安德内斯的阿洛玛天文台、南极洲的戴维斯站和库伦斯伯恩本身。其中两个激光雷达时间序列覆盖20年，在阿洛玛的测量提供了多个波长的激光雷达后向散射观测。激光雷达系统的一个独特特点是，它们也在白天运行。现有的激光雷达系统之一具有光谱分辨率，允许通过其多普勒展宽来分离气溶胶和分子散射。激光雷达原始观测将用于该项目的第一部分，以确定平流层气溶胶的后向散射和消光分布，以及可转换为气溶胶辐射强迫的平流层气溶胶光学厚度。此外，阿洛玛天文台的多波长观测还可以恢复气溶胶粒子的大小。在该项目的第二部分，将利用所反演的平流层气溶胶消光、光学厚度和颗粒大小的时间序列来描述平流层气溶胶负荷的变化和趋势，以及20多年期间北方中高纬度地区的相关辐射强迫。在这种情况下，季节变化、QBO和火山效应将是至关重要的。在几次弱至中等火山喷发期间，根据肢体分散观测技术进行的平流层气溶胶消光的卫星反演将受到粒子大小的制约。环境卫星上的SCIAMACHY仪器、ODIN上的OSIRIS以及索米卫星上的OMPS-LP仪器已经/正在应用卫星肢体散射技术，并依赖于对气溶胶颗粒大小的先验知识。拟议研究的预期结果将提供有关十年时间尺度上中、高纬度地区平流层气溶胶参数的变异性和趋势的重要新信息。

Stratospheric sulfate aerosols are of great importance for the climate system, because they scatter solar radiation, enhance the Earth's planetary albedo and lead to a surface cooling. They are important for stratospheric chemistry, because they facilitate chlorine activation even outside the polar vortex and they are known to play an important role in the formation of polar stratospheric clouds. Stratospheric aerosols are one of the contributors to the current global warming hiatus - according to the 5th assessment report of the Intergovernmenal Penal on Climate Change (IPCC). One of the most accurate methods to remotely sense stratospheric aerosols is based on ground-based lidar observations. Within the research project proposed here, high-quality lidar data sets at different locations - that have to date not been used to study stratospheric aerosols - will be employed for this purpose. The lidar systems are operated by the Leibniz-Institute of Atmospheric Physics (IAP) at Rostock University, Kühlungsborn (Germany) and are located at the ALOMAR observatory in Andenes (Norway), at Davis Station (Antarctica) and at Kühlungsborn itself. Two of the lidar time series cover 20 decades and the measurements at ALOMAR provide lidar backscatter observations at multiple wavelengths. A unique feature of the lidar systems is that they are operated also during daytime. One of the existing lidar system has a spectral resolution that allows separating aerosol and molecular scatter by its Doppler broadening. The lidar raw observations will be used in the first part of the project to determine stratospheric aerosol backscatter and extinction profiles, as well as stratospheric aerosol optical depth, which can be converted to aerosol radiative forcing. In addition, the multi-wavelength observations at the ALOMAR observatory allow the retrieval of aerosol particle size. In the second part of the project, the retrieved time series of stratospheric aerosol extinction, optical depth and particle size will be used to characterize the variability and trends in the stratospheric aerosol load and the associated radiative forcing at mid and high northern latitudes over a period of more than 2 decades. In this context, seasonal variations, QBO and volcanic effects will be of crucial importance. The particle size retrievals will provide essential constraints for satellite retrievals of stratospheric aerosol extinction based on the limb-scatter observation technique during a period with several weak to medium volcanic eruptions. The satellite limb-scatter technique was/is applied by the SCIAMACHY instrument on Envisat, OSIRIS on Odin as well as the OMPS-LP instrument on the Suomi satellite, and relies on a priori knowledge of the aerosol particle size. The expected outcome of the proposed research will provide important new information on the variability and trends in stratospheric aerosol parameters at mid and high latitudes at decadal time scales.