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，增强地球的行星辐射并导致表面冷却。它们对平流层化学很重要，因为它们甚至在极地涡旋之外也能促进氯的活化，而且已知它们在极地平流层云的形成中发挥重要作用。平流层气溶胶是目前全球变暖中断的贡献者之一-根据政府间气候变化公约（IPCC）的第五次评估报告。遥感平流层气溶胶最精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范围内，将为此目的使用不同地点的高质量激光雷达数据集，这些数据集迄今尚未用于研究平流层气溶胶。激光雷达系统由（德国）屈隆斯博恩罗斯托克大学莱布尼茨大气物理研究所操作，并设在（挪威）安德尼斯的ALOMAR天文台、（南极洲）戴维斯站和屈隆斯博恩本身。两个激光雷达时间序列涵盖20年，ALOMAR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之处在于它们也在白天运行。现有的激光雷达系统之一具有光谱分辨率，可以通过其多普勒展宽分离气溶胶和分子散射。激光雷达原始观测结果将用于该项目的第一部分，以确定平流层气溶胶后向散射和消光剖面，以及平流层气溶胶光学厚度，可将其转换为气溶胶辐射强迫。此外，ALOMAR观测站的多波长观测可用于反演气溶胶颗粒大小。在该项目的第二部分，将利用检索到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20多年来北方中高纬度地区平流层气溶胶负荷和相关辐射强迫的变化和趋势。在这种情况下，季节变化、QBO和火山效应将至关重要。粒子大小的检索将提供必要的限制，卫星检索平流层气溶胶消光的基础上的边缘散射观测技术，在一个时期内，有几个弱到中等火山爆发。Envisat卫星上的SCIAMACHY仪器、Odin卫星上的OSIRIS以及Suomi卫星上的OMPS-LP仪器过去/现在都采用了卫星边缘散射技术，该技术依赖于关于气溶胶颗粒大小的先验知识。拟议研究的预期成果将提供关于十年时间尺度上中高纬度平流层气溶胶参数变化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.