Particle Size Distributions within Arctic Polar Stratospheric Clouds to Complement Particle Composition and Scattering Measurements

对极地平流层臭氧损失的更完整的定量了解需要在几个领域进一步开展工作。极地平流层云（PSCs）中粒子的成核、生长、组成和沉积的微物理学就是这些领域之一。PSC粒子为激活氯所需的非均质化学提供了场所，氯随后会破坏臭氧。PSC颗粒所起的关键作用在北极最为明显，那里的臭氧损失基本上是由温度（PSC的替代物）逐年调节的。PSC发生的频率、持续时间和时间决定了平流层极涡中氯活化和反硝化的程度，从而决定了臭氧损失量。消除目前关于PSC形成温度、颗粒组成和颗粒相的一些不确定性，将允许对PSC处理的氯量和反硝化程度进行更仔细的建模。氯的活化和最终的臭氧损失取决于所有这些因素。这项工作利用了几个欧洲同事的邀请，他们在2000/2001和2001/2002冬季合作对PSC粒子进行联合测量。欧洲机构和他们的测量是：马克斯-普朗克-克恩物理研究所-海德堡，粒子组成cnrs -气象动力学实验室-巴黎，气相水蒸气浓度；CNR -罗马大气科学研究所，气溶胶后向散射和去极化；哥本哈根丹麦气象研究所，气溶胶后向散射和微物理/中尺度模拟。在先前的支持下，这四种仪器，加上这项工作中使用的粒子计数器，已经集成到一个气球贡多拉上，它将同时测量PSC粒子的组成、浓度、大小、去极化、后向散射和水的气相浓度。这个贡多拉于2000年1月首次在北极飞行。这笔拨款将用这套独特的仪器完成另外四次北极PSC测量。两种仪器将用于测量12种粒径等级的凝结核和半径=0.15 - 10.0毫米的气溶胶的环境浓度。从这些测量可以估计大小分布。为了估计PSCs中冷凝硝酸和水的体积，将包括第二个气溶胶计数器来测量平流层气溶胶的本底。该仪器将配备一个入口加热器，以便在采样前将气溶胶暴露在250 K的入口壁温度下约0.1 s后进行采样。除了为联合测量提供气溶胶大小分布和浓缩体积的估计外，工作将继续侧重于通过比较我们的大小分布测量值与若干波长的原位光学散射测量值来推断粒子折射率的方法，这是成分的函数。由这些比较得出的粒子折射率估计将用于解释粒子组成测量。这些新的联合测量是继2000年1月这种仪器配置的首次成功测量之后进行的。2000年1月的测量构成了PSC内单个粒子组成的第一次直接测量，与气溶胶大小、浓度、相位和光学性质的表征一致。这些测量揭示了PSC是由层层液滴和层层硝酸水合物组成的。各种仪器在捕捉云的精细分层结构方面的一致性令人印象深刻。云层的许多层都符合我们对PSCs的热力学理解，同时观察到一些新的富含HNO3的粒子类型。

Deshler OPP-0095158A more complete quantitative understanding of polar stratospheric ozone loss requires further work in several areas. The microphysics of the nucleation, growth, composition, and sedimentation of particles in polar stratospheric clouds (PSCs) is one of these areas. PSC particles provide sites for the heterogeneous chemistry required to activate chlorine, which then destroys ozone. The pivotal role played by PSC particles is most evident in the Arctic where ozone loss is essentially modulated by temperature, a surrogate for PSCs, from year to year. The frequency, duration, and timing of PSC occurrence determines the extent of chlorine activation and denitrification in the stratospheric polar vortex, and thus the amount of ozone loss. Removing some of the present uncertainties concerning PSC formation temperatures, particle composition, and particle phase will permit more careful modeling of the amount of chlorine processed by PSCs and the extent of denitrification. The activation of chlorine and ultimately ozone loss is dependent on all of these factors.This work takes advantage of invitations from several European colleagues to collaborate on joint measurements of PSC particles during the winters of 2000/2001 and 2001/2002. The European institutions and their measurements are: Max-Planck-Institut fur Kernphysik - Heidelberg, particle composition CNRS-Laboratoire de Meteorologie Dynamique - Paris, gas phase water vapor concentration; CNR - Istituto di Fisica dell'Atmosfera - Rome, aerosol backscatter and depolarization; and Danish Meteorological Institute - Copenhagen, aerosol backscatter and microphysical/mesoscale modeling. Under previous support these four instruments, plus the particle counters used in this work, have been integrated onto one balloon gondola which will simultaneously measure, in situ, PSC particle composition, concentration, size, depolarization, backscattering, and gas phase concentrations of water. This gondola was flown for the first time in January 2000 in the Arctic.This grant will complete four more Arctic PSC measurements with this unique set of instruments. Two instruments will be used to measure the ambient concentration of condensation nuclei and of aerosol with radii =0.15 - 10.0 mm in 12 size classes. From these measurements size distributions can be estimated. To provide estimates of the volume of the condensed nitric acid and water in the PSCs, a second aerosol counter will be included to measure the background stratospheric aerosol. This instrument will be fitted with an inlet heater, thus sampling aerosol after they have been exposed to an inlet wall temperature of 250 K for ~ 0.1 s prior to sampling.In addition to providing aerosol size distributions and estimates of condensed volume for the joint measurements, the work will continue to focus on methods to infer particle index of refraction, which is a function of composition, through comparisons of our size distribution measurements with in situ optical scattering measurements at a number of wavelengths. Estimates of particle index of refraction which result from these comparisons will be used in the interpretation of particle composition measurements.These new joint measurements will follow the first successful set of measurements by this configuration of instruments in January 2000. The January 2000 measurements constituted the first direct measurements of single particle composition within a PSC, coincident with a characterization of aerosol size, concentration, phase, and optical properties. These measurements revealed a PSC composed of layers of liquid droplets interspersed with layers of nitric acid hydrates. The agreement amongst the various instruments in capturing the fine layered structure of the cloud was impressive. Many layers of the cloud fit well within our thermodynamic understanding of PSCs while some new HNO3 rich particle types were observed.