CEDAR: Polar Mesospheric Clouds Using the Whole Atmosphere Community Climate Model 3

该项目将把全球模拟与极地中间层云(PMC)的地面和卫星观测相结合，以研究极地中间层云的形成、增长和消散机制。PMCs在阈值温度和水汽压下发生，并随着温度的降低呈指数增长，提供了对中间层条件高度敏感的指标。人为输入，包括航天飞机废气中的水蒸气，以及大气中甲烷和二氧化碳的长期增加，被认为是最近出现这些云(自1885年以来每年夏天都能观察到，但以前从未出现过)的原因，预计会导致它们的亮度和发生的长期变化。由于巨大的自然变异性，目前是否观察到了这种长期变化是一个有争议的问题。对PMC发生和亮度的自然影响包括太阳周期、火山喷发和动力扰动。这项提议的目标是将PMC和硫酸盐气溶胶微物理纳入贯穿中间层的全球化学气候模式，并调查火山扰动和航天飞机废气对PMC形成的影响。实现这些目标将有助于今后研究人为影响、太阳可变性、火山硫酸盐气溶胶和动力学的单独和耦合影响。这项工作将利用国家大气研究中心(NCAR)全大气社区气候模式3(WACCM3)，重点是通过与地面和卫星数据的比较来验证模型中的中间层动力学和化学。该项目是目前合作努力的继续，目的是将包括硫酸盐气溶胶和极地平流层云在内的多种气溶胶类型的微物理纳入WACCM3模式。特别令人感兴趣的是对最近关于中间层硫酸盐气溶胶层存在的一个假说的调查。这种新的PMC核来源解释了1991年Mt喷发后PMC发生率急剧下降的原因。皮纳图博。具有微观物理的WACCM3将在包括和不包括火山投入的情况下运行，以更好地了解每种投入对PMC变异性的影响。这将是第一次使用交互动力学和化学对PMC进行三维微观物理建模，从而能够进一步研究自然和人为对云的影响。该项目的更广泛影响包括它将促进的网络和伙伴关系、成果的广泛传播、公众宣传和对社会的好处。该项目将通过为研究生提供学习高层大气的机会来整合研究和教育。这项工作将是最近建立的一个项目的一部分，在该项目中，许多科学家和学生正在学习WACCM模型，以便与NCAR的科学家合作，将其应用于各种科学问题。将PMC微物理学纳入WACCM3将为高层大气研究界提供一个新的工具，使科学家能够更准确地测试PMC形成和演化的理论，解释观测结果，并了解中间层的变化和与较低海拔的耦合。将开发网站，描述目前对私营军校和全球变化的了解，面向学生和普通公众。

This project will combine global modeling with ground-based and satellite observations of polar mesospheric clouds (PMCs) to investigate formation, growth, and dissipation mechanisms of the clouds. PMCs occur at a threshold temperature and water vapor pressure and grow exponentially with reduced temperatures, providing highly sensitive indicators of mesospheric conditions. Anthropogenic inputs, including water vapor from space shuttle exhaust and long-term increases in atmospheric methane and carbon dioxide, are suggested causes for the recent appearance of these clouds (observed every summer since 1885, but never prior) and are predicted to produce long-term changes in their brightness and occurrence. Whether such long-term changes have yet been observed is a question currently debated, due to large natural variability. Natural influences on PMC occurrence and brightness include the solar cycle, volcanic eruptions, and dynamical perturbations. The goals of this proposal are to incorporate PMC and sulfate aerosol microphysics into a global chemistry climate model extending through the mesosphere and to investigate the influences of volcanic perturbations and space shuttle exhaust on PMC formation. Attainment of these goals will facilitate future investigations of the separate and coupled effects of anthropogenic influences, solar variability, volcanic sulfate aerosol, and dynamics. The work will utilize the National Center for Atmospheric Research (NCAR) Whole Atmosphere Community Climate Model 3 (WACCM3), with substantial focus on validating mesospheric dynamics and chemistry in the model via comparisons with ground-based and satellite data. The project is a continuation of current collaborative efforts to incorporate microphysics for a number of aerosol types, including sulfate aerosol and Polar Stratospheric Clouds, into the WACCM3 model. Of particular interest is investigation of a recent hypothesis on the existence of a mesospheric sulfate aerosol layer. This new source of nuclei for PMCs explains the dramatic decrease in PMC occurrence following the 1991 eruption of Mt. Pinatubo. WACCM3 with microphysics will be run with and without inclusion of volcanic input to better understand the influence of each on PMC variability. This will be the first time PMCs have been modeled microphysically in three dimensions with interactive dynamics and chemistry, enabling further study of natural and anthropogenic influences on the clouds. The broader impacts of the project include the networks and partnerships it will foster, the broad dissemination of results, public outreach, and benefits to society. The project will integrate research and education by offering graduate students opportunities to study the upper atmosphere. This work will be part of a recently instituted program in which a number of scientists and students are learning the WACCM model so that it can be applied to the various scientific issues, in collaboration with scientists at NCAR. Incorporation of PMC microphysics into WACCM3 will provide a new tool to the upper atmospheric research community, enabling scientists to more accurately test theories about PMC formation and evolution, interpret observations, and understand mesospheric change and coupling to lower altitudes. Websites will be developed to describe current understanding regarding PMCs and global change, aimed at both students and the general public.