PIRE: International Partnership for Cirrus Studies

PI：伊丽莎白·莫耶(芝加哥大学)合作PI：Thomas Ackerman(华盛顿大学)Peter Blossey(华盛顿大学)Stephan Fueglistaler(普林斯顿大学)邝志明(哈佛大学)非技术摘要：热带地区覆盖着一层无处不在的薄薄的高海拔冰云(卷云)，它占据了大气中最冷、最不被理解的部分之一--热带对流层顶层或TTL。当空气通过TTL时，它会被低至零下75摄氏度(-100华氏度)的温度有效地冷冻干燥，并将其水蒸气留在身后，形成微小的冰晶，在几天到几周的时间尺度上慢慢沉淀下来。由于TTL的高度是大多数飞机飞行高度的两倍多，因此只能通过卫星上的遥感仪器或少数美国和欧洲的专业研究飞机进行研究。在过去的十年里，新的卫星测量颠覆了我们对TTL的有限理解，这些测量表明，TTL的冰晶层比之前想象的要密集得多，对地球辐射收支的影响也更大。一种可能的解释是，快速上升的热带雷暴将水直接带到TTL，影响了比预期更高的高度。该计划将汇集一个国际团队进行协调研究，以促进对这一重要自然现象的了解。国际合作伙伴是法国、德国和瑞士。该奖项由气候和大尺度动力学项目共同资助。技术摘要PERE研究团队将整合各种努力来解决一系列问题：在水分和能量预算方面，深对流如何影响TTL？卷云内的内部动力如何影响它们的特征和持久性？什么因素决定了卷云形成的地点、时间和方式？而卷云又是如何影响大规模环流的呢？这些问题需要单独但联系起来的建模练习来解决深对流、TTL卷云和全球环流，因为这些问题在规模上有很大的不同。我们将生成第一个热带范围的卷云模拟，它结合了对微物理、辐射和动力学之间相互作用的显式处理与真实地表示TTL的边界条件，并将使用它来评估对卷云特性的控制以及由此对全球大气动力学的影响。我们与欧洲合作者的伙伴关系对于整合观测尤为重要，欧洲合作伙伴将带头开发基于观测的TTL卷云特征气候学。该项目还旨在利用新的观测：将于2017年夏季对亚洲季风上空的卷云进行采样的高空StratoClim飞机活动，以及在德国卡尔斯鲁厄的AIDA气溶胶和云室进行的卷云形成实验室研究。

PI: Elisabeth Moyer (University of Chicago)co-PIs: Thomas Ackerman (University of Washington)Peter Blossey (University of Washington)Stephan Fueglistaler (Princeton University) Zhiming Kuang (Harvard University)Nontechnical Abstract:The tropics are blanketed with a ubiquitous layer of thin, high-altitude ice clouds (cirrus) that occupies one of the coldest and least-understood parts of the atmosphere, the "tropical tropopause layer" or TTL. As air ascends through the TTL, it is effectively freeze-dried by temperatures as low as -75 Celsius (-100 Fahrenheit), and leaves its water vapor behind as minute ice crystals that settle out slowly over timescales of days to weeks. Because the TTL lies over twice as high as most aircraft can fly, it can be studied only by remote-sensing instruments on satellites or by a handful of specialized U.S. and European research aircraft. In the last decade, our limited understanding of the TTL has been upended by new satellite measurements that suggest its ice crystal layer is significantly denser than had been previously thought, and with a stronger effect on the Earth's radiation budget. One potential explanation is that fast-rising tropical thunderstorms carry water directly to the TTL, influencing altitudes higher than had been expected. This PIRE program will bring together an international team for coordinated studies that will advance knowledge of this important natural phenomenon. The international partners are France, Germany and Switzerland. This award is co-funded by the Climate and Large-Scale Dynamics program.Technical AbstractThe PIRE research team will integrate efforts to address a series of questions: How does deep convection affect the TTL, in terms of moisture and energy budgets? How do internal dynamics within cirrus affect their characteristics and persistence? What factors determine where, when, and how cirrus forms? And how do cirrus in turn affect large-scale circulations? These questions require separate but linked modeling exercises addressing deep convection, TTL cirrus, and the global circulation, as the problems differ substantially in scale. We will generate the first tropics-wide cirrus simulation that combines explicit treatment of the interactions among microphysics, radiation and dynamics with boundary conditions that realistically represent the TTL, and will use it to evaluate both controls on cirrus properties and resulting consequences for global atmospheric dynamics. Our partnership with European collaborators is especially important for integrating observations, and European partners will lead in developing observation-based climatologies of TTL cirrus characteristics. The project is designed to also leverage off new observations: the high-altitude StratoClim aircraft campaign that will sample cirrus over the Asian Monsoon in summer 2017, and laboratory studies of cirrus formation conducted at the AIDA Aeorsol and Cloud Chamber in Karlsruhe, Germany.