PHILEAS (Probing high latitude export of air from the Asian summer monsoon)

费城(探测亚洲夏季风的高纬度输出空气)北半球夏季的亚洲季风反气旋(AMA)被认为是对流层气团进入UTLS的主要途径，其中含有丰富的水汽、气溶胶前体和污染物。最近的观测表明，AMA的硝酸铵输送对UTLS气溶胶收支和亚洲对流层顶气溶胶层(ALAL)有很大贡献，这可能与卷云的形成有关。最近的飞机战役可能会表征AMA内部的组成和气溶胶含量，或者将在直接附近进行测量。相比之下，与季风相关的气团对全球北半球的影响在之前的光晕任务中已经观察到了。然而，一项关于AMA气团向北部最低平流层(LMS)的转变及其对气溶胶处理和化学成分的影响的研究仍然缺乏。在HALO任务TACTS/ESMVal和WISE期间，发现中北部太平洋是这一过渡的关键区域。观测和模式模拟表明，所谓的涡旋脱落输送对北半球UTLS有很强的增湿作用。这些涡旋构成了孤立的动力异常，它们与AMA分离，并开始与背景流一起移动。最初，各自的化学异常相对孤立地存在于落水涡中。动力和非绝热强迫导致这些孤立的异常随后被侵蚀，并混合到背景平流层中。此外，太平洋上空UTLS痕量气体的组成还受到夏末和秋季其他路径的影响：1)副热带急流的准水平输送；2)热带台风最终移向温带外的对流输送；3)热带外天气系统内的输送。这些综合过程影响了北太平洋UTLS的组成。我们将调查这些过程对UTLS的化学、气相和气溶胶成分的相对重要性。我们将特别研究季风反气旋在过渡到太平洋平流层时所释放出的细丝的动力学和化学演化，以估计它们对LMS北部气相和气溶胶成分的影响。总结起来，有三个主要的公开科学问题推动了菲利亚斯计划。1)路径是什么，从亚洲夏季风到温带UTLS的大气质量输送的时间尺度和动力学过程？2)季风反气旋脱落的大尺度涡流中气相和颗粒成分是如何演变的？3)季风脱落的涡旋如何影响温带外LMS的组成，特别是水汽和辐射活性物质？

PHILEAS (Probing high latitude export of air from the Asian summer monsoon)The Asian monsoon anticyclone (AMA) during northern summer is thought to be the major pathway for tropospheric air masses, rich in water vapour, aerosol precursors and pollutants, into the UTLS. Recent observations show evidence for a strong contribution of ammonium nitrate transport by the AMA to the UTLS aerosol budget and the Asian Tropopause Aerosol Layer (ATAL), likely relevant for cirrus cloud formation. Recent aircraft campaign could characterize the composition and aerosol content of the interior AMA or will measure in the direct vicinity. In contrast, the impact of the monsoon related air masses on the global northern hemisphere has been observed during previous HALO missions. However, a study focusing on the transition of the AMA air masses into the northern lowermost stratosphere (LMS) and its consequences for aerosol processing and chemical composition is still missing. During the HALO missions TACTS/ESMVal and WISE it turned out, that the northern central Pacific is a key region for this transition.Observations and model simulations suggest a strong moistening effect of the so-called eddy shedding transport on the northern hemisphere UTLS. These eddies constitute isolated dynamical anomalies which are detached from the AMA and start to travel with the background flow. Initially, the respective chemical anomalies are relatively isolated within the shed eddy. Dynamical and diabatic forcings lead to a subsequent erosion of these isolated anomalies and mixing into the background stratosphere. Furthermore, the UTLS trace gas composition over the Pacific is affected by additional pathways in late summer and autumn: i) quasi-horizontal transport across the subtropical jet ii) convective transport by tropical typhoons eventually moving towards the extratropics, and iii) transport within extratropical weather systems. These combined processes impact the composition of the UTLS over the northern Pacific. We will investigate the relative importance of these processes contributing to the chemical gas-phase and aerosol composition of the UTLS. We will particularly characterize the dynamical and chemical evolution of the filaments formerly shed from the monsoon anticyclone during their transition into the stratosphere over the Pacific to estimate their impact on the overall gas phase and aerosol composition of the northern LMS.Summarizing, there are three major open scientific questions that motivate the PHILEAS project.1) What are the pathways, time scales and dynamical processes of air mass transport from the Asian summer monsoon into the extratropical UTLS?2) How do gas-phase and particulate constituents evolve in large-scale eddies which are shed from the monsoon anticyclone?3) How does eddy shedding from the monsoon impact the extratropical LMS composition in particular the water vapor and radiatively active species?