Dynamical Variability of the Lower Atmosphere

Metadata record for data from AAS (ASAC) Project 3140 See the link below for public details on this project. Public Summary A thorough understanding of the coupling and dynamics of the Antarctic lower atmosphere is critical for understanding how it will respond to climate change. However, this region of the atmosphere has not been studied in sufficient detail. Energy and momentum are redistributed in the atmosphere by large scale planetary waves and small scale gravity (buoyancy) waves. By combining the high-resolution instruments from Davis with global satellite observations, these waves and their effect on the atmosphere will be understood. Results from this project will be of value to modellers for improving global climate models. Project objectives: This project will study the variability, dynamics and coupling of the Antarctic lower atmosphere. The objective is to determine some of the most important and urgently needed information for global climate models by examining high-resolution observational datasets. Areas where understanding is limited and need to be improved include the effects of atmospheric gravity (buoyancy) waves on the lower atmosphere and their relation to the cold biases observed in the polar stratospheres of models (Sato and Yoshiki, 2008), determining critical wave parameter information (Alexander et al., 2008a), and studying troposphere - stratosphere coupling, particularly in relation to the polar night jet (e.g. Baumgaertner and McDonald 2007, Hei et al 2008). In order to achieve this, data which are collected at Davis as part of the current ASAC projects: a) the lidar - project 737 (Klekociuk et al. 2003) and b) the VHF MST radar - project 2325 (Morris et al. 2006) will be analysed. These results will be combined with data collected by the Bureau of Meteorology (radiosondes and ozonesondes launched at Davis) and various satellites including the CHAMP (Challenging Minisatellite Payload) and COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) GPS radio occultation experiments (Alexander et al. 2008c). The multi-year ground-based observational records at Davis collected by the lidar and radar will be used to study the spatial and temporal variability of gravity waves in the troposphere and stratosphere over a wide range of scales. Waves and their sources will be identified and quantified. Such sources include the stratospheric polar night jet, orographic waves, tropospheric weather frontal systems and storms. The lidar and radar data will be combined with ozonesonde and radiosonde data from routine Bureau of Meteorology flights made at Davis for studies of stratosphere-troposphere interactions, dynamics, mixing, folding and mass transport across the tropopause. Satellite-based data, including those made by GPS radio occultation, will be used to set the Davis results into a regional and global scale context. The energy and momentum of small-scale gravity waves and large scale planetary waves will be examined. In particular, the stratospheric polar night jet will be studied to investigate wave generation and upward and downward propagation and understand how the downward propagating waves affect the troposphere. This project will establish a world-wide reputation for AAD as providing leading-edge studies, analysis and interpretation of the dynamic variability of the Antarctic lower atmosphere. Taken from the 2009-2010 Progress Report: Progress against objectives: Gravity wave activity associated with both the Antarctic and Arctic polar stratospheric vortices has been quantified using COSMIC GPS satellite data (Alexander et al. 2009). The high resolution nature of these data allowed information on regional scales and short duration wave processes to be identified and quantified. In particular, large intermittent bursts of orographic wave activity were identified above the Antarctic Peninsula. This has led to a continuing investigation of the effect of these waves on Polar Stratospheric Clouds (PSCs) by incorporation of CALIPSO satellite lidar data and MLS trace gas observations, both from the lower stratosphere. Foundations for this PSC / wave interaction were laid with work completed during the first year of project 3140, i.e. both the gravity wave analysis of Alexander et al (2009) and the planetary wave results of Alexander and Shepherd (2010). Lidar temperature data obtained in the upper troposphere - lower stratosphere (UTLS) region have been analysed and in particular one case study of a stratospheric intrusion during May 2008 has been identified and studied in detail. With the addition of satellite and radiosonde data, the lidar results are allowing quantification of small scale gravity wave parameters as the passage of a large scale planetary wave results in irreversible mixing of stratospheric air into the troposphere. Further UTLS experiments were run during winter 2009 by the chief investigator, thus allowing a statistical analysis of these events to be conducted in the future. A comparison between MST radar tropospheric winds and radiosonde winds revealed issues in the MST data which are still being addressed before these data become ready to use.来自AAS（ASAC）项目3140的数据集元数据记录 有关该项目的公开详情，请参阅下方链接。 公开摘要 深入理解南极低层大气的耦合机制与动力学特征，是明晰其如何响应气候变化的关键前提。但目前学界对该大气区域的研究尚不够充分细致。大气中的能量与动量，通过大尺度行星波与小尺度重力（浮力）波实现再分配。通过将戴维斯站（Davis）的高分辨率观测仪器数据与全球卫星观测数据相结合，本研究将厘清此类波系及其对大气的影响机制。本项目的研究成果，将为全球气候模型开发者优化模型提供重要参考。 项目目标 本项目将围绕南极低层大气的变异性、动力学特征与耦合机制展开研究。项目目标为：通过分析高分辨率观测数据集，获取全球气候模型开发亟需的关键信息。当前认知不足亟待完善的研究方向包括：大气重力（浮力）波对低层大气的影响及其与模型极地平流层冷偏差的关联（Sato与Yoshiki，2008）、关键波参数信息的确定（Alexander等，2008a），以及对流层-平流层耦合机制，尤其是与极夜急流相关的耦合过程（例如Baumgaertner与McDonald，2007；Hei等，2008）。 为达成上述目标，本项目将分析戴维斯站作为现有ASAC项目一部分所采集的数据：其一为激光雷达（lidar）相关数据（项目737，Klekociuk等，2003），其二为甚高频MST雷达（VHF MST radar）相关数据（项目2325，Morris等，2006）。研究团队还将结合澳大利亚气象局（Bureau of Meteorology）在戴维斯站施放的无线电探空仪（radiosonde）与臭氧探空仪（ozonesonde）数据，以及包括挑战型小卫星有效载荷（Challenging Minisatellite Payload，CHAMP）与气象、电离层与气候星座观测系统（Constellation Observing System for Meteorology, Ionosphere and Climate，COSMIC）GPS无线电掩星实验在内的多颗卫星观测数据（Alexander等，2008c）。 研究团队将利用激光雷达与雷达在戴维斯站采集的多年地基观测记录，分析多尺度范围内对流层与平流层内重力波的时空变异性。研究人员将对各类波系及其源区进行识别与量化分析。此类源区包括平流层极夜急流、地形重力波、对流层天气锋面系统与风暴系统。研究团队还将结合戴维斯站常规气象探空任务获取的臭氧探空与无线电探空数据，开展平流层-对流层相互作用、动力学过程、混合作用、折叠现象以及对流层顶跨区物质输送等相关研究。 基于卫星的观测数据（包括GPS无线电掩星数据）将用于将戴维斯站的观测结果置于区域与全球尺度的框架下进行分析。研究人员将对小尺度重力波与大尺度行星波的能量与动量分布展开分析。其中，将重点研究平流层极夜急流，以厘清波系的生成、向上与向下传播机制，并解析向下传播的波系如何对对流层产生影响。 本项目将助力AAD在南极低层大气动力学变异性的前沿研究、分析与解读领域建立全球声誉。 数据来源于2009-2010年度进展报告： 项目目标完成进展 研究团队利用COSMIC GPS卫星数据，对南极与北极极地平流层涡旋相关的重力波活动进行了量化分析（Alexander等，2009）。得益于此类数据的高分辨率特性，研究人员得以识别并量化区域尺度与短时程的波系过程信息。尤为重要的是，研究团队在南极半岛上空识别出间歇性大规模地形重力波活动事件。基于此，研究团队结合CALIPSO卫星激光雷达数据与低平流层微波临边探测器（Microwave Limb Sounder，MLS）痕量气体观测数据，持续开展此类波系对极地平流层云（Polar Stratospheric Clouds，PSCs）影响的相关研究。项目3140第一年完成的研究工作（包括Alexander等2009年的重力波分析与Alexander及Shepherd 2010年的行星波研究成果），为极地平流层云与波系相互作用的研究奠定了基础。 研究团队对对流层上层-平流层下层（upper troposphere - lower stratosphere，UTLS）区域获取的激光雷达温度数据进行了分析，其中针对2008年5月的一次平流层侵入事件开展了详细的案例研究。结合卫星与无线电探空数据后，激光雷达观测结果可用于量化小尺度重力波参数——大尺度行星波过境时，平流层空气会不可逆地混合进入对流层。首席研究员于2009年冬季开展了额外的UTLS观测实验，为后续开展此类事件的统计分析提供了条件。对MST雷达对流层风场与无线电探空风场的对比分析发现，MST雷达数据存在部分问题，目前仍在修复以确保数据可正式投入使用。