PEM West B Trajectory Data

PEM-West-B_Trajectory_Data is the trajectory data collected during the Pacific Exploratory Mission (PEM) West B suborbital campaign. Data collection for this product is complete.

During 1983-2001, NASA conducted a collection of field campaigns as a part of the Global Tropospheric Experiment (GTE) for developing advanced instrumentation to quantify atmospheric trace gases’ sources, sinks, and distribution. Among those was PEM, which intended to improve the scientific understanding of human influence on tropospheric chemistry. Part of the PEM field campaigns (PEM-West) were conducted over the northwestern Pacific region, considered the only major region in the northern hemisphere that is “relatively” free from direct anthropogenic influences. PEM-West was a part of the East Asian/North Pacific Regional Study (APARE). The overarching objectives of PEM-West were 1) to investigate the atmospheric chemistry of ozone (O3) and its precursors over the northwestern Pacific, including the examination of their natural budgets as well as the impact of anthropogenic sources; and 2) to investigate the atmospheric sulfur cycle over the region with emphasis on the relative importance and influence of continental vs marine sulfur sources. The two phases of PEM-West were conducted during differing seasons due to contrasting tropospheric outflow from Asia. The first phase, PEM-West A, was conducted over the western Pacific region off the eastern coast of Asia from September-October 1991, a season characterized by the predominance of flow from mid-Pacific regions. The second phase, PEM-West B, was conducted from February-March 1994, a period characterized by maximum air mass outflow.

To accomplish its objectives, the PEM-West campaign deployed the NASA DC-8 aircraft across the northwestern Pacific to gather latitudinal, longitudinal, and vertical profile sampling, as well as extensive sampling in both the marine boundary layer and free troposphere. The aircraft was equipped with a comprehensive suite of in-situ instrument packages for characterization of photochemical precursors, intermediate products, and airmass tracers, including O3, nitric oxide (NO), peroxyacetyl nitrate (PAN), nitrogen oxides (NOy), nonmethane hydrocarbons (NMHCs), hydrogen peroxide (H2O2), acetic acid (CH3OOH), carbon monoxide (CO), and formaldehyde (CH2O). Collectively, these measurements enabled the analyses of the photochemical production/destruction of O3 and the distribution of precursor species. In addition, the DC-8 was equipped with instruments for collecting sulfur measurements, including dimethyl sulfide (DMS), carbonyl sulfide (COS), sulfur dioxide (SO2), and carbon disulfide (CS2). Instruments that collected aerosol composition and microphysical properties were also aboard the DC-8. Both missions deployed a Differential Absorption Lidar (DIAL) system for measurements of O3 vertical profiles above and below the aircraft. One highlight of the project was that flight nine of PEM-West A flew over Typhoon Mireille while it made landfall on the coast of Japan. This allowed for a flight by the DC-8 to study the role of typhoons in the transport of trace gases. Detailed descriptions related to the motivation, implementation, and instrument payloads are available in the PEM-West A overview paper and the PEM-West B overview paper. A collection of the publications based on PEM-West A and B observation are available in the Journal of Geophysical Research special issues: Pacific Exploratory Mission-West Phase A and Pacific Exploratory Mission-West, Phase B (PEM-West B).

PEM-West-B_Trajectory_Data 是太平洋探索任务（Pacific Exploratory Mission, PEM）西翼B次轨道任务期间收集的轨迹数据集。本数据集的数据采集工作已全部完成。1983年至2001年间，美国国家航空航天局（National Aeronautics and Space Administration, NASA）作为全球对流层实验（Global Tropospheric Experiment, GTE）的组成部分，开展了一系列野外科考任务，旨在研发先进观测仪器，以量化大气痕量气体的来源、汇与分布格局。其中，太平洋探索任务（PEM）旨在深化人类活动对流层化学影响的科学认知。PEM野外科考任务的分支项目PEM-West，在西北太平洋区域开展，该区域被认为是北半球唯一“相对”不受直接人为活动干扰的主要区域。PEM-West隶属于东亚/北太平洋区域研究（East Asian/North Pacific Regional Study, APARE）。PEM-West的总体目标分为两点：其一，探究西北太平洋区域臭氧（O₃）及其前体物的大气化学过程，包括分析其自然收支特征与人为源的影响；其二，研究该区域的大气硫循环，重点对比大陆硫源与海洋硫源的相对重要性及其调控作用。由于亚洲对流层大气流出的季节特征存在显著差异，PEM-West分为两个阶段，于不同季节开展。第一阶段PEM-West A于1991年9—10月在亚洲东海岸外的西太平洋区域开展，该时段的主导气流源自中太平洋区域。第二阶段PEM-West B则于1994年2—3月进行，此时段大气团流出强度达到峰值。为达成研究目标，PEM-West科考任务依托NASA DC-8型飞机在西北太平洋空域开展采样作业，覆盖纬向、经向与垂直剖面观测，并对海洋边界层及自由对流层进行了大范围采样。该飞机搭载了一套完整的原位仪器组件，用于表征光化学前体物、中间产物和气团示踪剂，涵盖臭氧（O₃）、一氧化氮（NO）、过氧乙酰硝酸酯（PAN）、总氮氧化物（NOy）、非甲烷烃（NMHCs）、过氧化氢（H₂O₂）、乙酸（CH₃OOH）、一氧化碳（CO）与甲醛（CH₂O）。上述多组分测量数据共同支撑了臭氧的光化学生成/销毁过程以及前体物分布特征的分析工作。此外，DC-8还搭载了用于硫组分检测的仪器，涵盖二甲基硫（DMS）、羰基硫（COS）、二氧化硫（SO₂）与二硫化碳（CS₂）。机上同时配备了用于采集气溶胶组成与微物理特性的观测仪器。两次任务均部署了差分吸收激光雷达（Differential Absorption Lidar, DIAL）系统，用于测量飞机上下方的臭氧垂直剖面。本项目的一项标志性成果是，PEM-West A的第9次飞行在台风米雷（Typhoon Mireille）登陆日本海岸期间飞越该空域，使得DC-8得以开展台风在痕量气体输送中作用的相关研究。关于项目的立项动机、实施细节与仪器载荷的详细说明，可参阅PEM-West A综述论文与PEM-West B综述论文。基于PEM-West A与B观测数据发表的论文合集，收录于《地球物理研究期刊（Journal of Geophysical Research）》特刊：《太平洋探索任务-西翼A阶段》与《太平洋探索任务-西翼B阶段（PEM-West B）》。