Lagrangian Dry Point data regarding the sensitivity of stratospheric water vapour to variability in tropical tropopause temperatures and large-scale transport

This dataset contains results in support of a publication that investigates processes affecting water vapour entry to the stratosphere. The back trajectories were calculated using the OFFLINE trajectory model. Past publications have shown the key processes are temperatures in the tropical tropopause layer and large-scale transport into the stratosphere using trajectory methods. Lagrangian Dry Points (LDPs) are normally calculated as the minimum water vapour saturation mixing ratio experienced along a back-trajectory that has traversed from troposphere to tropical lower stratosphere in its recorded history. This study separated the two key processes by sampling alternative temperatures. These alternative temperatures are either time-shifted or averaged in time or longitude. This method is applied for two meteorological datasets: ERA-Interim (ERA-I) reanalysis for the period 1999-2009, and the UM-UKCA chemistry-climate model for eleven years of a repeat-year-2000 forcing scenario. The ERA-I trajectories were calculated by S Fueglistaler and S Liu for separate publications. The UM-UKCA climate model scenario was conducted by A Maycock. This dataset contains only the LDPs resulting from alternative-temperature sampling. The directory UM-UKCA/LDP-original-T/ provides a simple view of the original unmodified method to calculate LDPs. LDP-alt-T/ directories contain LDPs determined with time-shifted alternative temperature samplings. The time-shift is identified by the alternative initialisation date, denoted in the filename and file metadata. LDP-ave-T/ directories contain LDPs determine with averaged alternative temperature samplings. The averaging is identified by the variable name and metadata. In the variable names, shorthand and full-name identifiers include 6h (6 hourly instantaneous), ZM (zonal mean), 30DZM (30-day rolling window mean and zonal mean), 120DM, 90DM, 60DM, 30DM, 15DM, 14DM, 8DM, 7DM, 4DM, 2DM, 1DM (rolling window 120 day mean, 90 day mean, etc.). Note that various alternative temperatures are recorded at each LDP calculated from each alternative temperature. For more information on the directory structure, file naming conventions, variable naming conventions and attribute conventions please see the README.txt.

本数据集包含支撑一项学术出版物的研究结果，该研究探究了影响水汽进入平流层的各类物理过程。研究采用离线轨迹模型（OFFLINE trajectory model）计算了后向轨迹。过往研究已表明，核心过程包括热带对流层顶（tropical tropopause layer, TTL）的温度场，以及通过轨迹方法实现的向平流层的大尺度输送过程。拉格朗日干燥点（Lagrangian Dry Points, LDPs）的常规计算方式为：在一条从对流层出发、经历史轨迹抵达热带低平流层的后向轨迹上，取水汽饱和混合比的最小值作为LDPs。本研究通过对备选温度进行采样，实现了对上述两类核心过程的分离。这些备选温度可按时间偏移、时间平均或经度平均的方式生成。本方法应用于两类气象数据集：1999年至2009年的ERA-Interim（ERA-I）再分析资料，以及采用2000年重复强迫情景运行11年的UM-UKCA化学气候模式（UM-UKCA chemistry-climate model）。ERA-I的后向轨迹由S Fueglistaler与S Liu为其各自的学术出版物计算完成。UM-UKCA化学气候模式的该强迫情景由A Maycock完成构建。本数据集仅包含通过备选温度采样得到的LDPs。UM-UKCA/LDP-original-T/ 目录直观展示了计算LDPs的原始未修改方法。LDP-alt-T/ 目录包含通过时间偏移型备选温度采样得到的LDPs，该时间偏移量可通过备选初始日期识别，相关信息标注于文件名与文件元数据中。LDP-ave-T/ 目录包含通过平均型备选温度采样得到的LDPs，该平均方式可通过变量名与元数据识别。变量名中的简写与全称标识符包括：6h（6小时间隔瞬时值）、ZM（纬向平均，zonal mean）、30DZM（30天滑动窗口平均加纬向平均）、120DM、90DM、60DM、30DM、15DM、14DM、8DM、7DM、4DM、2DM、1DM（分别对应120天、90天等滑动窗口平均）。需注意：针对每一种备选温度计算得到的每个LDP，均会记录多种备选温度数据。若需了解更多关于目录结构、文件命名规范、变量命名规范与属性规范的细节，请参阅README.txt文件。