This dataset contains summary 3-year time-integrated data of the global mean volcanic stratospheric aerosol optical depth, effective radiative forcing and anomalous deposited sulfate on Antarctica and Greenland. The data are from 82 model simulations of volcanic eruptions that have different sulfur dioxide emissions, eruption latitudes and emission altitudes. Two ensembles were conducted for eruptions starting in January and July. Each simulation was run for ~3 years in a year 2000 timeslice condition. The simulations are from the Unified Model coupled with the United Kingdom Chemistry and Aerosol Scheme (UM-UKCA) and were conducted at a global resolution of 1.875 ° x 1.25°. This data were collected as part of the NERC Reconciling Volcanic Forcing and Climate Records throughout the Last Millennium (Vol-Clim) project. V3 is the latest data file to use.

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.