# CanESM5 COVID19 experiments
# ===========================
#
# Description:
# -----------
# This document describes customized climate model experiments
# that were run to quantify the impact of rapid reductions of CO2
# and aerosol emissions associated with COVID19. The experiments
# are described in the Fyfe et al. reference given below.
# 
# This data is generated and owned by CCCma, but it is made available
# under the Open Government License Canada:
#
# https://open.canada.ca/en/open-government-licence-canada
#
# If you intend to use this data you must attribute the data and 
# preferably collaborate with a CCCma scientist.
#
#
# The data are on the CCCma FTP server at:
#
# ftp://ftp.cccma.ec.gc.ca/pub/CCCMA/COVID19/
#
# Below this, the directory structure follows the CMIP6 convention. 
# Although these are not official CMIP6 experiments, we have created 
# a series of our own new experiment names with a format like:
#
# covid2019-[forcing]-[reduction]pct
#
# where [forcing] is "aer", "co2", "co2-aer", or "control" and [reduction] 
# is "100", "50", "25", "10" or "5". For each combination of these there are 
# 30 realizations, spanning at least 2019-2040, but for the control 2015-2040.
# These names represent the forcing and precentage of peak emissions reductions 
# (all applied over 2020 to 2022), and as described in Fyfe et al. (submitted). 
# So for example, phos for the 100% CO2 reduction experiment realization 1 would be found at:
#
# ftp://ftp.cccma.ec.gc.ca/pub/CCCMA/COVID19/pub/CCCMA/COVID19/CMIP6/CCCma/CCCma/CanESM5/\
#  covid2019-co2-100pct/r1i1p2f1/Omon/phos/gn/v20190429/phos_Omon_CanESM5_covid2019-co2-\
#  100pct_r1i1p2f1_gn_201901-204012.nc
#
# There are 16 experiments, 30 realization per experiment, 2 variables per realization 
# for a total of 960 expected files and about 50 GB of data. This script will retrieve them all.
#
# There are actually currently 491 files, because one experiment/realization 
# (covid2019-co2-5pct_r5i1p2f1) was not properly concatenated, so the files are in individual 
# years not a single chunk, which will be fixed in due course.
#
# Note on realizations:
# -------------------
#
# - all versions bear the variant label "p2", because this is the p2 variant of the model, 
#   as described here: https://gitlab.com/cccma/canesm/-/wikis/CanESM5-variants-p1-and-p2
#
# - 30 realizations are denominated using the "r" variant label, but all realizations are 
#   not created equal. In general, the first 5 realizations are fully independent (macro 
#   initialization from 50 year separations in the "p2" piControl), members 6-15 were 
#   macro-intialized, but from the "p1" piControl (very similar climate), while the remaining 
#   15 were started from the same restart as the first 15, but initialized via a 
#   micro-intialization procedure perturbing the random number generator for cloud physics in year 2015.
#
# Reference:
# Quantifying the Influence of COVID-19 Emission Reductions on Climate
#
# John C. Fyfe, Viatcheslav V. Kharin, Neil Swart, Gregory M. Flato, Michael
# Sigmond and Nathan Gillett
#
# Contact:
#
# neil.swart@canada.ca