Precipitation Driver and Response
Model Intercomparison Project
(PDRMIP)
Introduction
PDRMIP is an international effort to compare the changes in precipitation predicted by global climate
models. The project is led by CICERO and the participants of the present application, and supported
by the Research Council of Norway through the NORKLIMA project NAPEX.
This application requests allocation of computing resources to complete a series of simulations of
precipitation response to various climate drivers, using the NCAR CESM1 Earth System Model.
NCAR CESM1 is already running and performing well on abel, where we request resource allocation.
The participants are experienced users of HPC in general, and abel in particular, and have previously
utilized NOTUR resources e.g. through grants nr nn9188k and nn4701k.
This NOTUR application for CPU resources is accompanied by a related NORSTORE application for
storage of climate data from a range of groups.
Project description
Background
Precipitation is arguably the most direct link between the climate and human society. We depend
upon existing precipitation patterns for fresh water and food production, and global infrastructure is
designed to withstand current precipitation extremes. The future scenarios of precipitation changes
from global climate models do not agree very well on global nor regional scale.
However, recent studies have shown that precipitation changes from particular drivers of climate
change (such as greenhouse gases and various aerosol types) have evident similarities. A main
hypothesis of the PDRMIP project is that differences in anthropogenic and natural drivers of climate
change, both with regard to distribution and strength, is a crucial factor in the differences in the
precipitation response in current global climate models.
In PDRMIP, 5-10 major climate models will perform unified experiments, using common scenarios
and a standardized output. This output will be made freely available to the scientific community, to
encourage participation from other international modelling groups. PDRMIP is funded by the
Research Council of Norway, through the project NAPEX.
Simulations to be performed
CICERO will, amongst other things, provide output from the NCAR Community Earth System Model
(CESM1.03) for PDRMIP. As the leading institution in the project, we are also tasked with testing the
scenarios before they are implemented by the other models.
For the first phase of PDRMIP, twelve climate scenarios have been agreed on. For each of these, two
model configurations are needed – one that only investigates the atmospheric response while
keeping sea temperatures unchanged (fixed-SST runs), and one that allows the ocean to respond
dynamically to atmospheric changes (fully coupled runs).
The scenarios include changes in greenhouse gases (CO2 and methane), changes in solar insolation,
and a series of changes to aerosol concentrations. The fixed-SST runs need only 15 years of model
simulations per scenario, while the fully coupled runs require the aggregation of 100 years each to be
able to average out natural variability and also to study changes in extreme precipitation.
Expected project deliverables
The goal of PDRMIP is to contribute to the understanding of future climate change at the forefront of
international research. The participating groups each run and/or maintain a state-of-the-art climate
model, and are heavily involved in other ongoing model intercomparison projects such as CMIP and
GeoMIP.
PDRMIP will publish a series of papers in international journals, building on existing work from all
groups. In addition, the NAPEX project plans science outreach activities in Norway, through blogs,
newspaper articles and opinion pieces, that will be based on the results from PDRMIP.
Estimated CPU requirement
On the present abel configuration, CESM1.03 normally runs on 64 CPUs in parallel, simulating 10
model years per 24h of walltime. I.e. the model uses approx. 24*64/10 = 150 CPU hours per
simulated year.
We need 115 model years per case, for an estimated 20 cases, which gives a total abel CPU hour
requirement of ~350.000.
Similar estimates were used as a base for the project nn9188k, and found to be quite accurate. The
allotted CPU hours for that project were well utilized.
Current internal project members
Name
Position
Gunnar Myhre
Senior research fellow (CICERO)
Bjørn H. Samset
Senior research fellow (CICERO)
Øivind Hodnebrog
Senior research fellow (CICERO)
Jana Sillmann
Senior research fellow (CICERO)/
Researcher (UiO)