NERSC Initiative for Scientific Exploration (NISE) 2011 Awards

High resolution integration of CAM5 for extreme weather research

Michael Wehner, Lawrence Berkeley National Lab

Associated NERSC Project: Program for Climate Model Diagnosis and Intercomparison (mp193)
Principal Investigator: James Boyle, Lawrence Livermore National Lab

We propose to perform an AMIP simulation of the latest version NCAR Community Atmospheric Model (CAM5.1) at very high resolution. We have recently completed a 1 year simulation on hopper of this model at a horizontal resolution of approximately 25km. Our plans for this version of the code are extensive and later proposals for computer resources will be much larger. With this request, we want to perform a simulation of the recent past (1979-2009). Following the AMIP protocol, the sea surface temperature and sea ice concentration are specified from observations as lower boundary conditions to the atmosphere. The purpose of this simulation will be characterize the model's performance in simulating the recent past prior to making projections about future climate change. We will diagnose the model against available atmospheric observations. These will include but are not limited to surface air temperature, precipitation, mean sea level pressure, cloudiness and radiative balance. Our principal interest in high resolution models is the simulation of extreme weather events, especially precipitation, and how they may change as the climate warms. Our previous work has focused on heat waves, droughts, floods and most immediate to this project, tropical cyclones and hurricanes. This simulation will be benchmarked against observational measures of all these events. In addition, we have new capabilities in CRD to analyze atmospheric rivers. Sometimes called the "Pineapple Express", these huge excursions of tropical moisture into the extratropics are the source of major warm winter storms to the US west coast. Our preliminary analysis reveals a surprising amount of realism in the simulation of these events and the model will enable much greater understanding of how these patterns form than do the limited observations.

There is great internal and external interest in this simulation. Although our results are only one week old, we already have solicitations of data from LBNL's Earth Systems Division, NCAR, LLNL, and Princeton. We view the model output data as a public resource and will share it freely. We anticipate that we will distribute the data to the public as part of the CMIP5 and the Earth System Grid (hosted at NERSC). It is hard to estimate the number of papers that will come out of this simulation (and the later future projection simulations), but it will be many. We are confident that these simulations will be of high impact and policy relevant.

This simulation is a necessary step in increasing confidence in the projection of future changes in extreme weather. We will gain insight into hurricanes, severe storms and heat waves. The high fidelity of the simulation will aid policymakers in decisions on a much more local scale than is possible from previous climate model simulations.