CSL Allocations 2012

The following projects received CSL allocations for September 2012 to February 2014.

Atmosphere-ocean coupling causing ice-shelf melt in Antarctica

Project lead: David Bromwich, Ohio State University
Yellowstone allocation: 10.2 million core-hours
Sponsor: NSF

Understanding the mass balance of the Antarctic ice sheet is critical for projecting global sea-level change. Antarctica provides key climate records through deep ice cores, one of which is currently being extracted in West Antarctica. The Antarctic Ice Sheet also responds to climate phenomena with signatures on the decadal time scale, such as the El Niño-Southern Oscillation, the Southern Annular Mode, and the Pacific Decadal Oscillation. Important mesoscale phenomena in the atmosphere and ocean deliver heat to the bottom of the floating Antarctic ice shelves, such as those in the Amundsen Sea embayment. Therefore, a mesoscale approach is required to treat the system processes that melt Antarctic ice shelves. This project will combine a team of researchers to develop and couple a system model for the Antarctic with a regional scale emphasis. The coupled atmosphere-ocean-sea ice-ice shelf model will allow researchers to understand past decadal variability influences on melting ice shelves, as well as projecting the future impacts. The component system models include the polar-optimized version of the Weather Research and Forecasting model (Polar WRF) for the atmosphere. The ocean component will be the Regional Ocean Modeling System (ROMS), and the sea ice component will be the Los Alamos sea ice model (CICE). A thermodynamic ice shelf model that is already part of ROMS will be applied. Retrospective decadal simulations will be done to understand past variability. Downscaled future projections for Antarctica will be driven by the global National Center for Atmospheric Research (NCAR) Community Climate Model’s (CCSM) IPCC 5th Assessment simulations.

Intraseasonal to interannual prediction and predictability in a changing climate

Project lead: Benjamin Cash, Center for Ocean-Land-Atmosphere Studies (COLA)
Yellowstone allocation: 31 million core-hours
Sponsor: NSF

The numerical experiments proposed here are designed to assess the impact of (a) eddy-resolving ocean models and (b) empirical correction of a dominant mode of variability (the MJO) on intraseasonal to interannual prediction skill and predictability. The impact of these two approaches to improving model performance will be examined both separately and in conjunction. Evidence from prior studies indicates that increased resolution impacts the air-sea coupling globally, the magnitude of ENSO and associated teleconnections, and the model climatology. However, we do not have any assessment to date of how this increased resolution affects predictability and prediction, particularly regional features that are driven by the large-scale variability. Similarly, while there is evidence from observations that the state of the MJO predisposes the general circulation towards a given phase of the NAO, among other impacts, it remains to be determined whether or not that predictability can be realized by current climate models. The experiments proposed here include (i) control integrations, (ii) prediction experiments (initialized and compared with observed), and (iii) predictability experiments (initialized and compared with simulations). All experiments for which resources are requested here are designed to take advantage of output and expertise from complementary experiments that have been completed or are in progress using other resources.

Community Earth System Model project

Project lead: Marika Holland, NCAR
Yellowstone allocation: 140 million core-hours
Sponsors: NSF, DOE

The Community Earth System Model (CESM) project is a true community effort including collaboration with scientists from universities, national laboratories, and other research organizations to develop, continuously improve, and support the scientific use of a comprehensive Earth modeling system. The continued development and application of this modeling system has been facilitated largely through access to Climate Simulation Laboratory (CSL) computational resources. The CESM and its predecessor, the Community Climate System Model (CCSM), have been at the forefront of international efforts to understand and predict the behavior of Earth's climate, with model output used in many hundreds of peer-reviewed studies to better understand the processes and mechanisms responsible for climate variability and change. Here we request resources for continued development and application of the CESM modeling system, categorized as development and production simulations. The overarching development priorities for the project include the following themes: (1) improved coupling across components and understanding interactions; (2) incorporation of new parameterizations and processes; (3) advances in high-resolution simulation and new dynamical cores; (4) addressing CESM biases and other known shortcomings; and (5) software development. Resources for production simulations are requested to address the following broad themes: (1) contributions to nationally or internationally coordinated modeling and assessment activities; (2) benchmark simulations that document components and new capabilities of CESM; (3) climate variability assessment; (4) climate change characterization and detection/attribution: and (5) interannual to decadal prediction experiments. The simulations requested here will be used in numerous scientific applications by a broad research community.

A 60-year forced global 0.1-degree ocean/sea-ice simulation using CESM

Project lead: Julie McClean, Scripps Institution of Oceanography
Yellowstone allocation: 10 million core-hours
Sponsor: DOE

Climate change signals over the past decades have been amplified in high latitudes; the dramatic reduction of summer Arctic sea ice cover is a striking example. The problem of predicting climate change has therefore become compelling due to the need to understand the impact of near-term trends in the climate state both globally and regionally. Next-generation Earth System Models (ESMs) are expected to predict changes that result from the combination of anthropogenic climate change forcing, primarily from increasing greenhouse gases and aerosols, and decadal and longer-scale natural variability. Fine-resolution ESMs under development today couple weather-scale atmospheres to mesoscale oceans. It is proposed to conduct a 60-year global 0.1-degree coupled ocean/sea-ice forced with interannually varying reanalysis fluxes for 1948-2007. This simulation is in support of an effort to further develop and apply a fine-resolution global ESM using the Community Earth System Model (CESM) framework. It will be used to help understand biases and feedback errors in the fully coupled simulations. As well, this forced realization will be used for analyses of high-latitude regions. The shrinking summer Arctic ice cap motivates us to examine interannual/decadal changes in the Arctic marginal ice zones and their relationship to changes in large-scale atmospheric forcing, and oceanic movement of heat and freshwater. In the Southern Ocean, changes will be examined in terms of air-sea interaction, ocean/ice processes, and large-scale climate modes. A forced non-eddy-resolving 1.0-degree counterpart will be used to highlight the importance of eddies in the realistic depiction of Southern Ocean climate processes.

Influence of aviation aerosols and contrails on cirrus clouds and anthropogenic forcing

Project lead: Joyce Penner, University of Michigan
Yellowstone allocation: 11 million core-hours
Sponsor: FAA

The objective of this proposal is to examine the forcing and climate effects of aerosols emitted from aviation and to evaluate the adequacy of the aerosol and cloud treatments within the models used here by comparison with data. The team working on the project includes scientists from the DLR as well as the University of Michigan. Model results generated here are also being evaluated by comparison with data (in particular satellite data) being generated by separately funded researchers (Patrick Minnis, NASA Langley) within the FAA Aviation Climate Change Research Initiative (ACCRI) team. The primary research questions being addressed in this proposal are:

How do different modeling treatments of the emissions from aircraft lead to different spatial distributions of aerosols as well as NOx emissions, their effects on clouds, and climate forcing? What is the overall forcing associated with present day and future aircraft emissions in comparison with other projected emissions? How do off-line CTM estimates of aircraft climate forcing differ from estimates from a coupled GCM with a climate model? What is the strength of the coupling between clouds and aircraft NOx and aerosol emissions and climate change and is it possible to discern a climate impact from aircraft emissions? Does a complete life-cycle treatment of the formation of contrails alter the water cycle within the atmosphere in significant ways?

The broader impacts of this project mainly concern its policy implications. FAA works with CAEP (ICAO’s (International Civil Aviation Organization’s) Committee on Aviation Environmental Protection) to set standards for aircraft emissions. The overall project team results will establish uncertainties in the effects of aircraft on climate by having a number of research teams examining the effects of emissions with and without technological improvements in engine design. FAA is interested in both the effects of aircraft on climate and climate forcing.

Exploring climate modeling using CESM1

Project lead: Phil Rasch, Pacific Northwest National Laboratory
Yellowstone allocation: 15 million core-hours
Sponsor: DOE

This proposal requests computer resources to enhance various research activities being performed at PNNL and LLNL in collaboration with NCAR scientists. The goals of this project are (1) to evaluate and to improve the Community Earth System Model (CESM1) with a focus on process coupling and aerosol/macro/micro physical processes, (2) to quantify uncertainties in the Aerosol Indirect Effects (AIE), and (3) to compare high-resolution CAM and WRF simulations with virtually identical physical parameterizations. The project utilizes the Community Earth System Model (CESM1), the latest generation of the CCSM project (which is supported jointly by NSF and DOE under the BER and SciDAC projects. CESM1 (CAM5.0 physics) was released in July 2010 and its newest release version with CAM5.1 physics (release version of cesm1_0_3) was distributed in June 2011. This version of CESM1 has been used for CMIP5 activity by both NCAR and PNNL, and much of our research activity focuses on understanding and improving that model. This proposal is for resources to allow us to perform additional and unique simulations that we had not envisioned in our request to DOE’s NERSC.