Performance Engineering in the Community Atmosphere Model

The Community Atmosphere Model (CAM) is the atmospheric component of the Community Climate System Model (CCSM) and is the primary consumer of computer resources in typical CCSM simulations. Performance engineering has been an important aspect of CAM development throughout its existence. This paper briefly summarizes these efforts and their impacts over the past five years

Collaborative Research: Towards Advanced Understanding and Predictive Capability of Climate Change in the Arctic Using a High-Resolution Regional Arctic Climate Model

The primary research task completed for this project was the development of the Regional Arctic Climate Model (RACM). This involved coupling existing atmosphere, ocean, sea ice, and land models using the National Center for Atmospheric Research (NCAR) Community Climate System Model (CCSM) coupler (CPL7). RACM is based on the Weather Research and Forecasting (WRF) atmospheric model, the Parallel Ocean Program (POP) ocean model, the CICE sea ice model, and the Variable Infiltration Capacity (VIC) land model. A secondary research task for this project was testing and evaluation of WRF for climate-scale simulations on the large pan-Arctic model domain used in RACM. This involved identification of a preferred set of model physical parameterizations for use in our coupled RACM simulations and documenting any atmospheric biases present in RACM

A Pseudoproxy Evaluation of Bayesian Hierarchical Modeling and Canonical Correlation Analysis for Climate Field Reconstructions over Europe

A pseudoproxy comparison is presented for two statistical methods used to derive annual climate field reconstructions (CFRs) for Europe. The employed methods use the canonical correlation analysis (CCA) procedure presented by Smerdon et al. and the Bayesian hierarchical model (BHM) method adopted from Tingley and Huybers. Pseudoproxy experiments (PPEs) are constructed from modeled temperature data sampled from the 1250-yr paleo-run of the NCAR Community Climate System Model (CCSM) version 1.4 model by Ammann et al. Pseudoproxies approximate the distribution of the multiproxy network used by Mann et al. over the European region of interest. Gaussian white noise is added to the temperature data to mimic the combined signal and noise properties of real-world proxies. Results indicate that, while both methods perform well in areas with good proxy coverage, the BHM method outperforms the CCA method across the entire field and additionally returns objective error estimates

Response of Glacier Melt and Discharge to Future Climate Change, Susitna Basin, Alaska

A large dam for hydropower with a 67 km long reservoir is proposed in the Susitna basin, leading to multiple studies of the basin. This study focuses on the response of climate change of the Susitna basin glaciers and the effects on basin discharge

Erroneous Model Field Representations in Multiple Pseudoproxy Studies: Corrections and Implications

Pseudoproxy experiments evaluate statistical methods used to reconstruct climate fields from paleoclimatic proxies during the Common Era. These experiments typically employ output from millennial simulations by general circulation models (GCMs). It is demonstrated that multiple published pseudoproxy studies have used erroneously processed GCM surface temperature fields: the NCAR Community Climate System Model (CCSM), version 1.4, field was incorrectly oriented geographically and the GKSS ECHO-g FOR1 field was corrupted by a hemispheric-scale smoothing in the Western Hemisphere. These problems are not associated with the original model simulations; they instead arose because of incorrect processing of the model data for the pseudoproxy experiments. The consequences of these problems are evaluated for the studies in which the incorrect fields were used. Some quantitative results are invalidated by the findings: these include all experiments that used the corrupted ECHO-g field and those aspects of previous CCSM experiments that focused on Niño-3 reconstructions. Other results derived from the CCSM field can be reinterpreted based on the information provided herein and their qualitative characteristics remain similar

Final Report for DOE Grant DE-FG02-07ER64470 [“Incorporation of the HYbrid Coordinate Ocean Model (HYCOM) into the Community Climate System Model (CCSM): Evaluation and Climate Applications”]

The primary goal of the project entitled “Incorporation of the HYbrid Coordinate Ocean Model (HYCOM) into the Community Climate System Model (CCSM): Evaluation and Climate Applications” was to systematically investigate the performance of the HYbrid Coordinate Ocean Model (HYCOM) as an alternative oceanic component of the NCAR’s Community Climate System Model (CCSM). We have configured two versions of the fully coupled CCSM3/HYCOM: one with a medium resolution (T42) Community Atmospheric Model (CAM) and the other with higher resolution (T85). We have performed a comprehensive analysis of the 400-year fully coupled CCSM3/HYCOM simulations and compared the results with those from CCSM3/POP and with climatological observations, and also we have performed tuning of critical model parameters, including Smagorinsky viscosity, isopycnal diffusivity, and background vertical diffusivity. The analysis shows that most oceanic features are well represented in the CCSM3/HYCOM. The coupled CCSM3/HYCOM (T42) has been integrated for 400 years, and the results have been archived and transferred to the High Performance Computer in the Florida State Univesity. In the last year, we have made comprehensive diagnostics of the long-term simulations by the comparison with the original CCSM3/POP simulation and with the observations. To gain some understanding of the model biases, the mean climate and modes of climate variability of the two models are compared with observations. The examination includes the Northern and Southern Annular Modes (NAM and SAM), the Pacific-North-American (PNA) pattern, the Atlantic Multidecadal Oscillation (AMO), and the main Southern Ocean SST mode. We also compared the performance of ENSO simulation in the coupled models. This report summarizes the main findings from the comparison of long-term CCSM3/HYCOM and CCSM3/POP simulations

Applying Downscaled Global Climate Model Data to a Hydrodynamic Surface-Water and Groundwater Model

Precipitation data from Global Climate Models have been downscaled to smaller regions. Adapting this downscaled precipitation data to a coupled hydrodynamic surface-water/groundwater model of southern Florida allows an examination of future conditions and their effect on groundwater levels, inundation patterns, surface-water stage and flows, and salinity. The downscaled rainfall data include the 1996-2001 time series from the European Center for MediumRange Weather Forecasting ERA-40 simulation and both the 1996-1999 and 2038-2057 time series from two global climate models: the Community Climate System Model (CCSM) and the Geophysical Fluid Dynamic Laboratory (GFDL). Synthesized surface-water inflow datasets were developed for the 2038-2057 simulations. The resulting hydrologic simulations, with and without a 30-cm sea-level rise, were compared with each other and field data to analyze a range of projected conditions. Simulations predicted generally higher future stage and groundwater levels and surface-water flows, with sea-level rise inducing higher coastal salinities. A coincident rise in sea level, precipitation and surface-water flows resulted in a narrower inland saline/fresh transition zone. The inland areas were affected more by the rainfall difference than the sea-level rise, and the rainfall differences make little difference in coastal inundation, but a larger difference in coastal salinities

Assessment of Climate Change Scenarios on the Yukon River Basin

There are indications that the climate is going to experience drastic change in the future, as it has occurred in the past and is currently happening now. Climate simulations have shown some potential hydrologic effects of climate change in the Yukon River Basin due to changes in temperature and precipitation. The Yukon River Inter-Tribal Watershed Council currently does not utilize spatial software to manage, analyze, or produce maps of climate change scenarios in the Yukon River basin. It is important to create a geodatabase, determine differences in climate change scenarios, and calculate peak discharge rates in the different regions using geospatial techniques. Climate modeling is one of the best tools available to determine the trends in future climate. In this project, the temperature and precipitation differences for the 20th century (1980-1999) and mid-century (2040-2059), were determined with data from the National Center for Atmospheric Research (NCAR), Community Climate System Model (CCSM), indicating a future increase in temperature and precipitation. The U.S. Geological Survey regression equations, basin characteristics, and PythonWin were used to create a Python script and tool to calculate peak discharge rates. The methods used in this project allow it to be easily adapted for future projects in the Yukon River Basin

Arctic system on trajectory to new state

The Arctic system is moving toward a new state that falls outside the envelope of glacial-interglacial fluctuations that prevailed during recent Earth history. This future Arctic is likely to have dramatically less permanent ice than exists at present. At the present rate of change, a summer ice-free Arctic Ocean within a century is a real possibility, a state not witnessed for at least a million years. The change appears to be driven largely by feedback-enhanced global climate warming, and there seem to be few, if any processes or feedbacks within the Arctic system that are capable of altering the trajectory toward this “super interglacial” state