To Conduct and Analyze Simulations of Anthropogenic Climate Change Based on a Version of the CESM

The primary goal of the proposed research is to conduct and analyze simulations of anthropogenic climate change based on a version of the Community Earth System Model (CESM) in which the atmosphere and land-surface models are based on “super-parameterization.” We will develop and test a community version of this new model configuration to be called the SP-CESM. The effects of moist convection, stratiform cloudiness, radiative transfer, boundary-layer processes, and the land surface will be computed by embedding a cloud-resolving model (CRM) in each grid column of the SP-CESM. The CRM explicitly accounts for indirect aerosol effects by using the CESM’s global aerosol distribution and composition as input to a drop-activation parameterization. The land-surface model, which runs on the CRM’s grid, predicts exchanges of latent and sensible heat and CO2 with the global atmosphere, including those due to changes in fine-scale vegetation and land use. Our work will focus on anthropogenic climate change. We will perform at least one simulation of the pre-industrial climate, at least one of the twentieth century climate, and at least one of the twenty-first century climate based on emissions scenarios developed for use in the Fifth Assessment of the Intergovernmental Panel on Climate Change (AR5). The results will be shared with the scientific community, including scientists involved in AR5. Our analysis will focus on improving our understanding and prediction of critical processes and modes of decadal variability in the earth system, the interactions of the land surface hydrology and the atmosphere, and atmospheric cloud processes, including the indirect effect of anthropogenic aerosols on clouds and especially precipitation. These processes impact extreme hydrological cycle events such as droughts, floods, and episodes of extreme precipitation. We will use the model to better understand the feedbacks and changes to interannual and decadal modes of variability, with an eye towards increasing our predictive capacity. We will evaluate the SP-CESM against observations, and also compare it with the conventional CESM. The broader impacts of the proposed research are focused around improving predication for society, providing better tools that others can use, and training the next generation of scientists. The core activity of this project is to apply recent research progress to the problem of anthropogenic climate change, in order to help society better understand possible future impacts of anthropogenic emissions of greenhouse gases and particulates. Through the CESM project, our model will be released as open source code for other researchers to use and improve in the future. Finally, we will be training the next generation of scientists by employing and mentoring graduate students and post-docs. These young people will benefit from CMMAP’s extensive and mature Education and Diversity activities, which are designed in part to attract the participation of researchers from under-represented groups.

Project Term: 
2011 to 2014
Project Type: 
Science Focus Area (SFA)