Towards an Improved Understanding of Simulated and Observed Changes in Extreme Precipitation

EPA Grant Number: FP917182
Title: Towards an Improved Understanding of Simulated and Observed Changes in Extreme Precipitation
Investigators: DeAngelis, Anthony M.
Institution: Rutgers, The State University of New Jersey
EPA Project Officer: Michaud, Jayne
Project Period: September 1, 2010 through August 31, 2013
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2010) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Global Change


The purpose of this research is to develop a better scientific understanding of changes in extreme precipitation that have been observed over the 20th century and are likely to continue in response to increased greenhouse gases. The changes in extreme precipitation will be quantified and the mechanisms for such changes will be investigated. In particular, a major goal of the project is to elucidate the mechanisms for changes in regional extreme precipitation, which do not appear to be constrained by atmospheric moisture availability.

Global increases in the frequency and intensity of heavy precipitation have been linked with warmer temperatures and increased greenhouse gases. Such climate changes could have devastating impacts on human life, property, and ecosystems. This project will quantify the global and regional responses of extreme precipitation to increased greenhouse gases using current generation coupled climate models. The physical mechanisms associated with extreme precipitation changes will also be investigated.


The changes in extreme precipitation will be investigated with output from coupled atmosphere-ocean climate models from the Coupled Model Intercomparison Project Phase III (CMIP3). The model simulated daily precipitation and mechanisms for extreme precipitation will be evaluated by comparing 20th century simulations with gridded observations over the United States. Future changes in extreme precipitation in response to increased greenhouse gases will be assessed with the A1B emissions scenario simulations, in which atmospheric carbon dioxide concentrations increase to 720 parts per million by 2100. Quantifying changes in extreme precipitation will involve the use of a variety of statistical methods, where a large goal of the quantification will be to see if regional and global changes in extreme precipitation are constrained by atmospheric moisture. To understand the mechanisms responsible for extreme precipitation events, composites of the circulation and thermodynamic structure of simulated and observed weather systems that produce extreme precipitation will be developed and analyzed.

Expected Results:

The evaluation of climate model precipitation is expected to reveal biases in simulated mean and extreme precipitation which may be a result of coarse model resolution or inefficiencies in the precipitation generating mechanisms in models. The analysis of future extreme precipitation under the A1B emissions scenario is expected to show robust patterns of heavy precipitation change among the climate models. In particular, most regions are expected to show increased intensity of extreme precipitation events, while only very dry regions are expected to show decreases. This would result in a globally averaged increase in extreme precipitation intensity. Such expectations are consistent with existing studies on extreme precipitation change and preliminary results on this project. In terms of precipitation change mechanisms, globally averaged extreme precipitation is expected to increase according to atmospheric moisture following the Clausius-Clapeyron relationship. Regionally, the mechanisms for extreme precipitation change are likely to be more complicated, and include process such as changes in atmospheric circulation, atmospheric stability, El NiƱo, and land-atmosphere moisture fluxes. In summary, this project will provide a great amount of information about the way the climate system works and responds to anthropogenic activity, as well as highlight the good and bad aspects of climate model simulated precipitation.

Potential to Further Environmental/Human Health Protection
Increases in intense precipitation is likely to be one of the most devastating consequences of anthropogenic climate change. Quantifying the changes in extreme precipitation events is therefore vital to the public and policy makers as we face potentially serious consequences of global warming in current and future generations. Additionally, enhanced understanding of the mechanisms of extreme precipitation change can help improve our understanding of the climate system and lead to the development of better climate models.

Supplemental Keywords:

climate change, global, regional, greenhouse gases, global warming, extremes, precipitation, climate models, physical mechanisms,, RFA, Scientific Discipline, Air, climate change, Air Pollution Effects, Environmental Monitoring, Ecology and Ecosystems, Atmosphere, global change, green house gas concentrations, climate models, GHG, Global Climate Change

Progress and Final Reports:

  • 2011
  • 2012
  • Final