This is a grant under a Climate Variability and Predictability (CLIVAR) Program pilot project called DRICOMP, for the Drought in Coupled Models Project, which focuses on making initial explorations into the mechanisms of drought as they are represented in the output of global climate models and on attempting to assess the reliability of these models in simulating drought.
El Nino brings widespread drought to the tropics, including Mexico and northern South America. Stronger or more frequent El Nino events in the future will exacerbate drought risk in these highly vulnerable areas. Even if the frequency and intensity of El Nino events do not increase in the 21st century, more generalized warming of the tropical Pacific may still produce a tropical teleconnection resembling that associated with present-day El Nino conditions.
Whether or not operational seasonal forecasts can capture the conditions that cause tropical drought is an entirely open question. This study is an initial exploration of the patterns, spatial extent, and severity of El Nino induced tropical droughts during a control period in the 20th century in seasonal forecasts, which have updated realistic initial conditions but fixed greenhouse gases (GHGs), and in climate change projections, which have realistic GHG evolution but no observational updates. The projected changes in the strength of the identified patterns of tropical drought will then be examined for the 21st century runs. This research will attempt to address the following questions: . How well do coupled models simulate the pattern and intensity of tropical droughts associated with El Nino during the 20th century? . What are the primary differences of El Nino variability and change between seasonal prediction models and climate change models in the 20th century? . To what extent do patterns of interannual precipitation variability project on 21st century precipitation trends, and what is the spatial signature of the remaining trends?
Broader impacts of this project are in assessing the credibility of global climate model projections of changes in the frequency and severity of tropical droughts. It may also provide a basis for "recalibrating" the output of global climate models, so as to improve their reliability in projecting changes in tropical rainfall. The project will support the visit of Caio A. S. Coelho, a scientist at the Centro de Previsao de Tempo e Estudos Climaticos (CPTEC), an institute of the Brazilian Meteorological Service, to the United States to collaborate with the principal investigator. This will contribute to an ongoing collaboration between CPTEC and the International Research Institute for Climate and Society (IRI) at Columbia University.
