RAPID: Decadal Variability of the American Monsoons--An Assessment of CMIP5 Simulation

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

This is one of 16 Rapid Response (RAPID) projects funded as the result of a Dear Colleague Letter (NSF 11-006) encouraging diagnostic analyses of climate model simulations prepared for the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5). Research conducted in these projects is expected to lead to more detailed model intercomparisons, better understanding of robust model behaviors, and better understanding and quantification of uncertainty in future climate simulations. This project examines the simulation of the American Monsoon System (AMS) in simulations of the recent past from the Climate Model Intercomparison Project verson 5 (CMIP5). The main goals are to develop an extensive assessment of how realistic simulations are in representing the observed characteristics of the American Monsoon System (AMS) in the recent past, and to assess uncertainties in projected decadal climate changes in the AMS. More specifically, the project 1) Assesses the skill of CMIP5 model simulations in representing the climatological and statistical characteristics of the monsoons in the Americas including: circulation and precipitation features, subseasonal variance, onsets and demises, amplitudes and cross equatorial transitions. 2) Determines which CMIP5 models realistically represent the spatiotemporal variability of the monsoons in the present climate including near-term trends, frequency of very dry/wet seasons and statistical distributions of extreme precipitation events. 3) Examines which CMIP5 models skillfully represent the observed relationships between remote forcings and the American monsoons. These include the Madden-Julian Oscillation (MJO), El Niño/Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), Antarctic Oscillation (AAO), Atlantic Ocean and Intra-Americas Sea forcings. 4) Seeks to determine how much of the climate changes projected for the next decades in the Americas are explained by natural decadal variability and how much by greenhouse gases increases. The broader impact of the project lies in its support of the IPCC AR5, which is intended to provide information on climate change and its consequences to decision makers worldwide. The AMS affects water resources, agriculture, human health, ecosystems and biodiversity throughout a large and densely populated portion of the Americas. The impact of climate change on the AMS is not known, and this research will help to determine the extent to which models used to project climate change are capable of accurately representing the AMS system and its variability and change over the observed record.