Understanding and predicting climate variability and change at monsoon regions

Abstract

The chapter highlights selected scientific advances made under WCRP leadership in understanding climate variability and predictability at regional scales with emphasis on the monsoon regions. They are mainly related to a better understanding of the physical processes related to the ocean-land-atmosphere interaction that characterize the monsoon variability as well as to a better knowledge of the sources of climate predictability. The chapter also highlights a number of challenges that are considered crucial to improving the ability to simulate and thereby predict regional climate variability. The representation of multi-scale convection and its interaction with coupled modes of tropical variability (where coupling refers both to ocean-atmosphere and/or land-atmosphere coupling) remains the leading problem to be addressed in all aspects of monsoon simulations (intraseasonal to decadal prediction, and to climate change). Systematic errors in the simulation of the mean annual and diurnal cycles continue to be critical issues that reflect fundamental deficiencies in the representation of moist physics and atmosphere/land/ocean coupling. These errors do not appear to be remedied by simple model resolution increases, and they are likely a major impediment to improving the skill of monsoon forecasts at all time scales. Other processes, however, can also play an important role in climate simulation at regional levels. The influence of land cover change requires better quantification. Likewise, aerosol loading resulting from biomass burning, urban activities and land use changes due to agriculture are potentially important climate forcings requiring better understanding and representation in models. More work is also required to elucidate mechanisms that give rise to intraseasonal variability. On longer timescales an improved understanding of interannual to decadal monsoon variability and predictability is required to better understand, attribute and simulate near-term climate change and to assess the potential for interannual and longer monsoon prediction. A need is found to strengthen the links between model evaluation at the applications level and process-oriented refinement of model formulation. Further work is required to develop and sustain effective communication among the observation, model user, and model development communities, as well as between the academic and “operational” model development communities. More research and investment is needed to translate climate data into actionable information at the regional and local scales required for decisions.