Toward a Unified View of the American Monsoon Systems

Abstract

An important goal of the Climate Variability and Predictability (CLIVAR) research on the American monsoon systems is to determine the sources and limits of predictability of warm season precipitation, with emphasis on weekly to interannual time scales. This paper reviews recent progress in the understanding of the American monsoon systems and identifies some of the future challenges that remain to improve warm season climate prediction. Much of the recent progress is derived from complementary international programs in North and South America, namely, the North American Monsoon Experiment (NAME) and the Monsoon Experiment South America (MESA), with the following common objectives: 1) to understand the key components of the American monsoon systems and their variability, 2) to determine the role of these systems in the global water cycle, 3) to improve observational datasets, and 4) to improve simulation and monthly-to-seasonal prediction of the monsoons and regional water resources. Among the recent observational advances highlighted in this paper are new insights into moisture transport processes, description of the structure and variability of the South American low-level jet, and resolution of the diurnal cycle of precipitation in the core monsoon regions. NAME and MESA are also driving major efforts in model development and hydrologic applications. Incorporated into the postfield phases of these projects are assessments of atmosphere-land surface interactions and model-based climate predictability experiments. As CLIVAR research on American monsoon systems evolves, a unified view of the climatic processes modulating continental warm season precipitation is beginning to emerge.

Assessments of moisture fluxes east of the Andes in South America in a global warming scenario

“…It is also observed that the vertical wind shear in the SALLJ composite reaches values of about 8 m s −1 (Figure 7(b)). This shows that the regional model used in this study detected cases of SALLJs that satisfy even the modified Bonner criteria 1, as in the SALLJ event that occurred during December 2003 in the SALLJ field experiment (Vera et al, 2006c) and was studied by Saulo et al (2007). Figure 7 shows an intensification of the wind speed observed in the global warming climate.…”

Sub-seasonal Predictability of the Onset and Demise of the Rainy Season over Monsoonal Regions

“…The figure also indicates the domains selected to study specific monsoonal regions (black boxes), namely the North American monsoon (e.g., Adams and Comrie, 1997;Vera et al, 2006), the South American monsoon (e.g., Vera et al, 2006;Marengo et al, 2012;Carvalho and Cavalcanti, 2016), the West Africa monsoon (e.g., Nicholson, 2013), the East African monsoon (e.g., Nairobi, 1979;Mutai and Ward, 2000), the Indian monsoon (e.g., Webster et al, 1998;Krishnamurthy and Shukla, 2000;Prasad, 2005), the East Asia monsoon (e.g., Wang et al, 2001;Yihui and Chan, 2005), and the Northern Australia monsoon (e.g., Hendon and Liebmann, 1990).…”

Prospecting Glacial Ages and Paleoclimatic Reconstructions Northeastward of Nevado Coropuna (16° S, 73° W, 6377 m), Arid Tropical Andes

“…-Nothofagus: native of Patagonia, >3000 km toward the south. The SASM controls the seasonal precipitation cycle in tropical South America [55][56][57][58], involving several components: the South Atlantic Convergence Zone (SACZ); the convection over the Amazon basin and the ITCZ southward shift during the boreal winter/austral summer, when most of the annual precipitation occurs southward of the Amazon River (Figure 2). However, pollen within the Coropuna glaciers reveal different air masses fluxes.…”