Carolina Vera CIMA/Dept. of Atmos. and Ocean Sci. (UBA-CONICET) Co-Chair WCRP/CLIVAR/VAMOS Panel The Monsoon Systems of the Americas in the context of climate change

Variability of the American Monsoon Systems WHAT ARE NAME and MESA? The North American Monsoon Experiment (NAME) and the Monsoon Experiment South America (MESA) are two internationally coordinated efforts that aim to improve the description, simulation and prediction of the American monsoon systems, their variability, and roles in the global water cycle. A WCRP/CLIVAR program focused on the climate of the Americas. Now in its implementation phase Panel Co-Chairs: C. Vera (UBA, Argentina) W. Higgins (NOAA/CPC, USA)

CLIVAR Mission To observe, simulate and predict Earth’’s climate system, with focus on ocean- atmosphere interactions, enabling better understanding of climate variability, predictability and change, to the benefit of society and the environment in which we live. CLIVAR is an interdisciplinary research effort within the World Climate Research Program (WCRP)

Monsoon mature phase Climatological seasonal mean precipitation (shaded), 200-hPa streamlines (black contours) & vertically integrated moisture fluxes (arrows)

How well do models reproduce the annual cycle? 9-member ensemble run of the CPTEC/COLA AGCM forced by observed global SST anomalies for 1982–1991 (Marengo et al. 2003, Clim. Dyn.) Black: Observed, Purple: ensemble mean Light blue: individual members Annual Cycle of Precipitation

How well do models reproduce interannual variability? 9-member ensemble run of the CPTEC/COLA AGCM forced by observed global SST anomalies for 1982–1991 (Marengo et al. 2003, Clim. Dyn.) Black: Observed, Purple: ensemble mean Light blue: individual members Interannual variability of Precipitation anomalies

VAMOS Approach Climate models have deficiencies in reproducing regional climate features (diurnal cycle, transient variability, etc.) VAMOS seeks improved understanding of the key physical processes (diurnal cycle, convection, topography, etc.) that must be parameterized for improved simulation with dynamical models. VAMOS modeling activities include: data assimilation, global and regional AGCM, CGCM, seasonal forecasts, hydrological models, etc. VAMOS employs a multi-scale approach ranging from diurnal to interannual timescales and longer.

Diurnal cycle 21Z ~ 18 LST NAMSSAMS 21Z ~ 14 LST

South American Low-Level Jet Experiment Enhanced precipitation gauge network NOAA/P-3 Missions PIBALS Radiosondes

North American Monsoon Experiment (NAME) NAME HYPOTHESIS: The NAMS provides a physical basis for determining the degree of predictability of warm season precipitation over the region. The NAME 2004 Field Campaign (on going) is an unprecedented opportunity to gather extensive atmospheric, oceanic, and land-surface observations in the core region of the North American Monsoon over NW Mexico, SW United States, and adjacent oceanic areas.

Diurnal cycle Wet-day hourly rain rates for various elevation bands in the SMO from the NAME Event Raingauge Network (NERN) Time of Maximum hourly precipitation frequency from NERN Gochis et al. 2003

Mesoscale Variability MCS mature stage time occurrence frequency during SALLJEX. Bars in green represent the period November 15 to December 31, in black January 1 to February 15 (Zipser et al. 2004) Subtropical South America has the largest fractional contribution of PFs with MCSs to rainfall of anywhere on earth between 36 N and 36 S (Courtesy Nesbitt & Zipser) 05Z ~ 02 LST

Intraseasonal Variability Typical circulation features of the NAMS accompany wet and dry surges keyed to Yuma, AZ. (Higgins et al. 2004) H L H L H L + T. anom - T. anom + T. anom Typical circulation features of the SAMS accompany wet and dry conditions over Southeastern South America (e.g. Diaz and Aceituno 2003)

Intraseasonal Variability (MJO) Composite evolution of 200-hPa velocity potential anomalies associated with MJO events and points of origin of tropical disturbances that developed into hurricanes or typhoons.

Interannual Variability Role of SST anomalies (Doyle & Barros 2002) Role of land surface conditions Role of Large- scale circulation (Silvestri & Vera 2003) ND Precipitation PSI(200 hPa) Correlation coefficients between CPTEC model anomalies and observed anomalies of rainfall (Marengo et al. 2003) Aerosol plume produced by biomass burning at the end of the dry season and transported to the south (Freitas et al. 2004)

Trends JFM precipitation trends (Liebmann et al. 2004) Normalized annual departures of SALLJ-event annual counts Precipitation River stream flow SW Atlantic SSTs

VAMOS Contribution to GCOS Action Plan for South America Project Brief: Enhancement of the GUAN network in Central South America X Trinidad X Tabatinga The Global Climate Observing System (GCOS) was established in 1992 as a joint initiative of WMO,UNEP, IOC,UNESCO, and ICSU to provide the data necessary for climate system monitoring, climate change detection and response monitoring, application to the development of national economies, and research.

VAMOS Contribution to GCOS Action Plan for South America Project Brief: Enhancement of Sustained Surface and Subsurface observations in western Subtropical South Atlantic Climatological mean DJF precipitation. Red dots: locations of the Pirata Southwestern Extension Light blue dot: location of the proposed site for an atlas buoy.

VAMOS future challenges To strength links between climate variability and climate change VAMOS  WCRP-CLIVAR/WGCM  IPCC Link between climate variability and applications VAMOS  START/AIACC in the Americas (Big potential! Several VAMOS scientists are also AIACC Scientists already)

Thank you!