Moisture and heat budgets associated with the South American monsoon system and the Atlantic ITCZ

Abstract

Moisture and heat budgets in selected areas of the South American monsoon system (SAMS) and the equatorial Atlantic are examined for the 1979-2006 period. These areas are the Central Amazon (CAM), western Central Brazil (WCB), South Atlantic convergence zone (SACZ) and the Atlantic inter-tropical convergence zone (ITCZ). The moisture and heat budget terms are calculated using daily reanalyzed data, and filtered for the 0.4-1.2 year scale. Analyses are based on the correlation maps between these terms and the expansion coefficient of the SAMS mode, previously identified. The vertical structures of the moisture and heat budget terms are discussed and allow us to examine the thermodynamic reasoning of the SAMS relationship with the Atlantic ITCZ. Important differences in the moisture and heat budgets have been found among the analyzed areas. Except for the horizontal advection of q and T, indications of a wet and dry season appear in the anomalies of other terms 4 pentads earlier in the WCB than in the CAM. The SAMS and the ITCZ relate to each other through the moisture and heat budgets. A time lag of approximately 8 pentads is noted for the moisture sink (source) and heat source (sink) between the CAM and ITCZ regions during the wet (dry) season of both regions. Indeed, the largest negative (positive) values of the residue term and the largest positive (negative) values of the diabatic term occur at pentad 12 (44) for the CAM and at pentad 20 (52) for the ITCZ. The results here provide observational support to the relationship between the SAMS and the Atlantic ITCZ. © 2010 Royal Meteorological Society.