Lifecycle of South American Monsoon System simulated by CPTEC/INPE AGCM

Abstract

ABSTRACTThe lifecycle of South American Monsoon System (SAMS) plays an important role on the duration of the rainy season over large areas of South America, affecting the economy through impacts on agriculture, water resources and energy management. Numerical model prediction of SAMS onset, demise and related atmospheric features is an important tool to be used in management decisions in these sectors. This information is still missing in seasonal predictions, and the purpose of this study is to examine results of a climate simulation using the CPTEC/INPE AGCM to verify its ability in simulating the SAMS onset and demise as well as the associated atmospheric features. The SAMS lifecycle is identified using an index of the zonal humidity flux in the monsoon core. The model captured the atmospheric changes associated with the SAMS lifecycle, although showing differences in intensity and maximum locations of some variables, such as the magnitude of humidity flux, sea level pressure and omega, compared to reanalysis. During the onset, the model simulated the humidity flux direction changes, the eastward shifting of the South Atlantic Subtropical High and the northwesterly moisture flux east of tropical Andes. During the demise, the model simulated the easterly moisture flux directed toward the Amazon region and the reduction of northerly/northwesterly flow over northern South America, as well as the increase of Sea Level Pressure over the continent. Results obtained using a previous version of CPTEC/INPE AGCM are discussed, mainly the improvements, in the new version, of atmospheric variables and annual cycle of precipitation. The model was able to represent the main observed features of the SAMS lifecycle. The method can be useful to identify the onset and demise dates and could be applied to results of seasonal prediction prior to the rainy season, adding information to planning and management actions.