Multidecadal variability of moisture and heat budgets of the South American monsoon system

Abstract

The variability of sources or sinks of moisture and heat for the South American monsoon system (SAMS) region is investigated for the 1958-1995 period. So, moisture and heat budget equations are applied to data from the National Centers for Environmental Prediction (NCEP) reanalysis project. Sources or sinks of moisture and heat are the equation residues and are referred to as residue and diabatic terms, respectively. Using empirical orthogonal function (EOF) analysis, the dominant variability modes of these terms are obtained for the study period, with the monthly anomalies of the residue and diabatic terms employed. For residue EOF01, negative (positive) principal component (PC01) values correspond to positive (negative) residue anomalies over tropical South America (TSAM), which indicate a moisture source (sink) before (after) 1976, cold (warm) phase of the Pacific Decadal Oscillation (PDO). For the EOF01 of the diabatic term, negative (positive) PC01 values correspond to negative (positive) diabatic anomalies over TSAM, indicating a heat sink (source) before (after) 1976. Thus, a moisture source (sink) and a heat sink (source) occur over TSAM before (after) 1976. These findings are corroborated by composite analysis of the anomalies of precipitable water, 850 hPa air temperature, 500 hPa vertical pressure velocity, vertically integrated moisture flux (VIMF), VIMF divergence, and precipitation. In terms of system thermodynamics, these composites are indicative of SAMS weakening (strengthening) before (after) 1976, cold (warm) PDO phase.

Moisture flows on Southeast Brazil: Present and future climate

“…In addition to this feature of climate variability in the region, Garcia and Kayano (2015) found a low frequency variability scale of the residual term of the moisture balance in the period 1958–1995 using Empirical Orthogonal Functions, in which the dominant mode showed positive (negative) anomalies of the residue over the SAMS region, indicative of a source (sink) of moisture before (after) 1976. In addition, compound analysis has shown a possible weakening (strengthening) of SAMS before (after) 1976 (Garcia and Kayano, 2015).…”

Onset and demise dates of the rainy season in the South American monsoon region: A cluster analysis result

“…Although the South American monsoon system (SAMS) does not present typical monsoon wind direction reversion, as in the eastern Asia and Indian monsoon systems, its large‐scale atmospheric circulation patterns feature monsoon characteristics (Zhou and Lau, 1998). Also, a large continental portion presents a rainfall regime with a rainy summer and a dry winter that resembles the monsoon rainfall regime (Rao et al ., 1996; Zhou and Lau, 1998; Marengo et al ., 2001; Gan et al ., 2004; Liebmann et al ., 2007; Garcia and Kayano, 2009; 2011; 2013; 2015; Garcia et al ., 2016; 2017). Thus, studies on the onset and demise rainy season (ONR and DER, respectively) dates in the SAMS region might bring relevant results with socioeconomic implications to the population in tropical South America, because many economic sectors (energy generation, agriculture) depend on this information.…”

Sistema de Monção da América do Sul: padrões de variabilidade durante os últimos 21.000 anos

“…Em particular, Custódio (2017) HE et al, 2021;LIU et al, 2015LIU et al, , 2009LIU et al, , 2012MOHTADI;PRANGE;STEINKE, 2016;WEN et al, 2016), inclusive para identificar a variabilidade da precipitação sobre a América do Sul e as variações de TSM no Atlântico Sul (AGUIAR et al, 2020;MARSON et al, 2014;SANTOS et al, 2022;VENANCIO et al, 2020b;WAINER et al, 2015WAINER et al, , 2021. GARCIA et al, 2017;GARCIA;KAYANO, 2009KAYANO, , 2013KAYANO, , 2015SABOIA, 2015;MECHOSO, 2011;CAVALCANTI;HADA, 1996;VERA et al, 2006;ZHOU;LAU, 1998).…”