@Article{LiebmannKilMarAmbGli:1999:SuCoVa,
               author = "Liebmann, Brant and Kiladis, George N. and Marengo, Jose Antonio 
                         and Ambrizzi, Tercio and Glick, John D.",
          affiliation = "Climate Diagnostics Center, University of Colorado, Boulder, 
                         Colorado and Aeronomy Laboratory, National Oceanic and Atmospheric 
                         Administration, Boulder, Colorado and Center for Weather Forecasts 
                         and Climate Studies, National Institute for Space Studies and 
                         Department of Atmospheric Sciences, USP and Climate Diagnostics 
                         Center, University of Colorado, Boulder, Colorado",
                title = "Submonthly convective variability over South America and the South 
                         Atlantic convergence zone",
              journal = "Journal of Climate",
                 year = "1999",
               volume = "12",
               number = "7",
                pages = "1877--1891",
                month = "July",
             keywords = "rossby-wave propagation, scale common features, baiu frontal zone, 
                         tropical atmosphere, summer circulation, northern winter, time 
                         scales, oscilation, hemisphere, model.",
             abstract = "Relationships between deep convection over South America and the 
                         atmospheric circulation are examined, with emphasis on submonthly 
                         variations of the South Atlantic convergence zone (SACZ) during 
                         austral summer. Outgoing longwave radiation (OLR) is used as a 
                         proxy for convection, while the associated circulation patterns 
                         are depicted by the National Centers for Environmental Prediction 
                         Reanalysis. Over South America and the adjacent oceans, OLR 
                         fluctuations with periods less than 90 days show maximum variance 
                         in the SACZ and over central South America during 
                         December–February. There is a local minimum in variance over the 
                         southern Amazon Basin, where mean convection is at a maximum. OLR 
                         spectra display several statistically relevant peaks corresponding 
                         to periods of less than 30 days over tropical South America, with 
                         the relative proportion of higher-frequency power increasing as 
                         the base grid point is moved to the southeast within the SACZ. 
                         Correlations between submonthly (2–30-day) OLR in the vicinity of 
                         the SACZ and 200-mb streamfunction reveal the preferred path of 
                         Rossby wave energy impinging on the SACZ from the midlatitudes of 
                         the Southern Hemisphere. Episodes of enhanced convection within 
                         the SACZ, indicated by negative OLR anomalies, occur at the 
                         leading edge of upper-level troughs propagating into the region. 
                         The corresponding pattern at 850 mb reveals that the disturbances 
                         are nearly equivalent barotropic west of South America but tilt 
                         westward with height in the region of the SACZ. Negative low-level 
                         temperature anomalies lie to the southwest of the convection. The 
                         results are consistent with baroclinic development along an 
                         associated cold front. Convection over the southwestern Amazon 
                         Basin on submonthly timescales is seen to progress into the region 
                         from the south. Upper-level anomalies, which at times may play a 
                         role in the initiation of the convection, move eastward and 
                         rapidly become decoupled from the convection. Low-level cold air 
                         along the eastern flank of the Andes appears linked to the 
                         convection as it moves northward. In contrast, convection over the 
                         southeastern Amazon is accompanied by disturbances moving into the 
                         area from the Atlantic, but there is little sign of a low-level 
                         temperature anomaly. In this case convection seems to result in 
                         cross-equatorial outflow into the North Atlantic, rather than be 
                         the result of forcing from the extratropics. The authors speculate 
                         that the relatively stable position of the SACZ is associated with 
                         a Rossby wave guide, which ultimately is related to the 
                         large-scale circulation driven by sources and sinks of diabatic 
                         heating. It also appears that the SACZ forms when the 
                         northwesterly flow associated with a low-level trough is able to 
                         tap moisture from the Amazon.",
           copyholder = "SID/SCD",
                 issn = "0894-8755",
             language = "en",
           targetfile = "Liebmann_Submonthly convective variability.pdf",
        urlaccessdate = "03 maio 2024"
}