Daily precipitation data from three stations in subtropical Argentina are used to describe intraseasonal variability (20–90 days) during the austral summer. This variability is compared locally and regionally with that present in outgoing longwave radiation (OLR) data, in order to evaluate the performance of this variable as a proxy for convection in the region. The influence of the intraseasonal activity of the South American Seesaw (SASS) leading convection pattern on precipitation is also explored. Results show that intraseasonal variability explains a significant portion of summer precipitation variance, with a clear maximum in the vicinity of the SASS subtropical center. Correlation analysis reveals that OLR can explain only a small portion of daily precipitation variability, implying that it does not constitute a proper proxy for precipitation on daily timescales. On intraseasonal timescales, though, OLR is able to reproduce the main features of precipitation variability. The dynamical conditions that promote the development of intraseasonal variability in the region are further analyzed for selected summers. Seasons associated with a strong intraseasonal signal in precipitation variability show distinctive wet/dry intraseasonal periods in daily raw data, and are associated with a well defined SASS-like spatial pattern of convection. During these summers, strong large-scale forcing (such as warm El Niño/Southern Oscillation (ENSO) events and/or tropical intraseasonal convective activity), and Rossby-wave-like circulation anomalies extending across the Pacific Ocean, are also observed.
Intraseasonal variability South America Precipitation Convection Warm season
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The authors thank Gilbert Compo for his scientific inputs, and the anonymous reviewers for their valuable comments. This work was supported by University of Buenos Aires (X264) and ANPCyT (BID 1728/OC-AR—PICT25269).
Carvalho LMV, Jones C, Liebmann B (2004) The South Atlantic convergence zone: intensity, form, persistence, and relationships with intraseasonal to interannual activity and extreme rainfall. J Climate 17:88–108CrossRefGoogle Scholar
Casarin DP, Kousky VE (1986) Anomalias de precipitação no sul do Brasil e variações na circulação atmosférica. Rev Bras Meteorol 1:83–90Google Scholar
Díaz A, Aceituno P (2003) Atmospheric circulation anomalies during episodes of enhanced and reduced convective cloudiness over Uruguay. J Climate 16:3171–3185CrossRefGoogle Scholar
Duchon CE (1979) Lanczos filtering in one and two dimensions. J Appl Meteor 18:1016–1022CrossRefGoogle Scholar
Garreaud RD, Battisti DS (1999) Interannual (ENSO) and interdecadal (ENSO-like) variability in the southern hemisphere tropospheric circulation. J Climate 12:2113–2123CrossRefGoogle Scholar
Grimm AM, Barros VR, Doyle ME (2000) Climate variability in southern South America associated with El Niño and La Niña Events. J Climate 13:35–58CrossRefGoogle Scholar
Liebmann B, Smith CA (1996) Description of a complete (interpolated) outgoing longwave radiation dataset. Bull Am Meteor Soc 77:1275–1277Google Scholar
Liebmann B, Hendon HH, Glick JD (1994) The relationship between tropical cyclones of the western Pacific and Indian Oceans and the Madden–Julian oscillation. J Meteor Soc Japan 72:401–411Google Scholar
Liebmann B, Kiladis GN, Marengo JA, Ambrizzi T, Glick JD (1999) Submonthly convective variability over South America and the South Atlantic convergence zone. J Climate 12:1877–1891CrossRefGoogle Scholar
Liebmann B, Kiladis GN, Vera CS, Saulo AC, Carvalho LMV (2004) Subseasonal variations of rainfall in South America in the vicinity of the low-level jet east of the Andes and comparison to those in the South Atlantic convergence zone. J Climate 17:3829–3842CrossRefGoogle Scholar
Lim GH, Wallace JM (1991) Structure and evolution of baroclinic waves as inferred from regression analysis. J Atmos Sci 48:1718–1732CrossRefGoogle Scholar
Madden RA, Julian PR (1971) Detection of a 40–50 day oscillation in the zonal wind in the tropical Pacific. J Atmos Sci 28:702–708CrossRefGoogle Scholar
Madden RA, Julian PR (1972) Description of global-scale circulation cells in the tropics with a 40–50 day period. J Atmos Sci 29:1109–1123CrossRefGoogle Scholar
Mo KC, Higgins RW (1998) The Pacific–South American mode and tropical convection during the southern hemisphere winter. Mon Wea Rev 126:1581–1596CrossRefGoogle Scholar
Nogués-Paegle J, Mo KC (1997) Alternating wet and dry conditions over South America during summer. Mon Wea Rev 125:279–291CrossRefGoogle Scholar
Nogués-Paegle J, Byerle LA, Mo KC (2000) Intraseasonal modulation of South American summer precipitation. Mon Wea Rev 128:837–850CrossRefGoogle Scholar
Sardeshmukh PD, Compo GP, Penland C (2000) Changes of probability associated with El Niño. J Climate 13:4268–4286CrossRefGoogle Scholar