• Baethgen, W., and Coauthors, cited. 2001: Climatology and hydrology of the Plata Basin, WCRP/CLIVAR/VAMOS, 2001. [Available online at http://www.clivar.org/organization/vamos/Publications/laplata.pdf.].

  • Barros, V., , Doyle M. , , González M. , , Camilloni I. , , Bejaran R. , , and Caffera R. M. , 2002: Climate variability over subtropical South America and the South American monsoon: A review. Meteorologica, 27 , 3357.

    • Search Google Scholar
    • Export Citation
  • Barros, V., , Chamorro L. , , Coronel G. , , and Baez J. , 2004: The major discharge events in the Paraguay River: Magnitudes, source regions, and climate forcings. J. Hydrometeor., 5 , 11611170.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Berbery, E. H., , and Collini E. A. , 2000: Springtime precipitation and water vapor flux over southeastern South America. Mon. Wea. Rev., 128 , 13281346.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Berbery, E. H., , and Barros V. R. , 2002: The hydrologic cycle of the La Plata basin in South America. J. Hydrometeor., 3 , 630645.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Berbery, E. H., , Luo Y. , , Mitchell K. E. , , and Betts A. K. , 2003: Eta Model estimated land surface processes and the hydrologic cycle of the Mississippi basin. J. Geophys. Res., 108 .8852, doi:10.1029/2002JD003192.

    • Search Google Scholar
    • Export Citation
  • Betts, A. K., , and Miller M. J. , 1986: A new convective adjustment scheme. Part II: Single column tests using GATE wave, BOMEX, ATEX and Arctic air-mass data sets. Quart. J. Roy. Meteor. Soc., 112 , 693710.

    • Search Google Scholar
    • Export Citation
  • Bolton, D., 1980: The computation of equivalent potential temperature. Mon. Wea. Rev., 108 , 10461053.

  • Camilloni, I. A., , and Barros V. R. , 2003: Extreme discharge events in the Paraná River and their climate forcing. J. Hydrol., 278 , 94106.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Casarin, D. P., , and Kousky V. E. , 1986: Anomalias de precipitação no sul do Brasil e variações na circulação atmosférica (Precipitation anomalies in southern Brazil and variations in the atmospheric circulation). Rev. Bras. Meteor., 1 , 8390.

    • Search Google Scholar
    • Export Citation
  • Chen, F., , Mitchell K. , , and Schaake J. , 1996: Modeling of land surface evaporation by four schemes and comparison with FIFE observations. J. Geophys. Res., 101 , D3. 72517268.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Cosgrove, B. A., and Coauthors, 2003: Land surface model spin-up behavior in the North American Land Data Assimilation System (NLDAS). J. Geophys. Res., 108 .8845, doi:10.1029/2002JD003316.

    • Search Google Scholar
    • Export Citation
  • Diaz, A., , and Aceituno P. , 2003: Atmospheric circulation anomalies during episodes of enhanced and reduced convective cloudiness over Uruguay. J. Climate, 16 , 31713185.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Doyle, E. M., , and Barros V. R. , 2002: Midsummer low-level circulation and precipitation in subtropical South America and related sea surface temperature anomalies in the South Atlantic. J. Climate, 15 , 33943410.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ek, M. B., , Mitchell K. E. , , Lin Y. , , Grunmann P. , , Rogers E. , , Gayno G. , , Koren V. , , and Tarpley J. D. , 2003: Implementation of Noah land surface model advances in the National Centers for Environmental Prediction operational mesoscale Eta Model. J. Geophys. Res., 108 .8851, doi:10.1029/2002JD003296.

    • Search Google Scholar
    • Export Citation
  • Fu, R., , Zhu B. , , and Dickinson R. E. , 1999: How do atmosphere and land surface influence seasonal changes of convection in the tropical Amazon? J. Climate, 12 , 13061321.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gan, M. A., , Kousky V. E. , , and Ropelewski C. F. , 2004: The South America monsoon circulation and its relationship to rainfall over west-central Brazil. J. Climate, 17 , 4766.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Grimm, A. M., , Ferraz S. E. T. , , and Gomes J. , 1998: Precipitation anomalies in southern Brazil associated with El Niño and La Niña events. J. Climate, 11 , 28632880.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Herdies, D. L., , da Silva A. , , Silva Dias M. A. F. , , and Nieto Ferreira R. , 2002: Moisture budget of the bimodal pattern of the summer circulation over South America. J. Geophys. Res., 107 .8075, doi:10.1029/2001JD000997.

    • Search Google Scholar
    • Export Citation
  • Janjić, Z. I., 1990: The step-mountain coordinate: Physical package. Mon. Wea. Rev., 118 , 14291443.

  • Janjić, Z. I., 1994: The step-mountain eta coordinate model: Further developments of the convection, viscous sublayer, and turbulence closure schemes. Mon. Wea. Rev., 122 , 927945.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jones, C., , and Carvalho L. M. V. , 2002: Active and break phases in the South American monsoon system. J. Climate, 15 , 905914.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kodama, Y. M., 1993: Large-scale common features of the sub-tropical convergence zones (the Baiu frontal zone, the SPZ, and the SACZ). Part II: Conditions of the circulations for generating the STCZs. J. Meteor. Soc. Japan, 71 , 581610.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kousky, V. E., 1988: Pentad outgoing longwave radiation climatology for the South American sector. Rev. Bras. Meteor., 3 , 217231.

  • Kousky, V. E., , and Cavalcanti I. F. A. , 1988: Precipitation and atmospheric circulation anomaly patterns in the South American sector. Rev. Bras. Meteor., 3 , 199206.

    • Search Google Scholar
    • Export Citation
  • Kousky, V. E., , and Ropelewski C. F. , 1997: The Tropospheric Seasonally Varying Mean Climate over Western Hemisphere (1979–1995). NCEP/Climate Prediction Center Atlas 3, 24 pp. [Available online at http://www.cpc.ncep.noaa.gov/research_papers/ncep_cpc_atlas/3/.].

  • Kousky, V. E., , Kayano M. T. , , and Cavalcanti I. F. A. , 1984: A review of the Southern Oscillation: Oceanic–atmospheric circulation changes and related rainfall anomalies. Tellus, 36A , 490504.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Labraga, J. C., , Frumento O. , , and Lopez M. , 2000: The atmospheric water vapor cycle in South America and the tropospheric circulation. J. Climate, 13 , 18991915.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Liebmann, B., , Kiladis G. N. , , Vera C. S. , , Saulo A. C. , , and Carvalho L. M. V. , 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 , 38293842.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Luo, Y., , Berbery E. H. , , and Mitchell K. E. , 2005: The operational Eta Model precipitation and surface hydrologic cycle of the Columbia and Colorado basins. J. Hydrometeor., 6 , 341370.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Marengo, J. A., , Soares W. R. , , Saulo C. , , and Nicolini M. , 2004: Climatology of the low-level jet east of the Andes as derived from the NCEP–NCAR reanalyses: Characteristics and temporal variability. J. Climate, 17 , 22612280.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Mohr, K. I., , and Zipser E. J. , 1996: Defining mesoscale convective systems by their 85-GHz ice-scattering signatures. Bull. Amer. Meteor. Soc., 77 , 11791189.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nogués-Paegle, J., , and Mo K. C. , 1997: Alternating wet and dry conditions over South America during summer. Mon. Wea. Rev., 125 , 279291.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nogués-Paegle, J., and Coauthors, 2002: Progress in Pan American CLIVAR research: Understanding the South American monsoon. Meteorologica, 27 , 332.

    • Search Google Scholar
    • Export Citation
  • Paegle, J. N., and Coauthors, 2001: American low level jets—A scientific prospectus and implementation plan. International CLIVAR Project Office, Southampton, United Kingdom, 120 pp. [Available online at http://www.clivar.org/organization/vamos/Publications/alls.pdf.].

  • Rickenbach, T. M., , Ferreira R. N. , , Halverson J. B. , , Herdies D. L. , , and Silva Dias M. A. F. , 2002: Modulation of convection in the southwestern Amazon basin by extratropical stationary fronts. J. Geophys. Res., 107 .8040, doi:10.1029/2000JD000263.

    • Search Google Scholar
    • Export Citation
  • Robertson, A. W., , and Mechoso C. R. , 2000: Interannual and interdecadal variability of the South Atlantic convergence zone. Mon. Wea. Rev., 128 , 29472957.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rodell, M., , Houser P. R. , , Berg A. A. , , and Famiglietti J. S. , 2005: Evaluation of 10 methods for initializing a land surface model. J. Hydrometeor., 6 , 146155.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rodwell, M. J., , and Hoskins B. J. , 2001: Subtropical anticyclones and summer monsoons. J. Climate, 14 , 31923211.

  • Ropelewski, C. F., , and Halpert M. S. , 1987: Global and regional scale precipitation patterns associated with the El Niño–Southern Oscillation. Mon. Wea. Rev., 115 , 16061626.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Schaake, J. C., , Koren V. I. , , Duan Q. Y. , , Mitchell K. , , and Chen F. , 1996: Simple water balance model for estimating runoff at different spatial and temporal scales. J. Geophys. Res., 101 , D3. 74617475.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Shi, W., , Higgins R. W. , , Yarosh E. , , and Kousky V. E. , 2000: The Annual Cycle and Variability of Precipitation in Brazil. NCEP/Climate Prediction Center Atlas 9, 24 pp. [Available online at http://www.cpc.ncep.noaa.gov/research_papers/ncep_cpc_atlas/9/.].

  • Silva, V. B. S., , and Kousky V. E. , 2001: Variabilidade intra-sazonal de precipitação sobre o leste do Brasil durante o verão de 1999/2000 (Intraseasonal variability of precipitation over eastern Brazil during the summer 1999/2000). Rev. Bras. Meteor., 16 , 187199.

    • Search Google Scholar
    • Export Citation
  • Siqueira, J. R., , and Machado L. A. T. , 2004: Influence of frontal systems on the day-to-day convection variability over South America. J. Climate, 17 , 17541766.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Velasco, I., , and Fritsch J. M. , 1987: Mesoscale convective complexes in the Americas. J. Geophys. Res., 92 , D8. 95919613.

  • Virji, H., 1981: A preliminary study of summertime tropospheric circulation patterns over South America estimated from cloud winds. Mon. Wea. Rev., 109 , 599610.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yang, Z. L., , Dickinson R. E. , , Henderson-Sellers A. , , and Pitman A. J. , 1995: Preliminary study of spin-up processes in land-surface models with the first stage data of Project for Intercomparison of Land-surface Parameterization Schemes Phase 1(a). J. Geophys. Res., 100 , D8. 1655316578.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zhou, J., , and Lau K. M. , 1998: Does a monsoon climate exist over South America? J. Climate, 11 , 10201040.

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Intense Rainfall Events Affecting the La Plata Basin

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  • 1 Department of Atmospheric and Oceanic Science/ESSIC, University of Maryland, College Park, College Park, Maryland
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Abstract

The circulation features associated with intense precipitation events over the La Plata Basin (LPB) during the austral summers of 2001/02 and 2002/03 are investigated using the Eta Model runs generated at the University of Maryland. Based on the main mode of variability over LPB, two regions were selected: (i) the region of Brazil that is at the core of the South American summer monsoon system (SAMS) and (ii) the central region of LPB in southeastern South America (SESA). First, a comparison between the 24-h total precipitation in the Eta Model and the 24-h observed precipitation was made. Results show that the Eta Model captures well the temporal variability of precipitation events in both regions, although a positive bias is noticed over SAMS. Likewise, the model reproduces the distribution of precipitation rate over SESA, but not over SAMS. Nevertheless, the distribution of the moisture flux convergence intensity, which represents the dynamical forcing, is closer in shape to the observed precipitation distribution, suggesting that the model can be a useful tool in identifying the forcing for heavy precipitation events over both regions.

Composites of atmospheric and surface variables were constructed for intense precipitation events during austral summer over both regions. Intense rainfall over the central La Plata Basin (SESA) is linked to an amplified upper-tropospheric midlatitude wave pattern in which rainfall occurs just east of an enhanced cyclonic circulation. Accompanying this circulation pattern, an enhanced low-level jet (LLJ) transports warm, moist air from the Amazon toward the region, contributing to an increase in the thermal contrast over SESA. The combined patterns of thermal and dynamical variables suggest that large-scale systems, like frontal systems, are important in producing intense rainfall events. The SAMS region events have a similar upper-level structure as in SESA, but they are longer lived. In this case, the moisture fluxes are determined by an eastward shift of the LLJ, but also directly from the Amazon Basin to the north. As expected, precipitation events produce large increases of simulated runoff. The largest impact is on the SESA region, affecting the streamflow of the Paraná, Paraguay, and Uruguay, the three main rivers of the LPB.

Corresponding author address: Ernesto Hugo Berbery, Department of Atmospheric and Oceanic Science/ESSIC, University of Maryland, College Park, 3427 Computer and Space Sciences Building, College Park, MD 20742-2425. Email: berbery@atmos.umd.edu

Abstract

The circulation features associated with intense precipitation events over the La Plata Basin (LPB) during the austral summers of 2001/02 and 2002/03 are investigated using the Eta Model runs generated at the University of Maryland. Based on the main mode of variability over LPB, two regions were selected: (i) the region of Brazil that is at the core of the South American summer monsoon system (SAMS) and (ii) the central region of LPB in southeastern South America (SESA). First, a comparison between the 24-h total precipitation in the Eta Model and the 24-h observed precipitation was made. Results show that the Eta Model captures well the temporal variability of precipitation events in both regions, although a positive bias is noticed over SAMS. Likewise, the model reproduces the distribution of precipitation rate over SESA, but not over SAMS. Nevertheless, the distribution of the moisture flux convergence intensity, which represents the dynamical forcing, is closer in shape to the observed precipitation distribution, suggesting that the model can be a useful tool in identifying the forcing for heavy precipitation events over both regions.

Composites of atmospheric and surface variables were constructed for intense precipitation events during austral summer over both regions. Intense rainfall over the central La Plata Basin (SESA) is linked to an amplified upper-tropospheric midlatitude wave pattern in which rainfall occurs just east of an enhanced cyclonic circulation. Accompanying this circulation pattern, an enhanced low-level jet (LLJ) transports warm, moist air from the Amazon toward the region, contributing to an increase in the thermal contrast over SESA. The combined patterns of thermal and dynamical variables suggest that large-scale systems, like frontal systems, are important in producing intense rainfall events. The SAMS region events have a similar upper-level structure as in SESA, but they are longer lived. In this case, the moisture fluxes are determined by an eastward shift of the LLJ, but also directly from the Amazon Basin to the north. As expected, precipitation events produce large increases of simulated runoff. The largest impact is on the SESA region, affecting the streamflow of the Paraná, Paraguay, and Uruguay, the three main rivers of the LPB.

Corresponding author address: Ernesto Hugo Berbery, Department of Atmospheric and Oceanic Science/ESSIC, University of Maryland, College Park, 3427 Computer and Space Sciences Building, College Park, MD 20742-2425. Email: berbery@atmos.umd.edu

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