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Abstract:

Midlatitude disturbances such as intense cold fronts and cutoff lows are a very important cause of severe-weather events over the southern part of South America, particularly during the austral winter months. Behind cold fronts, cold air from higher latitudes is forced to flow equatorward to the east of the Andes. Occasionally fronts might produce cold surges in tropical latitudes, with freezing temperatures (referred as to GEADAS in Portuguese) over crop-growing areas of southern, southeastern, and central Brazil. The structure and dynamical processes of winter synoptic-scale waves associated with cold surges over South America are documented in this paper. It is shown that the rotated extended empirical orthogonal function technique is capable of extracting well-defined regional patterns from 850-hPa meridional-wind perturbation fields. Over South America, waves behave very differently in the lower and middle troposphere: while upper-level waves propagate northeastward as they cross the Andes, evolving in a manner consistent with the concept of Rossby wave dispersion, at lower levels, waves tend to conform to the shape of the mountain range, in agreement with the theory of topographic Rossby waves. However, it was found that cold surges do not seem to result from the generation of rotationally trapped waves. Significant differences have been found between synoptic-scale patterns associated with cold surges over extratropical South America (NO GEADA composites) and synoptic-scale patterns associated with major cold-air outbreaks that produce extreme low temperatures at tropical regions (GEADA composites). While both surges are characterized by a long-wave pattern consisting of a cyclonic perturbation over South America and anticyclonic perturbation behind over the southern Pacific Ocean, at the early stages of GEADA composites, two additional features were identified: a subpolar and subtropical short-wave pattern. The presence of the upper-level subtropical cyclonic perturbation is associated with the subtropical jetstream location farther north, which would facilitate the equatorward penetration of frontal systems. In addition, this cyclonic perturbation enhances rising motion at subtropical and tropical latitudes that is associated with a well-defined secondary circulation with its descending branch over central Argentina. It is shown that this configuration favors the rapid and equatorward penetration of the subpolar short-wave trough, the temperature decrease over southern Brazil, and the anticyclone intensification over central Argentina. Thus the presence of the subtropical upper-level feature plays a key role on the cold-surge occurrence over tropical regions of South America.

Registro:

Documento: Artículo
Título:A diagnostic study of cold-air outbreaks over South America
Autor:Vera, C.S.; Vigliarolo, P.K.
Filiación:CIMA/Depto. de Cie. de la Atmosfera, Universidad de Buenos Aires/CONICET, Buenos Aires, Argentina
CIMA, Ciudad Universitaria, Pabellón 2, 2do. piso, 1428 Buenos Aires, Argentina
Palabras clave:cold air; frontal feature; synoptic meteorology; South America
Año:2000
Volumen:128
Número:1
Página de inicio:3
Página de fin:24
DOI: http://dx.doi.org/10.1175/1520-0493(2000)128<0003:ADSOCA>2.0.CO;2
Título revista:Monthly Weather Review
Título revista abreviado:Mon Weather Rev
ISSN:00270644
CODEN:MWREA
Registro:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00270644_v128_n1_p3_Vera

Referencias:

  • Algarbe, V.R., Cavalcanti, I., Características da Circulação atmosférica associadas a ocorrência de geadas no sul do Brasil (1988) Setimo Congresso Brasileiro de Meteorología, pp. 351-355. , Belo Horizonte, Brazil, SBMET
  • Berbery, E.H., Vera, C.S., Characteristics of the Southern Hemisphere winter storm track with filtered and unfiltered data (1996) J. Atmos. Sci., 53, pp. 468-481
  • Nogués-Paegle, J., Horel, J., Wavelike Southern Hemisphere extratropical teleconnections (1992) J. Atmos. Sci., 49, pp. 155-177
  • Bluestein, H.B., (1992) Synoptic-Dynamic Meteorology in Midlatiludes. Vol. 1, Principles of Kinematics and Dynamics, 1, 431p. , Oxford University Press
  • Colle, B.A., Mass, C.F., The structure and evolution of cold surges east of the Rocky Mountains (1995) Mon. Wea. Rev., 123, pp. 2577-2610
  • Chang, C.-P., Lau, K.M.W., Northeasterly cold surges and near-equatorial disturbances over the winter MONEX during December 1974. Part II: Planetary-scale aspects (1980) Mon. Wea. Rev., 108, pp. 298-312
  • Chang, E.K.M., Downstream development of baroclinic waves as inferred from regression analysis (1993) J. Atmos. Sci., 50, pp. 2038-2053
  • Chu, P.-S., Park, S.-U., Regional circulation characteristics associated with a cold surge event of east Asia during winter MONEX (1984) Mon. Wea. Rev., 112, pp. 955-965
  • Figueroa, S.N., Nobre, C.A., Precipitation distribution over central and western tropical South America (1990) Climanálise, 5, pp. 36-45
  • Fortune, M., Kousky, V.E., Two severe freezes in Brazil: Precursors and synoptic evolution (1983) Mon. Wea. Rev., 111, pp. 181-196
  • Gan, M.A., Rao, V.B., The influence of the Andes Cordillera on transient disturbances (1994) Mon. Wea. Rev., 122, pp. 1141-1157
  • Hoskins, B.J., James, I.N., White, G.H., The shape, propagation, and mean-flow interaction of large-scale weather systems (1983) J. Almos. Sci., 40, pp. 1592-1612
  • Hsu, H.-H., Propagation of low-level circulation features in the vicinity of mountain ranges (1987) Mon. Wea. Rev., 115, pp. 1864-1892
  • Lau, K.-H., Lau, N.-C., Observed structure and propagation characteristics of tropical summertime synoptic-scale disturbances (1990) Mon. Wea. Rev., 118, pp. 1888-1913
  • The energetics and propagation dynamics of tropical summertime synoptic-scale disturbances (1992) Mon. Wea. Rev., 120, pp. 2523-2539
  • Lau, K.-M., Chan, P., Aspects of the 40-50 day oscillation during the northern winter as inferred from outgoing longwave radiation (1985) Mon. Wea. Rev., 113, pp. 1889-1909
  • Lichtenstein, E.R., Some influences of the Andes cordillera on the synoptic-scale circulation (1989) Extended Abstracts, Third Int. Conf. on Southern Hemisphere Meteorology and Oceanography, pp. 190-191. , Buenos Aires, Brazil, Amer. Meteor. Soc
  • Lim, G.H., Wallace, J.M., Structure and evolution of baroclinic waves as inferred from regression analysis (1991) J. Atmos. Sci., 48, pp. 1718-1732
  • Marengo, J., Cornejo, A., Satyamurty, P., Nobre, C., Cold surges in tropical and extratropical South America: The strong event in June 1994 (1997) Mon. Wea. Rev., 125, pp. 2759-2786
  • O'Lenic, A.E., Livezey, R.E., Practical considerations in the use of rotated principal component analysis (RPCA) in diagnostics studies of upper-air height fields (1988) Mon. Wea. Rev., 116, pp. 1682-1689
  • Rusticucci, M., Vargas, W., Synoptic situations related to spells of extreme temperatures over Argentina (1995) Meteor. Appl., 2, pp. 291-300
  • Schultz, D., Bracken, W.E., Bosart, L., Hakim, G., Bedrick, M., Dickinson, M., Tyle, K., The 1993 superstorm cold surge: Frontal structure, gap flow, and extratropical impact (1997) Mon. Wea. Rev., 125, pp. 5-39
  • Planetary- and synoptic-scale signature associated with Central American cold surges (1998) Mon. Wea. Rev., 126, pp. 5-27
  • Trenberth, K.E., Observed Southern Hemisphere eddy statistics at 500 mb; frequency and spatial dependence (1981) J. Atmos. Sci., 38, pp. 2585-2605
  • (1992) Global Analyses from ECMWF and Atlas of 1000 to 10 Mb Circulation Statistics, 191p. , NCAR Tech. Note NCAR/TN-373+STR, [Available from National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000.]
  • Weare, B.C., Nasstrom, J.S., Examples of extended empirical orthogonal function analyses (1982) Mon. Wea. Rev., 110, pp. 481-485
  • Wu, M.C., Chan, J.C.L., Upper-level features associated with winter monsoon surges over South China (1997) Mon. Wea. Rev., 125, pp. 317-340
  • Yu, J.-Y., Hartmann, D.L., Orographic influences on the distribution and generation of atmospheric variability in a GCM (1995) J. Atmos. Sci., 52, pp. 2428-2443

Citas:

---------- APA ----------
Vera, C.S. & Vigliarolo, P.K. (2000) . A diagnostic study of cold-air outbreaks over South America. Monthly Weather Review, 128(1), 3-24.
http://dx.doi.org/10.1175/1520-0493(2000)128<0003:ADSOCA>2.0.CO;2
---------- CHICAGO ----------
Vera, C.S., Vigliarolo, P.K. "A diagnostic study of cold-air outbreaks over South America" . Monthly Weather Review 128, no. 1 (2000) : 3-24.
http://dx.doi.org/10.1175/1520-0493(2000)128<0003:ADSOCA>2.0.CO;2
---------- MLA ----------
Vera, C.S., Vigliarolo, P.K. "A diagnostic study of cold-air outbreaks over South America" . Monthly Weather Review, vol. 128, no. 1, 2000, pp. 3-24.
http://dx.doi.org/10.1175/1520-0493(2000)128<0003:ADSOCA>2.0.CO;2
---------- VANCOUVER ----------
Vera, C.S., Vigliarolo, P.K. A diagnostic study of cold-air outbreaks over South America. Mon Weather Rev. 2000;128(1):3-24.
http://dx.doi.org/10.1175/1520-0493(2000)128<0003:ADSOCA>2.0.CO;2