Wintertime Precipitation Episodes in Central Chile: Associated Meteorological Conditions and Orographic Influences

Mark Falvey Departamento de Geofísica, Universidad de Chile, Santiago, Chile

Search for other papers by Mark Falvey in
Current site
Google Scholar
PubMed
Close
and
René Garreaud Departamento de Geofísica, Universidad de Chile, Santiago, Chile

Search for other papers by René Garreaud in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

Central Chile (32°–35°S) is a mountainous and densely populated strip of land between the South American Pacific coast and the main divide of the Andes, 5000 m in height. In this study, wintertime precipitation episodes in central Chile are characterized using precipitation gauge, river discharge, radiosonde, and Special Sensor Microwave Imager (SSM/I) passive microwave radiometer observations over a 10-yr period (1993–2002). Precipitation episodes that typically occur as cold frontal rainstorms move over the region from west to east, within which the cross-mountain flow is blocked at lower levels. The influence of the Andes on the climatological precipitation pattern extends several hundred kilometers upstream of the coast. Over the mainland, the wintertime precipitation is most strongly related to the height of the mean topography surrounding the rain gauge sites, rather than the actual altitudes of the instruments, although higher-elevation locations are not well sampled by available rainfall observations. Between the coast and foothills of the Andes, the precipitation pattern is relatively uniform despite the complex coastal topography. On the western face of the Andes climatological enhancement factors of between 1 and 3 are inferred.

Regression analysis against radiosonde data at a coastal site reveals that the precipitation is strongly related to the zonal (cross mountain) moisture flux. The strongest relationship is found when the moisture flux is multiplied by the relative humidity. This variable explains 50% of the variance in daily area average precipitation in central Chile and up to 60% of the variance in the daily precipitation recorded at individual stations. The factors contributing to events of heavy precipitation enhancement in the Andes were examined. Events of heavy, but isolated, precipitation in the Andes tend to occur in the warmer, prefrontal sector of approaching storms and are associated with unusually high moisture fluxes near to and above the crest of the mountain range. Strongly frontal episodes, characterized by widespread rainfall throughout central Chile, lead to variable, but on average rather weak, enhancement in the Andes.

Corresponding author address: Dr. Mark Falvey, Departamento de Geofísica, Universidad de Chile, Blanco Encalada 2002, Santiago, Chile. Email: falvey@dgf.uchile.cl

Abstract

Central Chile (32°–35°S) is a mountainous and densely populated strip of land between the South American Pacific coast and the main divide of the Andes, 5000 m in height. In this study, wintertime precipitation episodes in central Chile are characterized using precipitation gauge, river discharge, radiosonde, and Special Sensor Microwave Imager (SSM/I) passive microwave radiometer observations over a 10-yr period (1993–2002). Precipitation episodes that typically occur as cold frontal rainstorms move over the region from west to east, within which the cross-mountain flow is blocked at lower levels. The influence of the Andes on the climatological precipitation pattern extends several hundred kilometers upstream of the coast. Over the mainland, the wintertime precipitation is most strongly related to the height of the mean topography surrounding the rain gauge sites, rather than the actual altitudes of the instruments, although higher-elevation locations are not well sampled by available rainfall observations. Between the coast and foothills of the Andes, the precipitation pattern is relatively uniform despite the complex coastal topography. On the western face of the Andes climatological enhancement factors of between 1 and 3 are inferred.

Regression analysis against radiosonde data at a coastal site reveals that the precipitation is strongly related to the zonal (cross mountain) moisture flux. The strongest relationship is found when the moisture flux is multiplied by the relative humidity. This variable explains 50% of the variance in daily area average precipitation in central Chile and up to 60% of the variance in the daily precipitation recorded at individual stations. The factors contributing to events of heavy precipitation enhancement in the Andes were examined. Events of heavy, but isolated, precipitation in the Andes tend to occur in the warmer, prefrontal sector of approaching storms and are associated with unusually high moisture fluxes near to and above the crest of the mountain range. Strongly frontal episodes, characterized by widespread rainfall throughout central Chile, lead to variable, but on average rather weak, enhancement in the Andes.

Corresponding author address: Dr. Mark Falvey, Departamento de Geofísica, Universidad de Chile, Blanco Encalada 2002, Santiago, Chile. Email: falvey@dgf.uchile.cl

Save
  • Aceituno, P., 1988: On the functioning of the Southern Oscillation in the South American sector. Part I: Surface climate. Mon. Wea. Rev., 116 , 505524.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • American Society of Civil Engineers (ASCE), 1996: Hydrology Handbook. 2d ed. ASCE, 800 pp.

  • Banta, R. M., 1990: The role of mountain flows in making clouds. Atmospheric Processes over Complex Terrain, Meteor. Monogr., No. 45, Amer. Meteor. Soc., 229–283.

    • Crossref
    • Export Citation
  • Bell, T. L., and Kundu P. N. , 2000: Dependence of satellite sampling error on monthly averaged rain rates: Comparison of simple models and recent studies. J. Climate, 13 , 449462.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Benjamin, S. G., Brown J. M. , Brundage K. J. , Schwartz B. E. , Smirnova T. G. , and Smith T. L. , 1998: RUC-2—The Rapid Update Cycle version 2. NWS Tech. Procedures Bulletin 448, NOAA/NWS, 18 pp.

  • Berg, W., and Avery S. K. , 1995: Evaluation of monthly rainfall estimates derived from the Special Sensor Microwave/Imager (SSM/I) over the tropical Pacific. J. Geophys. Res., 100 , D1. 12951316.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bousquet, O., and Smull B. F. , 2003: Observations and impacts of upstream blocking during a widespread orographic precipitation event. Quart. J. Roy. Meteor. Soc., 129 , 391409.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Carlson, T. N., 1998: Mid-Latitude Weather Systems. Amer. Meteor. Soc., 507 pp.

  • Carrasco, J. F., Casassa G. , and Quintana J. , 2005: Changes of the 0°C isotherm and the equilibrium line altitude in central Chile during the last quarter of the 20th century. Hydrol. Sci. J., 50 , 933948.

    • Search Google Scholar
    • Export Citation
  • Carruthers, D. J., and Choularton W. T. , 1983: A model of the feeder-seeder mechanism of orographic rain including stratification and wind-drift effects. Quart. J. Roy. Meteor. Soc., 109 , 575588.

    • Search Google Scholar
    • Export Citation
  • Casassa, G., 1995: Glacier inventory in Chile: Current status and recent glacier variations. Ann. Glaciol., 21 , 317322.

  • Chu, C-M., and Lin Y-L. , 2000: Effects of orography on the generation and propagation of mesoscale convective systems in a two-dimensional conditionally unstable flow. J. Atmos. Sci., 57 , 38173837.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Corripio, J. G., and Purves R. S. , 2005: Surface energy balance of high altitude glaciers in the central Andes: The effect of snow penitentes. Climate and Hydrology in Mountain Areas, C. de Jong, D. Collins, and R. Ranzi, Eds., Wiley & Sons, 15–29.

    • Search Google Scholar
    • Export Citation
  • Dettinger, M., Redmond K. , and Cayan D. , 2004: Winter orographic precipitation ratios in the Sierra Nevada—Large-scale atmospheric circulations and hydrologic consequences. J. Hydrometeor., 5 , 11021106.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Durran, D. R., and Klemp J. B. , 1982: The effects of moisture on the Brunt–Väisälä frequency. J. Atmos. Sci., 39 , 21522158.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Efron, B., and Tibshirani R. J. , 1993: An Introduction to the Bootstrap. Chapman and Hall, 436 pp.

  • Egger, J., and Hoinka K. P. , 1992: Fronts and orography. Meteor. Atmos. Phys., 48 , 336.

  • Falvey, M., and Garreaud R. D. , 2005: A numerical case study of an orographically enhanced frontal system in central Chile. Croat. Meteor. J., 40 , 486489.

    • Search Google Scholar
    • Export Citation
  • Fountain, A. G., and Tangborn W. V. , 1985: The effect of glaciers on streamflow variations. Water Resour. Res., 21 , 579586.

  • Fuenzalida, H., Sanchez R. , and Garreaud R. , 2005: A climatology of cut off lows in the Southern Hemisphere. J. Geophys. Res., 110 .D1801, doi:10.1029/2005JD005934.

    • Search Google Scholar
    • Export Citation
  • Garreaud, R., and Rutllant Y. J. , 1996: Análisis meteorológico del los aluviones de Antofagasta y Santiago de Chile en el periodo 1991–1993. Atmósfera, 9 , 251271.

    • Search Google Scholar
    • Export Citation
  • Grimm, A., Barros V. , and Doyle M. , 2000: Climate variability in southern South America associated with El Niño and La Niña events. J. Climate, 13 , 3558.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hayes, P., Rasmussen L. A. , and Conway H. , 2002: Estimating precipitation in the central Cascades of Washington. J. Hydrometeor., 3 , 335346.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hill, F. F., Browning K. A. , and Bader M. J. , 1981: Radar and rain gauge observations of orographic rain over south Wales. Quart. J. Roy. Meteor. Soc., 107 , 643670.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Houze, R. A., 1993: Cloud Dynamics. International Geophysics Series, Vol. 53, Academic Press, 573 pp.

  • Houze, R. A., and Medina S. , 2005: Turbulence as a mechanism for orographic precipitation enhancement. J. Atmos. Sci., 62 , 35993623.

  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77 , 437471.

  • Medina, S., and Houze R. A. Jr., 2003: Air motions and precipitation growth in alpine storms. Quart. J. Roy. Meteor. Soc., 129 , 345371.

  • Medina, S., Smull B. F. , Houze R. A. Jr., and Steiner M. , 2005: Cross-barrier flow during orographic precipitation events: Results from MAP and IMPROVE. J. Atmos. Sci., 62 , 35803598.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Montecinos, A., and Aceituno P. , 2003: Seasonality of the ENSO-related rainfall variability in central Chile and associated circulation anomalies. J. Climate, 16 , 281296.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Montecinos, A., Diaz A. , and Aceituno P. , 2000: Seasonal diagnostic and predictability of rainfall in subtropical South America based on tropical Pacific SST. J. Climate, 13 , 746758.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Neiman, P. J., Ralph F. M. , White A. B. , Kingsmill D. E. , and Persson P. O. G. , 2002: The statistical relationship between upslope flow and rainfall in California’s coastal mountains—Observations during CALJET. Mon. Wea. Rev., 130 , 14681492.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Neiman, P. J., Persson P. O. G. , Ralph F. M. , Jorgensen D. P. , White A. B. , and Kingsmill D. E. , 2004: Modification of fronts and precipitation by coastal blocking during an intense landfalling winter storm in southern California: Observations during CALJET. Mon. Wea. Rev., 132 , 242273.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Overland, J. E., and Bond N. A. , 1993: The influence of coastal orography: The Yakutat storm. Mon. Wea. Rev., 121 , 13881397.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Overland, J. E., and Bond N. A. , 1995: Observations and scale analysis of coastal wind jets. Mon. Wea. Rev., 123 , 29342941.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Pandey, G. R., Cayan D. R. , and Georgakakos K. P. , 1999: Precipitation structure in the Sierra Nevada of California during winter. J. Geophys. Res., 104 , D10. 1201912030.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Pandey, G. R., Cayan D. R. , Dettinger M. D. , and Georgakakos K. P. , 2000: A hybrid model for interpolating daily precipitation in the Sierra Nevada of California during winter. J. Hydrometeor., 1 , 491506.

    • Search Google Scholar
    • Export Citation
  • Pizarro, J. G., and Montecinos A. , 2000: Cutoff cyclones off the subtropical coast of Chile. Preprints, Sixth Int. Conf. on Southern Hemisphere Meteorology and Oceanography, Santiago, Chile, Amer. Meteor. Soc., 278–279.

  • Rasmussen, L. A., and Tangborn W. V. , 1976: Hydrology of the North Cascades region, Washington. 1: Runoff, precipitation, and storage characteristics. Water Resour. Res., 12 , 187202.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rasmussen, L. A., Conway H. , and Hayes P. S. , 2001: Estimating Olympic Peninsula precipitation from upper air wind and humidity. J. Geophys. Res., 106 , 14931501.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rivera, A., Acuña C. , Casassa A. G. , and Bown F. , 2002: Use of remotely sensed and field data to estimate the contribution of Chilean glaciers to eustatic sea-level rise. Ann. Glaciol., 34 , 367372.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Roe, G. H., 2005: Orographic precipitation. Annu. Rev. Earth Planet. Sci., 33 , 645671.

  • Rutllant, J., and Fuenzalida H. , 1991: Synoptic aspects of the central Chile rainfall variability associated with the Southern Oscillation. Int. J. Climatol., 11 , 6376.

    • Search Google Scholar
    • Export Citation
  • Saavedra, N., and Foppiano A. J. , 1992: Monthly mean pressure model for central Chile. Int. J. Climatol., 12 , 469480.

  • Sankarasubramanian, A., and Vogel R. M. , 2002: Annual hydroclimatology of the United States. Water Resour. Res., 38 , 10831093.

  • Sinclair, M. R., 1994: A diagnostic model for estimating orographic precipitation. J. Appl. Meteor., 33 , 11631175.

  • Smith, E. A., and Coauthors, 1998: Results of WetNet PIP-2 Project. J. Atmos. Sci., 55 , 14831536.

  • Smith, R. B., 1979: The influence of mountains on the atmosphere. Advances in Geophysics, Vol. 21, Academic Press, 87–230.

    • Crossref
    • Export Citation
  • Smolarkiewicz, P. K., and Rotunno R. , 1990: Low Froude number flow past three-dimensional obstacles. Part II: Upwind flow reversal zone. J. Atmos. Sci., 47 , 14981511.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wentz, F. J., 1997: A well-calibrated ocean algorithm for SSM/I. J. Geophys. Res., 102 , 87038718.

  • Wilks, D. S., 1995: Statistical Methods in the Atmospheric Sciences: An Introduction. Academic Press, 467 pp.

  • Wratt, D. S., Revell M. J. , Sinclair M. R. , Gray W. R. , Henderson R. D. , and Chater A. M. , 2000: Relationships between air mass properties and mesoscale rainfall in New Zealand’s Southern Alps. Atmos. Res., 52 , 261282.

    • Crossref
    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 1361 403 28
PDF Downloads 805 225 26