• Bendix, J., 2000: Precipitation dynamics in Ecuador and northern Peru during the 1991/92 El Niño: A remote sensing perspective. Int. J. Remote Sens., 21 (3) , 533548. doi:10.1080/014311600210731.

    • Search Google Scholar
    • Export Citation
  • Douglas, M. W., , and W. Fernandez, 1997: Strengthening the meteorological sounding network over the tropical eastern Pacific Ocean and the Intertropical Americas. WMO Bull., 46 , 348351.

    • Search Google Scholar
    • Export Citation
  • Douglas, M. W., , and J. Murillo, 2008: The Pan American Climate Studies Sounding Network (PACS-SONET). Bull. Amer. Meteor. Soc., 89 , 17091725.

    • Search Google Scholar
    • Export Citation
  • Douglas, M., , M. Peña, , J. L. Santos, , N. Ordinola, , and L. Flores, 1999: El Niño 1997–1998 as seen from PACS-SONET observations. Preprints, Second Hayes Symp. on Seasonal-to-Interannual Climate Variability—1997/1998 ENSO Cycle, Dallas, TX, Amer. Meteor. Soc., 43–46.

  • Enfield, D. B., 1989: El Niño, past and present. Rev. Geophys., 27 , 159187.

  • Goldberg, R. A., , M. G. Tisnado, , and R. A. Scofield, 1987: Characteristics of extreme rainfall events in northwestern Peru during the 1982–1983 El Niño period. J. Geophys. Res., 92 , C13. 1422514241.

    • Search Google Scholar
    • Export Citation
  • Horel, J. D., , and A. G. Cornejo-Garrido, 1986: Convection along the coast of northern Peru during 1983: Spatial and temporal variation of clouds and rainfall. Mon. Wea. Rev., 114 , 20912105.

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

  • Knapp, K. R., 2004: ISCCP B1 Data at NCDC: A new climate resource. Preprints, 13th Satellite Meteorology and Oceanography Conf., Norfolk, VA, Amer. Meteor. Soc., P6.5. [Available online at http://ams.confex.com/ams/pdfpapers/77999.pdf.].

  • Liebmann, B., , and C. A. Smith, 1996: Description of a complete (interpolated) outgoing longwave radiation dataset. Bull. Amer. Meteor. Soc., 77 , 12751277.

    • Search Google Scholar
    • Export Citation
  • Peña, M., , and M. W. Douglas, 2002: Characteristics of wet and dry spells over the Pacific side of Central America during the rainy season. Mon. Wea. Rev., 130 , 30543073.

    • Search Google Scholar
    • Export Citation
  • Philander, S. G., 1990: El Niño, La Niña, and the Southern Oscillation. Academic Press, 286 pp.

  • Philander, S. G., 2004: Our Affair with El Niño: How We Transformed an Enchanting Peruvian Current into a Global Climate Hazard. Princeton University Press, 288 pp.

    • Search Google Scholar
    • Export Citation
  • Takahashi, K., 2004: The atmospheric circulation associated with extreme rainfall events in Piura, Peru, during the 1997–1998 and 2002 El Niño events. Ann. Geophys., 22 , 39173926.

    • Search Google Scholar
    • Export Citation
  • Trewartha, G. T., 1962: The Earth’s Problem Climates. University of Wisconsin Press, 334 pp.

  • Wang, C., , S-P. Xie, , and J. A. Carton, 2004: A global survey of ocean-atmosphere and climate variability. Earth Climate: The Ocean–Atmosphere Interaction, Geophys. Monogr., Vol. 147, Amer. Geophys. Union, 1–19.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 15 15 3
PDF Downloads 6 6 1

Synoptic Variability of Rainfall and Cloudiness along the Coasts of Northern Peru and Ecuador during the 1997/98 El Niño Event

View More View Less
  • 1 National Severe Storms Laboratory, Norman, Oklahoma
  • | 2 Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma
  • | 3 Universidad de Piura, Piura, Peru
  • | 4 National Weather Service, Omaha, Nebraska
© Get Permissions
Restricted access

Abstract

This paper describes the meteorological conditions associated with large fluctuations in rainfall over the coastal regions of northern Peru and Ecuador during the 1997/98 El Niño event. Using data from a network of routine rain gauges and special gauges established just prior to the onset of heavy rains, it is shown that large variations in the daily rainfall on quasi-weekly time scales occurred during the period January–April 1998. These rainfall fluctuations were approximately in phase along the coast from near the equator to ∼7°S. The daily rainfall data was averaged to develop a subset of wet and dry days, and then these dates were used as the basis for compositing. Special pilot balloon observations were composited with respect to the wet and dry days, showing that westerly and northerly wind anomalies are associated with wet spells. Composites of the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis and outgoing longwave radiation (OLR) data support a modest association of anomalous westerly wind events with enhanced rainfall.

The relationship observed between westerly zonal wind anomalies and rainfall west of the Andes during 1998 suggested using the NCEP reanalysis to develop composites based on westerly wind events observed during other years. Zonal wind anomalies at 700 hPa were used as the primary criterion for stratifying “wet” and “dry” days, despite reservations about the association between rainfall and zonal wind. Compositing Geostationary Operational Environmental Satellite (GOES) and OLR data for 220 west wind anomaly events from the months of January–April for the years 1990–2005 showed that they are associated with enhanced cloudiness that propagates eastward at ∼10 m s−1. The composites using NCEP reanalyses show the evolution of the wind field associated with the wet days and suggest a link between extratropical wave passages across North America and anomalous westerly wind events off the coast of Ecuador and northern Peru.

Corresponding author address: Dr. Michael W. Douglas, National Severe Storms Laboratory, 120 David L. Boren Blvd., Norman, OK 73072. Email: michael.douglas@noaa.gov

Abstract

This paper describes the meteorological conditions associated with large fluctuations in rainfall over the coastal regions of northern Peru and Ecuador during the 1997/98 El Niño event. Using data from a network of routine rain gauges and special gauges established just prior to the onset of heavy rains, it is shown that large variations in the daily rainfall on quasi-weekly time scales occurred during the period January–April 1998. These rainfall fluctuations were approximately in phase along the coast from near the equator to ∼7°S. The daily rainfall data was averaged to develop a subset of wet and dry days, and then these dates were used as the basis for compositing. Special pilot balloon observations were composited with respect to the wet and dry days, showing that westerly and northerly wind anomalies are associated with wet spells. Composites of the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis and outgoing longwave radiation (OLR) data support a modest association of anomalous westerly wind events with enhanced rainfall.

The relationship observed between westerly zonal wind anomalies and rainfall west of the Andes during 1998 suggested using the NCEP reanalysis to develop composites based on westerly wind events observed during other years. Zonal wind anomalies at 700 hPa were used as the primary criterion for stratifying “wet” and “dry” days, despite reservations about the association between rainfall and zonal wind. Compositing Geostationary Operational Environmental Satellite (GOES) and OLR data for 220 west wind anomaly events from the months of January–April for the years 1990–2005 showed that they are associated with enhanced cloudiness that propagates eastward at ∼10 m s−1. The composites using NCEP reanalyses show the evolution of the wind field associated with the wet days and suggest a link between extratropical wave passages across North America and anomalous westerly wind events off the coast of Ecuador and northern Peru.

Corresponding author address: Dr. Michael W. Douglas, National Severe Storms Laboratory, 120 David L. Boren Blvd., Norman, OK 73072. Email: michael.douglas@noaa.gov

Save