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  • Author or Editor: Angel G. Cornejo-Garrido x
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Angel G. Cornejo-Garrido
and
Peter H. Stone

Abstract

The heat budget of the Walker circulation near 10°S is studied. The primary drive for the circulation is the heating due to zonal variations in condensation. The relative heating and cooling at different longitudes is balanced approximately by adiabatic cooling and heating due to rising and sinking motions. In the region where the condensation heating is a maximum two different analyses indicate that the evaporation is a minimum, even though the sea surface temperature is a maximum. This is because the surface heating is dominated by the insolation, which is a minimum in the region of enhanced condensation where the cloud cover is a maximum. This implies that the region of enhanced condensation is associated with a region of moisture convergence rather than with a region of enhanced evaporation, and that the sea surface temperature gradients only play a secondary role in forcing the Walker circulation.

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John D. Horel
and
Angel G. Cornejo-Garrido

Abstract

Streamflow and historical records indicate that flooding in northern Peru was more severe during 1983 than during any year since 1891. A case study of the meteorological conditions along the northwest coast of South America from 10°S to 10°N during 1982–83 is presented. Station rainfall and satellite-derived outgoing infrared observations are used to deduce the structure and time evolution of convection in this region.

Substantial rainfall amounts were first observed along the western slopes of the Andes Mountains and coastal plain of southern Ecuador during November and December 1982, and it continued to rain in this region through June 1983. In northern Peru, the onset of the rains along the coastal plain was delayed until January 1983 and ended abruptly during mid-June 1983. Convective activity was much greater along the coastal strip than over the eastern equatorial Pacific to the cast of 100°W until May-June 1983. In addition, cloudiness was strongly modulated on the diurnal time scale, with more clouds during the night and early morning than during the afternoon.

The distribution of rainfall along the Peruvian littoral is compared to local changes in sea surface temperature, surface equivalent potential temperature, and surface wind. These comparisons suggest that abnormally high coastal ocean temperatures during the first half of 1983 aided the outbreak of convection during this period. However, the latitudinal extent and timing of the rainfall was quite different from that of sea surface temperature or surface equivalent potential temperature.

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