Rainfall in Peru: Introduction

The climate of coastal Peru and southwestern Ecuador is mainly controlled by the Humboldt current, a cold ocean current which travels northward along the coastline of Chile and Peru before dispersing near the equator. The current helps cause dry conditions to persist continuously along the Peruvian littoral, making the land strip between the Andes and the Pacific Ocean one of the most arid deserts in the world. Every few years this condition is disturbed by a phenomenon called El Niņo, characterized by an ocean warming which appears off the coastlines of northwestern Peru and southwestern Ecuador. This warming modifies the Humboldt current destroying the persistent high pressure zone normally induced by the Humboldt on the west side of the Andes, which in turn generates major changes in the local meteorology and climate [13]. Excessive and severe rainstorms are the most disastrous consequences of El Niņo, and such storms can cause great damage to human life, property, crops, and animal life. The rainfall from such episodes causes the flooding of existing rivers, huaycos (mudslides), and the sudden creation of new rivers and lakes.

The 1982-1983 El Niņo has received wide attention for its severity [10]. In Peru alone, it was responsible for much loss of life, damage affecting over 80% of the highway system, railroad washouts, and material loss estimated in the billions of dollars. The heating of the ocean off the Peruvian coast during El Niņo periods has also caused the loss of much marine life. For example, the El Niņo of 1972 virtually destroyed the Peruvian anchovy fishing industry, which at that time represented a significant percentage of the world's protein supply with a catch of about 12 million tons per year [11]. Such destruction emphasizes the need to better understand the meteorological forces unleashed by this powerful ocean-air interaction.

Goldberg et al [6] have investigated the mesoscale structure of severe rainfall events during the 1982-1983 period by examining daily data from 66 rainfall stations in the Chiura-Piura region of northwestern Peru. Figure 1 shows the location of this region, which was selected because it was most severely affected by the 1982-1983 El Niņo and because the data were highly reliable and complete.

Figure 1. Location of Peruvian Rainfall Stations.

These data support the study of rainfall characteristics over this localized region during El Niņo and non-El Niņo periods, as a function of elevation, geographic location, and time of year.


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Last modified on March 02, 1999, G. Scott Owen, owen@siggraph.org