El Nino The climate over large parts of South America is strongly influenced by the El Nino. During warm episodes, drier-than-normal conditions are generally observed across northeastern South America during July-March, while enhanced precipitation tends to be observed throughout southeastern South America during November-February and throughout central Chile during the austral winter. Also, above-average temperatures are typically observed along the west coast of South America from May-April Brazil Winter and Spring Highlights-Precipitation was below normal across northern Brazil and parts of the Amazon Basin during June- November.
Over northern Brazil, deficits of 180-360 mm were recorded. These conditions caused a reduction in the level of many rivers throughout the region, which impacted the generation of hydroelectric power in the northern states of Brazil. The dryness was linked to anomalous large-scale subsidence, in association with a weakened upper-level anticyclonic circulation. and with a reduced low-level inflow of warm, moist air into the region. During October, much of the heavy rainfall was associated with intense mesoscale convective systems triggered by extratropical frontal systems moving through the region.
Time series of daily October precipitation are for two cities (Cruz Alta and Campos Novos) in the southern part of Brazil. For the month as a whole, both cities recorded extremely large totals of over 500 mm, with much of the rain falling during two distinct periods: 916 and 2931 October. In the first period, totals approached 300 mm in both cities, while in the second period totals reached 130 mm at Cruz Alta and 180 mm at Campos Novos. These downpours were linked to larger-scale convective systems that resulted in numerous rivers overflowing their banks and flooding in many cities.
Winter Precipitation in central Chile-In central Chile (30°-40°S), the rainy season typically lasts from May-October, and reaches maximum strength during June-July. Most of the region normally receives more than 75% of its annual rainfall during this rainy season, with totals in the North typically reaching 200-300 mm and totals in the South exceeding 800 mm. During May-October 1997, precipitation totals ranged from 300-400 mm in the North to 900-1000 mm in the South. averaging 100-300 mm above normal throughout the region.
The area-mean precipitation was above-average during every month except August, with 200% of normal recorded across the region during June. Northwestern Peru warmth-Surface air temperatures in northwestern coastal Peru and western coastal Ecuador exhibit a well-defined annual cycle that is controlled by the SSTs over the extreme eastern Pacific. This annual cycle exhibits an August-October minimum and a March-April maximum. Interannual variations in surface temperature throughout the region are strongly controlled by the ENSO, with warmer (colder) than normal conditions observed during Pacific warm (cold) episodes.