CPC Banner
Expert Assessments

Climate Assessment Table of Contents

Regional Climate Highlights - South America

Typical La Niņa-related impacts in South America include wetter-than-normal conditions over the Amazon basin and northern South America, and drier-than-normal conditions over southern Brazil, Uruguay and northeastern Argentina (Aceituno, 1988; Ropelewski and Halpert, 1989). These average features display considerable seasonality, with the wetter-than-normal conditions extending into Northeast Brazil during March–May and being confined to extreme northern South America during September–December, and the drier-than-normal conditions farther south being most prominent from September–December.

Many of the precipitation anomalies observed over South America during 1999 (Fig. 55) are consistent with those recorded during past cold episodes. Above-average precipitation was observed over the Amazon basin during DJF 1998–99 and MAM 1999 (Figs. 55a, b) and over extreme northern South America throughout the year.

In northern Venezuela the persistent pattern of above-normal rainfall resulted in saturated soil conditions, and was a contributing factor in producing the devastating floods and landslides in that country during 14–17 December 1999. High resolution experimental satellite estimates of precipitation during 15–17 December indicate that up to 475 mm fell in coastal sections near Caracas (Rod Scofield, NESDIS, personal communication). Local observations (Luis Hidalgo, personal communication) indicate that in the vicinity of the coast and along the slopes of the coastal mountains rainfall totals may have been up to twice as large as the satellite estimates.

Farther south, rainfall deficits accumulated substantially during SON over southern Brazil, Paraguay, Uruguay (Fig. 57a) and also over northeastern Argentina (Fig. 57b), consistent with La Niņa-related conditions. Rainfall deficits for the season exceeded 200 mm in portions of these regions (Figs. 55d, 57).

In other parts of northern South America, the observed rainfall pattern during 1999 deviated from that expected during cold episodes. For example, coastal Ecuador and northern Peru experienced above-average rainfall during DJF 1998–99 (Fig. 56a), while portions of northeastern Brazil experienced rainfall deficits during DJF and MAM (Figs. 56a, b).