Interaction between Coastal Upwelling and Local Winds at Cabo Frio, Brazil: An Observational Study

Abstract

The relationships between coastal upwelling and local winds at Cabo Frio (Brazil) are studied using SST and time series of surface wind for a 10-yr period (1971?80). The results show that the seasonal variations of SST and local winds are closely related. Sea-breeze circulation is intensified by the enhancement of the land?sea temperature gradient due to cold water upwelling near the coast; coastal upwelling, in turn, is associated with strong northeasterlies. This result confirms the conclusions of earlier modeling studies. Interannual variability is also apparent in the results. During the period from 1971 to 1980, the highest SST values occur during the years 1972?73 (strong El Niño event) and the lowest occur in 1977 (moderate El Niño event). This suggests some possible effects of atmospheric teleconnections on South Atlantic SSTs. However, a record longer than 10 yr is needed to confirm the connection with El Niño and La Niña events. Time?frequency analyses of the SST and zonal wind series for 1975?77 are done using Morlet wavelet analysis. The global wavelet spectra for these variables show strong peaks at 24 and 157 h (approximately 6.6 days). These analyses also indicate that the sea breeze occurs at Cabo Frio almost year-round and confirm the relationships with the coastal upwelling in the region.