Étude de la variabilité saisonnière et interanuelle de la résurgence de la Guajira (Colombie) par analyse de données satellitaires AMI-WIND, SEAWINDS ET AVHRR / Study of the seasonal and interannual variability of the Guajira upwelling (Colombia) based on the analysis of AMI-Wind, SeaWinds and AVHRR satellite data
Journal Publication ResearchOnline@JCUAbstract
The Guajira peninsula, located in the North-West of Colombia, is subject to Northern Trade Winds blowing quasi-parallel to the coast all along the year, at the origin of the set up of an upwelling. The study on Guajira upwelling was carried out using remote sensing data. It is based on the use of two databases that cover respectively twenty and fifteen years. The first database is constituted of NOAA AVHRR images from 1985 to 2005, and the second by ERS-1 and 2 AMI-Wind scatterometer data from 1991 to 2000, as well as QuikScat Sea Winds data from 1999 to 2005.The presence of the upwelling can easily be detected on NOAA AVHRR images due to a halo corresponding to lower sea surface temperatures. In order to define the upwelling variability, the speed and direction of the wind, the lowest and mean temperatures, an upwelling index and the upwelling extension were systematically determined along several sections from Guajira and Venezuela coasts to the Haiti and Dominican Republic coasts. On a seasonal scale, the upwelling presence is directly linked to the Northern Trade Winds intensity (which is mainly controlled by the southern movements of the IZTC) and their orientation to the coast. During the wind season, from December to February, the IZTC is located in its extreme Southern position (0-5° S), and the Northern Trade Winds reach their maximum intensity and blow parallel to the coast. Consequently, the upwelling signal, low in December, increases until February when the resurgence intensity and extension are maximum. During the transition season, the Northern Trade Winds weaken and their orientation is mainly in an easterly direction. In parallel, the oceanic response is reduced from March to May when the upwelling is more rarely observed. Although the force of the Northern Trade Winds is highest to the one occurring during the wind season, the resumption of the upwelling is rarely observed during the "Veranillo". Finally, the rain season is accompanied by IZTC migration northwards (10-12° NR), leading to a reduction in the intensity of the Northern Trade Winds from August to October. Then, the winds are less oriented parallel to the coasts of the Guajira and the strength of the minimal wind is insufficient to induce upwelling formation. On an interannual scale, the upwelling shows frequent variations possibly linked to ENSO events in the Pacific. El Niño phenomena result systematically in a reduction in the Northern Trade Winds, the year following their appearance in the Pacific Ocean. This Pacific-Caribbean interconnection is especially illustrated in 1998 by a maximum reduction in the trade winds following the strong El Niño event of 1997. In addition, the weakening of the atmospheric forcing induces a quasi automatic lower upwelling intensity. Conversely, the years following the Niña events of 1996, 1998 and 1999 show a resumption of the Northern Trade Winds intensity and therefore upwelling intensity.
Journal
N/A
Publication Name
N/A
Volume
7
ISBN/ISSN
1028-7736
Edition
N/A
Issue
N/A
Pages Count
14
Location
N/A
Publisher
Editions Scientifiques
Publisher Url
N/A
Publisher Location
N/A
Publish Date
N/A
Url
N/A
Date
N/A
EISSN
N/A
DOI
N/A