Investigating an extreme meteo-oceanographic event in the southern Brazil from in situ observations and modeling results

• Main Authors: Borges, D. M., Varona, H. L., Alonso, M. F., Araujo, M., /Hernandez, Fabrice
• Format: Text
• Language: English
• Published: 2023
• Subjects: Numerical modeling; Strong pressure gradient; South Atlantic Ocean; Wind; wave; Swell
• Online Access: https://www.documentation.ird.fr/hor/fdi:010090103

In March 2016, the passage of a cold front on the southern coast of Brazil generated extreme meteooceanographic conditions along the southern Brazilian coast. This work investigates the wave field evolution during this period from in situ observations and numerical modeling. The observations were obtained from high-frequency measurements performed in four sites along the coastline (Santos, Tramandai, Rio Grande, and Cassino). The wavefield simulations were performed by coupling the Global Forecast System (GFS) reanalysis and the WAVEWATCH-III (WW3) ocean wave model. In a synoptic analysis was observed that not only the cold front caused the high wave in the area, but the interaction between the front post-high-pressure center and a low-pressure center generated a substantial pressure gradient area along the Brazilian coast with winds between 17.1 and 20.7 m s-1 reaching up to 24.4 m s-1. Model estimates confirm the presence of high waves between 6.0 and 6.5 m on the Southern coast of Brazil. Also, in the adjacent deep waters of the South Atlantic Ocean, highly simulated waves reached significant wave heights of 9 m. An analysis of the model input wind indicates that the GFS winds represented very well the trends and evolution of the wind registered by ocean buoys, with a small phase error. The t-test shows no significant differences in any buoys, with p-value = 0.73 and p-value = 0.78, with a significance level of 0.05. The best WW3 domain identified to simulate the wavefield off the coast of Southern do Brazil was 70 degrees W -4 degrees W longitude and 55 degrees S -13 degrees S latitude. Two buoys and two ondographic records in the area were used to evaluate the simulations in shallow water. In contrast, a reanalysis with satellite data assimilation was used to compare the simulations. In shallow water, the results for significant height of Wind and Swell Waves (SWH) show how the WW3 model slightly advances the maximum SWH time in relation to the buoys and ondographs records. This maximum SWH simulated by WW3 ...