Análise da velocidade e direção do vento na parte Leste setentrional do Nordeste do Brasil.

Abstract

This study analyzed the daily wind cycle behavior over several states in the Northeast region of Brazil. The objective was to analyze the hourly wind behavior in the states of Piauí (PI), Ceará (CE), Rio Grande do Norte (RN), Paraíba (PB), and Pernambuco (PE), investigating the possible occurrence of Aracati-type winds in addition to those occurring in Ceará. To this end, hourly wind data were used, covering the period from January 1, 2014, to December 31, 2023, from 37 automatic stations provided by the National Institute of Meteorology (INMET). Annual hourly and monthly averages were calculated considering the months of March, April, September, and October throughout the daily cycle, as well as the frequency of wind direction for each hour. The results show that, in Ceará, especially in the months of September and October, along the Jaguaribe River and its main tributaries, a flow with intensity and direction typical of a breeze originates at the mouth and propagates along the riverbed for approximately 300 km. It is noteworthy that this flow is called the Aracati wind by local residents. In the Seridó region, encompassing areas of Rio Grande do Norte and Paraíba, west of the Borborema Plateau, as well as west of the Ipanema River Valley in Pernambuco, an intensification of the wind was also observed in the first half of the night during the months of September and October. However, in these locations, no channeled flow along river channels was observed, as the winds observed were from the east/southeast, which may characterize a Foehn-type wind descending the Borborema Plateau, associated with trade winds, possibly intensified by the strong temperature gradient between the coast and the interior in the late afternoon, which favors an increase in the gradient and intensity of the wind and, possibly, a mountain-valley type wind. In Pernambuco, in the São Francisco Valley, a significant increase in wind speed was observed during the night, peaking around 11:00 PM in Cabrobó. This behavior suggests an Aracati-type wind, flowing along the São Francisco River channel and reaching distances of up to 450 km from the mouth. In Piauí, specifically in Parnaíba, the influence of the sea breeze was identified during the afternoon. For locations up to approximately 280 km from the coast, a relative maximum wind speed was observed during the night, possibly associated with the strong temperature gradient between the coast and the interior at the end of the afternoon, which induces an increase in the pressure gradient and, consequently, in wind intensity. In other locations, stronger winds were observed between 08:00 and 13:00 (GMT) and weaker winds between 19:00 and 04:00 (GMT). In Ceará, it is concluded that the Aracati wind acts exclusively along the Jaguaribe River and its tributaries, from the mouth to approximately 300 km, while along the São Francisco River, a wind with characteristics similar to the Aracati was identified, reaching approximately 450 km from the mouth. The intensification of night winds in the Sertões of Paraíba and Rio Grande do Norte

does not present characteristics of the Aracati-type wind, being more compatible with the action of foehn-type winds, or mountain-valley winds descending the west coast of the Borborema Plateau, associated with an increase in trade winds.