Variability of Sea Breezes Over the Cameroonian Coast and Their Interaction With the West African Monsoon

Abstract

The sea breeze characteristics of over two coastal areas of Cameroon were studied. The study used 3-hourly wind (speed and direction), rainfall, and atmospheric pressure data of 4 years (2006–2009) at Tiko and 5 years (2011–2015) at Ebodje to examine various characteristics of sea breezes. Statistics are presented that describe the occurrence, onset and cessation, and strength of the sea breezes. The frequency of occurrence clearly shows two regimes by two maxima (November and March) at Tiko and (January and July) at Ebodje. The results show that a sea breeze usually starts few hours (about 3–4 h) after the sunrise as a light onshore surface wind, has a mean duration of about 9 h at Tiko, and occurs during all seasons at both coastal areas. The sea breeze occurrence is found to be strongly influenced by the West African monsoon winds, and its onset and cessation times show a pronounced seasonal variation. The sea breeze strength is greater at Tiko than that at Ebodje during the West African monsoon season. Average daily hodographs for Tiko reveals that the sea breeze circulation is in both clockwise and anticlockwise rotation. There would be a significant seasonal effect of large-scale flows on sea breeze hodograph patterns. A wind roses analysis at Ebodje shows a high temporal variability of sea breeze frequencies at 09:00 (Local Standard Time: LST) in the south direction (36%), then at 15:00 LST in the west direction (26%), because of the preponderance of calm atmospheric situations conducive to its onset. Therefore, the circulation of the sea breeze is influenced by local factors (topography and vegetation). This phenomenon in the coastal regions of Cameroon can be the main factor controlling the transport of accidental near shore oil slicks and air pollutants.

Dendrometrical Structure and Physicochemical Analysis of Mangrove Sediments from the Nyong River Estuary (Cameroon, Atlantic Coast)

“…The dominant plant formations in the Nyong estuary man-grove sample quadrats are Avicennia germinans and Rhizophora racemosa. The height of the trees found there is between 4.86 m and 13.46 m and the circumference is between 0.08 and 0.58 m. These dimensions are close to those recorded in the Shark River estuary in Florida in the USA, which has a rainfall (2000 mm/year) close to the coastal zone through which the Nyong estuary passes [59][60][61]. The dimensions of the Nyong vegetation are even smaller than those found in the Bamosso mangrove (southwest coast of Cameroon) where the average height is equal to 20.20 m and the average diameter to 2.65 m [62].…”

“…Secondly, in Bamosso, they develop on soils that are rich in water and uncrystallised minerals due to the large amount of organic matter. These soils also have an abundance of humus and are well oxygenated [60][61][62][63][64]. The forest vegetation of the Nyong estuary is evergreen, dominated by mangroves and interspersed with shrubby grassland in the upstream part of the estuary [65].…”