**3. Conclusion and discussions**

This study examined the dynamics of LSB circulation across the Guinean coast of West Africa. The earlier observational study shows the occurrence of LSB throughout the year with seasonal variability in the region. While LSB circulation formed everywhere along the Guinean coasts, the hodographs exhibited both theoretically expected CR and "anomalous" Counter-Coriolis ACR. Due to the complex, nonlinear nature of LSBs, numerical modeling presented the only possible method by which to understand the underlying dynamics of this mesoscale phenomenon.

A numerical simulation was therefore performed, with ERA-Interim and CFS as forcing data, using the adjusted WRF-ARW model code and subsequently evaluated for accuracy using local observations. The diurnal evolutions of modeled and observed onshore/offshore winds were found to be in good agreement. While WRF model offers great operational forecasting capabilities, effectively no options for dynamical analysis are available. The basic dynamical equations are embedded deeply in the solver and remain inaccessible to the user. This presents a serious limitation to those using WRF to investigate the dynamics driving the LSB circulation, even though the model demonstrates excellent performance and accuracy. In order to overcome this limitation, the model original code was adjusted to allow for the extraction of the individual tendency terms of the horizontal momentum equations [7, 16].

Generally, the terms found to have significant contribution to the total momentum balance of LSB circulation over the domain included pressure gradient (subsequently separated into surface and synoptic components), advection, and horizontal and vertical diffusion. Since the region is close to the equator, Coriolis term generally did not have significant effects on the LSB circulation. The rate of rotation of the total horizontal momentum tendency was plotted for the entire domain. Two regions (for CR and ACR) with one CR and ACR for each of CFS and ERA around the coastline area were selected for term-by-term dynamical analysis. Following [7, 16], the strength of rotation due to each component of the horizontal momentum equations was determined for the selected regions. The direction of rotation was found to be a result of a complex interaction between surface and synoptic pressure gradients,



*Numerical Simulation of Land and Sea Breeze (LSB) Circulation along the Guinean Coast… DOI: http://dx.doi.org/10.5772/intechopen.107339*

advection, and horizontal and vertical diffusions. However, higher variability as well as unlikely individual term magnitudes suggests that the simulation requires further improvements to be considered conclusive. For more investigations, an idealized simulation should be carried out using a similar domain configuration as that of a real case.

Consequent upon all the above numerical simulations, it can be concluded that:

