Sea breezes
are low-level atmospheric flows that move from the sea to land. They typically
form during warm days when the temperature difference between the land and sea
surfaces becomes large enough. This temperature difference occurs because
seawater, having a higher heat capacity, heats up more slowly than land. In
this thesis, we study a non dimensional mathematical model that describes the
horizontal velocity of sea breezes in two regions: the Gulf of Carpentaria
(Australia) and Calgary (Canada). The model was derived in [4] by writing
the Navier-Stokes equations in rotating spherical coordinates. After
non dimensionalisation and assuming a specific form of the solution, they
obtained the non dimensional model. Furthermore, the model was complemented by
two homogeneous Dirichlet boundary conditions, representing the no-slip
condition at Earth’s surface and the presence of a thermal inversion layer. In
[11], their work was extended by studying the corresponding Sturm-Liouville
problem for various mass density functions to determine the existence and
uniqueness of the solutions to the model. Building on the work in [11], we
analysed the solvability of the model and determined the numerical solutions for
two physically relevant mass density functions. These functions were chosen to
ensure that zero is not an eigenvalue. The Fredholm alternative then implies
that the solution is unique. On the other hand, if zero were an eigenvalue,
then the Fredholm alternative implies that we could have an infinite number of solutions,
which is physically unrealistic. For the first mass density function, the
eigenvalue problem was written as the hyper geometric equation. For the Gulf of
Carpentaria (where β > 0), we proved analytically that zero is not an
eigenvalue. However, since the parameter β is negative for the Calgary region,
we were unable to prove this analytically. Instead, we demonstrated numerically
that the eigenvalues closest to zero were λ807 = −828 and λ808 = 790,
confirming that zero is not an eigenvalue. Using the finite difference method,
we then computed the velocity profiles for three different forcing functions.
We first considered the breezes in the Gulf of Carpentaria. In the first case
we assumed zero forcing, the result showed that in the absence of any forcing,
sea breezes do not occur. For the second case we assumed a non-zero constant
forcing, resulting in a uniform velocity profile. Lastly, with an increasing
quadratic forcing function, the velocity increased quadratically with height,
reaching its maximum just below the thermal inversion layer. Similarly, we
computed the velocity profiles for the Calgary region. From these computations,
we found that the breezes were flowing in the opposite direction and with higher
velocities. These differences arise due to the Coriolis force, which forms due
to Earth’s rotation. This force deflects winds to the right in the Northern
Hemisphere and to the left in the Southern Hemisphere. Furthermore, the
Coriolis force is zero at the equator and grows with latitude, which explains
the higher velocities. Finally, we considered the model for the second mass
density function, which includes the weak effect the boundaries have on the
flow. For the Gulf of Carpentaria it was again proven analytically that zero
was not an eigenvalue, while for the Calgary region, the eigenvalues closest to
zero were λ501 ≈ −351 and λ502 ≈ 3030. Similar to the first mass density
function, we used the finite difference method to compute the velocity
profiles. The results showed that the profileswere identical to those obtained
with the first mass density function. This similarity occurs because the two
mass density function exhibit similar parabolic behaviour. Moreover, the same
forcing functions were used in both cases.