  A reaction-diffusion-advection model is proposed and investigated to
understand the invasive dynamics of Aedes aegypti mosquitoes. The free boundary
is introduced to model the expanding front of the invasive mosquitoes in a
heterogenous environment. The threshold $R^D_0$ for the model with Dirichlet
boundary condition is defined and the threshold $R^F_0(t)$ for the free
boundary problem is introduced, and the long-time behavior of positive
solutions to the reaction-diffusion-advection system is discussed. Sufficient
conditions for the mosquitoes to be eradicated or to spread are given. We show
that, if $R^F_0(\infty)\leq 1$, the mosquitoes always vanish, and if
$R^F_0(t_0)\geq 1$ for some $t_0\geq 0$, the mosquitoes must spread, while if
$R^F_0(0)<1<R^F_0(\infty)$, the spreading or vanishing of the mosquitoes
depends on the initial number of mosquitoes, or mosquitoes' invasive ability on
the free boundary.
