As a point of discussion, please consider the following schematic of our hindcast validation of Hurricane Katrina:
In our hurricane hindcasts, such as the validations of Katrina and Rita described in papers to be published in Monthly Weather Review, the simulations are performed in two stages. First, a spin-up simulation is run for several days before the start of the hurricane winds, so that the tides and rivers can reach a dynamic equilibrium in the resonant basin of the Gulf of Mexico. Then the solution from that spin-up simulation is used as the initial condition for the hurricane hindcast simulation. For example, for Katrina, we employ an 18-day, tides/rivers spin-up simulation that starts on 07 August 2005, and then we run a 7-day, hurricane simulation that starts on 25 August 2005. The solution from the spin-up simulation is used to hot-start the hurricane simulation.
There are two ways in which the coupled SWAN+ADCIRC could be hot-started during this hindcast. First, it is always hot-started at the beginning of its simulation, at 2005/08/25/0000Z. Although SWAN is not run during the tides/rivers spin-up simulation, because its action is forced entirely by the hurricane winds, we do run ADCIRC during that stage. Thus, when the coupled SWAN+ADCIRC model is employed in the second stage, we must hot-start the ADCIRC half of the simulation. SWAN starts from scratch at the beginning of the hurricane simulation.
Second, we may need to hot-start at some time during the SWAN+ADCIRC stage if it ended abruptly, due to machine failure, user interruption, etc. Instead of re-starting that stage at its beginning, we would rather hot-start in the middle. Then both SWAN and ADCIRC would need to be hot-started, using an intermediate solution as an initial condition for the remainder of the simulation.
Thus, there are two distinct methods in which SWAN+ADCIRC might be hot-started. The first method, in which SWAN is cold-started and ADCIRC is hot-started, would occur in the transition between simulations in the Katrina hindcast. The second method would hot-start both SWAN and ADCIRC, such as at some intermediate time during the second stage of the Katrina hindcast. Instructions for both methods are included below.
It emphasizes our transition from the loose coupling with structured-mesh wave models to the tight coupling with the unstructured-mesh version of SWAN. The rectangle in the upper right and the triangle in the lower left are meant to “pop” from the sides of the poster, as shown in the picture to the right. By running on the same unstructured mesh, SWAN and ADCIRC can pass information locally, on the same core or across inter-core boundaries, without the need for global communication.
