Hi, I am running CMAQ5.3 and I have a very basic question. How the spinning up days affect the CMAQ model outputs? And How the boundary conditions will affect the model running results with different length of Spinning up days? Really thanks a lot.
there really isn’t a universal answer like “after xx days, the effect of initial conditions decreases to yy” that will hold true in all cases. In general, the effects of initial conditions will diminish faster for smaller domains while the effects of boundary conditions would be larger for smaller domains, but the exact impacts will depend on the domain, species of interest, and meteorological conditions.
A few years ago, we looked at this for a specific domain and case in this technical note and found that a commonly-used 10 day spin-up period may not always be sufficient, but this isn’t generalizable. The note also includes references to some other studies.
To study the impacts of initial and boundary conditions for your case and domain, you could run tests with different spin-up periods and/or boundary conditions, and you could also use ISAM which tracks the impacts of initial and boundary conditions on simulated pollutant fields.