CMAQ spin-up length


I have a very basic question, how do you determine the length of the spin up period. Is there a parameter in CMAQ that could help with that?


Hi Lin,

the appropriate spin up period generally depends on the size of the domain, meteorological conditions during the time period being simulated, and the lifetime of the pollutant considered with respect to chemistry and deposition. In general, smaller domains require shorter spin-up periods than larger domains. For continental-scale domain simulations focusing on ozone and PM2.5, we often use 10-14 days for spin-up, though arguably depending on circulation patterns and the season the run is being initialized in longer periods might sometimes be necessary. For hemispheric domains, typical spin-up periods range from a season to a year, depending on which fields are used for initialization.

Within CMAQ, you could use inert tracers or ISAM to estimate the persistence of initial conditions for your domain and time period of interest. We used inert tracers in a brief 2017 study investigating this issue for continental scale applications focused on ozone and PM2.5.