Dear Suman,

The spin up time is the time the model takes for the input/ouput values of an annual to reach a steady state. However, if you are doing a seasonal model then it will not reach a steady state because it is part of an annual cycle which is continually changing throughout the seasonal cycle.

You will have to incorporate your model within an annual model and run the annul model for several years until it reaches a steady state. Running a seasonal model, March through June, will always give the same results for every run since input values for March will always be the same. The output values form June are not suitable as input values for March. For March you need the output values for February which you do not have.

HTH,

Cheers, Alastair.

Could you tell us, which climate model and which time period you are using? Do you run with an active ocean or do you prescribe sea-surface temperatures from observations/reanalysis or another existing model simulation?

Hello Suman,

The spin up for a global model takes a long model time, depending on the state one has started. Usually the spinup of the ocean part, which is actually the longest time of a coupled ocean-atmosphere model, is determined by the time it takes for the deep ocean to come to the steady state (whether it's the steady state may be assessed by looking at the kinetic energy whether reaching an asymptote). However, if you begin your spinup from a very good initial state, especially in the deep ocean (from an ocean climatology, for example; see some available at http://www.nodc.noaa.gov/), the spinap may be dramatically shorter. If you clarify exactly what you are going to do, I am sure many RG members could've come up with more deliberated suggestions... Hope this may be helpful. Good luck!

The spin-up issue was also mentioned briefly in one of my studies several years ago below:

Article Land Cover Change Effects on the Climate of the La Plata Basin

I hope my late reply can help.