Hi, njn01Thank you for reply. Sorry for my unclear question. You are right, you know what I wanted to ask. I have been puzzled in the problem with initial conditions for POP2 in CESM1_2_0. for a long time.(1) There is a very powerful inputdata "COREv2" in the compset CIAF for POP2. COREv2 is a interannual year forcing data which varying from year to year. The dataset contains 62 years of data: 1948 - 2009. Now, I want to run a model with compset CIAF. The "RUN_TYPE" is startup as default setting. The "RUN_STARTDATE" is 1948-01-01. What inputdata (or initial condition) will be used for this model at the start? If I change "RUN_STARTDATE" to any other date, such as "1978-05-01", what inputdata (or initial condition) will be used at the start? Does it use the COREv2 data in the RUN_STARTDATE? And, there is a description of initialization about POP2 in the webpage: http://www.cesm.ucar.edu/models/cesm1.2/pop2/doc/faq/#initializationIt says,***What is the startup/spunup initialization option in POP2? The startup/spunup initialization option is a specialized active-ocean model suboption available in the CESM1.2 POP2 model which can be used only in conjunction with a CESM "startup" case; it is not designed to work with "hybrid" or "branch" cases.
The recommended method for initializing the CESM active ocean model (POP2) in a CESM startup case is to use the default settings; these initialize the ocean model from Levitus initial conditions and a state of rest. Occasionally, however, researchers are interested in a startup run in which only the ocean model is initialized from a "spun up" ocean condition generated from a previous CESM run. To accommodate their request, a nonstandard method of initializing POP2 in a startup case was developed. It is called the startup_spunup option. It is a research option that is designed for use by expert users only.***Does it mean that it will initialize POP2(with compset CIAF) by using climatological values of temperature and salinity from databases and assuming the velocity field is zero at the start? (2) If I want to initialize a POP2 model by using the observed data at the start, and then model will continue to run by itself without using observed data. How to do that?You maybe still confused with my question, so I would like to express a case what I want to do.POP2 model start from 1990-01-01. I want to use a observed data to initialize the model at the start. I think the initial data maybe at 1989-12-31 in the COREv2 dataset. But I am not sure what inputdata I can use to initialize the model. And then model will run 4 seasons without using observed data. I think model will use observed data(COREv2 dataset) to continue run if I use the default setting.After do this, I will use initial condition with small perturbation to simulate POP2 model. I would like to see what will happen due to the different initial condition. That is problem about ensemble forecasting. I am not good at English, but I hope you can understand and help me. I have stopped here for a long time.Thank you very much.zhixiong