GSWP-2 Initialization and Spin-up

The ten-year GSWP-2 baseline period spans the calendar years 1986-1995.  However, the initial time for integrations is 1 July 1982.  The reason is to provide a spinup period so that the models will be adequately equilabrated and have a reasonably realistic climate state at the beginning of 1986 that both reflects climate anomalies in the preceeding years, and is consistent with the model itself.

Initial conditions will be posted on the GSWP-2 data servers, but they will be described here.  The start date is in boreal summer, so that all ice-free land points can be safely initialized with no snow cover.  Likewise, canopy interception and other surface water stores should begin at zero.  As in GSWP-1, soil wetness at all points and all layers shoulde be initialized at 75% of saturation.  Soil temperature should be initialized at the mean June air temperature at all layers.  For models that predict vegetation, LAI, NDVI, and FPAR are available from ISLSCP-II from the beginning of 1982.  Data from July 1982 can be used to initialize the vegetation state. To summarize:
Spin-up will be performed using data beginning 0300UTC 1 July 1982.  There are two phases to the spin-up period.  In the first phase, LSS integrations will loop through the first 12 months of forcing data until the modeler is satisfied that soil moisture and temperature has spun up and sufficiently equilibrated. 

A lesson from GSWP-1 pilot project was that this spin-up process overly amplifies the impact of climate anomalies from that year on the land surface state variables.  Therefore, the models will then proceed with their integrations forward from July 1983 – December 1985 so as to converge to a realistic “land climate” at the start of the evaluation period.  The 10-year baseline integration, which will be evaluated within the group of GSWP participants and later released to the community at large, covers the 10-year period from 0000UTC 1 January 1986 up to 0000UTC 1 January 1996.

Not all of the data sets for the spin-up period are available from ISLSCP-II.  COLA has all of the required NCEP/DOE reanalysis fields for the period, but not all of the same observed data sets used for hybridization of the data are available.  Also, the 3-hourly SRB radiation data are not avaiable before 1986.  As a result, there will be some differences in the forcing data between the spin-up period and the 10-year baseline period: