IfM-GEOMAR Ocean Analysis Disclaimer

The archive contains two sets of analyses for IfM-GEOMAR: one created to initialized the decadal ENSEMBLES hindcasts (Ocean Analysis 1 in the THREDDS) and the other one to initialize the seasonal hindcasts (Ocean Analysis 2). The NetCDF headers are the same in both cases, except for experiment_id, which takes the value 0001 (0000) for the Ocean Analysis 1 (2).

The MPI model (Jungclaus et al., 2006) was used by IfM-GEOMAR for the analyses and hindcasts. The analyses were produced using only SST observations and a coupled initialization technique (Keenlyside et al., 2005). The method involves running the coupled model with relaxation of model SST to observations. The relaxation constant is strong (0.25 day-1) between 30ºS and 30ºN, and decreases linearly to zero between 30-60ºS and between 30-60ºN. Poleward of 60ºS and 60ºN the model is fully coupled. The analysis simulations include natural and anthropogenic forcings.

In the analysis for seasonal (decadal) hindcasts daily full SST (SST anomalies) are assimilated into the model. In the decadal case, observed SST anomalies are assimilated into the model by first adding them to the model climatology and then nudging the constructed field into the coupled model. The model and observed climatologies are computed with respect to the period 1950-2000. The NCEP-reanalysis (Kalnay et al., 1996) skin temperature (obtained from the Climate Diagnostics Center) is used for the observed SST. After November 1981, these data correspond to an optimal interpolation analysis of linearly interpolated SST to daily values. Prior to this, the data are an EOF-based reconstruction of observed SST.

There are three members in both analyses, covering the period 1950-2005. The initial state for the three analyses was taken from three 20th-century IPCC runs with all major forcing included (Roeckner, 2005: IPCC MPI-ECHAM5_T63L31 MPI-OM_GR1.5L40 20C3M_all run no.1: atmosphere monthly mean values MPImet/MaD Germany. World Data Center for Climate. CERA-DB "EH5-T63L31_OM_20C3M_1_MM"). The model climatology used for constructing the SST anomalies was computed using these three runs.

Kalnay, E., et al., 1996: The NCEP/NCAR 40-year reanalysis project. Bull. Amer. Meteor. Soc., 77, 437-471.

Related Publications

Jungclaus, J.H., N.S. Keenlyside, M. Botzet, H. Haak, J.-J. Luo, M. Latif, J. Marotzke, U. Mikolajewicz and E. Roeckner, 2006: Ocean circulation and Tropical Variability in the Coupled Model ECHAM5/MPI-OM. J. Climate, 19, 3952-3972.

Keenlyside, N.S., M. Latif, M. Botzet, J. Jungclaus and U. Schulzweida, 2005: A coupled method for initializing El Niño Southern Oscillation forecasts using sea surface temperature. Tellus, 57A, 340-356.