National Aeronautics and Space Administration

Project Overview

The NASA GMAO seasonal forecasts are produced with the Goddard Earth Observing System (GEOS) AOGCM (GEOS-S2S_2.1). The atmospheric component (Rienecker et al. 2008; Molod et al. 2015) is discretized on a cubed sphere grid (Putman and Lin, 2008) at approximately ½ ° horizontal resolution with 72 vertical layers. The current version includes the recently developed two-moment cloud microphysics and an interactive aerosol model. The ocean component is version 5 of the Geophysical Fluid Dynamics Laboratory (GFDL) Modular Ocean Model (MOM5) (Griffies 2012), discretized on a tripolar grid and run at a horizontal resolution of approximately ½ ° with 40 vertical layers.

The land component is the Catchment Land Surface Model (Koster et al. 2000). Sea ice is represented with the Los Alamos Sea Ice model (CICE4) (Hunke and Lipscomb 2010). The system is initialized using MERRA-2 atmospheric reanalysis (Gelaro et al. 2017) and the GMAO Interim Ocean Analysis. The analysis incorporates sub-surface temperature and salinity data from available CTDs and Argo floats, temperature data from XBTs and moored arrays, and along-track altimetry. The analysis is nudged to the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA, Donlon et al. 2012) sea surface temperatures, and uses the EUMETSAT OSI-SAF sea ice concentration provided with OSTIA. Sea ice thickness is model-derived. Ensemble members are produced with initial states at 5-day intervals, with additional members at the end of the month based on perturbations of the atmospheric and ocean states.

References

Donlon, C.J., M. Martin, J. Stark, J. Roberts-Jones, E. Fiedler, and W. Wimmer, 2012. The Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) system. Remote Sens. Environ., 116, 140-158. doi:10.1016/j.rse.2010.10.017.

Gelaro, R., W. McCarty, M.J. Suarez, R. Todling, A.M. Molod, L.L. Takacs, C. Randles, A. Darmenov, M.G. Bosilovich, R.H. Reichle, K. Wargan, L. Coy, R.I. Cullather, S.R. Akella, V. Bachard, A.L. Conaty, A. da Silva, W. Gu, R.D. Koster, R.A. Lucchesi, D. Merkova, G.S. Partyka, S. Pawson, W.M. Putman, M.M. Rienecker, S.D. Schubert, M.E. Sienkiewicz, and B. Zhao, 2017. The Modern-Era Retrospective Analysis for Research and Applications, Version-2 (MERRA-2). J. Climate, 30, 5419-5454. DOI 10.1175/JCLI-D-16-0758.1.

Griffies, S.M., 2012. Elements of the Modular Ocean Model. GFDL Ocean Group Technical Report No. 7, NOAA/Geophysical Fluid Dynamics Laboratory, 632 p.

Hunke, E.C., and W.H. Lipscomb, 2010. CICE: the Los Alamos sea ice model documentation and software user’s manual. T-3 Fluid Dynamics Group, Los Alamos National Laboratory, 76 p.

Koster, R. D., M. J. Suarez, A. Ducharne, M. Stieglitz, and P. Kumar, 2000. A catchment-based approach to modeling land surface processes in a general circulation model: 1. Model structure. J. Geophys. Res., 105, 24809-24822. doi:10.1029/2000JD900327.

Molod, A.M., L.L. Takacs, M. Suarez, and J. Bacmeister, 2015. Development of the GEOS-5 atmospheric general circulation model: evolution from MERRA to MERRA2. Geosci. Model Dev, 8, 1339-1356. doi: 10.5194/gmd-8-1339-2015.

Rienecker, M.M., M. J. Suarez, R. Todling, J. Bacmeister, L. Takacs, H.-C. Liu, W. Gu, M. Sienkiewicz, R. D. Koster, R. Gelaro, I. Stajner, and J. E. Nielsen, 2008. The GEOS-5 Data Assimilation System - Documentation of Versions 5.0.1, 5.1.0, and 5.2.0. Technical Report Series on Global Modeling and Data Assimilation, NASA/TM–2008–104606, Vol. 27, 1-118 pp.