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YOTC: Year of Tropical Convection (August 2008 - July 2009)

YOTC, a joint activity of the World Climate Research Programme (WCRP) and World Weather Research Programme (WWRP)/THORPEX was a year of coordinated observing, modeling, and forecasting with a focus on organized tropical convection, its prediction, and predictability. The intent was to "exploit the vast amounts of existing and emerging observations, the expanding computational resources and the development of new, high-resolution modeling frameworks".

GMAO Support for YOTC

The GMAO analysis and experimental forecast products for YOTC were provided from an experimental deterministic forecasting system. This system is comprised of a 3-dimensional variational data assimilation system (3D-Var), using the GEOS-5 atmospheric model with the grid-point statistical interpolation (GSI) analysis developed in collaboration with NCEP. The global model's horizontal grid spacing for YOTC is 1/4° × 1/3°---twice the resolution of the routine GEOS-5 products.

The specific contributions provided by GMAO included both assimilation and forecast products. The assimilation products consist of 1/4° analyses produced every 6 hours by the GSI and higher frequency products produced by the atmospheric model during the corrector segment of the Incremental Analysis Update (IAU). Forecast products were identical to the model generated assimilation products but from once.daily 5-day forecasts from the 0Z analysis. For the model-generated products, the 3D fields were output at 3-hourly intervals and the 2D fields were hourly. The 3D fields were a combination of instantaneous state variables and time averaged diagnostics. All hourly fields were time averages.

Please contact Dr. Gi-Kong Kim if you would like access to these data.

A list of product collections is given in the downloadable PDF file, GMAO_YOTC_Product_Collections.

Details of the specific collections, including definitions and units, can be found in the MERRA product file specification document, available at:

In addition, aerosol products consistent with the analyses are available. The GMAO YOTC data set begins in January 2009 and will extend through the end of the YOTC period. Selected time periods from 2008 may also be available before the completion of the YOTC project.

Cautions and Caveats:

The GMAO's YOTC products are experimental products that are generated on a best effort basis. The system used to generate the products is part of our parallel validation suite and may be upgraded at any time to correct bugs or deficiencies.

Data Policy:

The GMAO's YOTC data products are openly available to the community. Their predictions are experimental and are produced for research purposes only. Use of the forecasts for purposes other than research is not recommended. Publications based in whole or in part on data supplied by GMAO should contain an acknowledgment concerning the supplied data.

Contact Information:


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. NASA Technical Report Series on Global Modeling and Data Assimilation, NASA/TM-2008-104606, Vol. 27, 97 pp.
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