Begin Main Content

Presenter: Ricardo Todling

Seminar Title: The GMAO 4d-Var and its Adjoint-based Tools

GEOS-5 Data Assimilation System (DAS) is a 3d-var system that uses the Grid-point Statistical Interpolation (GSI) analysis, developed in collaboration with NOAA/NCEP, and an AGCM developed at Goddard, combining the finite-volume hydrodynamics of GEOS-4 and physical packages tuned to provide a reliable hydrological cycle for the integration of the Modern Era Retrospective-analysis for Research and Applications (MERRA). The MERRA system is currently operational and the next generation GEOS-DAS is under intense development with a prototype now available and undergoing scientific evaluation.

A prototype system adds the capability of 4d-var to the GEOS-DAS through modifications to the GSI. Many of the hooks necessary to implement a weak-constraint version of 4d-var are already in place, however, the initial experimentation focuses on the strong-constraint approach. The development of 4d-var and the prototype system has also led to the development of the adjoint of the GSI -- an effective tool for studying analysis sensitivity to the observations, as well as to the background and to the analysis error statistics. Moreover, the prototype system brings together various GCM adjoint-based tools, originally designed in GEOS-4 and now upgraded to work in the GEOS-5-context -- including tools for generating and studying singular vectors and forecast sensitivities. The prototype system combines these various adjoint-based tools to provide GEOS-DAS not only with additional capability of 4d-var but also with the capability to support observation impact applications using either 3d-var or 4d-var.

This presentation discusses the progress of the GMAO 4d-var development and shows preliminary results with the prototype GEOS-DAS. This presentation also introduces some of the adjoint-based tools available in the prototype system and shows results of some applications.

return to Seminars