Showing papers by "Eugenia Kalnay published in 1996"
TL;DR: The NCEP/NCAR 40-yr reanalysis uses a frozen state-of-the-art global data assimilation system and a database as complete as possible, except that the horizontal resolution is T62 (about 210 km) as discussed by the authors.
Abstract: The NCEP and NCAR are cooperating in a project (denoted “reanalysis”) to produce a 40-year record of global analyses of atmospheric fields in support of the needs of the research and climate monitoring communities. This effort involves the recovery of land surface, ship, rawinsonde, pibal, aircraft, satellite, and other data; quality controlling and assimilating these data with a data assimilation system that is kept unchanged over the reanalysis period 1957–96. This eliminates perceived climate jumps associated with changes in the data assimilation system. The NCEP/NCAR 40-yr reanalysis uses a frozen state-of-the-art global data assimilation system and a database as complete as possible. The data assimilation and the model used are identical to the global system implemented operationally at the NCEP on 11 January 1995, except that the horizontal resolution is T62 (about 210 km). The database has been enhanced with many sources of observations not available in real time for operations, provided b...
28,145 citations
Journal Article•
TL;DR: In this article, an ensemble of possible oceanic initial conditions are integrated forward, coupled with the atmosphere, which can not only offer a good description of initial uncertainty but can also serve as a new diagnostic tool, describing the leading instabilities associated with different ENSO episodes.
Abstract: In this paper we discuss the construction of ensemble predictions for anomalies associated with El-Nino/Southern Oscillations (ENSOs), which depend on the coupling of the atmosphere and ocean. First we distinguish between two types of ensembles. In the boundary forcing ensembles, which have been used so far in seasonal to interannual predictions/simulations, the ensemble approach is applied only on the atmosphere ; the boundary SST is assumed to be known (or perfectly predicted), In the forecasts no information is retained from the atmospheric initial state ; the system is driven by the anomalous boundary forcing only. In the initial value ensemble that we propose for the coupled ocean-atmosphere system on the ENSO time scales, an ensemble of possible oceanic initial conditions are integrated forward, coupled with the atmosphere. The atmospheric initial conditions are still forgotten in this approach, but the oceanic predictions can be improved due to the nonlinear filtering process that the ensemble offers. We propose the use of the breeding method, successfully applied in atmospheric ensemble predictions, for generating the flow dependent, growing type of errors present in oceanic analyses. The bred growing vectors represent an extension into nonlinear systems of the leading local Lyapunov vectors that describe maximum sustainable growth in a linear sense. We argue that the breeding method can not only offer a good description of initial uncertainty but can also serve as a new diagnostic tool, describing the leading instabilities associated with different ENSO episodes.
8 citations