Variational assimilation of time sequences of surface observations with serially correlated errors
Open Access
- 1 January 1999
- journal article
- Published by Stockholm University Press in Tellus A: Dynamic Meteorology and Oceanography
- Vol. 51 (4) , 469
- https://doi.org/10.3402/tellusa.v51i4.13963
Abstract
Assimilation of observations from frequently reporting surface stations with a four-dimensional variational assimilation system (4D-Var) is described. A model for the serial observation errorcorrelation is applied to observed time sequences of surface pressure observations, whereby therelative weight of the mean information over the temporal variations is decreased in the assimilation.Variational quality control is performed jointly for each time sequence of observations soas to either keep or reject all observations belonging to a time sequence. The operationalpractice at ECMWF has previously been to use just one pressure datum from each stationwithin each 6-h assimilation time window. The increase of observational information used inthese assimilation experiments results in a small but systematic increase in the short-range forecast accuracy. The r.m.s. of the analysis increments is decreased in the experiments, whichmeans there is an improved consistency between the background and the observations. A s...Keywords
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