D37    Slant delay validation and observation error report.

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This is part of work-package 6300, the purpose of which is observation operator development for slant delays.

Objectives:  To develop a slant delay observation operator for NWP.

Methodology/Work Description: In order to obtain realistic results the errors and correlation of the GPS slant delays must be modelled first. Observations for at network of ground based receivers will be simulated from a 3D water vapour field and used for assimilation trials. The goal of these simulations is to test our software and to estimate the capability of a network of GPS receivers to reconstruct refractivity field inhomogeneities at different scales. In addition we need to determine an optimal discretisation and interpolation scheme of the refractivity field to be used for the processing of observational data. The retrieved fields will be validated against water vapour radiometer measurements during the CLIWANET campaign.

These modelled assumptions and the errors and correlation introduced will be studied with the aim at deriving a valid mapping model with sufficient accuracy for the considered applications. The subsequent derivations of slant delays follows this new strategy and will be test on a 3-month dataset of slant delays.

Deliverable. KNMI  has carried out a validation study on GPS troposhperic slant delays and modelled the error characteristics.
The report is available here, Validation and Error Modelling of GPS Tropospheric Slant Delays. For further information contact John de Vries at jdevries@knmi.nl.