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Background error covariance functions for vector wind analyses using Doppler‐radar radial‐velocity observations
Author(s) -
Xu Qin,
Liu Shun,
Xue Ming
Publication year - 2006
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1256/qj.05.202
Subject(s) - covariance , covariance function , radial velocity , radar , interpolation (computer graphics) , doppler effect , mathematics , rational quadratic covariance function , geodesy , physics , geology , computer science , covariance intersection , statistics , telecommunications , stars , motion (physics) , classical mechanics , astronomy
A two‐dimensional form of cross‐covariance function between the radar radial‐ and tangential‐components (with respect to the direction of radar beam) of background wind errors is derived. Like the previously derived auto‐covariance function for the radial component, this cross‐covariance function is homogeneous but non‐isotropic in the horizontal. The auto‐ and cross‐covariance functions are used with the statistical interpolation technique to perform a vector wind analysis from Doppler radial‐velocity observations on a conical surface of low‐elevation radar‐scans. The structures of the two covariance functions are compared and interpreted in terms of the influence of a single‐point radial‐velocity observation on the analysed vector wind field. The utility and value of these covariance functions are demonstrated through analysis experiments that use either simulated radial‐velocity data from idealized flows or real radar observations. The results of the statistical interpolation scheme utilizing the proposed covariance functions are shown to be superior to the results of traditional VAD technique. The proposed technique can actually be considered a generalization of the traditional VAD technique. Copyright © 2006 Royal Meteorological Society