Wednesday, 6 August 2003
A 3DVAR method for Doppler radar wind analysis with using recursive filters
In this paper, we propose a method of dual-Doppler radar analysis based on a 3DVAR approach. In it, a cost function, including background term and radial observation term, is minimized through a limited memory, quasi-Newton conjugate-gradient algorithm with the mass continuity equation imposed as a weak constraint. In the method, the background error covariance matrix, though simple in this case, is modeled by a recursive filter. Furthermore, the square root of the background error matrix is used as a preconditioning step. The current method is applied to Doppler radar observation of a supercell storm. It is shown that the horizontal circulations, both within and around the storms, including the strong updraft, and associated downdraft, are well analyzed. Because no explicit integration of the anelastic mass continuity equation occurs, error accumulation during the integration is avoided. As a result, the method is less sensitive to boundary uncertainties.