Numerical experiments for Typhoon Dan incorporating AMSU-A retrieved data with 3DVM

Abstract

Two sets of assimilation experiments on a landfalling typhoon—Typhoon Dan (1999) over the western North Pacific were designed to compare the performances of two kinds of variational data assimilation schemes that are the 3-Dimensional Variational data assimilation of Mapped observation (3DVM) and the 4-dimensional variational data assimilation (4DVar). Results show that: (1) both the 3DVM and 4DVar successfully improved the simulations of typhoon intensity and track incorporating the satellite AMSU-A retrieved temperature and wind data into the initial conditions, and the 3DVM more significantly due to the flow-dependent of background error covariance matrix and observation error covariance matrix like 3-dimensional variational data assimilation (3DVar) circle; (2) inclusions of extra model integration iterations at each observation time in the 3DVM make it more consistent with prediction model; (3) the 3DVM is much more time-saving due to the exclusion of the adjoint technique in it.