4DDA OF RADAR ECHO AND DOPPLER VELOCITY BY AN ATMOSPHERIC MODEL WITH A CONCEPTUAL PRECIPITATION MODEL

Abstract

Four dimensional data assimilation (4DDA) system of three-dimensional distributions of radar reflective factor and Doppler velocity by a hydrostatic atmospheric model with a conceptual precipitation model will be proposed. The 4DDA is realized by the variational method for Doppler velocity and the extended Kalman filter for radar reflective factor. The method was applied to a rainfall event observed by two neighboring operational volume-scanning radars one of which is the Doppler radar. As a result, it was found that introducing such the assimilation method improves the prediction accuracy of three hours lead time. However, a limitation of used hydrostatic mesoscale model was also found. In the initial condition after assimilation, there is a little heavy rainfall area at the position different from radar observation. This shows that there is a discrepancy between the time evolution of observations and the time evolution that governing equations of the used model requires.