P-31

An investigation of flow-dependency and a comparison of time-mapping methods using a new NHM-EnVar System

S. Origuchi, K. Aonashi, T. Kawabata, and M. Kunii (Meteorological Research Institute)

The newly developed ensemble-based variational system (EnVar; Zupanski et al. 2008) in the Meteorological Research Institute was applied to the typhoons Talas and Roke in 2011, and flow-dependency was evaluated through experimental results of 3DEnVar-FGAT and 4DEnVar. In the case of typhoon Talas that moved with a slow speed, there was not large differences between the airflows that were analyzed by 3DEnVar-FGAT and 4DEnVar. In the case of typhoon Roke that moved with a fast speed, the airflow distribution was fluctuated from the typhoon circulation in the experiment result of 3DEnVar-FGAT, while the airflow distribution in experiment result of 4DEnVar had a smooth typhoon circulation. The time-mappings of the 4DEnVar were also investigated by using the following two methods. In the method (1), the control variables in an analysis slot were used for all time slots under the assumption of a linearity (Liu et al. 2008), and the extended control variables for all time slots were simultaneously estimated in the method (2). The comparison of the typhoon circulations calculated by the two methods indicated that the estimation of the extended control variables provided the fields closer to the first guess than those estimated with assumption of a linearity.