2021-09-30[Event Report]The 81st DA Seminar on September 30, 2021

Dr. Shunsuke Noguchi from JAMSTEC gave a talk about the data assimilation of global whole neutral atmosphere and the forecast experiments focusing on gravity waves using the analysis data.

His group has recently developed the data assimilation system JAGUAR-DAS using the Japanese Atmospheric GCM for Upper Atmosphere Research (JAGUAR) and the LETKF. Along with the conventional observation data sets (Koshin et al., 2020), Aura MLS satellite temperature retrieval data is assimilated in the middle atmosphere. Recent updates including the assimilation of additional satellite temperature observations and further optimization of 4D-LETKF have significantly improved the analysis representation (Koshin et al., 2021 in review). JAGUAR-DAS provides the analysis up to about 150 km height in the lower thermosphere, which is beyond the model top of most existing reanalysis data sets. Thus the analysis data is suitable for various studies of middle atmospheric dynamics.

Two forecast experiments are performed, focusing on (1) drastic change of gravity wave activities around the significant sudden stratospheric warming event and (2) concentric gravity waves emitted from strong tropical cyclones. The high resolution version (T639) of the JAGUAR is used in both experiments. The analysis field of JAGUAR-DAS with relatively low resolution (T42) is applied for the initialization and spectral nudging. The benefits of using a high resolution model and spectral nudging are discussed.

Author: Arata Amemiya

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