5:15 PM - 7:15 PM
[PPS05-P09] Validation of data assimilation using Akatsuki LIR observations through observation system simulation experiments on Venus
Keywords:Venus atmosphere, Data assimilation, Akatsuki
This study aims to produce objective analysis of Venus by assimilating temperature data obtained from the Akatsuki Longwave Infrared Camera (LIR) using the atmospheric data assimilation system for Venus, “ALEDAS-V” [2], which is based on the atmospheric general circulation model for Venus, “AFES-Venus” [1]. LIR observations capture both dayside and nightside near the cloud tops, but because it takes about four months to transition from dayside to nightside observations, observations from one side are continuously acquired for several months. Therefore, before assimilating actual observation data, it is necessary to fully understand the impact of spatial bias on assimilation. Sugimoto et al. [3] conducted observation system simulation experiments (OSSEs) using only dayside and nightside data focusing on the phase of thermal tides. In this study, we conduct long-term OSSEs using synthetic observations that more closely resemble actual LIR observations and report the validation results based on the improvement in the speed of super-rotation.
The figures show the latitudinal and vertical cross-sections of the zonal-mean zonal wind (color, m/s) and temperature (contour, K) averaged over the last month of the six-month experiment period (Earth time). In the experiment without the assimilation (free run; Figure a), the super-rotation (zonal wind at around 70 km altitude) has a speed of about 130 m/s, which is faster than previously observed (~100 m/s). In the experiment in which synthetic observations of only the dayside were assimilated (Figure b), the super-rotation decelerated significantly, while in the experiment in which synthetic observations of only the nightside were assimilated (Figure c), the super-rotation accelerated at the equator. Both of these results are significantly different from the observations. This presentation will also introduce the results of adjusting various parameters in the data assimilation system to minimize the impact of spatial bias in the observational data.
[1] Sugimoto, N., M. Takagi, and Y. Matsuda (2014a), J. Geophys. Res. Planets, 119, 1950–1968.
[2] Sugimoto, N., A. Yamazaki, T. Kouyama, H. Kashimura, T. Enomoto, and M. Takagi (2017), Sci. Rep., 7(1), 9321.
[3] Sugimoto, N., Y. Fujisawa, N. Komori, H. Ando, T. Kouyama, M. Takagi (2022), Geosci. Lett. 9, 44.
The figures show the latitudinal and vertical cross-sections of the zonal-mean zonal wind (color, m/s) and temperature (contour, K) averaged over the last month of the six-month experiment period (Earth time). In the experiment without the assimilation (free run; Figure a), the super-rotation (zonal wind at around 70 km altitude) has a speed of about 130 m/s, which is faster than previously observed (~100 m/s). In the experiment in which synthetic observations of only the dayside were assimilated (Figure b), the super-rotation decelerated significantly, while in the experiment in which synthetic observations of only the nightside were assimilated (Figure c), the super-rotation accelerated at the equator. Both of these results are significantly different from the observations. This presentation will also introduce the results of adjusting various parameters in the data assimilation system to minimize the impact of spatial bias in the observational data.
[1] Sugimoto, N., M. Takagi, and Y. Matsuda (2014a), J. Geophys. Res. Planets, 119, 1950–1968.
[2] Sugimoto, N., A. Yamazaki, T. Kouyama, H. Kashimura, T. Enomoto, and M. Takagi (2017), Sci. Rep., 7(1), 9321.
[3] Sugimoto, N., Y. Fujisawa, N. Komori, H. Ando, T. Kouyama, M. Takagi (2022), Geosci. Lett. 9, 44.