Impact of Data Assimilation on Thermal Tides in the Case of Venus Express Wind Observation

Sugimoto, Norihiko; Kouyama, T.; Takagi, Masahiro

doi:10.1029/2019gl082700

Cited by 12 publications

(21 citation statements)

References 35 publications

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“…Gravity measurements at higher spatial and temporal resolution than Juno using multiple spacecraft should be helpful for gas giants. To make the best use of observational data and reveal the dynamics behind them, data assimilation using GCMs (Sugimoto et al 2017(Sugimoto et al , 2019b) is promising. Observations of the atmospheres of exoplanets and evaluation of their zonal winds would enable an extensive parameter study that cannot be done with the solar system planets only.…”

Section: Key Observationsmentioning

confidence: 99%

Superrotation in Planetary Atmospheres

et al. 2020

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Superrotation is a dynamical regime where the atmosphere circulates around the planet in the direction of planetary rotation with excess angular momentum in the equatorial region. Superrotation is known to exist in the atmospheres of Venus, Titan, Jupiter, and Saturn in the solar system. Some of the exoplanets also exhibit superrotation. Our understanding of superrotation in a framework of circulation regimes of the atmospheres of terrestrial planets is in progress thanks to the development of numerical models; a global instability involving planetary-scale waves seems to play a key role, and the dynamical state depends on the Rossby number, a measure of the relative importance of the inertial and Coriolis forces, and the thermal inertia of the atmosphere. Recent general circulation models of Venus's and Titan's atmospheres demonstrated the importance of horizontal waves in the angular momentum transport in these atmospheres and also an additional contribution of thermal tides in Venus's atmosphere. The atmospheres of Jupiter and Saturn also exhibit strong superrotation. Recent gravity data suggests that these superrotational flows extend deep into the planet, yet currently no single mechanism has been identified as driving this superrotation. Moreover, atmospheric circulation models of tidally locked, strongly Understanding the Diversity of Planetary Atmospheres Edited by François Forget,

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Section: Key Observationsmentioning

confidence: 99%

Superrotation in Planetary Atmospheres

et al. 2020

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“…We set the assimilation cycle to 6 hourly intervals with 1 hourly observation window. Observation error is set to 3 m/s with an inflation size of 10% based on the previous works [22,23]. The localization parameters are 400 km in horizontal and log P = 0.4 in vertical, where P is pressure.…”

Section: Methodsmentioning

confidence: 99%

“…Observations are inputted from t = 3 to t = 9 h if they are available, and LETKF outputs analysis at t = 6 h. Observation period is 1 month from January 1, 2005. Details are found in the previous works [22,23].…”

Section: Methodsmentioning

confidence: 99%

“…Data assimilation has been widely conducted for the Earth and Mars atmospheres, which is one of the best ways to reduce error between model results and observations e.g., [21]. Recently, the first data assimilation system for the Venus atmosphere named ALEDAS-V (AFES LETKF Data Assimilation System for Venus) has been developed [22] using Local Ensemble Transform Kalman Filter (LETKF) based on AFES-Venus, which enables us to improve structures of the thermal tide by using the wind velocity data derived from the Venus Monitoring Camera onboard the Venus Express (VMC/VEX) [23]. In addition, Sugimoto et al [24] conducted observing system simulation experiments (OSSE) for radio occultation measurements among small satellites.…”

Section: Introductionmentioning

confidence: 99%

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Observing System Simulation Experiment to Reproduce Kelvin Wave in the Venus Atmosphere

et al. 2020

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Planetary-scale 4-day Kelvin-type waves at the cloud top of the Venus atmosphere have been reported from the 1980s, and their significance for atmospheric dynamics has been pointed out. However, these waves have not been reproduced in Venus atmospheric general circulation models (VGCMs). Recently, horizontal winds associated with the planetary-scale waves at the cloud top have been obtained from cloud images taken by cameras onboard Venus orbiters, which could enable us to clarify the structure and roles of Kelvin-type waves. In order to examine this possibility, our team carried out an idealized observing system simulation experiment (OSSE) with a data assimilation system which we developed. The wind velocity data provided by a CCSR/NIES (Center for Climate System Research/National Institute for Environmental Studies) VGCM where equatorial Kelvin-type waves were assumed below the cloud bottom was used as idealized observations. Results show that 4-day planetary-scale Kelvin-type waves are successfully reproduced if the wind velocity between 15° S and 15° N latitudes is assimilated every 6 h at 70 km altitude. It is strongly suggested that the Kelvin-type waves could be reproduced and investigated by the data assimilation with the horizontal wind data derived from Akatsuki ultraviolet images. The present results also contribute to planning future missions for understanding planetary atmospheres.

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“…So far, the first data assimilation system for the Venus atmosphere named VALEDAS (Venus AFES LETKF Data Assimilation System) has been successfully developed 11) using Local Ensemble Transform Kalman Filter 12) (LETKF; the details are explained in Section 2) based on AFES-Venus, because AFES-Venus has enabled us to reproduce many kinds of phenomena in the Venus atmosphere as mentioned above. The phase distributions of the thermal tide have been successfully improved by VALEDAS with the wind velocity derived from the Venus Monitoring Camera onboard Venus Express (VMC/VEX) 13) . From 2016, the Japanese Venus Climate Orbiter "Akatsuki" has been observing the Venus atmosphere and many observation data has been accumulated so far.…”

Section: Introductionmentioning

confidence: 99%

Observing system simulation experiment for radio occultation measurements of the Venus atmosphere among small satellites

Sugimoto

Abe

Kikuchi

et al. 2019

J. JSCE

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We have developed the Venus AFES (atmospheric GCM (general circulation model) for the Earth Simulator) LETKF (local ensemble transform Kalman filter) data assimilation system (VALEDAS) to make full use of observations. In this study, radio occultation measurements among small satellites are evaluated by the observing system simulation experiment (OSSE) of VALEDAS. Idealized observations are prepared by a French Venus Atmospheric GCM in which the cold collar is realistically reproduced. Reproducibility of the cold collar in VALEDAS is tested by several types of observations. The results show that the cold collar is successfully reproduced by assimilating at least 2 or 3 vertical temperature profiles in the polar region every 4 or 6 hours. Therefore, the radio occultation measurements among three satellites in polar orbits would be promising to improve the polar atmospheric structures at about 40-90 km altitudes.

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Impact of Data Assimilation on Thermal Tides in the Case of Venus Express Wind Observation

Cited by 12 publications

References 35 publications

Superrotation in Planetary Atmospheres

Superrotation in Planetary Atmospheres

Observing System Simulation Experiment to Reproduce Kelvin Wave in the Venus Atmosphere

Observing system simulation experiment for radio occultation measurements of the Venus atmosphere among small satellites

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