Possible physical cause of the zonal wind collapse on Titan

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• 作者：Jianping Li^a ; ^c ; ^{ljp@lasg.iap.ac.cn} ; Dong Liu^b ; ^c ; Athena Coustenis^d ; Xinhua Liu^e
• 关键词：Titan ; Zonal wind collapse ; Planetary general circulation model (PGCM) ; Angular velocity ; Superrotation
• 刊名：Planetary and Space Science
• 出版年：2012
• 期刊代码：60_00320633
• 类别：ph
• 出版时间：April, 2012
• 卷：63-64
• 期：Complete
• 页码：150-157
• 文件大小：691 K

摘要

A high-resolution vertical profile of Titan's winds was inferred from ground-based radiotelescopes, which recorded the Doppler Wind Experiment measurements of the carrier frequency during the Huygens mission (). It indicates the existence of a wind shear layer with surprisingly low wind speed nearing zero, at altitudes between 60 and 100 km. We call this phenomenon the 鈥榸onal wind collapse鈥? Titan's stratosphere is also characterized by an atmospheric superrotation. To identify the physical cause of the zonal wind collapse on Titan, we employ a Planetary General Circulation Model (PGCM) to simulate Titan's general circulation and vertical profiles of the zonal wind under different scenarios of angular velocities. The results show that both the zonal wind collapse and superrotation are closely associated with the magnitude of angular velocity and occur in the slowly rotating regime. This result may be a general phenomenon applicable beyond Titan. In addition, the Community Atmosphere Model version 2 (CAM2) was used to simulate the Earth's atmosphere under different rotation periods for two different physical parameterizations. The zonal wind collapse also observed on Earth is reproduced mainly for a dry atmosphere in the case of rotation periods between 5-50 days and is related to a positive meridional temperature gradient. Besides, a moist process does not only suppress the zonal wind collapse, but also may have an impact on the strength of the superrotation.