15 Feb 2023
 | 15 Feb 2023
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Simulated Long-term Evolution of the Thermosphere during the Holocene: 2. Circulation and Solar Tides

Xu Zhou, Xinan Yue, Yihui Cai, Zhipeng Ren, Yong Wei, and Yongxin Pan

Abstract. On timescales longer than the solar cycle, long-term changes in CO2 concentration and geomagnetic field have the potential to affect thermospheric dynamics. In this paper, we investigate the thermospheric dynamical response to these two factors during the Holocene, using two sets of ~12,000-yr control runs by the coupled thermosphere-ionosphere model, GCITEM-IGGCAS. The main results indicate that increased/decreased CO2 will enhance/weaken the thermospheric circulation throughout the Holocene, but this effect is nonlinear. The cooling effect of CO2 in the thermosphere further provides plausible conditions for atmospheric tidal propagation and increases the thermospheric tidal amplitude. Geomagnetic variations induce hemispheric asymmetrical responses in the thermospheric circulation. Large changes in the circulation occur at high latitudes in the hemisphere with distant magnetic poles drift, inferring a crucial role of geomagnetic non-dipole variations in circulation changes. A positive correlation between the diurnal migrating tide (DW1) and geomagnetic dipole moment is revealed for the first time. The amplitude of DW1 in temperature will increase by ~1–3 K for each 1×1022 Am2 increase in dipole moment.

Xu Zhou et al.

Status: open (until 29 Mar 2023)

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  • RC1: 'Comment on egusphere-2023-234', Anonymous Referee #1, 22 Feb 2023 reply

Xu Zhou et al.

Xu Zhou et al.


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Short summary
Secular variations in CO2 concentration and geomagnetic field can affect the dynamics of the upper atmosphere. In this paper, we examine how these two factors influence the dynamics of the upper atmosphere during the Holocene, using two sets of ~12,000-yr control runs by the coupled thermosphere-ionosphere model. The main results show that: 1. increased CO2 enhances the thermospheric circulation, but non-linearly. 2. Geomagnetic variation induced a significant hemispheric asymmetrical effect.