5:15 PM - 7:15 PM
[U12-P01] Revisiting the greenhouse effects of non-greenhouse gases: Dependency on the relative humidity model
Keywords:Planetary atmosphere, Climate modeling
The atmospheres of Earth-like planets, including early Earth, may contain large amounts of CO due to degassing from reducing mantles (e.g., Sossi et al. 2020) or photochemical instability of atmospheric CO2 (e.g., Hu et al. 2020). In terms of planetary climate, non-greenhouse gases including CO have been known to contribute to both warming and cooling (e.g., Goldblatt et al., 2009; Wordsworth & Pierrehumbert, 2013), but its underlying mechanisms were not fully understood. In our previous study (Taki et al. 2024 JpGU presentation), it was revealed that the climate effects of non-greenhouse gases are caused mainly by the response of water vapor content. While 1D climate models require a prescription of the relative humidity profile, our previous study suggests that the climate of a planet with a CO-rich atmosphere is strongly influenced by the treatment of water content in the atmosphere. Moreover, there is no widely-accepted formulation to treat relative humidity and associated adiabat in 1D models.
This study aims i) to test self-consistent formulation of relative humidity and convective adiabat, and ii) to investigate the impact of different relative humidity prescription on the climate. While our previous study (Taki et al. 2024 JpGU presentation) assumed a troposphere saturated with water vapor (the relative humidity to be 100%), we consider different relative humidity profiles including those developed for current Earth and hotter environments (Manabe & Wetherald 1967; Kasting & Ackerman 1986). We used and updated the CLIMA module of ATMOS (Kasting et al. 1984; Arney et al. 2016), which implements a 1D radiative-convective equilibrium model.
In this presentation, we first provide some updates necessary to maintain consistency within the 1-D climate model when using relative humidity models. Then, using the updated model, we re-examined the response of the climate to an increase in non-greenhouse gases. We compare the differences between the results of several relative humidity models and evaluate the impact of the relative humidity models on the climate of Earth-like planets with the CO-rich atmosphere.
This study aims i) to test self-consistent formulation of relative humidity and convective adiabat, and ii) to investigate the impact of different relative humidity prescription on the climate. While our previous study (Taki et al. 2024 JpGU presentation) assumed a troposphere saturated with water vapor (the relative humidity to be 100%), we consider different relative humidity profiles including those developed for current Earth and hotter environments (Manabe & Wetherald 1967; Kasting & Ackerman 1986). We used and updated the CLIMA module of ATMOS (Kasting et al. 1984; Arney et al. 2016), which implements a 1D radiative-convective equilibrium model.
In this presentation, we first provide some updates necessary to maintain consistency within the 1-D climate model when using relative humidity models. Then, using the updated model, we re-examined the response of the climate to an increase in non-greenhouse gases. We compare the differences between the results of several relative humidity models and evaluate the impact of the relative humidity models on the climate of Earth-like planets with the CO-rich atmosphere.