Calculated and observed climate change in the thermosphere, and a prediction for solar cycle 24

Abstract

[1] The long-term change of thermospheric neutral density has been investigated using satellite drag measurements and through sensitivity studies using upper atmosphere general circulation models. The magnitude of the change has been quantified in both approaches, and the source of the secular change attributed to the concentration changes of greenhouse gases. In this study, we use CO 2 concentration measured at Mauna Loa Observatory and solar variation based on a proxy model to calculate the secular change of thermosphere neutral density for the last three decades, using a global mean upper atmosphere model. Our results show that the average density decrease at 400 km from 1970 to 2000 is 1.7% per decade. To quantify the impact of solar activity on the secular change of neutral density, we also calculated the long-term density change under solar minimum and solar maximum conditions for the same time period. The average trends at 350 km and 450 km are 2.2% per decade and 2.9% per decade for solar minimum conditions, while at solar maximum, they are 0.7% per decade and 0.8% per decade, respectively. These model results are compared to estimates of thermosphere density change derived from satellite drag observations, showing good agreement. In addition, based on a recent forecast of the intensity of solar cycle 24, we predict that the long-term change of thermospheric neutral density from 2006 to the end of solar cycle 24 will be $2.7% per decade at 400 km.

Thermospheric Density: An Overview of Temporal and Spatial Variations

“…These observational findings are qualitatively consistent with modeling results by Roble and Dickinson (1989). Using CO 2 concentrations measured at Mauna Loa, Qian et al (2006) calculated neutral density trend for the period from 1970 to 2000, and found an average density trend of −1.7%/decade at 400 km. Model simulations also showed that this density trend corresponds to a neutral temperature trend of −5.4 K for this three decades at 400 km.…”

“…Model simulations also showed that this density trend corresponds to a neutral temperature trend of −5.4 K for this three decades at 400 km. Figure 9 shows altitude profiles of the temperature trend and neutral density trend from 1970 to 2000, from the model simulations of Qian et al (2006).…”

“…In addition, the density trend increases with altitude. The solar cycle dependence is due to the relative importance of CO 2 infrared cooling and NO infrared cooling under different solar activity conditions (Qian et al 2006). These observational findings are qualitatively consistent with modeling results by Roble and Dickinson (1989).…”

Thermospheric atomic oxygen density estimates using the EISCAT Svalbard Radar

“…The rate of decrease in density at 400 km has been estimated to range from 2% to 5% per decade at solar maximum and minimum, respectively [Emmert et al, 2004[Emmert et al, , 2008. Modeling work places a slightly lower estimate on the thermospheric density decline of typically 1% to 2% per decade at 400 km [Qian et al, 2006]. The cause of this contraction is linked to the long-term increases in CO 2 concentration, which have resulted in warming of the troposphere.…”

A Change in the Solar He ii EUV Global Network Structure as an Indicator of the Geo-Effectiveness of Solar Minima

“…This measured lower EUV irradiance combined with the modeled effects, e.g. due to the amount of CO 2 in the Earth's atmosphere (Roble and Dickinson, 1989;Qian et al, 2006) caused McIntosh, 2009) the proposed approach may be used to explore how the change in the spatial scale of the TR network affects the Earth's thermosphere.…”