Abstract
Energetic particle precipitation (EPP) is known to be an important source of chemical changes in the polar middle atmosphere in winter. Recent modeling studies further suggest that chemical changes induced by EPP can also cause dynamic changes in the middle atmosphere. In this study, we investigated the atmospheric responses to the precipitation of medium-to-high energy electrons (MEEs) over the period 2005–2013 using the Specific Dynamics Whole Atmosphere Community Climate Model (SD-WACCM). Our results show that the MEE precipitation significantly increases the amounts of NOx and HOx, resulting in mesospheric and stratospheric ozone losses by up to 60% and 25% respectively during polar winter. The MEE-induced ozone loss generally increases the temperature in the lower mesosphere but decreases the temperature in the upper mesosphere with large year-to-year variability, not only by radiative effects but also by adiabatic effects. The adiabatic effects by meridional circulation changes may be dominant for the mesospheric temperature changes. In particular, the meridional circulation changes occasionally act in opposite ways to vary the temperature in terms of height variations, especially at around the solar minimum period with low geomagnetic activity, which cancels out the temperature changes to make the average small in the polar mesosphere for the 9-year period.
Highlights
The variation of the solar irradiance with solar activity has been considered to be one of the major natural forcings influencing climate changes
In order to further investigate the associations between the ozone depletion and NOx and HOx in Figure 3, we present the differences of NOx, HOx, and ozone between the control and medium-to-high energy electrons (MEEs) runs in the polar coordinate in Figures 4 and 5
We investigated the chemical and dynamical effects driven by the MEE precipitation in the polar winter during the period of 2005–2013 by using SD-Whole Atmosphere Community Climate Model (WACCM) simulations
Summary
The variation of the solar irradiance with solar activity has been considered to be one of the major natural forcings influencing climate changes. Damiani et al [20] showed that EPP causes, on average, upper stratospheric ozone depletion of about 10–15% on a monthly basis, which can contribute to climate variability on regional scales by influencing the thermal and dynamical aspects of the atmosphere. Recent modeling studies have shown that the model results of the polar mesospheric changes of NOx and HOx by energetic electrons can be improved by including MEE [15,28,29,30,31]. Andersson et al [15] performed model simulations with the EPP forcing by SPEs, auroral electrons, and MEE over decadal time scales and suggested an average polar ozone variability of 12–24% in the mesosphere and 5–7% in the middle and upper stratosphere, which is significantly attributed to MEE in the total EPP forcing. The results of the simulation will be analyzed in terms of the chemical and dynamic changes of the atmosphere in both the Northern hemisphere (NH) and Southern hemisphere (SH)
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