Effects of Energetic Particle Precipitation on Stratospheric Temperature During Disturbed Stratospheric Polar Vortex Conditions.

Recently, observational and re‐analysis studies have outlined potentially enhanced influence of Energetic Particle Precipitation (EPP) either at times preceding Sudden Stratospheric Warmings (SSW) or when the distribution of planetary wave activity is suitable. In addition, significant correlations have been found between EPP and the occurrence rate of SSWs when the phases of the Quasi‐Biennial Oscillation (QBO) are taken into account. Here we study the influence of EPP during disturbed stratospheric polar vortex conditions using chemistry‐climate model SOCOL‐MPIOM3 over the 20th century. When classifying disturbed conditions, the definition of minor SSWs are utilized along with a temperature gradient (day‐to‐day variations) criteria at 90°N and 10 hPa acting as a measure of the strength of the events. We find no influence of EPP on the occurrence rate of disturbed conditions over the last 100 year period. However, conditions preceding and during the disturbances are significantly different when EPP forcing is included into the model. This is especially true for stratospheric disturbances occurring in February. Furthermore, there is a clear tendency that the EPP effect becomes more notable after the 1950s. Our results imply that EPP forcing could be important for the stratospheric conditions during winter and that pre‐conditioning forced by atmospheric disturbances are an important factor when considering how the mechanism operates. Plain Language Summary: Energetic particles precipitating into the atmosphere is known to produce nitric (NOx) and hydrogen (HOx) oxides. These molecules are known to be associated with ozone (O3) loss, which is further shown to impact the temperature and weather patterns of the middle atmosphere. Recently, studies have shown that this impact could potentially be largest during winter time when the polar vortex experiences disturbed and unstable conditions. To study the impact of energetic particle precipitation (EPP) during these conditions, we use model data from the chemistry‐climate model SOCOL‐MPIOM3 over the period 1900–2008. In the model runs, we have 10 experiment ensembles which include ionization rates from historical records of EPP, and eight reference ensembles excluding these ionization rates. Our results show no relationship between EPP and the rate of occurrence of disturbed polar vortex conditions. However, conditions preceding and during disturbed times are significantly different when EPP ionization rates are included. Also, the results show that this effect only becomes noticeable after the 1950s, indicating that this mechanism might become even more important in the future. Key Points: We investigate links between Energetic Particle Precipitation and atmospheric dynamics during times of disturbed stratospheric polar vortexBy usage of model data, significant temperature anomalies are observed in the middle stratosphere, consistent with observational studiesA disturbed polar vortex (enhanced planetary wave activity), favor stratospheric temperature impact by Energetic Particle Precipitation [ABSTRACT FROM AUTHOR]