Modeling study on the polar middle atmospheric responses to medium energy electron (MEE) precipitation

Abstract

Energetic particle precipitation (EPP) is an important source of chemical changes in the polar middle atmosphere during winter. Recently, it has been suggested from modeling study that chemical changes by EPP can cause dynamical changes of the atmosphere. Here, we study the atmospheric and climatic responses to the precipitation of medium-energy electron (MEE) during 2005-2013 by using Specific Dynamics Whole Atmosphere Community Climate Model (SD-WACCM). Results show that MEE precipitation significantly increases the amount of NOx and HOx, resulting in mesospheric and stratospheric ozone decreases by up to 55% and 20% respectively during polar winter. The ozone loss due to MEE precipitation induces the radiative warming in the polar lower mesosphere by up to 1.5 K averaged 9 years and by temporarily maximum of 24 K. The zonal wind reduces by down to 3 m s-1 averaged for 9 years and by temporarily maximum of 30 m s-1 in the polar middle atmosphere. The radiative warming was significantly disturbed in July 2009 during southern hemispheric winter. The disturbance of the radiative effect seems to generate due to the decrease of ozone loss in the lower mesosphere and the lower thermosphere even though the ozone loss in the upper stratosphere and middle mesosphere generate normally or greatly. The reduced ozone loss in the lower mesosphere and lower thermosphere induce the disturbance of radiative effect during wintertime and furthermore, the dynamic effect may be activated. To persist in the radiative effect by ozone loss during polar winter, the ozone loss in the altitude ranges of 50-60 km and 80-100 km seems important.