Simulation of energetic particle precipitation effects during the 2003–2004 Arctic winter

Abstract

Energetic particle precipitation (EPP) during the 2003–2004 Arctic winter led to the production and subsequent transport of reactive odd nitrogen (NOx = NO + NO2) from the mesosphere and lower thermosphere (MLT) into the stratosphere. This caused NOx enhancements in the polar upper stratosphere in April 2004 that were unprecedented in the satellite record. Simulations of the 2003–2004 Arctic winter with the Whole Atmosphere Community Climate Model using Specified Dynamics (SD‐WACCM) are compared to satellite measurements to assess our understanding of the observed NOx enhancements. The comparisons show that SD‐WACCM clearly displays the descent of NOx produced by EPP but underestimates the enhancements by at least a factor of four. Comparisons with NO measurements in January and February indicate that SD‐WACCM most likely underestimates EPP‐induced NO production locally in the mesosphere because it does not include precipitation of high energy electrons. Comparisons with temperature measurements suggest that SD‐WACCM does not properly simulate recovery from a sudden stratospheric warming in early January, resulting in insufficient transport from the MLT into the stratosphere. Both of these factors probably contribute to the inability of SD‐WACCM to simulate the stratospheric NOx enhancements, although their relative importance is unclear. The work highlights the importance of considering the full spectrum of precipitating electrons in order to fully understand the impact of EPP on the atmosphere. It also suggests a need for high‐quality meteorological data and measurements of NOx throughout the polar winter MLT.

A semi-empirical model for mesospheric and stratospheric NO<sub><i>y</i></sub> produced by energetic particle precipitation

“…The adjusted descent rates for the 2004 event are also in good agreement with previous estimates of the vertical component of the meridional circulations using MIPAS temperatures and diabatic heating rates (Randall et al, 2015). During both events, the descent rates decrease rapidly towards the stratopause, where they take values of around 200 m day −1 .…”

“…The negative trend in the geomagnetic activity level is closely related to the reduction of solar cycle amplitudes encountered for cycles 23 and 24. As the decline of solar activity is expected to continue in the coming decades (Steinhilber and Beer, 2013), this is likely to affect the long-term NO y trend by counteracting the expected increase caused by growing N 2 O emissions (Ravishankara et al, 2009).…”

Assessing the ability to derive rates of polar middle-atmospheric descent using trace gas measurements from remote sensors

“…The downward transport of nitrogen oxide (NO), produced at around 110 km through energetic particle precipitation (EPP) events (e.g. Barth and Bailey, 2004;Randall et al, 2005Randall et al, , 2007Randall et al, , 2015, garners particular attention because NO x (NO + NO 2 ) catalytically destroys ozone in the stratosphere. Periods of strong atmospheric descent are known to coincide with the timing of sudden stratospheric warmings (SSWs; e.g.…”

HEPPA-II model–measurement intercomparison project: EPP indirect effects during the dynamically perturbed NH winter 2008–2009

“…Using the KArlsruhe SImulation Model of the middle Atmosphere (KASIMA) with specified dynamics below 48 km and prescribed NO x concentrations from MIPAS night-time NO 2 observations above 55 km, Reddmann et al (2010) calculated the amount of EPP-NO x entering the stratosphere from July 2002 to March 2004. KASIMA reproduced the MIPAS observations of NO x entering the stratosphere reasonably well, even during the SSW winter 2003/2004.…”

“…They found that non-orographic GWD is primarily responsible for driving the circulation that results in the descent of CO from the thermosphere following the warmings. Randall et al (2015) investigated the NO x descent during the Arctic winter/spring of 2004 with Whole Atmosphere Community Climate Model (WACCM) simulations that were nudged to Modern-Era Retrospective Analysis for Research and Applications (MERRA) data. They found that their simulated NO x , although qualitatively reproducing the enhanced descent after the ES event, was up to a factor of 5 too low compared with satellite observations.…”