Precipitation of energetic particles into the atmosphere greatly disturbs the chemical composition from the upper stratosphere to the lower thermosphere. Most important are changes to the budget of atmospheric nitric oxides (NOx = N, NO, NO 2) and to atmospheric reactive hydrogen oxides (HOx = H, OH, HO 2), which both contribute to ozone loss in the stratosphere and mesosphere. The impact of energetic particle precipitation on the chemical composition of the atmosphere has been studied since the 1960s, and there are a number of observations as well as model studies concerning especially the auroral impact and large solar particle events. Changes to the NOx budget due to energetic particle precipitation can be quite long-lived during polar winter and can then be transported down into the lower mesosphere and stratosphere, where NOx is one of the main participants in catalytic ozone destruction. Energetic particle precipitation can also affect temperatures and dynamics of the atmosphere from the source region down to the stratosphere and possibly even down to the surface, due to a coupling of chemical composition changes affecting atmospheric heating and cooling rates, the mean circulation, and wave propagation and breaking. Thus, energetic particle precipitation impacts have been implemented in chemistry-climate models reaching from the surface up to the mesosphere or lower thermosphere. However, there are still a number of open questions in the theoretical description of the energetic particle precipitation impact; the most important are uncertainties in the formation rate of different NOx species due to energetic particle precipitation, and the complex coupling between chemical changes, atmospheric heating and cooling rates, and atmospheric dynamics.

spheric models to reproduce observed atmospheric perturbations generated by SPEs, particularly with respect to NO y and ozone changes. We have further assessed the meteorological conditions and their implications for the chemical response to the SPE in both the models and observations by comparing temperature and tracer (CH 4 and CO) fields.Simulated SPE-induced ozone losses agree on average within 5 % with the observations. Simulated NO y enhancements around 1 hPa, however, are typically 30 % higher than indicated by the observations which are likely to be related to deficiencies in the used ionization rates, though other error sources related to the models' atmospheric background state and/or transport schemes cannot be excluded. The analysis of the observed and modeled NO y partitioning in the aftermath of the SPE has demonstrated the need to implement additional ion chemistry (HNO 3 formation via ion-ion recombination and water cluster ions) into the chemical schemes. An overestimation of observed H 2 O 2 enhancements by all models hints at an underestimation of the OH/HO 2 ratio in the upper polar stratosphere during the SPE. The analysis of chlorine species perturbations has shown that the encountered Published by Copernicus Publications on behalf of the European Geosciences Union. 9090 B. Funke et al.: HEPPA intercomparison study differences between models and observations, particularly the underestimation of observed ClONO 2 enhancements, are related to a smaller availability of ClO in the polar night region already before the SPE. In general, the intercomparison has demonstrated that differences in the meteorology and/or initial state of the atmosphere in the simulations cause a relevant variability of the model results, even on a short timescale of only a few days.

We have compared composition changes of NO, NO₂, H₂O₂, O₃, N₂O, HNO₃, N₂O₅, HNO₄, ClO, HOCl, and ClONO₂ as observed by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat in the aftermath of the "Halloween" solar proton event (SPE) in October/November 2003 at 25–0.01 hPa in the Northern Hemisphere (40–90&deg; N) and simulations performed by the following atmospheric models: the Bremen 2d Model (B2dM) and Bremen 3d Chemical Transport Model (B3dCTM), the Central Aerological Observatory (CAO) model, FinROSE, the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA), the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model, the modeling tool for SOlar Climate Ozone Links studies (SOCOL and SOCOLi), and the Whole Atmosphere Community Climate Model (WACCM4). The large number of participating models allowed for an evaluation of the overall ability of atmospheric models to reproduce observed atmospheric perturbations generated by SPEs, particularly with respect to NO_y and ozone changes. We have further assessed the meteorological conditions and their implications on the chemical response to the SPE in both the models and observations by comparing temperature and tracer (CH₄ and CO) fields. <br><br> Simulated SPE-induced ozone losses agree on average within 5% with the observations. Simulated oy enhancements around 1 hPa, however, are typically 30% higher than indicated by the observations which can be partly attributed to an overestimation of simulated electron-induced ionization. The analysis of the observed and modeled NO_y partitioning in the aftermath of the SPE has demonstrated the need to implement additional ion chemistry (HNO₃ formation via ion-ion recombination and water cluster ions) into the chemical schemes. An overestimation of observed H₂O enhancements by all models hints at an underestimation of the OH/HO₂ ratio in the upper polar stratosphere during the SPE. The analysis of chlorine species perturbations has shown that the encountered differences between models and observations, particularly the underestimation of observed ClONO₂ enhancements, are related to a smaller availability of ClO in the polar night region already before the SPE. In general, the intercomparison has demonstrated that differences in the meteorology and/or initial state of the atmosphere in the simulations causes a relevant variability of the model results, even on a short timescale of only a few days

[1] Precipitating solar protons contribute to ozone depletion in the atmosphere; a particles and electrons also precipitate during solar energetic particle (SEP) events. If the SEP is accompanied by a shock, then magnetospheric particles can also be injected into the atmosphere as the shock hits the magnetosphere. Both particle species in both particle populations show distinct energy spectra (and thus penetration depth in the atmosphere) and precipitate in different regions: the SEP inside the polar cap and the magnetospheric particles inside the auroral oval. In this paper, we reevaluate the 3-D spatial and temporal precipitation patterns of these particle populations for the October-November 2003 event and compare the results to conventional approaches using only protons in evaluating SEP consequences. The main results are as follows: (1) The 3-D model AIMOS gives a very differentiated picture of the global ionization maps; (2) if only protons are considered, the differences between the 3-D model and the conventional approach of homogeneous precipitation inside the polar cap are small in NO x production and ozone depletion in the mesosphere and stratosphere; and (3) the consideration of electrons in addition to protons leads to significant increases in atmospheric ionization in the mesosphere, less so in the stratosphere. This is reflected in changes in the chemical composition as shown here for ozone depletion and an increase of NO x .

In this paper, recent software project management tools and their possible advantages, disadvantages, and possible limitations will be discussed, with respect to their application in scientific projects in geoscience and climate science.-96.6 % state that their knowledge about software development comes from self studies;Published by Copernicus Publications on behalf of the European Geosciences Union.