HEPPA-I: Composition changes after the “Halloween” solar proton event

The HEPPA-I exercise has focused on the intercomparison of MIPAS/Envisat data obtained in the aftermath of the “Halloween” SPE (26 October – 30 November 2003) with state of the art GCMs and CTMs. The large number of models participating in this exercise allowed for an evaluation of the overall ability of atmospheric models to reproduce observed atmospheric perturbations generated by SPEs, particularly with respect to NOy and ozone changes. This model validation represents a mandatory first step towards an...Read more

HEPPA-II: EEP indirect effects during the unusual 2009 NH polar winter

HEPPA-II exercise focuses on EPP indirect effects (i.e., polar winter NOx descent). This is motivated, on one hand, by the higher potential of EPP indirect effects to influence middle atmospheric composition on longer time scales compared to direct effects (i.e., SPEs) and, on the other hand, by its large variability related to dynamical modulations, making its representation in current atmospheric models challenging. In particular, the 2008/2009 NH polar winter resulted to be a very interesting period because...Read more

SOLARIS Coordinated Experiments I

A) Coordinated Model Runs to Investigate Aliasing of Different Factors in the Tropical Lower Stratosphere

Recently, the discrepancy between modelling studies and observations regarding the vertical structure in the tropical solar signal, as shown by the WMO (2007), has been reduced in both CCMVal-1 reference simulations (Austin et al., 2008) and CCMVal-2 simulations (SPARC CCMVal, 2010, chapter 8). Similarly, other recent simulations with CCMs...Read more

SOLARIS-HEPPA Coordinated Experiments I

The increasing number of model simulations to be performed for international activities like the IPCC or the WMO ozone assessment present a burden for all modelling groups. In order to reduce the amount of extra model runs and activities, SOLARIS-HEPPA introduced two scenario simulations within the CCMI simulation request to a) address the uncertainty in solar forcing and b) investigate the role of solar forcing for the future with respect to a new grand minimum in solar activity.

a) Uncertainty in solar forcing

So far the...Read more

The Solar Model Inter-comparison Project (SolarMIP) is a SPARC/SOLARIS initiative to compare the coupled ocean-atmosphere model response to variability in solar irradiance in the CMIP5 (Coupled Model Intercomparison Project phase 5) model simulations. SolarMIP aims at examining the model responses to the 11-year solar cycle variations with special care on (a) the stratospheric response, which is dominated by ozone absorption of incoming UV-radiation and (b) the surface response, which is believed to be a combination of direct heating of the tropical SSTs and indirect effects via the...Read more