ROSA Working Package 3

The Bremen chemistry transport model (CTM) framework (e.g. Sinnhuber et al., 2003), which has been successfully developed to assess e.g. polar ozone losses or the total inorganic bromine budget of the lower stratosphere, is to be adapted to describe the formation, growth, transport and removal of aerosol in the stratosphere, hereafter referred to as "aerosol dynamics". This aerosol scheme needs to be coupled interactively to the CTMs chemical cycle and the modeled formation and loss processes of PSCs. The existing and validated aerosol module SAM2 (Hommel et al., 2011) will be used for this purpose. In addition to the model calculated ozone field, the prognostic aerosols are then coupled to the model's radiation scheme, allowing a degree of coupling between the model chemistry and tracer transport, enabling the CTM to study aerosol induced feedbacks of ozone on3 tracer transport. The following tasks are required to complete this work package:

WP 3.1 Implementation of aerosol dynamics scheme into the CTM and coupling with chemistry and radiation schemes.

WP 3.2 Validation of both the modeled global aerosol burden and the integrated aerosol size in the stratosphere against available, evaluated climatologies derived from satellite observations (SAGE II, III, HALOE) for the post-Pinatubo period. Also, available in-situ measurements from balloon soundings or aircrafts have to be considered (Deshler et al., 2003; Deshler et al., 2006; Hofmann et al., 2009).

WP 3.3 Investigation of the horizontal and altitude variation of modeled aerosol particle size. This is relevant for the improvement of the SCIAMACHY limb retrievals of stratospheric aerosols because for the latter currently a phase function is assumed which is independent of altitude and latitude.

WP 3.4 Evaluation of the new SCIAMACHY aerosol climatology (WP 1, WP 2). Initially the existing SCIAMACHY aerosol extinction profile data set will be used here. Later, the improved limb data set as well as the occultation data set – which also includes aerosol particle size information – will be employed.

WP 3.5 Validation of the data sets of present day aerosol in the lower stratosphere, derived from other satellite instruments (CALIPSO, OSIRIS, GOMOS, later NPP/OMPS).