In the SOLIC project, uncertainties of the solar-induced decadal climate variability from the lower thermosphere down to the ocean are quantified, an important component of reliable climate predictions. Observations and parameterization studies indicate a contribution of solar cycle variability to climate variability, but the quantification of this contribution remains a difficult task, not only because of limited observational data, but also due to complex non-linear interactions for the transfer of the solar signal from the upper to the lower atmosphere.

Research activities within SOLIC will focus on an integrated solar cycle analysis by studying i) the degree and quality of the solar processes incorporated in three state-of-the-art chemistry-climate models with respect to radiative and auroral processes as well as dynamics, ii) the discrepancies in 11-year solar irradiance forcing, and iii) the model formulation, especially the model’s top height and the role of the ocean. This will be complemented by comparing the simulated response to other existing chemistry-climate model (CCM) simulations as well as simulations with general circulation models with active ocean (AOGCMs). The goals of SOLIC are directly linked to the international WCRP/SPARC-SOLARIS/HEPPA initiative ( and SOLIC will provide the German contribution to it.

Work package 1 (WP1) of SOLIC investigates the minimum necessary spectral resolution required in the SW radiation code of a model in order to simulate the atmospheric heating response to the solar cycle. WP2 is dedicated to the precipitation of ionized particles and the development of a parametrization of auroral effects for CCMs, both as an upper boundary condition for low-top models, and as a source term in the upper mesosphere/lower thermosphere for the high-top models. WP3 examines the sensitivity of atmospheric signals to different spectral solar irradiance data sets as well as the effects of geomagnetic activity. WP4 analyzes the propagation pathways of the solar signal (radiative and particle effects) from the upper atmosphere down to the ocean. The importance of stratospheric "top-down" and tropospheric-oceanic "bottom-up" processes is analyzed.

Project partner: (in alphabetic order)
Prof. Dr. Ulrike Langematz (FUB, Co-PI)
Prof. Dr. Katja Matthes (GEOMAR, PI)
Dr. Miriam Sinnhuber (KIT, Co-PI)

Prof. Dr. Katja Matthes
GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel