Secondary sulphate aerosols and cirrus clouds detection with SEVIRI during Nabro volcano eruption

Secondary sulphate aerosols (SSAs) and cirrus clouds in the upper troposphere–lower stratosphere (UTLS) are two key atmospheric con-stituents that can modulate the Earth’s radiative balance. In this article, we present a new preliminary detection algorithm for UTLS SSAs with the Spinning Enhanced Visible and Infrared Imager (SEVIRI) geosta-tionary instrument. This algorithm is used in combination with a well-established existing clouds classification algorithm, to provide, in per-spective, a combined tool to better characterize the aerosol–cirrus interactions at the regional scale and at very high temporal resolution, thus potentially contributing to the understanding of the SSAs’ direct– indirect impact on the Earth’s radiative balance. This new combined tool is tested on the Nabro volcano eruption of June–July 2011, which is known to have emitted a great amount of SSA gaseous precursors in the UTLS and to have interacted with the peculiar Asian monsoon dynamics during summer 2011. Although volcanic aerosol–cirrus interactions are not analysed in details at this stage, this work demonstrates that this can be carried out with SEVIRI by introducing a new dedicated SSA product. First results of the new SSA detection algorithm are encouraging towards the use of this combined product.