The aim of this project is to combine the individual strengths of two of the most important instruments available to study the stratospheric aerosol, with the overarching goal of reaching a better representation and understanding of the stratospheric aerosol.

The limb-scattering OMPS-LP provides horizontal coverage, but is limited to relatively faint aerosol layers. The nadir-viewing lidar CALIOP has excellent vertical resolution and can sample the densest aerosol layers, but have difficulties in low aerosol loading conditions and has limited horizontal coverage. OMPS-LP and CALIOP thus complement each other well but there is need for guidelines on when and how to use data from the respective satellite. Our project aims at providing such guidelines, which are crucial for studies of stratospheric aerosol sources and properties. The soon-to-be launched ESA space lidar ATLID and future OMPS-LP instruments will be added once they start producing data.

We will use the dataset to investigate the stratospheric aerosol’s load, sources, and properties, and their variation in time and space. It covers an era with variations in the stratospheric aerosol due to increased wildfire impact, clear indication of human impact, and several volcanic eruptions.
We will use the latest data products from the two satellite instruments as test datasets to evaluate how and during which conditions to use data from the respective satellite. OMPS-LP provides data at six wavelengths, and CALIOP at two, with a third channel providing depolarization of the lidar beam. Together these will be used to estimate particle size distribution (color ratios) and particle shape (depolarization ratio). The performance of data from the different channels (wavelengths and depolarization) will be investigated in different aerosol load conditions and during periods and regions with varying sources of aerosol.

For OMPS-LP we use the recently released level-2 product version 2.0 (Taha, 2020)). This was used in our recent publication (Martinsson et al., 2022), and was produced by our collaborator Dr. Ghassan Taha.
For CALIOP we use our in-house dataset produced by the applicant, based on level-1b data. It is more or less optimized for dense aerosol, making it a very suitable data to combine with OMPS-LP.

The combined OMPS-LP/CALIOP dataset will be used to investigate the aerosol load and properties (size and shape) in periods of influence from anthropogenic, wildfire, and volcanic origin. The underwater Hunga-Tonga eruption, Jan 2022, is especially interesting since it brought large amount of water and likely sea-salts to the stratosphere. We will combine our aerosol dataset with SO2 data to investigate aerosol formation from this eruption as well as the particle properties. Furthermore, we will combine the aerosol dataset with vertically resolved SO2 produced in a co-occurring project, to study additional volcanic eruptions.

We will study the short- and long-term fate of stratospheric wildfire smoke from several wildfires since 2006, by combining our aerosol dataset with H2O observations from the satellite instrument MLS. This is a follow up on our previous studies where we found that ~90% of smoke injected to the stratosphere was lost within weeks, likely due to oxidation of organics in the smoke particles.

Anthropogenic impact on the stratosphere will be investigated by first studying the background aerosol. We will then study regions and periods where anthropogenic aerosol is expected to be most abundant, i.e. East Asia in summertime.

Aerosol particles and their influence on clouds hold the largest uncertainties in today’s climate projections. Understanding aerosol properties, abundance, and sources are therefore of paramount importance for our understanding of the climate. The proposed project will provide insight into these and provide the stratospheric research community and climate modelers with an aerosol dataset containing quantitative data also on the densest aerosol layers.