Project A01:
Aerosol-Cloud inTeraction and water Vapour transport in high UPdraft regimes (ACTIV-UP)

Brief Summary

Convective processes play a critical role in the Earth’s energy balance through the redistribution of heat, moisture and aerosols in the atmosphere. They are characterized by high updrafts with turbulent and diabatic processes where cloud formation and cloud properties differ from those formed in mid-latitude frontal systems. Particularly ice clouds evolving at the top of deep convective systems – so called anvil cirrus – exert a net heating at the top of the atmosphere. Locally, they can transport water vapor efficiently into the UTLS and the stratosphere e.g. in overshooting anvil tops. The representation of subgrid-scale convective cloud processes in models is yet a challenge and requires adequate parametrizations based on robust observations of cloud properties and water vapor transport pathways. The aerosol impact on cloud formation in convective systems has been the focus in many aerosol cloud interaction studies. However, disentangling the relative impact of the aerosol type and concentration and updraft velocities on the microphysical cloud properties over the lifetime of a convective cloud is one of the largest remaining questions in anthropogenic climate forcing and requires dedicated observations. Particularly the impact of aerosol concentration and updraft velocities as well as the impact of radiative and latent heating on ice particle number and ice mass concentrations in the anvil are important parameters to assess their climate impact.
Spaceborne observations of aerosol and cloud particle number that provide a large dataset on liquid and cirrus cloud properties have significantly advanced in the past. However observations of small scale processes that determine the life cycle of convective systems and anvil clouds need to be validated with high resolution measurements to improve retrieval methods for global observations. Here we attempt to partially fill this gap by proposing new in-situ measurements from a dedicated aircraft campaign with the DLR-Falcon 20 to detect water vapor, aerosol and cloud properties as well as updraft velocities in convective systems in the UTLS above continental Europe and the Mediterranean Sea. In-situ measurements of water vapor, the particle size distribution (PSD), as well as chemical and microphysical properties of aerosol and clouds will be performed in central and southern Europe in autumn 2021. The following research questions will be addressed: What is the aerosol concentration in the inflow region of convection above continental Europe and the Mediterranean Sea? Is there a measurable effect of pollutants on the PSD in convective systems? How do high-updraft regimes and diabatic processes change the water vapor distribution in the UT, the turbulent H₂O flux into the LS and the radiation budget of the UTLS? Is the water vapor distribution near convection well represented in numerical weather prediction models? How do the cloud properties in convective cirrus differ from cirrus formed in other high updraft regimes such as WCBs? How do these processes affect the UTLS radiation budget and climate?

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