28 Apr 2022
28 Apr 2022
Status: this preprint is currently under review for the journal ACP.

Aerosol characteristics and polarimetric signatures for a deep convective storm over north-western part of Europe – modeling and observations

Prabhakar Shrestha1, Jana Mendrok2, and Dominik Brunner3 Prabhakar Shrestha et al.
  • 1Institute of Geosciences, Meteorology Department, Bonn University, Bonn, Germany
  • 2Deutscher Wetterdienst, Offenbach, Germany
  • 3Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland

Abstract. The Terrestrial Systems Modeling Platform (TSMP) was extended with a chemical transport model and polarimetric radar forward operator to enable detailed studies of aerosol-cloud-precipitation interactions. The model was used at km scale (convection permitting) resolution to simulate a deep convective storm event over Germany, which produced large hail, high precipitation and severe damaging winds. The ensemble model simulation was in general able to capture the storm structure, its evolution and spatial pattern of accumulated precipitation - however, the model was found to underestimate regions of high accumulated precipitation (> 35 mm) and convective area fraction in the early period of the storm. While the model tends to simulate too high reflectivity in the downdraft region of the storm above the melting layer (mostly contributed by graupel), the model also simulates very weak polarimetric signatures in this region, compared to the radar observations. The findings of the study remained almost unchanged when using much narrow cloud drop size distribution (CDSD), acknowledging the missing feedback between aerosol physical and chemical properties and CDSD shape parameters.

The km scale simulation showed that the strong updraft in the convective core produces "aerosol tower" like features, increasing the aerosol number concentrations and hence increasing the cloud droplet number concentration and reducing the mean cloud drop size. This could be also a source of discrepancy between the simulated polarimetric features like differential reflectivity (ZDR) and specific differential phase (KDP) columns along the vicinity of the convective core compared to the X-band radar observations. Besides, the evaluation of simulated trace gases and aerosols were encouraging, however a low bias was observed for aerosol optical depth (AOD), which could be partly linked to an underestimation of dust mass in the forcing data associated with a Saharan dust event.

This study illustrates the importance and the additional complexity associated with the inclusion of chemistry transport model when studying aerosol-cloud-precipitation interactions. But, along with polarimetric radar data for model evaluation, it allows to identify and better constrain the traditional 2-moment bulk cloud microphysical schemes used in the numerical weather prediction models for weather and climate.

Prabhakar Shrestha et al.

Status: open (until 15 Jun 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Prabhakar Shrestha et al.

Prabhakar Shrestha et al.


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Short summary
The study extends the TSMP with gas-phase chemistry, aerosol dynamics and radar forward operator to enable detailed studies of aerosol-cloud-precipitation interactions. This new capability is demonstrated using a case study of deep convective storm, which showed that the strong updraft in the convective core of the storm produced "aerosol tower" like features, which effected the size of the hydrometeors and the simulated polarimetric features (e.g. ZDR and KDP columns).