Implementation of a novel seeding material (NaCl/TiO2) for precipitation enhancement in WRF: Description of the model and spatiotemporal window tests

Precipitation enhancement might play a key role in combating constantly increasing frequency of occurrence of draughts in many areas around the globe. This article is a numerical study of the performances of two precipitation enhancers using seven different spatiotemporal windows. The investigated artificial aerosols are the pure NaCl-being a well-researched seeding material-and the core/shell NaCl/TiO2 (abbreviated as CSNT)-being a novel seeding material very recently developed. The activation properties of CSNT are for the first time incorporated into the Weather Research and Forecasting (WRF) model. The performances of two seeding materials, as well as their benchmark against the control case without seeding are investigated in terms of the accumulated surface precipitation and cloud microphysics processes. This study shows multiple advantages of the new seeding agent in terms of both the total accumulated surface precipitation and the increased precipitation area. The best location for release of CSNT in terms of the highest increase of precipitation amount is when both cyclonic and anticyclonic cells are seeded. The largest increase of precipitation area is found when the seeding takes place in front of the cloud and below the cloud base. In this case, the seeded cloud with CSNT releases precipitation over approximately 2 times larger area that the unseeded cloud. The conducted numerical experiments showed that the introduction of CSNT into the cloud environment significantly increases the number concentration of cloud droplets and ice.