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Study Implements Novel Seeding Material for Precipitation Enhancement in WRF

In the last few decades, the frequency of droughts has constantly increased on a global level and is likely to accelerate further in the coming decades. Precipitation enhancement might play a key role in combating drought events and alleviating their detrimental impacts on crops and the environment. Precipitation enhancement can be achieved by introducing a seeding material into the cloud environment to alter a set of cloud microphysical processes leading to rainfall generation. Various numerical models have been used to validate and assess the performances of seeding materials prior to their eventual field testing.

To a gain a better understanding of the passive and active behavior of seeding materials in different locations, Prof. Linda Zou, a first cycle awardee of UAE Research Program for Rain Enhancement Science (UAEREP) and professor at the Khalifa University, carried out a numerical study of the performances of two precipitation enhancers including her proposed novel NaCl/TiO2 composite nanomaterial using seven different numerical experiments in which the seeding materials are released at different locations in respect to the developed supercell.

The study investigated the precipitation enhancing properties of pure NaCl, a well-researched seeding material, and the recently developed core/shell sodium chloride/titanium dioxide NaCl/TiO2 (abbreviated as CSNT), and compared the seeding results against the control, unseeded case. The study incorporated for the first time the activation properties of CSNT into the Weather Research and Forecasting (WRF) model.

The results showed multiple advantages of the new seeding agent in terms of both the total accumulated surface precipitation and the increased precipitation area. The study also found that 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 study also concluded that 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 two 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 liquid water droplets and ice particles which contribute to increased rainfall.

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