juha tonttila, harri kokkola, tomi raatikainen, jaakko ... · hygroscopic cloud seeding a potential...
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Model investigation into rain enhancement by hygroscopic seeding in mixed-phase convective clouds
Juha Tonttila, Harri Kokkola, Tomi Raatikainen, Jaakko Ahola, Hannele Korhonen, and Sami Romakkaniemi
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Background● Hygroscopic cloud seeding a potential way to enhance
rainfall → improve water security● Semi-idealized LES simulations based on observations at
UAE
– Moderate convective precipitation events (cloud top 8-10 km)
● Is the expected enhacement of collision-coalescence due to hygroscopic seeding the main process also in mixed-phase convective clouds?
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Model
● UCLALES-SALSA
– LES coupled with sectional aerosol-cloud microphysics model
– Rimed ice description follows the P3 (Morrison and Milbrandt, 2015) approach
– Rain drop formation and growth determined directly from collision-coalescence
– Non-equlibrium condensation
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Key findings● Increased rainfall is associated with an increase in rime fraction in all simulations
Histogram sampling height, meters
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Key findings● Divide precip events into warm and cold process dominated cells (melting ice → precip as an
indicator)
● Absolute rainfall & absolute increase due to seeding always larger in ”cold dominated” cells → introduction of hygroscopic particles leads to significant enhancement in riming and the cold precipitation process
● Results show sensitivity to model configuration (aerosol, moisture…); investigation is on-going
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Thank you!