Modelling the precipitation enhancement by hygroscopic cloud - PowerPoint PPT Presentation

This material is based on work supported by the National Center of Meteorology, Abu Dhabi, UAE under the UAE Research Program for Rain Enhancement Science. Modelling the precipitation enhancement by hygroscopic cloud seeding in warm and mixed-phase clouds using UCLALES-SALSA J Tonttila 1 , A Afzalifar 2 , H Kokkola 1 , S Romakkaniemi 1 1) FMI Kuopio 2) Aalto Univ, Helsinki

Introduction ● Weather modification as means to improve water availability? ● Rain enhancement by hygroscopic cloud seeding ● Seeding effects not fully understood – Attribution – Mixed-phase clouds ● Simulations with UCLALES-SALSA – Simple Sc case – evaluation – Mixed-phase convective clouds at the UAE

Rain enhancement ● Seeding by hygroscopic particles, ~similar to GCCN ● E.g. flare burning, pre-milled salt particles fewfef ● At activation: competition for water vapor → reduced CDNC → more rain ● Fast growing cloud droplets → enhance collision- coalescence → more rain ● Very large GCCN → effectively direct drizzle/rain ● Mixed-phase clouds: change droplet distribution → change cold precip process

Model description: UCLALES-SALSA Directly from collision- coalescence CNT based parameterizations, P3 (Morrison & Milbrandt, 2015) methodology

Evaluation with marine Sc ● Based on a field experiment (Jung et al. 2015, ACP) ● Seeding – Proxy composition: Sea salt – Two modes: 1.5 um, 8 um – Initial plume concentrations 1 cm-3, 10 cm-3 – Point source emission, full slab injection

Evaluation with marine Sc Uclales-salsa Jung et al. 2015

Mixed-phase convective clouds ● Seeding: similar to the Sc case ● Inject to full domain slab ● Initialization: NWP & measurements Seedin layer ~cloud base

Mixed-phase convective clouds Precip rate Frequency Rime fraction

Conclusions ● UCLALES-SALSA to study rain enhancement via cloud seeding ● Microphysical response to seeding in good agreement between U-S and observations in Sc ● Seeding-increased rime fraction suggests enhanced rain in mixed-layer convective clouds ● High injection rates needed for a discernible signal

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