Modelling the precipitation enhancement by hygroscopic cloud - - PowerPoint PPT Presentation

Modelling the precipitation enhancement by hygroscopic cloud seeding in warm and mixed-phase clouds using UCLALES-SALSA

J Tonttila1, A Afzalifar2, H Kokkola1, S Romakkaniemi1

1) FMI Kuopio 2) Aalto Univ, Helsinki

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.

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

Jung et al. 2015 Uclales-salsa

Mixed-phase convective clouds

• Seeding: similar to the Sc case
• Inject to full domain slab
• Initialization: NWP &

measurements

~cloud base Seedin layer

Mixed-phase convective clouds

Frequency Rime fraction Precip rate

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

Thank you!