Impacts of Dust Mixing State on Cloud Microphysics I-Chun Tsai1, Jen-Ping Chen1, Yi-Chiu Lin1, Chein-Jung Shiu2 and Charles Chung Kuang Chou2 Department of Atmospheric Sciences, National Taiwan University Research Center for Environmental Changes, Academia Sinica

sulfate/ nitrate/ ammonium Aerosol mixtures sulfate/ nitrate/ ammonium mineral dust sea salt EC OC aggregate core with shell RH Core with Shell better CCN and IN (?) stronger absorption heterogeneous chemistry mixture state

Dust nucleation rate Immersion freezing rate (haze) Immersion (haze)

Model & simulation setup MM5 + CMAQ physics-based multimodal aerosol scheme 3 moments log-normal size distribution case: 2006/03/14-20 VOC (Zhang et al., 2009) Add SOA emission plot (but what species……)._ dust (Wang et al., 2000) SO2 (Zhang et al., 2009) soot (Zhang et al., 2009)

Multi-modal aerosol scheme hygroscopic aerosol size Number density dust/soot size Number density mixture size Number density dust

Impacts on aerosol properties Mi,mix – Mi,no_mix Mi : the ith moment M0: number, M2: surface area, M3: volume % Dust source Sulfate source Open ocean Taiwan M0 -17.7 -12.8 79.9 -10.6 M2 -24.4 -31.7 52.8 50.9 M3 -39.9 -53.6 -7.7 -22.34

Single Scattering Albedo mix_ex mix mix

Single Scattering Albedo in Taipei

CCN concentration at 0.1% ss. Inorganic CCN Increase due to dust mixing 109 m-3 1010 m-3 Increase due to soot mixing 109 m-3 Dust: order of magnitude differences (under strong dust storm activity) Soot: a factor of 2 to 3 differences No mix case CCN

Internal (dust/sulfate) Nucleation rate at -20C External (dust) Internal (dust/sulfate) 106 m-3 s-1 106 m-3 s-1 Internal - external 106 m-3 s-1 Pure dust coated dust Ammonium sulfate up to 10% differences

Summary Mixing (coagulation) between these two types aerosols greatly affects Aerosol microphysical processes Cloud microphysical processes: CCN # (and ice nucleation rate) Effect of aerosol mixing on cloud initiation CCN (at 0.1% supersaturation) generally increased due to aerosol mixing Solute coating may cause a switch of nucleation mode from deposition nucleation to “immersion freezing” Solute coating suppress dust nucleation; enhance soot nucleation at above -28C but suppress at lower temperatures On-line calculation by coupled WRF-CLR-kosa (Lin, 11/06 11:25 AM)

Thank You

Correction of refractive index Dust (1.544,-0.025)+ sulfate mixture(1.53,-1e-7) Toon and Ackerman (1981)

Internal (soot/sulfate) Nucleation rate at -20C External (soot) Internal (soot/sulfate) Internal - external Pure soot coated soot Ammonium sulfate Mixing enhance soot nucleation at -20C

Internal (soot/sulfate) Nucleation rate at -30C External (soot) Internal (soot/sulfate) Internal - external Pure soot coated soot Ammonium sulfate Mixing suppress soot nucleation at -30C