ICE - Laboratory experiment goals

• Basic scientific understanding• Check performance of airborne instruments• Develop new measurement techniques & combining

methods (CVI -> CFDC)

STRENGTHS:

Environment control

Repeatability

Mechanistic studies

Test specific aerosol types (dust, bacteria, ..)

Crystal growth habits & rates

Effects of organic coatings, electric charge, ..

Laboratory Experiments A. Cloud types

Layer• upslope

• stratus

Wave

Cumulus• warm base

• cold base

Laboratory Experiments B. Discussion Topics-AIDA

desert dustPaulF summarized yesterday

Sulfuric acid coated soot aerosolsnew JGR paper, in press

AIDA (Aerosol Interactions and Dynamics in the Atmosphere)

84 m3

AIDA - Sulfuric acid coated soot aerosolsice nucleating threshold

Koop, T., B. P. Luo, A. Tsias, and T. Peter (2000), Water activity as the determinantfor homogeneous ice nucleation in aqueous solutions, Nature, 406 (6796), 611–614.

Koop

w. sat

Lab (& modeling) studies

Description Measurements Variables

water cloud formation rh > 100%

CCN spectra, haze & cloud drop conc, particle sizes

(1) CCN chemistry, sizes & conc, LCL, updraft (2) internally mixed or externally mixed

aerosol; organic films

Homog. freezingrh < 100%

same, plus ice crystals

artificial CCN properties (ammonium sulfate, sulfuric acid, sodium chloride, ..)

Heterog. freezing rh < 100%

same, + IN activation spectra (T, rh)

(1) Externally mixed aerosol: artificial CCN & IN; aerosol chemistry

(2) Internally mixed aerosol

Heterog. freezing rh > 100%

same same - (how important is the presence of the liquid phase?)

laboratory-generated surrogates of naturally particles: sea-salt; mineral dust; soot

natural airrh < 100% rh > 100%

same natural air

entrainment-mixing same Aerosol size, chem, elec charge, ..

Measurement challenges

Ice nucleation modes:

• deposition ………………………….X

• condensation-freezing…………..X

• contact-freezing…………………X

• evaporation-freezing ……………?

• electro-freezing…………………?

Discriminating liquid from ice at small sizes (~1 µm)

Development of new techniques to measure ice nuclei

Aerosol concentrator (to improve statistics)

Lab studies – possible participants

NCAR– EOL, ACD

NOAA– Aeronomy Lab, ..

International collaborations:– Germany, Japan, UK,

Switzerland

U.S. universities– CSU– DRI– Michigan Tech.– South Dakota SMT– PennState– Washington– Colorado– Wyoming

Fluid dynamics modeling of instruments

Computational mesh at inlet

Compare FLUENT vs approx.thermodynamic trajectories

Compare FLUENT vs approx.velocity profile