M-PACE Measurements of IN are consistent with long-lived nature of clouds

Binned data from 60 s averages over entire project

[IN] variability and dependence on [IN] variability and dependence on supersaturation in mixed-phase regime supersaturation in mixed-phase regime

measured at altitude for different localesmeasured at altitude for different locales

0.00001

0.0001

0.001

0.01

0.1

1

5 10 15 20 25 30 35 40

Ice supersaturation (%)

IN C

on

cen

trat

ion

(cm

-3) Florida Summer

2002

Colorado Winter1994

North DakotaSummer 1993

Alaska Fall 2004

Meyers et al. (1992)

0.00001

0.0001

0.001

0.01

0.1

1

-10 -5 0 5 10

water supersaturation (%)IN

co

nce

ntr

atio

n (

cm-3

)

ND summer 1993

CO Winter 1994

FL Summer 2002

AL Fall 2004

Relevance: Mixed phase clouds

Ice nucleation by coated dusts amenable Ice nucleation by coated dusts amenable to parameteric/threotical treatmentsto parameteric/threotical treatments

Classical theory applied to iron oxide/H2SO4/H2O freezing

120

130

140

150

160

170

180

210 215 220 225 230 235

Temperature (degK)

RH

ice

(%)

theory (m = -0.1)theory (m = -0.3)100 nm data200 nm data

aw(het) < aw(hom)

Exploited for parameterization by Kärcher and Lohmann (2003, JGR)

Water activity based freezing theory applied to heterogeneous freezing

Archuleta et al. (2005)

Adapted from Zuberi et al. (2002, GRL)

Archuleta et al. (2005)

200

210

220

230

240

250

260

270

0.40.60.81

Water Activity (aw)

Tem

pera

ture

(K

)

Treated

Al2O3

(200 nm)Thet0

ΔTm

ΔTm

aiw

Bulk Freezing T

Δaw

homog.

Nucleation rate for iron oxide particles (sizes to 200 nm)

Laboratory natural dust sample comparisions Laboratory natural dust sample comparisions – size and generation method matter– size and generation method matter

100

110

120

130

140

150

160

170

180

-65 -55 -45 -35 -25 -15TEMPERATURE (oC)

RH

i (%

)

200 nm atomized, 1%

AZ-AIDA (d=350 nm,s=1.5)

200 nm drygen, 10%

300 nm drygen, 10%

400 nm drygen, 10%

RHw = 100%

90%80%70%

Note similarity of behavior to large mineral particles studied by Roberts and Hallett (1968, QJRMS)