Studies of meteoric smoke particles in the middle and upper

atmosphere using WACCM

Meteoric ablation Strategy for a global model of MSP Mesospheric metal layers MSP formation and preliminary results

Wuhu Feng, John Plane, Martyn Chipperfield, Dan Marsh, Diego Janches, Charles Bardeen, Sandy James

• Large uncertainty in IDP

(2-300 tonnes/day)

• Source of metal layer

• Re-condense into MSP

Meteoric ablation

Mass=5µg, SZA=35o, V=21 km/s

Chemical ablation model (CABMOD) profiles

Different metals are released at different altitudes

WACCM/CARMA

Whole Atmosphere Community Climate Model

• Detailed dynamics/physics/chemistry from troposphere to lower thermosphere (0-140 km)

• Options to use different meteorological analyses (GEOS5, MERRA, ECMWF).

Community Aerosol and Radiation Model for Atmosphere

• Detailed microphysics (sedimentation, coagulation, nucleation, growth and evaporation, Brownian diffusion, dry/wet deposition, optical properties etc.)

• Assume smoke material density of 2g/cm-3, 28 bins (0.2-102 nm)

Metal chemistry for neutral and ions

WACCM(metals)

CARMA(MSP)

MIF

Ablation

IDP

Deposition

Metal Chemistry Modules (Fe, Si, Na, Mg, Ca, K), ~130 reactions

Lidar, rocket and satellite

Marsh et al. (JGR, 2013) Feng et al. (JGR, 2013)

Na MIF: 4.6 tonnes/day Fe MIF: 2.2 tonnes/day

Seasonal variation of Na and Fe layers

Fe, Si, Na, Mg neutral/ion/reservoir species

4 dominant reservoir species used to form MSP(18 extra reactions)

Meteoric elements in MSP ratios

Fe : Mg : Na : Si 7 : 2 : 2 : 3

1. Exothermic polymerisation reactions

NaHCO3 + Fe(OH)2 H = -157 kJ mol-1

Mg(OH)2 + Mg(OH) 2 H = -268 kJ mol-1

2. Condensation reactions with Si(OH)4 produce silicates

Mg(OH)2 + Si(OH)4 + H2O

FeOH+ Si(OH)4 + H2O

H = -61 kJ mol-1

H = -21 kJ mol-1

Meteoric smoke formation pathways

hP

a

The smoke material explicitly formed by metal chemistry enters the model in the smallest size bin (0.2 nm)

Seasonal variation in MSP concentration.

Largest MSP concentration (10,000 cm-3) matches rocket data.

80

15

5.5

20

40

60

95

115

Meteoric smoke particle concentration

Strong MSP descent into the stratosphere occurs inside the polar vortex

MSP size distribution and transport

Different MSP size distribution at different altitudes

Extinction / km-1

10-10 10-9 10-8 10-7 10-6 10-5

Alti

tude

/ km

40

50

60

70

80HematiteOlivine PyroxeneSOFIE extinction

MSP extinction

The SOFIE spectrometer on the AIM satellite is able to measure extremely small optical extinctions in solar occultation

We assume MSP in different types (Fe2O3, (FexMg1-x)2SiO4, FeSiO3)

Extinction cannot be modelled using the WACCM smoke distribution in the upper stratosphere and lower mesosphere, based on a meteoric input of ~2 t d-11.037 m

Summary and conclusions

First self-consistent global model of meteoric smoke.

MIF varied to match lidar/satellite measurements: Fe (2.2 t/day), Na (4.6 t/day), Mg(0.4 t/day)

Good simulation of mesospheric metal layers. The meteoric input required to model the metal layers is MUCH too small to model the observed smoke extinction. Resolving this will be a big challenge.