1. Studies of meteoric smoke particles in the middle and upper atmosphere using WACCM
Wuhu Feng, John Plane, Martyn Chipperfield, Dan Marsh,
Diego Janches, Charles Bardeen, Sandy James
Meteoric ablation
Strategy for a global model of MSP
Mesospheric metal layers
MSP formation and preliminary results

2. Meteoric ablation Large uncertainty in IDP (2-300 tonnes/day)
Source of metal layer
Re-condense into MSP
Mass=5µg, SZA=35o, V=21 km/s
Chemical ablation model (CABMOD) profiles
Different metals are released at different altitudes

3. Metal Chemistry Modules (Fe, Si, Na, Mg, Ca, K), ~130 reactions
WACCM/CARMA
IDP
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 ( nm)
Metal chemistry for neutral and ions
Ablation
MIF
Metal Chemistry Modules (Fe, Si, Na, Mg, Ca, K), ~130 reactions
WACCM
(metals)
CARMA
(MSP)
Lidar, rocket and satellite
Deposition

4. Seasonal variation of Na and Fe layers
Na MIF: 4.6 tonnes/day
Fe MIF: 2.2 tonnes/day
Marsh et al. (JGR, 2013)
Feng et al. (JGR, 2013)

5. 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 : : 2 : 3

6. Meteoric smoke formation pathways
Exothermic polymerisation reactions
H = -157 kJ mol-1
NaHCO3 + Fe(OH)2 
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
H = -61 kJ mol-1
FeOH+ Si(OH)4  H2O
H = -21 kJ mol-1

7. Meteoric smoke particle concentration
115
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. 95 80
hPa 60 40 20 15
5.5

8. MSP size distribution and transport
Strong MSP descent into the stratosphere occurs inside the polar vortex
Different MSP size distribution at different altitudes

9. 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-1
1.037 m

10. 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.