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Studies of meteoric smoke particles in the middle and upper atmosphere using WACCM

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

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Studies of meteoric smoke particles in the middle and upper atmosphere using WACCM

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  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. 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 (0.2-102 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 : Si7 : 2 : 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.

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