DYNAMO Webinar Series Dynamics of the Madden-Julian Oscillation Field Campaign Climate Variability & Predictability

Aerosols in the Indian Ocean November AOT Average: MODIS Aerosol measurements on the R/V Revelle: Measured the sub and supermicrometer aerosol chemical (filter-based and real-time), physical (size), and optical properties (scattering and absorption) Clean Marine Anthropogenically Influenced Aerosol

Aerosols in the Indian Ocean November AOT Average: MODIS 1.How does the MJO affect aerosol properties over the Indian Ocean? 1.How could continental aerosol affect the MJO?

Tian et al., 2008 Aerosols and the MJO: Effect of Enhanced MJO Convection on Aerosols (Satellite Measurements) TOMS Aerosol Index: measures concentration of absorbing aerosol only. MODIS and AVHRR Aerosol Optical Thickness: measures concentration of scattering and absorbing aerosol Negative correlation between rainfall and aerosol concentration anomalies (more rain: less aerosol) Positive correlation between rainfall and aerosol concentration anomalies (more rain: more aerosol optical thickness)

Leg 2: Oct 4-Oct 30: More Marine Aerosol Weak MJO event late October Leg 3: Nov 8-Dec 7: More Continental Aerosol Strong MJO event late November Aerosol Source Regions HYSPLIT backtrajectories October-early December is the shoulder season after the Asian summer monsoon: wind direction over the Indian Ocean changing from primarily southerly to primarily northerly. 7 day 200 m height aerosol back trajectories

Leg 2: Oct 1-Oct 30: Dominant marine aerosol source, primarily acidic sulfate Leg 3: Nov 8-Dec 7: Dominant continental aerosol source, more ammonium sulfate, nssK + (biomass burning tracer). Submicron Aerosol Concentration Increased with more Continental Sources MJO EVENT

Wind speed average of ~ 3 m/s, aerosol transport from the Asian continent Dominance of accumulation mode continental aerosols Wind speed average of ~10 m/s, increased precipitation Rainout of continental aerosols, dominance of primary marine (e.g. sea salt) coarse-mode aerosols. Enhanced Convection:Suppressed Convection:Increased Convection Increase in O 3 as the marine boundary layer height rises, introduction of submicrometer particles from the FT to the MBL. Observed Aerosol Response to the MJO: November 2011

MJO Effect on Aerosol Optical Properties: Enhances scattering, absorbing aerosols removed (active convection), suppresses scattering, absorbing aerosols can build up (suppressed convection) Scattering : Sea Salt, Sulfate (SSA~1) Absorbing: Dust (0.7), Biomass Burning (0.85), Black Carbon (0.3): mostly from continental sources

Aerosol chemistry: response to the MJO: Large increase in supermicrometer sea salt aerosol and decrease in submicrometer sulfate, organic, ammonium aerosol

Aerosol Response to the MJO Sea Salt Aerosol Continental Aerosol Cloud Droplets Rain Droplets Suppressed Convection: Longer aerosol lifetime Increased Convection: Aerosol transport from the free troposphere Enhanced Convection: Sea-salt aerosol formed from breaking waves due to high winds Enhanced Convection: Heavy precipitation, aerosol rainout Suppressed Convection: Reintroduction of continental aerosols

Conclusions Convection associated with the MJO wave greatly affects local aerosol properties. More continental aerosol transport during the dry season and larger MJO anomaly signal during the dry season. – Aerosol direct and indirect effects on convection potentially enhanced. – Is there a feedback loop between MJO convection and aerosol?