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Modelling and Measurements of the interactions between aerosols and clouds during ACTIVE

Modelling and Measurements of the interactions between aerosols and clouds during ACTIVE. P. Connolly  , G. Vaughan , K. Bower, T. W. Choularton  , M. W. Gallagher , M. Flynn, G. Allen. A.Heymsfield , A. Bansemer. School of Earth,Atmospheric and Environmental Sciences,

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Modelling and Measurements of the interactions between aerosols and clouds during ACTIVE

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  1. Modelling and Measurements of the interactions between aerosols and clouds during ACTIVE P. Connolly, G. Vaughan,K. Bower, T. W. Choularton, M. W. Gallagher, M. Flynn, G. Allen. A.Heymsfield, A. Bansemer. School of Earth,Atmospheric and Environmental Sciences, The University of Manchester. NCAR, USA

  2. This study Campaign 1 Nov Dec Test SurveyHector Mixed survey/Hector Single-cellular Hector Multi-cellular Hector Mini-monsoon

  3. This study Campaign 2 Test SurveyHector Monsoon Aged anvil Lidar Monsoon trough Inactive Monsoon Westerly Monsoon Single-cellular Hector Multi-cellular Hector

  4. Summary • Around 30 flights with each aircraft in and around tropical convection • Inflow conditions change from polluted early in November (smoke from biomass burning) to very clean in Jan/Feb • Hectors observed in polluted and clean regimes • Monsoon convection observed in the second half of January

  5. Question • Can we observe the thermodynamic indirect effect? AND How important is it?

  6. LEM Model framework Large eddy model • Island heat fluxes and roughness length - MODIS. • Droplet activation – Twomey 1959: N=Csk • Maritime: C=240cm-3, Continental: C=720cm-3. • 2-moment bulk microphysical scheme. • 3-moment graupel scheme-density of graupel. • Radiation code – LW, SW.

  7. Important to predict number of activated droplets and raindrops Heterogeneous freezing of rain Bigg 1953

  8. Ice Mass for CB Drop Number = 120 cm-3

  9. Ice Number for CB Drop Number = 120 cm-3

  10. Ice Mass for CB Drop Number = 360 cm-3

  11. Ice Number for CB Drop Number = 360 cm-3

  12. Two Hectors… Mid-level dry layer: A feature of tropical easterlies (subsidence) Data – Peter May

  13. 6 Feb 2006 -clean Satellite data from BoM, aircraft tracks by G. Allen

  14. Rapid latent heat release (freezing of rain, riming) Slower latent heat release (growth of liquid by condensation)

  15. Strong effect when no dry layer

  16. 16 Nov 2005 - polluted 17:00 15.45 Satellite data from BoM, aircraft tracks by G. Allen

  17. No strong indirect effect when Dry layers are present

  18. 16 Nov (polluted)

  19. 6 Feb (clean)

  20. Conclusion • Two case studies are consistent with high aerosol concentrations pre-monsoon and low post monsoon. • The thermodynamic indirect effect is strongly dependent on the dryness of the sounding below the melting level. • For deep convective clouds, the presence of rain above the freezing level is vital to the indirect effects. • It is vital to accurately predict the droplet number concentration in order to ascertain these effects.

  21. Egrett payload † alternates Chemistry Met/Position Aerosol Humidity Cloud Physics

  22. Dornier payload Chemistry Met/Position Aerosol

  23. Modelling mixed phase clouds EMM Parcel model – detailed sectional microphysics • CRM – • Bulk 2-moment microphysics. • Explicit ice density. • Broad-band radiation module. • Eulerian grid. Down-draft T2, P2 Ascending cloud layers T1, P1 Lagrangian tracking of precipitation

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