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Scientific objectives: Characterize variations of the coastal BL, clouds, and aerosols

Boundary layer, cloud, and aerosol variability in the southeast Pacific coastal marine stratocumulus during VOCALS- REx.

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Scientific objectives: Characterize variations of the coastal BL, clouds, and aerosols

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  1. Boundary layer, cloud, and aerosol variabilityin the southeast Pacific coastal marinestratocumulus during VOCALS-REx XueZheng……, Bruce Albrecht, Haf Jonson, DjamalKhelif, Graham Feingold, Patrick Minnis, Kirk Ayers, Patrick Chuang, ShaunnaDonaher, DioneRossiter, and Jesus Ruiz-Plancarte RSMAS, University of Miami 03/21/2011

  2. Point Alpha (20oS; 72oW) From VOCALS Program Summary VOCALS--Hypothesis 1a: Aerosol-Cloud-Drizzle Interactions • Scientific objectives: • Characterize variations of the coastal BL, clouds, and aerosols • The first-hand evidence of cloud-aerosol-turbulence interactions in the coastal marine Sc

  3. CIRPAS Twin Otter Instrumentation Date

  4. Synoptic Conditions 700-hPa SLP • Subtropical high, a low-level trough,and a mid-latitude trough • ~ Oct. 29 – Nov. 4 an intense mid-latitude disturbance. (Rahn and Garreaud, 2010; Toniazzo et al., 2011) Point Alpha NCEP/NCAR Reanalysis

  5. Composite Fields from Satellite Observations Cloud fraction (%) LWP (g/m2) Re (micron) Surf. Wind and Div. • Generally solid cloud • Relatively low LWP and Re thin and polluted cloud • QuikSCAT surf. wind: 4.1±1.5 ms-1 , 175o (Southerly wind ) • Average Div: ~ 3X10-6 s-1 GOES-10 from Minnis and Ayers QuikSCAT

  6. Cloud Liquid Water Path 17.5oS 20oS Oct. 19 GOES10 Ch1 22.5oS 75oW 70oW

  7. Cloud Liquid Water Path 17.5oS 20oS Oct. 24 22.5oS 75oW 70oW

  8. Cloud Liquid Water Path 17.5oS 20oS Nov. 1 22.5oS 75oW 70oW

  9. Cloud Liquid Water Path 17.5oS 20oS Nov. 8 22.5oS 75oW 70oW

  10. Cloud Liquid Water Path 17.5oS 20oS Nov. 12 22.5oS 75oW 70oW

  11. Boundary Layer Structure • Well mixed BL with strong inversion • Relatively low wind speed with strong veritical wind shear • Some complications involving wind shear within the BL, moist layers above, strong decoupled BL with cumulus below

  12. Turbulence structure • Relatively weak turbulence in the BL • Entrainment rates (average of 1.5±0.6 mms-1) • Cloud top radiative cooling Vertical vel. variance total water flux heat flux

  13. BL Variations • Inversion height varied between 1000 and 1500 m • SST gradually increased • the 30-m fluxes LHF SHF

  14. Aerosol and Cloud Properties

  15. Aerosol Indirect Effect

  16. LWP and Sub-cloud CCN Nov. 2 Nov. 1 Oct. 29 Oct. 30 (Zheng et al. GRL 2010)

  17. Conclusions • Typical non-drizzling, well-mixed stratocumulus topped BL on days when synoptic and meso-scale influences are small • Aerosol variability driven by boundary layer flow and processes. • Entrainment rates and turbulence were weaker than that in the BL over the open ocean west of Point Alpha and the BL off the coast of the NE Pacific (Bretherton et al. 2010; Stevens et al. 2005). • During the typical well-mixed BL days, the LWP increased with the CCN concentrations (Zheng et al. GRL 2010) • On the other hand, meteorological factors and the decoupling processes can have large influences on the cloud LWP variations

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