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“POC’s are the Norm” Hypothses - Flow Chart for SEP

Nov 13, 2008 ~18:40. RF13. 20S. 30S. “POC’s are the Norm” Hypothses - Flow Chart for SEP. Clean marine aerosol advected into south of SEP that is in quasi equilibrium with low CO air and small 30 nm mode entrained from FT & grown via DMS.

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“POC’s are the Norm” Hypothses - Flow Chart for SEP

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  1. Nov 13, 2008 ~18:40 RF13 20S 30S “POC’s are the Norm” Hypothses - Flow Chart for SEP Clean marine aerosol advected into south of SEP that is in quasi equilibrium with low CO air and small 30 nm mode entrained from FT & grown via DMS Warmer surface waters heat and raise MR as air advects North under stronger subsidence inversion leads to clean turbulent St deck and increased entrainment “Clean layer” develops under strong inversion near cloud top via sedimentation of larger droplets leading to stabilization. Layer suppresses entrainment but may be eroded by more active night time convection. Meanwhile drizzle gradually reduces CCN throughout MBL Clean FT aerosol above cloud CCN<15/cc @ %S-0.3 Polluted aerosol above cloud CCN>40/cc @ %s=0.3 Entrained CCN insufficient to compensate for drizzle, drizzle enhanced, Reff larger and transition to POC occurs. Clean layer no loonger eroded by clouds and entrainment suppressed. Entrained CCN sufficient to partially or fully compensate for drizzle loss and transition to POC delayed or suppressed, Reff smaller - depending on pollution concentration Persistent above cloud flow probably coupled to upslope-downslope flow will spread out with easterly flow above clouds embeded in a southerly boundary layer flow at probably 200-500km/day. Clouds responding to entrinement from this upper layer will take on archlike shape anchored to the land sources. Long range FT transport can also add aerosol to the clouds elsewhere. WITHOUT THIS COMBUSTION SOURCE OF CCN – POCS WOULD BE THE NORMAL DEMISE OF THE St CLOUDS Polluted Clean

  2. RF 11 11/7/2008 18:00UT RF 11 11/6/2008 18:00UT Blue circle/arrows – large scale divergent MBL flow implies entrainment in clear air 3 days before 11/9/2011

  3. Nov 13, 2008 ~18:40 RF13 20S 30S RF13

  4. Nov 6, 2008 Nov 7, 2008 Nov 8, 2008 Nov 9, 2008 Nov 10, 2008 20S RF11 south 30S Nov 11, 2008 Nov 12, 2008 Nov 13, 2008 Nov 14, 2008 Nov 15, 2008 RF13 20S RF14 20S 20S RF 12 south 30S 30S 30S

  5. RF14 24hr later Crude check on clouds 24 hr later looks like layer may be part of an arc of pollution impacting clouds RF14 24hr later

  6. RF13 SO2 sourced from pollution aloft into ultraclean layer RF11 South SO2 (140pptv) sourced from below (DMS?) into clean layer Low cloud fraction No precip 4 days

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