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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. - PowerPoint PPT Presentation
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““POC’s are the Norm” Hypothses - Flow Chart POC’s are the Norm” Hypothses - Flow Chart for SEPfor 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
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.
Clean FT aerosol above cloud CCN<15/cc @ %S-0.3 Polluted aerosol above cloud CCN>40/cc @ %s=0.3
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
Nov 13, 2008~18:40RF13RF13
20S
30S
CleanPolluted
RF 11 11/7/2008 18:00UT
RF 11 11/6/2008 18:00UTBlue circle/arrows – large scale divergent MBL flow implies entrainment in clear air 3 days before 11/9/2011
Nov 6, 2008 Nov 7, 2008 Nov 8, 2008 Nov 9, 2008 Nov 10, 2008
Nov 11, 2008 Nov 12, 2008 Nov 13, 2008 Nov 14, 2008 Nov 15, 2008
RF14RF14
RF11southRF11south
RF13RF13
RF 12southRF 12south
20S
20S 20S 20S
30S 30S 30S
30S
RF14
RF14
24hrlater
24hrlater
Crude check on clouds 24 hr later looks like layer may be part of an arc of pollution impacting clouds