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Atmospheric profiling to better understand fog and low level cloud life cycle
ARM/EU workshop on algorithms , 13-14 May 2013
J. Delanoe (LATMOS), JC. Dupont (IPSL), M. Haeffelin (IPSL)
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Aerosol profiling T/RH profiling Water profilingWind profiling
Backscatter signal CL31 ceilometer ALS450 lidar
Aerosol optical properties DF20, DF20+ diffusometer Nephelometer
Aerosol size distribution SMPS, CPC, Welas
Brightness temperature Hatpro MWR
T/RH in-situ measurement Tethered balloon (0-300m) Mast sensors (0-30m) Radiosounding (0 -25km)
Reflectivity & Dop. velocity BASTA cloud radar
Dropplet size distribution FM100
Liquid water content PVM
3D wind speedSodar PA2, Doppler lidar WLS7 & WLS70, UHF radar
3D wind speedCup anemometerSonic anemometerRadiosounding
+ Extinction closure combining size distribution and visibility+ CL31 backscattering versus visibility and LOAC on tethered balloon
+ Evaluation of MWR retrieval with tethered balloon+ Analysis of T/RH profile variability for F and QF
+ Estimation of LW vertical profile combining in-situ and BASTA data+ Comparisons between FM100 and PVM
+ Evaluation of sodar, WLS and UHF radar versus in-situ sensors+ Effect of mast on in-situ measurement
JC Dupont (IPSL), J. Delanoe (LATMOS)
JC. Dupont(IPSL), L. Musson-Genon (CEREA)
E. Dupont (CEREA)
JC Dupont (IPSL), D. Legain (CNRM)
S. Pal (LMD), T. Elias (HYGEOS), M.
Haeffelin (IPSL), JB. Renard (LPC2E)
Atmospheric profiling to better understand fog and low level cloud life cycle
Red : Remote sensingBlue : in-situ
RETRIEVAL
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CASE 1Stratus Lowering without fog. Why ?
Ceilometer
Cloud radar BASTA doppler velocity
Cloud radar BASTA reflectivity
1st case study: 5 January 2013High pressure system (1033 hPa), very low stratus cloudAdvection: 10m/s at 400mCase of stratus lowering due to advection of moisture + lifting due to precipitation
4Stratus appears for Z >-35dBZ (after 7UTC)Drizzle below the cloud base Cloud top is constant
CL31: backscatter signal
Wet air advection after 5 UTC (9 to 17 mm)Leading to stratus lowering with bigger LWP
Downward flux
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Visibilimeter : surface visibility
BASTA : cloud reflectivity
Stratus cloud lowering, 400m to 70m between 6 and 14 UTC
Sonic anemometer : vertical wind speed at 10m
HATPRO MWR : Integrated water vapor
HATPRO MWR : Liquid Water Path
CASE 1The stratus lowering phase…1/2
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SODAR:North-West advection
W: Heating by the surface, cooling by the top CT2: high level of turbulence at cloud top when stratus lowering period
SODAR
SODAR
SODAR
SODAR
CASE 1The stratus lowering phase…2/2
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Z =0 dBZ at 14 UTCCloud top is max (670m) at 14 UTC Cloud base is min (60m) at 14 UTC
Visibilimeter : surface visibility
BASTA : cloud reflectivity
MAST : T until and after 11UTC Tand RH reaches saturation at 14 at 30m
CASE 1The developed stratus phase…
HATPRO MWR : Liquid Water Path
Hotplate TPS3100 : low precipitation level
Precipitation rate is 0.005mm/hr after 14UTCLinked with max value of ZDrizzle droplet fall on the ground
Fog-Monitor 100 : Droplet number and size distribution
Very low droplet concentration, <6 particles / cm3
Saturation of LWP around 300g/m²Biggest droplets fall on the ground
Surface
Total column
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Cloud base lifting at 17 UTC Z after 17 UTC and of cloud top
Visibilimeter : surface visibility
BASTA : cloud reflectivity
Sodar : wind speed (clear air)
CASE 1The stratus lifting phase…
HATPRO MWR : Liquid Water Path
Cup anemometer : wind speed at 10m
No dynamics at 19UTC, WS~m/s
Fog-Monitor 100 : Droplet number and size distribution
No drizzle after 18 UTCNo droplet
Downward flux stops after 16UTC, no wet air entrainment and so LWP
Surface
Total column
wind speed along the vertical after 17 UTCLow wind shearLow vertical mixing
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Vertical profile of particle size distribution between 0.5 and 150µm.
With LOAC (Light Optical Aerosol Counter) Developped in LPC2E French Lab.
at 08 UTC.Z ~ -35dBZ
Small Aerosols
Drop
Droplet
Cloud base
Size Size
Alti
tude
(m
)
Concentration (#/cm3)
CASE 1Vertical profiles of ASD and DSD
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Aérosols hydratés …. activation
Peak of droplet size
Ceilometer
BASTA cloud radar doppler velocity
CASE 2A radiative fog event
BASTA cloud radar doppler reflectivity
Peak of droplet vertical velocity
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CASE 2Liquid water closure ?
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231 2 3
Liquid water path
Surface liquid water content
Surface droplet concentration
Basta reflectivity
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1
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3
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Strong wind shear : 12 m/s at 350m agl
Updraft air due to solar heating :+0.5m/s
Important turbulent flux at fog top
SODAR
SODAR
SODAR
SODAR
CASE 2Role of wind shear …