1 atmospheric profiling to better understand fog and low level cloud life cycle arm/eu workshop on...

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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



MAST : T until and after 11UTC Tand RH reaches saturation at 14 at 30m

CASE 1The developed stratus phase…


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



Sodar : wind speed (clear air)

CASE 1The stratus lifting phase…


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 …

12Updraft

Droplet vertical velocity around -0.4m/s

LIDAR DOPPLER

LIDAR DOPPLER

LIDAR DOPPLER

Clear air

Cloudy air

CASE 2Role of droplet vertical velocity

1 atmospheric profiling to better understand fog and low level cloud life cycle arm/eu workshop on...

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