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Atmospheric profiling to better understand fog and low level cloud life cycle

Atmospheric profiling to better understand fog and low level cloud life cycle. J. Delanoe (LATMOS), JC. Dupont (IPSL), M. Haeffelin (IPSL). ARM/EU workshop on algorithms , 13-14 May 2013. Atmospheric profiling to better understand fog and low level cloud life cycle. RETRIEVAL.

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Atmospheric profiling to better understand fog and low level cloud life cycle

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  1. Atmospheric profiling to better understand fog and low level cloud life cycle J. Delanoe (LATMOS), JC. Dupont (IPSL), M. Haeffelin (IPSL) ARM/EU workshop on algorithms , 13-14 May 2013

  2. Atmospheric profiling to better understand fog and low level cloud life cycle RETRIEVAL Aerosol profiling T/RH profiling Wind profiling Water profiling S. Pal (LMD), T. Elias (HYGEOS), M. Haeffelin (IPSL), JB. Renard (LPC2E) JC. Dupont(IPSL), L. Musson-Genon (CEREA) E. Dupont (CEREA) JC Dupont (IPSL), D. Legain (CNRM) JC Dupont (IPSL), J. Delanoe (LATMOS) 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) 3D wind speed Sodar PA2, Doppler lidar WLS7 & WLS70, UHF radar 3D wind speed Cup anemometer Sonic anemometer Radiosounding Reflectivity & Dop. velocity BASTA cloud radar Dropplet size distribution FM100 Liquid water content PVM + 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 + Evaluation of sodar, WLS and UHF radar versus in-situ sensors + Effect of mast on in-situ measurement + Estimation of LW vertical profile combining in-situ and BASTA data + Comparisons between FM100 and PVM 2 Red : Remote sensing Blue : in-situ

  3. CASE 1 Stratus Lowering without fog. Why ? Ceilometer Cloud radar BASTA doppler velocity Cloud radar BASTA reflectivity 1st case study: 5 January 2013 High pressure system (1033 hPa), very low stratus cloud Advection: 10m/s at 400m Case of stratus lowering due to advection of moisture + lifting due to precipitation

  4. CASE 1 The stratus lowering phase…1/2 CL31: backscatter signal Sonic anemometer : vertical wind speed at 10m Downward flux + Stratus cloud lowering, 400m to 70m between 6 and 14 UTC HATPRO MWR : Integrated water vapor Visibilimeter : surface visibility  Wet air advection after 5 UTC (9 to 17 mm) Leading to stratus lowering with bigger LWP BASTA : cloud reflectivity HATPRO MWR : Liquid Water Path Stratus appears for Z >-35dBZ (after 7UTC) Drizzle below the cloud base Cloud top is constant

  5. CASE 1 The stratus lowering phase…2/2 SODAR SODAR SODAR SODAR 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

  6. CASE 1 The developed stratus phase… Hotplate TPS3100 : low precipitation level BASTA : cloud reflectivity Precipitation rate is 0.005mm/hr after 14UTC Linked with max value of Z Drizzle droplet fall on the ground Z =0 dBZ at 14 UTC Cloud top is max (670m) at 14 UTC Cloud base is min (60m) at 14 UTC Fog-Monitor 100 : Droplet number and size distribution Visibilimeter : surface visibility Surface Very low droplet concentration, <6 particles / cm3 MAST : T  until and after 11UTC T and RH reaches saturation at 14 at 30m HATPRO MWR : Liquid Water Path Total column Saturation of LWP around 300g/m² Biggest droplets fall on the ground

  7. CASE 1 The stratus lifting phase… Cup anemometer : wind speed at 10m BASTA : cloud reflectivity No dynamics at 19UTC, WS~m/s Cloud base lifting at 17 UTC  Z after 17 UTC and  of cloud top Fog-Monitor 100 : Droplet number and size distribution Visibilimeter : surface visibility Surface No drizzle after 18 UTC No droplet Sodar : wind speed (clear air) HATPRO MWR : Liquid Water Path Total column • wind speed along the vertical after 17 UTC Low wind shear Low vertical mixing Downward flux stops after 16UTC, no wet air entrainment and so LWP

  8. CASE 1 Vertical profiles of ASD and DSD 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 Cloud base Drop Droplet Altitude (m) Small Aerosols Size Size Concentration (#/cm3)

  9. CASE 2 A radiative fog event Aérosols hydratés …. activation Ceilometer BASTA cloud radar doppler velocity Peak of droplet vertical velocity BASTA cloud radar doppler reflectivity Peak of droplet size

  10. CASE 2 Liquid water closure ? 2 3 Liquid water path 1 3 Surface liquid water content 3 Surface droplet concentration 2 1 2 3 3 Basta reflectivity 1

  11. CASE 2 Role of wind shear … Strong wind shear : 12 m/s at 350m agl SODAR SODAR Updraft air due to solar heating :+0.5m/s SODAR Important turbulent flux at fog top SODAR

  12. CASE 2 Role of droplet vertical velocity LIDAR DOPPLER LIDAR DOPPLER Droplet vertical velocity around -0.4m/s LIDAR DOPPLER Cloudy air Clear air Updraft

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