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

22 Aerosol profilingT/RH profilingWater 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 speed Sodar PA2, Doppler lidar WLS7 & WLS70, UHF radar 3D wind speed Cup anemometer Sonic anemometer Radiosounding + 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 sensing Blue : in-situ RETRIEVAL

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 Stratus 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 + 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 1 The stratus lowering phase…1/2

5 SODAR: North-West advection W: Heating by the surface, cooling by the top CT 2 : high level of turbulence at cloud top when stratus lowering period SODAR CASE 1 The stratus lowering phase…2/2

6 Z =0 dBZ at 14 UTC Cloud 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 T  and RH reaches saturation at 14 at 30m CASE 1 The developed stratus phase… HATPRO MWR : Liquid Water Path Hotplate TPS3100 : low precipitation level Precipitation rate is 0.005mm/hr after 14UTC Linked with max value of Z Drizzle droplet fall on the ground Fog-Monitor 100 : Droplet number and size distribution Very low droplet concentration, <6 particles / cm 3 Saturation of LWP around 300g/m² Biggest droplets fall on the ground Surface Total column

7 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 1 The 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 UTC No droplet Downward flux stops after 16UTC, no wet air entrainment and so LWP  Surface Total column  wind speed along the vertical after 17 UTC Low wind shear Low vertical mixing

8 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 Altitude (m) Concentration (#/cm 3 ) CASE 1 Vertical profiles of ASD and DSD

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

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

11 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 CASE 2 Role of wind shear …

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