Working group on space-based winds January 27-30, 2009 Destin, FL Sara C. Tucker, Wm. Alan Brewer, Scott Sandberg, Mike Hardesty CIRES, University of Colorado and NOAA/ESRL/CSD With thanks to Dan Wolfe and other scientists and crew of the RHB TexAQS and VOCALS cruises Lidar wind measurements in the Southeastern Pacific lower troposphere: stratus versus clear conditions

VOCALS 2008: The VAMOS Ocean-Cloud- Atmosphere-Land Study Regional Experiment VAMOS : Variability of the American Monsoon Systems A study in the region of the Southeastern Pacific to improve understanding of: the processes controlling properties of stratocumulus clouds and ocean transport of cold fresh water offshore, aerosol, drizzle, cloud interactions, and the chemical and physical interactions between ocean, atmosphere, and land. HIGH RESOLUTION DOPPLER LIDAR (HRDL) – VOCALS Wavelength2.02 µm Pulse Energy2-3 mJ Pulse Repetition Frequency 200 Hz Maximum Range4-8 km Range Resolution30 m Beam rate2 Hz ScanningFull Hemispheric Precision15-30 cm/s

Ship-based studies help to characterize wind (horizontal wind profiles and vertical winds) and scattering over the oceans Arctic (IPY) cruise  Southeastern Pacific Data in the tropics and down near -21 South Lidar, cloud radar (w-band), c-band, flux tower, sondes, & lots of oceanography (Buoys 101) HRDL RV Brown – VOCALS 2008

VOCALS 2008: Stratus deck over the SEP

VOCALS 2008: Ship locations and HRDL scans Low elevation conical High elevation conical Elevation scans Zenith 0 10 Scan pattern repeated every 20 minutes micron backscatter intensity Vertical Velocity

Horizontal mean wind speed & direction Vertical velocity variance, σ w 2 Wideband SNR (proxy for backscatter) Dynamical Profiles of horizontal wind speed and direction and small scale σ w 2 Turbulence strength and mixing height Rolls, outflows/convergence, divergence, etc. Atmospheric decoupling Cloud base velocity Aerosol Backscatter Aerosol layers Spatial variability in vertical and horizontal planes Cloud base height and cloud fraction Atmospheric decoupling Atmospheric Studies with the NOAA/ESRL High Resolution Doppler Lidar (HRDL)

HRDL - RV Brown, VOCALS 2008: Horizontal mean wind speed HRDL - RV Brown, VOCALS 2008: Horizontal mean wind direction

HRDL VOCALS Wind Roses at 20, 300, 800, and 1200 m alts. Distributions of: wind direction (outline) and of speed in each directional bin (distribution displayed using color intensity). 20 m 300 m 800 m 1200 m

VOCALS 2008: HRDL SNR and clouds dB Stratus deck over much of the Southeastern Pacific During VOCALS: ~90% cloud cover (according to HRDL signals) In port HRDL RV Brown VOCALS 2008 – 20 min Zenith wbSNR 10/21/08-11/30/08

VOCALS 2008: HRDL-derived Cloud Height vs. lat/lon

What’s going on above the stratus deck?

Are MBL winds different under stratus vs. under “clear sky”?

HRDL VOCALS: Distributions of horizontal mean wind speed and direction vs. altitude

HRDL VOCALS: Statistics of horizontal mean wind speed and direction vs. altitude

Differences in observed statistics Cloud deck wind stats - Scattered/No Cloud wind stats Lowest ~500 m wind speed averages are slightly lower under the stratus deck Lowest ~500 m wind direction averages are more southerly under the stratus deck Not huge differences but…

Implications of SEP cloud cover for use of future Space-Based Wind Lidar data What will this mean for models? –Weather forecasting –Aerosol transport (smelters, fires, etc.) –Aerosol generation (sea-salt): winds/turbulence/waves –Aerosol/cloud interactions (winds/turbulence) Still need to factor in vertical winds during clear periods Would buoy (surface) data suffice for some applications? Surface wind speeds are almost always lower than those aloft. Combine with other types of satellite (i.e. Scatterometer, visible imagery) data?

HRDL – VOCALS 2008: Cloudy vs. cloud-free vertical profiles Mixing was typically shallower and weaker during scattered/cloud-free periods - usually due to less cloud-top-cooling-driven convection and less air-sea temperature difference. HRDL zenith signal strength (relative aerosol backscatter) HRDL vertical velocity Cloud layer Mean horizontal wind profiles

HRDL zenith signal strength (relative aerosol backscatter) HRDL vertical velocity Cloud layer Mean horizontal wind profiles Cool colors  falling air/particles Warm colors  rising air How representative of cloud particles are the in-situ surface measurements? HRDL – VOCALS 2008: turbulence & decoupling underneath clouds

Atmospheric Decoupling in the Southeastern Pacific

Just getting started… Impact of vertical velocities Vertical transport (etrainment & venting) Mixing heights Aerosol layer(s) Relationship between MBL winds & SST Higher temporal resolution cloud height, % cloud cover, & time of day Model implications Thanks to NASA, NOAA/CPPA and NOAA/HOA for funding this work

HRDL VOCALS: Cloud height vs. Mixing Height and observations of decoupling UTC ~9 pm local Mixing heights to come – to be compared to cloud base from ceilometer