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Ground-based Lidar Operations

Mini-MOPA CO2 Doppler lidar Scan Strategy

The following information applies to the Mini-MOPA CO2 Doppler lidar. Coordination with OPAL is mentioned when appropriate. Both lidar instruments are colocated at the Cornelia Fort Ground Site for the duration of the study.

  • Survey Sequence (executed every 45 min)
    • Constant elevation scans (covering 360° in azimuth): 0° (if useful), 1°, 2°, 3°, 5°, 10°, 15°, and 30° above the horizon.
    • Constant azimuth scans (horizon-to-horizon): beginning at 0°, 20°, 40°, 60°, 80°, 100°, 120°, 140°, and 160° azimuth.
  • To fill out the rest of the 45-min time period, scans will be chosen according to the time of day, current meteorological conditions, and scientific objectives.

Daytime Convective Boundary Layer (CBL)
Scientific Objectives: vertical mixing intensity in the CBL, evening collapse of CBL, turbulent kinetic energy (TKE)/momentum flux calculations within the CBL, cloud venting

  • Vertically pointing scans that measure w (vertical motion) for ~30 min. Coordinate with OPAL.
  • TKE, momentum flux scans for ~30 min (elevation angles of 35.5° and 50.8°).
  • If moderate daytime winds - especially southwesterly winds (urban outflow):
    • Azimuth sector scans (Δ azimuth = 30° - 50°) into the wind (SW) or downwind (NE) to document variability in the wind and aerosol fields. Repeat for 10-15 min or more. Use lowest elevation angle that isn't obstructed. Coordinate with OPAL pointing horizontally upwind or downwind.
    • Can intersperse some shallow vertical scans (spanning < 30° elevation from surface) pointing upwind or downwind for 2-5 min. If time permits, execute cross-wind vertical scans.
  • OPAL - emphasize vertically pointing scans.

Evening Transition, Nighttime
Scientific Objectives: development of low level jet (LLJ) and inertial oscillation (IO), buildup of stable boundary layer (SBL)*, 'leakage', and mixing height * highest priority objective

  • Cold air layer buildup and structure of vertical and horizontal eddies, waves, and layers: Repeated shallow upwind or downwind vertical scans (spanning < 30° elevation from surface) and
  • Repeated shallow upwind or downwind azimuth sector scans (lowest elevation angle without obstruction).
  • For both horizontal and vertical scans, can increment small changes in angle and obtain small volume of measurements.
  • If winds are strong and mixing down to the surface (i.e., there is an absence of a cold air buildup), then execute TKE/momentum flux scans between survey scans.
  • If documenting the LLJ, use deeper along-wind vertical scans.
  • OPAL - emphasize vertical scanning (coordinate with Mini-MOPA CO2 Doppler lidar).

Morning Transition
Scientific Objectives: dissolution of nighttime boundary layer (NBL), fumigation of layers

  • Same strategy as nighttime transition.