Contributions to DEEPWAVE from the DLR Dassault Falcon 20 Draft

Contributions to DEEPWAVE from the DLR Dassault Falcon 20
Draft April 17, 2013 by RBS
Additions April 23 2013 by AD
If the DLR Falcon is able to join the DEEPWAVE campaign in New Zealand in 2014, there are a number of
contributions it could make to the program. A preliminary list is given below. Hopefully the Falcon would
have its new data acquisition system by then. The Principle Investigators would be Markus Rapp and
Andreas Dornbrack. They would be invited to join the DEEPWAVE steering committee. There would be
a meeting of the steering committee in advance of the project to finalize flight tracks and other details
of the project.
Falcon Contributions
1. Additional flight level measurement of vertical momentum and energy flux. (Note that energy
flux requires differential GPS and accurate static pressure, along with gust probe vertical velocity
a. At altitudes from 4 to 11 km, below the NGV
b. On parallel tracks to the NGV tracks
c. On shorter tracks than the long 400 km NGV tracks
2. Disturbed wind field and gravity waves over the S. Alps terrain using the 2 μm Doppler wind lidar
system1. The instrument performs a conical step-and-stare scan around the vertical axis with a
nadir angle of 20°. The horizontal resolution of the wind profiles (5–10 km) is determined by the
time needed for one scanner revolution (24 times 1 or 2 s as accumulation time per scan
position, plus 6 s for the scanner motion) and the aircraft velocity (160–240 m s-1). The vertical
resolution of 100 m is determined by the pulse length of 400 ns of the laser. The dominant
horizontal scale of airflow over the S. Alps is probably between 10 and 200 km. So the horizontal
resolution of the Doppler wind lidar might capture the wave structures larger than 30 km. A
faster in-plane scan strategy will improve the spatial resolution. Nadir observations in high
resolution are possible to measure the vertical wind component alone. During a flight switching
between the different observing strategies is possible.
3. 3-D surveys of ambient and disturbed wind and temperature profiles over the sea, below the
aircraft, upwind and downwind of New Zealand. This can be done using dropsondes and the
Lidar Wind system. This is important for observing how the airflow approaches and flows
around the mountains.
Weissmann, M., R. Busen, A. Dörnbrack, S. Rahm, and O. Reitebuch, 2005: Targeted Observations with
an airborne wind lidar, J. Atmos. Ocean. Techn., 22, 1706-1719.
4. Mapping out the cloud field over the S. Alps using the backscatter intensity of the down-looking
lidar. As the DEEPWAVE flights will be done at night, we will have no other observations of
clouds over New Zealand. Cloud mapping is important as clouds may alter the generation of
vertically propagating gravity waves. Expected cloud types include
a. Lenticular (liquid or ice) clouds
b. Undulating alto-stratus
c. Shallow convective clouds
Airborne Doppler wind lidar observations in the lee of Greenland during a so-called tip jet event which
occurred on November 23 2003. Upper two panels: wind direction and speed from gust probe
(uppermost rows) and Doppler wind lidar from analyzing one-scanner revolution data. Middle panel:
vertical wind from gust probe. Lower two panels: horizontal wind analyzed from four scanner revolution
data and backscatter intensity. Black areas mark either clean air or regions of low signal-to-noise ratio,
e.g. below clouds.