Download Operations of the airborne Doppler lidar WIND during AMMA SOP2a1

Operations of the airborne Doppler lidar WIND during AMMA
SOP2a1
The French-German airborne Doppler lidar WIND participated to the AMMA SOP2a1 from
the 30th of June (date of arrival) to the 14th of July (date of departure). A total of 7 flights were
carried out (see Table 1):
- 2 of them were the transit flights to (30th of June) and from (14th of July) Niamey
during which the lidar was operated successfully and produced scientifically
interesting results.
- 4 were scientific missions (3rd, 7th, 10th and 12th of July),
- one was a short (1hr) test flight (on the 6th of July) that had no scientific objectives but
still produced high-quality data.
The signals acquired during the 4 scientific missions and two transit flights are now
processed. The results show that all the flights were successful (see Figure 1 for an
example) except for the one on the 3rd of July. On that day, the lidar encountered several
technical difficulties, some of them caused by the climatic conditions prevailing in Niamey
(overheating of some electronic equipment for instance). As a consequence, no useful data
could be retrieved from the signals.
The transit flight on the 30th of June offers a nice North-to-South cross-section of the African
dynamics from Djerba (Tunisia) to Niamey with a nice transition from mainly westerly to
easterly winds at about 30.5 degrees of latitude, a detailed documentation of the northern
border of the African Easterly Jet in the mid-troposphere, and the observation of the ITD and
the monsoon flow at lower levels south of 18 degrees of latitude.
The flights on the 7th and 10th of July were coordinated with water-vapour lidar LEANDRE II
aboard the French Falcon flying along the same trajectory at the same time. Both flights (see
flight tracks in Figure 5) were dedicated to the observation of the North-South structure of the
monsoon flow. The flight of the 7th is a particularly interesting because both WIND and
LEANDRE II operated nominally. Profiles of water vapour and wind were thus simultaneously
measured along the same trajectory, from which it should be possible to derive water-vapour
fluxes. On the 10th, LEANDRE II operated on a single wavelength (instead of two) with the
consequence that no water vapour was measured. There still remains the measurement of
aerosol backscatter from which the main features of the local dynamics are visible. A
comparison with WIND will be conducted.
The flight on the 12th was dedicated to the second objective pursued by the WIND system
during the campaign: the observation of MCS. WIND took-off at noon and made
measurements around the region of convective initiation. A part of this region was
documented later in the afternoon by the ATR.
WIND left Niamey on the 14th of July. A transit via Agadir (Marocco) was organized in order
to fly over the Heat-Low. Due to technical problems (part of the technical staff was not
aboard the aircraft on that day) and the presence of clouds, data acquired on that day display
gaps, in particular over the Heat-Low. It nonetheless remains that the major features of the
dynamics in this region are documented and should bring useful data for scientific studies.
Useful information on the instrument WIND, how it operates and what processing is needed
to recover wind profiles can be found in:

Werner C., P.H. Flamant, O. Reitebuch, C. Loth, F. Köpp, P. Delville, J. Streicher, P.
Drobinski, S. Rahm, B. Romand, E. Nagel, C. Boitel, M. Kleir, D. Bruneau, H. Herrmann, A.
Dabas, 2001: WIND Instrument. Optical Engineering, 40, 115-125.

Reitebuch, O., C. Werner, I. Leike, P. Delville, P. H. Flamant, A. Cress, D. Engelbart, 2001:
Experimental Validation of Wind Profiling Performed by the Airborne 10m Heterodyne
Doppler Lidar WIND. Journal of Atmospheric and Oceanic Technology, 18, 1331-1344.
The wind products should be available very soon from AMMA web-site.
Flight #
1
Date
30 June
Type
Transect
Start
time
(UTC)
08:50
End time Comments
(UTC)
12:35
Oberpfaffenhoffen to Niamey via Djerba.
Data of good quality.
2
3 July
ITD (I1.1)
Combined with LEANDRE II. Many technical
problems, no useful data
6 July
Test
Short, test flight. Data of good quality but short flight
track.
3
7 July
ITD (I1.1)
05:47
08:44
Combined with LEANDRE II. Data of good quality.
4
10 July
ITD(I1.1)
06:14
09:41
Combined with LEANDRE II. WIND acquired very
good data, but LEANDRE II operated on a single
wavelength. Profiles of aerosol backscatter available,
but no water vapour data.
5
12 July
MCS (I2)
12:03
15:28
Combined with the F-ATR.
6
14 July
Transect
06:06
09:15
Niamey Agadir. Flight over the Heat Low. Data of
lower quality due to clouds (over the Heat-Low in
particular) and weaker signal strength.
Table 1: Summary of WIND flights during AMMA SOP2a1. The flights with a red background color yielded no
useful results. All other flights (green background) were highly successful.
AEJ
AEJ
Monsoon flow
Harmatta
n
ITD
Monsoon flow
Figure 1: Wind profiles measured by WIND on the 7th of July (first leg away from Niamey, see Figure 4). The top
graph displays the wind force, the bottom graph, the wind direction. The main features of the local dynamics are
clearly visible: the monsoon flow with a south direction extending to about 18.7 degrees to the North; further
North, the Harmattan with an almost opposite direction; above, at about 4km of altitude, the African Easterly Jet
(AEJ).
Figure 2: Flight track on 30th of June (transit Djerba –
Niamey).
Figure 3: Flight track on the test flight of the 6th of July.
Figure 4: Flight track on the 7th of July.
Figure 5: Flight track on the 10th of July.
Figure 6: Flight track on the 12th of July.
Figure 7: Flight track on the 14th of July during the
return transit flight via Agadir, Marocco.