The Earth Explorer Atmospheric Dynamics Mission

(ADM-Aeolus) of ESA will be the first-ever satellite to

provide global observations of wind profiles from

space. Its single payload, namely the Atmospheric

Laser Doppler Instrument (ALADIN) is a directdetection

high spectral resolution Doppler Wind Lidar

(DWL), operating at 355 nm, with a fringe-imaging

receiver (analysing aerosol and cloud backscatter) and a

double-edge receiver (analysing molecular backscatter).

In order to meet the stringent mission requirements on

wind retrieval, ESA is conducting various science

support activities for the consolidation of the on-ground

data processing, calibration and sampling strategies.

Results from a recent laboratory experiment to study

Rayleigh-Brillouin scattering and improve the

characterisation of the molecular lidar backscatter

signal detected by the ALADIN double-edge Fabry-

Perot receiver will be presented in this paper. The

experiment produced the most accurate ever-measured

Rayleigh-Brillouin scattering profiles for a range of

temperature, pressure and gases, representative of

Earth’s atmosphere. The measurements were used to

validate the Tenti S6 model, which is implemented in

the ADM-Aeolus ground processor.

First results from the on-going Vertical Aeolus

Measurement Positioning (VAMP) study will be also

reported. This second study aims at the optimisation of

the ADM-Aeolus vertical sampling in order to

maximise the information content of the retrieved

winds, taking into account the atmospheric dynamical

and optical heterogeneity. The impact of the Aeolus

wind profiles on Numerical Weather Prediction (NWP)

and stratospheric circulation modelling for the different

vertical sampling strategies is also being estimated

de Kloe, J.

Houchi, K.

Körnich, H.

Le Rille, O.

Marseille , G. J.

Reitebuch, O.

Schyberg, H.

Stoffelen, A.

Straume, A.-G.

Ubachs, W.

van de Water, W.

Vieitez, M. O.

Witschas, B.

English

Rille, O.

Straume, A.G.

Vieitez, M.O.

Ubachs, W.M.G.

Marseille, G.J.

Kloe, J.

DSpace at VU

 ESA’S WIND LIDAR MISSION ADM-AEOLUS: ON-GOING SCIENTIFIC ACTIVITIES 
RELATED TO CALIBRATION, RETRIEVAL AND INSTRUMENT OPERATION 
Olivier Le Rille1, Anne-Grete Straume1, Ofelia Vieitez2, Wim Ubachs2, Benjamin Witschas3, Gert-Jan 
Marseille4, Jos de Kloe4, Ad Stoffelen4, Karim Houchi4, Heiner Körnich5 and Harald Schyberg6 
1European Space Agency (ESA/ESTEC) 
Keplerlaan 1, Postbus 299, 2200AG Noordwijk, The Netherlands, olivier.lerille@esa.int 
2Laser Centre VU University Amsterdam 
3Institute of Atmospheric Physics, German Aerospace Centre (DLR) 
4Royal Netherlands Meteorological Institute (KNMI) 
5Department of Meteorology Stockholm University (MISU) 
6Norwegian Meteorological Institute (Met.no) 
 
ABSTRACT 
The Earth Explorer Atmospheric Dynamics Mission 
(ADM-Aeolus) of ESA will be the first-ever satellite to 
provide global observations of wind profiles from 
space. Its single payload, namely the Atmospheric 
Laser Doppler Instrument (ALADIN) is a direct-
detection high spectral resolution Doppler Wind Lidar 
(DWL), operating at 355 nm, with a fringe-imaging 
receiver (analysing aerosol and cloud backscatter) and a 
double-edge receiver (analysing molecular backscatter).  
In order to meet the stringent mission requirements on 
wind retrieval, ESA is conducting various science 
support activities for the consolidation of the on-ground 
data processing, calibration and sampling strategies. 
Results from a recent laboratory experiment to study 
Rayleigh-Brillouin scattering and improve the 
characterisation of the molecular lidar backscatter 
signal detected by the ALADIN double-edge Fabry-
Perot receiver will be presented in this paper. The 
experiment produced the most accurate ever-measured 
Rayleigh-Brillouin scattering profiles for a range of 
temperature, pressure and gases, representative of 
Earth’s atmosphere. The measurements were used to 
validate the Tenti S6 model, which is implemented in 
the ADM-Aeolus ground processor. 
First results from the on-going Vertical Aeolus 
Measurement Positioning (VAMP) study will be also 
reported. This second study aims at the optimisation of 
the ADM-Aeolus vertical sampling in order to 
maximise the information content of the retrieved 
winds, taking into account the atmospheric dynamical 
and optical heterogeneity. The impact of the Aeolus 
wind profiles on Numerical Weather Prediction (NWP) 
and stratospheric circulation modelling for the different 
vertical sampling strategies is also being estimated.  
1. ADM-AEOLUS MISSION CONCEPT 
ADM-Aeolus [1,2] is ESA’s second Earth Explorer 
Core Mission within the Living Planet Programme. The 
aim of the mission is to provide global observations of 
wind profiles with a resolution and an accuracy that 
will fill in one of the major deficiencies of the current 
Global Observing System (GOS) as defined by the 
World Meteorological Organisation (WMO) [3].  By 
providing about 3,000 globally distributed wind profiles 
per day in cloud-free regions and above thick cloud, 
with an accuracy comparable to that of radiosonde 
measurements, Aeolus data will find wide application 
in NWP and climate modelling, improving the accuracy 
of weather forecasts and advancing our understanding 
of tropical dynamics and processes relevant to climate 
variability. 
 
ADM-Aeolus spacecraft will fly in a sun-synchronous 
dusk/dawn polar orbit at 408 km altitude, in order to 
provide global coverage each day with a 7-days repeat 
cycle. The spacecraft will carry a single payload, the 
ALADIN direct-detection high spectral resolution 
DWL instrument. ALADIN comprises a single-mode, 
120 mJ, 100 Hz pulse repetition frequency, diode 
pumped and frequency tripled Nd-YAG laser (355 nm), 
a 1.5 m diameter Cassegrain afocal telescope, a Fizeau 
interferometer (from here on referred to as the Mie 
channel, analysing aerosol and cloud backscatter), a 
sequential Fabry-Perot interferometer (from here on 
referred to as the Rayleigh channel, analyse molecular 
backscatter) and two accumulation charge coupled 
devices (ACCD), one for each receiver channel 
detector. The laser will operate in burst mode, which 
means that the 50 km averaged wind observations will 
consist of 700 shots, taken over 7 seconds and followed 
by 21 seconds of downtime. This leads to a spacing of 
the 50 km observations with 200 km. During the 7 
seconds measurement period, the satellite will sample 
the atmosphere from 30 km altitude down to the surface 
in cloud-free regions. It will mainly sample the zonal 
wind component, delivering layer-averaged 
horizontally projected line-of-sight (HLOS) winds with 
a precision of 1-2 m/s (random error) and a vertical 
resolution varying between 250 m and 2 km. In total, 24 
Mie and 24 Rayleigh samples will be available per 
measurement. 
 2. SUPPORT STUDIES 
In the frame of mission development work, various 
studies are conducted to support the retrieval algorithm 
processor development as well as instrument calibration 
and sampling strategies. 
2.1 Rayleigh-Brillouin Scattering Experiment 
The Rayleigh channel of ALADIN samples parts of the 
molecular backscatter signal spectrum, whose shape is 
described by Rayleigh-Brillouin scattering theory. In 
order to correctly infer the Doppler shift of the return 
lidar signal from the double-edge Fabry-Perot 
measurements, the shape of the molecular return and its 
dependency of the local pressure and temperature needs 
to be known. A previous study showed that the so-
called Tenti S6 model [4] is the most accurate and 
suitable Rayleigh-Brillouin scattering model existing 
today, which lead to the implementation of the model in 
the ADM-Aeolus wind processing retrieval [5]. The 
model had, however, never been validated for gas 
mixtures representative for the Earth’s atmosphere, in 
particular not for humid air. It was therefore 
recommended in [5] to perform a follow-up study to 
further validate the Tenti model. Through the ESA’s 
General Studies Programme, it was decided to launch a 
laboratory experiment, aimed at directly measuring 
Rayleigh-Brillouin backscattered UV light in dry and 
humid air, for the pressure and temperature conditions 
representative of Earth’s atmosphere [6]. The study was 
conducted by the Laser Centre VU University 
Amsterdam in the Netherlands, in collaboration with 
the University of Nijmegen, Eindhoven University of 
Technology, the Royal Netherlands Meteorological 
Institute KNMI and the German Aerospace Centre 
DLR. 
The combination of a Spontaneous Rayleigh-Brillouin 
Scattering (SRBS) experiment and a Coherent 
Rayleigh-Brillouin Scattering (CRBS) experiment 
allowed for an independent test of two versions of the 
Tenti model (S6 and S7). Measurements were 
performed in the pressure range between 300 mbar and 
3 bar for the SRBS experiment and between 1 and 3 bar 
for the CRBS experiments, in pure nitrogen, pure 
oxygen, as well as dry air (a mixture of nitrogen and 
oxygen). SRBS measurements were also performed in 
humid air. An example of measured SRBS profiles is 
presented in figure 1 with comparison with the Tenti S6 
and S7 models. 
The study allowed for an optimization of the transport 
coefficients that are inputs to the Tenti model and 
concluded that the updated Tenti S6 model describes 
the shape of the backscattered light from nitrogen, 
oxygen and dry air the best, and within 98% accuracy. 
The study also confirmed negligible effect of humidity 
on Rayleigh-Brillouin line shape (figure 2).  
 
Figure 1. Model (Tenti S6 and S7) and measured SRBS 
profiles, for measurements at 300 mbar, 1 bar and 3 bar 
(from top to bottom), in nitrogen, oxygen and dry air (from 
left to right), at ambient temperature, 365 nm wavelength and 
90o scattering angle. Local deviations between Tenti S6 
model and measured SRBS profiles are within 1-2%. 
 
Figure 2. Left: spontaneous RB profiles measured at 
0% humidity (black) and 100% humidity (red), at 1 bar. 
Right: Difference between 0% humidity and 100% humidity 
measurements, divided by the maximum of 0% humidity 
measurement. 
In addition, the obtained SRBS-CRBS profiles were 
shown to be the most accurate ever measured and will 
form the basis for further scientific research. 
2.2 Vertical Aeolus Measurement Positioning 
study 
The Vertical Aeolus Measurement Positioning (VAMP) 
study, conducted by the Royal Netherlands 
Meteorological Institute (KNMI), the Meteorology 
Department Stockholm Institute (MISU) and the 
Norwegian Meteorological Institute [7], aims at 
optimizing the impact of ADM-Aeolus wind 
observations in NWP and other general circulation 
model (GCM) applications. In order to do this, 
strategies for the vertical positioning of the Mie and 
Rayleigh sampling bins need to be defined. 
Heterogeneous atmospheric scenes with large optical 
and dynamical variations are the most challenging for 
wind retrieval [7]. The Aeolus operations allows for up 
to 8 changes of the vertical sampling per orbit on 
 average. This opens the possibility of targeted sampling 
strategies, e.g. as a function of climate region. 
This experiment involved the analysis of atmosphere 
dynamics and atmosphere optics. ECMWF model wind 
field analyses covering three-month periods and all 
seasons are used to generate the global statistics of 
horizontal wind, vertical wind and wind shear, whereas 
collocated CALIPSO level-1 attenuated backscatter 
data are used to provide the extinction and backscatter 
statistics for aerosols and clouds, after conversion to 
355 nm. In order to address the well-known 
underestimation of ECMWF model wind variability on 
scale smaller than 150 km, a database of high-
resolution radiosondes has been created and cloud 
resolving model simulations have been performed to 
complete and adjust the derived wind statistics. 
Figures 3 and 4 gives respectively the horizontal wind 
and the wind shear statistics as a function of climate 
zones for the whole month of August 2007. The 
maximum wind shear (around 0.04 s-1) occurs near the 
surface and the tropopause. Figure 5 illustrates the 
derived backscatter statistics for the same climates 
zones and the same period of time. The retrieved 
median CALIPSO backscatter is between the reference 
model atmosphere median profile [8] and the retrieved 
backscatter from LITE [9] in September 1994, taken 
during a “dirty” period, shortly after the 1991 Pinatubo 
eruption. A remarkable increased backscatter is found 
over the South Pole above 10 km, due to the presence 
of polar stratospheric clouds in summer. 
 
Figure 3. Horizontal wind statistics as a function of 
climate zones for the period August 2007.  Left, from to 
bottom: north-hemisphere mid latitude region 40oN-60oS, 
tropics 20oS-20oN, and south-hemisphere mid latitude region 
40oS-60oS. Right, from top to bottom: north-hemisphere 
subtropics region 20oN-40oN, south-hemisphere subtropics 
region 20oS-40oS, and south-hemisphere polar region 60oS-
90oS.  
 
Figure 4. Vertical wind shear statistics (horizontal line-
of-sight projection) as a function of climate zones for the 
period August 2007. 
 
Figure 5. Backscatter statistics at 355 nm as a function 
of climate zones for the period August 2007. The red (mean) 
and black curves (10%, 25%, 50%, 75%, 90% percentiles) 
correspond to one month of retrieved backscatter data from 
CALIPSO. The green solid line denotes the reference model 
atmosphere (RMA) median profile. The purple solid line 
corresponds to the median backscatter derived from LITE 
data (cloud-free scenes only). The blue line is the molecular 
backscatter. 
The combine analysis of strong wind dynamics and 
large optical variability allowed designing optional 
sampling scenarios while assessing their performance in 
terms of retrieved quality winds, as a function of 
altitude, geographic region and season. It allowed also 
defining quality control methods for the wind retrieval, 
so that scenes with large variability can be properly 
treated.  
Impacts of pre-selected sampling scenarios on NWP 
forecasts and stratospheric dynamics will finally be 
 assess during a simplified vertical one-dimensional 
assimilation system and a data assimilation ensemble 
technique [10] 
 
Figure 6. Two sampling scenarios defined in the 
VAMP study to optimize retrieved wind quality and NWP 
impact (red is Mie channel, blue is Rayleigh channel). 
3. CONCLUSION 
Status and results of recent studies in support of the 
ADM-Aeolus mission have been presented in this 
paper. The Rayleigh-Brillouin Scattering experiment 
led to a validation and improvement of the Tenti S6 
model, used in the operational processing of ADM-
Aeolus wind measurements. Some important issues 
dealing with wavelength, scattering angle and 
temperatures dependencies of the Rayleigh-Brillouin 
spectral shape as well as polarisation effects remain 
open and will be further studies in a follow-on activity.  
The Vertical Aeolus Measurement Positioning study 
aims at defining optional sampling scenarios in order to 
ensure the retrieval of good quality winds and 
maximize the impact of ADM-Aeolus wind 
measurements on NWP and climate modelling. The 
study analyse critical atmosphere (dynamical and 
optical) characteristics that will be challenging for 
ADM-Aeolus, and will provide important inputs to the 
quality control of the Aeolus wind products. 
REFERENCES 
[1] Stoffelen A., J. Pailleux, E. Källén, J.M. Vaughan, 
L. Isaksen, P. Flamant, W. Wergen, E. Andersson, H. 
Schyberg, A. Culoma, M. Meynart, M. Endemann, P. 
Ingmann, 2005: The Atmospheric dynamics mission for 
global wind measurement, Bull. Am. Meteorol. Soc., 
86, pp. 73-87. 
[2] European Space Agency ESA, 2008: ADM-Aeolus 
Science Report, ESA SP-1311. 
[3] World Meteorological organisation (WMO), 2001: 
Statement of Guidance Regarding How Well Satellite 
Meet WMO User Requirements in Several Applications 
Areas, Sat-26, WMO/TD No. 1052. 
[4] C. D. Boley, R. C. Desai and G. Tenti, 1972:  
"Kinetic models and brillouin scattering in a molecular 
gas," Can. J. Phys., 50, 2158. 
[5] Dabas A., M.L. Denneulin, P. Flamant, C. Loth, A. 
Garnier, A. Dofli-Bouteyre, 2007: Correcting winds 
measured with a Rayleigh Doppler lidar from pressure 
and temperature effects, Tellus, 60, pp. 206-215. 
[6] Ubachs W., van Duijn W.-J, Vieitez M.O., Van de 
Water W., Dam N., ter Meulen J.J., Meijer A.S., de 
Kloe J., Stoffelen A., Aben E.A.A., 2009: A 
Spontaneous Rayleigh-Brillouin Scattering Experiment 
for the Characterization of Atmospheric Lidar 
Backscatter, Executive Summary, ESA contract no. 
AO/1-5467/07/NL/HE. 
[7] Marseille G.J., A. Stoffelen, J. de Kloe, K. Houchi, 
H. Körnich, H. Schyberg, A.G. Straume, O. Le Rille, 
2009: ADM-Aeolus Vertical Sampling scenarios, 
Proceed 8th International Symposium on Tropospheric 
Profiling, ISBN 978-90-6960-233-2. 
[8] Vaughan, J.M., N.J. Geddes, P.H. Flamant and C. 
Flesia, 1998: Establishment of a backscatter coefficient 
and atmospheric database, DERA Report, ESA contract 
no. 12510/97/NL/RE, DERA/EL/ISET/ CR980139 /1.0. 
[9] Winker, D. M., Couch, R. H., and McCormick, M. 
P., 1996: An overview of LITE: NASA's Lidar In-space 
Technology Experiment, Proc. IEEE, 84, 2, pp. 164-
180.  
[10] Tan D., E. Anderson, M. Fisher and L. Isaksen, 
2007: Observing-system impact assessment using a data 
assimilation ensemble technique: application to the 
ADM-Aeolus wind profiling mission, Q.J.R. Meteorol. 
Soc., 133, pp. 381-390. 
 


ESA's wind Lidar mission ADM-AEOLUS; on-going scientific activities related to calibration, retrieval and instrument operation

Institute of Transport Research:Publications

 ESA’S WIND LIDAR MISSION ADM-AEOLUS: ON-GOING SCIENTIFIC ACTIVITIES RELATED TO CALIBRATION, RETRIEVAL AND INSTRUMENT OPERATION Olivier Le Rille1, Anne-Grete Straume1, Ofelia Vieitez2, Wim Ubachs2, Benjamin Witschas3, Gert-Jan Marseille4, Jos de Kloe4, Ad Stoffelen4, Karim Houchi4, Heiner Körnich5 and Harald Schyberg6 1European Space Agency (ESA/ESTEC) Keplerlaan 1, Postbus 299, 2200AG Noordwijk, The Netherlands, olivier.lerille@esa.int 2Laser Centre VU University Amsterdam 3Institute of Atmospheric Physics, German Aerospace Centre (DLR) 4Royal Netherlands Meteorological Institute (KNMI) 5Department of Meteorology Stockholm University (MISU) 6Norwegian Meteorological Institute (Met.no)  ABSTRACT The Earth Explorer Atmospheric Dynamics Mission (ADM-Aeolus) of ESA will be the first-ever satellite to provide global observations of wind profiles from space. Its single payload, namely the Atmospheric Laser Doppler Instrument (ALADIN) is a direct-detection high spectral resolution Doppler Wind Lidar (DWL), operating at 355 nm, with a fringe-imaging receiver (analysing aerosol and cloud backscatter) and a double-edge receiver (analysing molecular backscatter).  In order to meet the stringent mission requirements on wind retrieval, ESA is conducting various science support activities for the consolidation of the on-ground data processing, calibration and sampling strategies. Results from a recent laboratory experiment to study Rayleigh-Brillouin scattering and improve the characterisation of the molecular lidar backscatter signal detected by the ALADIN double-edge Fabry-Perot receiver will be presented in this paper. The experiment produced the most accurate ever-measured Rayleigh-Brillouin scattering profiles for a range of temperature, pressure and gases, representative of Earth’s atmosphere. The measurements were used to validate the Tenti S6 model, which is implemented in the ADM-Aeolus ground processor. First results from the on-going Vertical Aeolus Measurement Positioning (VAMP) study will be also reported. This second study aims at the optimisation of the ADM-Aeolus vertical sampling in order to maximise the information content of the retrieved winds, taking into account the atmospheric dynamical and optical heterogeneity. The impact of the Aeolus wind profiles on Numerical Weather Prediction (NWP) and stratospheric circulation modelling for the different vertical sampling strategies is also being estimated.  1. ADM-AEOLUS MISSION CONCEPT ADM-Aeolus [1,2] is ESA’s second Earth Explorer Core Mission within the Living Planet Programme. The aim of the mission is to provide global observations of wind profiles with a resolution and an accuracy that will fill in one of the major deficiencies of the current Global Observing System (GOS) as defined by the World Meteorological Organisation (WMO) [3].  By providing about 3,000 globally distributed wind profiles per day in cloud-free regions and above thick cloud, with an accuracy comparable to that of radiosonde measurements, Aeolus data will find wide application in NWP and climate modelling, improving the accuracy of weather forecasts and advancing our understanding of tropical dynamics and processes relevant to climate variability.  ADM-Aeolus spacecraft will fly in a sun-synchronous dusk/dawn polar orbit at 408 km altitude, in order to provide global coverage each day with a 7-days repeat cycle. The spacecraft will carry a single payload, the ALADIN direct-detection high spectral resolution DWL instrument. ALADIN comprises a single-mode, 120 mJ, 100 Hz pulse repetition frequency, diode pumped and frequency tripled Nd-YAG laser (355 nm), a 1.5 m diameter Cassegrain afocal telescope, a Fizeau interferometer (from here on referred to as the Mie channel, analysing aerosol and cloud backscatter), a sequential Fabry-Perot interferometer (from here on referred to as the Rayleigh channel, analyse molecular backscatter) and two accumulation charge coupled devices (ACCD), one for each receiver channel detector. The laser will operate in burst mode, which means that the 50 km averaged wind observations will consist of 700 shots, taken over 7 seconds and followed by 21 seconds of downtime. This leads to a spacing of the 50 km observations with 200 km. During the 7 seconds measurement period, the satellite will sample the atmosphere from 30 km altitude down to the surface in cloud-free regions. It will mainly sample the zonal wind component, delivering layer-averaged horizontally projected line-of-sight (HLOS) winds with a precision of 1-2 m/s (random error) and a vertical resolution varying between 250 m and 2 km. In total, 24 Mie and 24 Rayleigh samples will be available per measurement.  2. SUPPORT STUDIES In the frame of mission development work, various studies are conducted to support the retrieval algorithm processor development as well as instrument calibration and sampling strategies. 2.1 Rayleigh-Brillouin Scattering Experiment The Rayleigh channel of ALADIN samples parts of the molecular backscatter signal spectrum, whose shape is described by Rayleigh-Brillouin scattering theory. In order to correctly infer the Doppler shift of the return lidar signal from the double-edge Fabry-Perot measurements, the shape of the molecular return and its dependency of the local pressure and temperature needs to be known. A previous study showed that the so-called Tenti S6 model [4] is the most accurate and suitable Rayleigh-Brillouin scattering model existing today, which lead to the implementation of the model in the ADM-Aeolus wind processing retrieval [5]. The model had, however, never been validated for gas mixtures representative for the Earth’s atmosphere, in particular not for humid air. It was therefore recommended in [5] to perform a follow-up study to further validate the Tenti model. Through the ESA’s General Studies Programme, it was decided to launch a laboratory experiment, aimed at directly measuring Rayleigh-Brillouin backscattered UV light in dry and humid air, for the pressure and temperature conditions representative of Earth’s atmosphere [6]. The study was conducted by the Laser Centre VU University Amsterdam in the Netherlands, in collaboration with the University of Nijmegen, Eindhoven University of Technology, the Royal Netherlands Meteorological Institute KNMI and the German Aerospace Centre DLR. The combination of a Spontaneous Rayleigh-Brillouin Scattering (SRBS) experiment and a Coherent Rayleigh-Brillouin Scattering (CRBS) experiment allowed for an independent test of two versions of the Tenti model (S6 and S7). Measurements were performed in the pressure range between 300 mbar and 3 bar for the SRBS experiment and between 1 and 3 bar for the CRBS experiments, in pure nitrogen, pure oxygen, as well as dry air (a mixture of nitrogen and oxygen). SRBS measurements were also performed in humid air. An example of measured SRBS profiles is presented in figure 1 with comparison with the Tenti S6 and S7 models. The study allowed for an optimization of the transport coefficients that are inputs to the Tenti model and concluded that the updated Tenti S6 model describes the shape of the backscattered light from nitrogen, oxygen and dry air the best, and within 98% accuracy. The study also confirmed negligible effect of humidity on Rayleigh-Brillouin line shape (figure 2).   Figure 1. Model (Tenti S6 and S7) and measured SRBS profiles, for measurements at 300 mbar, 1 bar and 3 bar (from top to bottom), in nitrogen, oxygen and dry air (from left to right), at ambient temperature, 365 nm wavelength and 90o scattering angle. Local deviations between Tenti S6 model and measured SRBS profiles are within 1-2%.  Figure 2. Left: spontaneous RB profiles measured at 0% humidity (black) and 100% humidity (red), at 1 bar. Right: Difference between 0% humidity and 100% humidity measurements, divided by the maximum of 0% humidity measurement. In addition, the obtained SRBS-CRBS profiles were shown to be the most accurate ever measured and will form the basis for further scientific research. 2.2 Vertical Aeolus Measurement Positioning study The Vertical Aeolus Measurement Positioning (VAMP) study, conducted by the Royal Netherlands Meteorological Institute (KNMI), the Meteorology Department Stockholm Institute (MISU) and the Norwegian Meteorological Institute [7], aims at optimizing the impact of ADM-Aeolus wind observations in NWP and other general circulation model (GCM) applications. In order to do this, strategies for the vertical positioning of the Mie and Rayleigh sampling bins need to be defined. Heterogeneous atmospheric scenes with large optical and dynamical variations are the most challenging for wind retrieval [7]. The Aeolus operations allows for up to 8 changes of the vertical sampling per orbit on  average. This opens the possibility of targeted sampling strategies, e.g. as a function of climate region. This experiment involved the analysis of atmosphere dynamics and atmosphere optics. ECMWF model wind field analyses covering three-month periods and all seasons are used to generate the global statistics of horizontal wind, vertical wind and wind shear, whereas collocated CALIPSO level-1 attenuated backscatter data are used to provide the extinction and backscatter statistics for aerosols and clouds, after conversion to 355 nm. In order to address the well-known underestimation of ECMWF model wind variability on scale smaller than 150 km, a database of high-resolution radiosondes has been created and cloud resolving model simulations have been performed to complete and adjust the derived wind statistics. Figures 3 and 4 gives respectively the horizontal wind and the wind shear statistics as a function of climate zones for the whole month of August 2007. The maximum wind shear (around 0.04 s-1) occurs near the surface and the tropopause. Figure 5 illustrates the derived backscatter statistics for the same climates zones and the same period of time. The retrieved median CALIPSO backscatter is between the reference model atmosphere median profile [8] and the retrieved backscatter from LITE [9] in September 1994, taken during a “dirty” period, shortly after the 1991 Pinatubo eruption. A remarkable increased backscatter is found over the South Pole above 10 km, due to the presence of polar stratospheric clouds in summer.  Figure 3. Horizontal wind statistics as a function of climate zones for the period August 2007.  Left, from to bottom: north-hemisphere mid latitude region 40oN-60oS, tropics 20oS-20oN, and south-hemisphere mid latitude region 40oS-60oS. Right, from top to bottom: north-hemisphere subtropics region 20oN-40oN, south-hemisphere subtropics region 20oS-40oS, and south-hemisphere polar region 60oS-90oS.   Figure 4. Vertical wind shear statistics (horizontal line-of-sight projection) as a function of climate zones for the period August 2007.  Figure 5. Backscatter statistics at 355 nm as a function of climate zones for the period August 2007. The red (mean) and black curves (10%, 25%, 50%, 75%, 90% percentiles) correspond to one month of retrieved backscatter data from CALIPSO. The green solid line denotes the reference model atmosphere (RMA) median profile. The purple solid line corresponds to the median backscatter derived from LITE data (cloud-free scenes only). The blue line is the molecular backscatter. The combine analysis of strong wind dynamics and large optical variability allowed designing optional sampling scenarios while assessing their performance in terms of retrieved quality winds, as a function of altitude, geographic region and season. It allowed also defining quality control methods for the wind retrieval, so that scenes with large variability can be properly treated.  Impacts of pre-selected sampling scenarios on NWP forecasts and stratospheric dynamics will finally be  assess during a simplified vertical one-dimensional assimilation system and a data assimilation ensemble technique [10]  Figure 6. Two sampling scenarios defined in the VAMP study to optimize retrieved wind quality and NWP impact (red is Mie channel, blue is Rayleigh channel). 3. CONCLUSION Status and results of recent studies in support of the ADM-Aeolus mission have been presented in this paper. The Rayleigh-Brillouin Scattering experiment led to a validation and improvement of the Tenti S6 model, used in the operational processing of ADM-Aeolus wind measurements. Some important issues dealing with wavelength, scattering angle and temperatures dependencies of the Rayleigh-Brillouin spectral shape as well as polarisation effects remain open and will be further studies in a follow-on activity.  The Vertical Aeolus Measurement Positioning study aims at defining optional sampling scenarios in order to ensure the retrieval of good quality winds and maximize the impact of ADM-Aeolus wind measurements on NWP and climate modelling. The study analyse critical atmosphere (dynamical and optical) characteristics that will be challenging for ADM-Aeolus, and will provide important inputs to the quality control of the Aeolus wind products. REFERENCES [1] Stoffelen A., J. Pailleux, E. Källén, J.M. Vaughan, L. Isaksen, P. Flamant, W. Wergen, E. Andersson, H. Schyberg, A. Culoma, M. Meynart, M. Endemann, P. Ingmann, 2005: The Atmospheric dynamics mission for global wind measurement, Bull. Am. Meteorol. Soc., 86, pp. 73-87. [2] European Space Agency ESA, 2008: ADM-Aeolus Science Report, ESA SP-1311. [3] World Meteorological organisation (WMO), 2001: Statement of Guidance Regarding How Well Satellite Meet WMO User Requirements in Several Applications Areas, Sat-26, WMO/TD No. 1052. [4] C. D. Boley, R. C. Desai and G. Tenti, 1972:  "Kinetic models and brillouin scattering in a molecular gas," Can. J. Phys., 50, 2158. [5] Dabas A., M.L. Denneulin, P. Flamant, C. Loth, A. Garnier, A. Dofli-Bouteyre, 2007: Correcting winds measured with a Rayleigh Doppler lidar from pressure and temperature effects, Tellus, 60, pp. 206-215. [6] Ubachs W., van Duijn W.-J, Vieitez M.O., Van de Water W., Dam N., ter Meulen J.J., Meijer A.S., de Kloe J., Stoffelen A., Aben E.A.A., 2009: A Spontaneous Rayleigh-Brillouin Scattering Experiment for the Characterization of Atmospheric Lidar Backscatter, Executive Summary, ESA contract no. AO/1-5467/07/NL/HE. [7] Marseille G.J., A. Stoffelen, J. de Kloe, K. Houchi, H. Körnich, H. Schyberg, A.G. Straume, O. Le Rille, 2009: ADM-Aeolus Vertical Sampling scenarios, Proceed 8th International Symposium on Tropospheric Profiling, ISBN 978-90-6960-233-2. [8] Vaughan, J.M., N.J. Geddes, P.H. Flamant and C. Flesia, 1998: Establishment of a backscatter coefficient and atmospheric database, DERA Report, ESA contract no. 12510/97/NL/RE, DERA/EL/ISET/ CR980139 /1.0. [9] Winker, D. M., Couch, R. H., and McCormick, M. P., 1996: An overview of LITE: NASA's Lidar In-space Technology Experiment, Proc. IEEE, 84, 2, pp. 164-180.  [10] Tan D., E. Anderson, M. Fisher and L. Isaksen, 2007: Observing-system impact assessment using a data assimilation ensemble technique: application to the ADM-Aeolus wind profiling mission, Q.J.R. Meteorol. Soc., 133, pp. 381-390.  

A Spontaneous Rayleigh-Brillouin Scattering Experiment for the Characterization of Atmospheric Lidar Backscatter, Executive Summary, ESA contract no.

ADM-Aeolus Vertical Sampling scenarios,

An overview of LITE: NASA's Lidar In-space Technology Experiment,

Correcting winds measured with a Rayleigh Doppler lidar from pressure and temperature effects,

Establishment of a backscatter coefficient and atmospheric database,

Kinetic models and brillouin scattering in a molecular gas,&quot;

Observing-system impact assessment using a data assimilation ensemble technique: application to the ADM-Aeolus wind profiling mission,

Statement of Guidance Regarding How Well Satellite Meet WMO User Requirements

The Atmospheric dynamics mission for global wind measurement,

ESA´s Wind Lidar Mission ADM-Aeolus: On-Going Scientific Activities Related to Calibration, Retrieval and Instrument Operation

VU Research Portal

VU Research PortalESA's wind Lidar mission ADM-AEOLUS; on-going scientific activities related tocalibration, retrieval and instrument operationRille, O.; Straume, A.G.; Vieitez, M.O.; Ubachs, W.M.G.; Witschas, B.; Marseille, G.J.;Kloe, J.; Stoffelen, A.; Houchi, K.; Körnich, H.; Schyberg, H.published in25th International Lidar Radar Conference Proceedings2010Link to publication in VU Research Portalcitation for published version (APA)Rille, O., Straume, A. G., Vieitez, M. O., Ubachs, W. M. G., Witschas, B., Marseille, G. J., Kloe, J., Stoffelen, A.,Houchi, K., Körnich, H., & Schyberg, H. (2010). ESA's wind Lidar mission ADM-AEOLUS; on-going scientificactivities related to calibration, retrieval and instrument operation. In 25th International Lidar Radar ConferenceProceedingsGeneral rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.E-mail address:vuresearchportal.ub@vu.nlDownload date: 13. Dec. 2021 ESA’S WIND LIDAR MISSION ADM-AEOLUS: ON-GOING SCIENTIFIC ACTIVITIES RELATED TO CALIBRATION, RETRIEVAL AND INSTRUMENT OPERATION Olivier Le Rille1, Anne-Grete Straume1, Ofelia Vieitez2, Wim Ubachs2, Benjamin Witschas3, Gert-Jan Marseille4, Jos de Kloe4, Ad Stoffelen4, Karim Houchi4, Heiner Körnich5 and Harald Schyberg6 1European Space Agency (ESA/ESTEC) Keplerlaan 1, Postbus 299, 2200AG Noordwijk, The Netherlands, olivier.lerille@esa.int 2Laser Centre VU University Amsterdam 3Institute of Atmospheric Physics, German Aerospace Centre (DLR) 4Royal Netherlands Meteorological Institute (KNMI) 5Department of Meteorology Stockholm University (MISU) 6Norwegian Meteorological Institute (Met.no)  ABSTRACT The Earth Explorer Atmospheric Dynamics Mission (ADM-Aeolus) of ESA will be the first-ever satellite to provide global observations of wind profiles from space. Its single payload, namely the Atmospheric Laser Doppler Instrument (ALADIN) is a direct-detection high spectral resolution Doppler Wind Lidar (DWL), operating at 355 nm, with a fringe-imaging receiver (analysing aerosol and cloud backscatter) and a double-edge receiver (analysing molecular backscatter).  In order to meet the stringent mission requirements on wind retrieval, ESA is conducting various science support activities for the consolidation of the on-ground data processing, calibration and sampling strategies. Results from a recent laboratory experiment to study Rayleigh-Brillouin scattering and improve the characterisation of the molecular lidar backscatter signal detected by the ALADIN double-edge Fabry-Perot receiver will be presented in this paper. The experiment produced the most accurate ever-measured Rayleigh-Brillouin scattering profiles for a range of temperature, pressure and gases, representative of Earth’s atmosphere. The measurements were used to validate the Tenti S6 model, which is implemented in the ADM-Aeolus ground processor. First results from the on-going Vertical Aeolus Measurement Positioning (VAMP) study will be also reported. This second study aims at the optimisation of the ADM-Aeolus vertical sampling in order to maximise the information content of the retrieved winds, taking into account the atmospheric dynamical and optical heterogeneity. The impact of the Aeolus wind profiles on Numerical Weather Prediction (NWP) and stratospheric circulation modelling for the different vertical sampling strategies is also being estimated.  1. ADM-AEOLUS MISSION CONCEPT ADM-Aeolus [1,2] is ESA’s second Earth Explorer Core Mission within the Living Planet Programme. The aim of the mission is to provide global observations of wind profiles with a resolution and an accuracy that will fill in one of the major deficiencies of the current Global Observing System (GOS) as defined by the World Meteorological Organisation (WMO) [3].  By providing about 3,000 globally distributed wind profiles per day in cloud-free regions and above thick cloud, with an accuracy comparable to that of radiosonde measurements, Aeolus data will find wide application in NWP and climate modelling, improving the accuracy of weather forecasts and advancing our understanding of tropical dynamics and processes relevant to climate variability.  ADM-Aeolus spacecraft will fly in a sun-synchronous dusk/dawn polar orbit at 408 km altitude, in order to provide global coverage each day with a 7-days repeat cycle. The spacecraft will carry a single payload, the ALADIN direct-detection high spectral resolution DWL instrument. ALADIN comprises a single-mode, 120 mJ, 100 Hz pulse repetition frequency, diode pumped and frequency tripled Nd-YAG laser (355 nm), a 1.5 m diameter Cassegrain afocal telescope, a Fizeau interferometer (from here on referred to as the Mie channel, analysing aerosol and cloud backscatter), a sequential Fabry-Perot interferometer (from here on referred to as the Rayleigh channel, analyse molecular backscatter) and two accumulation charge coupled devices (ACCD), one for each receiver channel detector. The laser will operate in burst mode, which means that the 50 km averaged wind observations will consist of 700 shots, taken over 7 seconds and followed by 21 seconds of downtime. This leads to a spacing of the 50 km observations with 200 km. During the 7 seconds measurement period, the satellite will sample the atmosphere from 30 km altitude down to the surface in cloud-free regions. It will mainly sample the zonal wind component, delivering layer-averaged horizontally projected line-of-sight (HLOS) winds with a precision of 1-2 m/s (random error) and a vertical resolution varying between 250 m and 2 km. In total, 24 Mie and 24 Rayleigh samples will be available per measurement.  2. SUPPORT STUDIES In the frame of mission development work, various studies are conducted to support the retrieval algorithm processor development as well as instrument calibration and sampling strategies. 2.1 Rayleigh-Brillouin Scattering Experiment The Rayleigh channel of ALADIN samples parts of the molecular backscatter signal spectrum, whose shape is described by Rayleigh-Brillouin scattering theory. In order to correctly infer the Doppler shift of the return lidar signal from the double-edge Fabry-Perot measurements, the shape of the molecular return and its dependency of the local pressure and temperature needs to be known. A previous study showed that the so-called Tenti S6 model [4] is the most accurate and suitable Rayleigh-Brillouin scattering model existing today, which lead to the implementation of the model in the ADM-Aeolus wind processing retrieval [5]. The model had, however, never been validated for gas mixtures representative for the Earth’s atmosphere, in particular not for humid air. It was therefore recommended in [5] to perform a follow-up study to further validate the Tenti model. Through the ESA’s General Studies Programme, it was decided to launch a laboratory experiment, aimed at directly measuring Rayleigh-Brillouin backscattered UV light in dry and humid air, for the pressure and temperature conditions representative of Earth’s atmosphere [6]. The study was conducted by the Laser Centre VU University Amsterdam in the Netherlands, in collaboration with the University of Nijmegen, Eindhoven University of Technology, the Royal Netherlands Meteorological Institute KNMI and the German Aerospace Centre DLR. The combination of a Spontaneous Rayleigh-Brillouin Scattering (SRBS) experiment and a Coherent Rayleigh-Brillouin Scattering (CRBS) experiment allowed for an independent test of two versions of the Tenti model (S6 and S7). Measurements were performed in the pressure range between 300 mbar and 3 bar for the SRBS experiment and between 1 and 3 bar for the CRBS experiments, in pure nitrogen, pure oxygen, as well as dry air (a mixture of nitrogen and oxygen). SRBS measurements were also performed in humid air. An example of measured SRBS profiles is presented in figure 1 with comparison with the Tenti S6 and S7 models. The study allowed for an optimization of the transport coefficients that are inputs to the Tenti model and concluded that the updated Tenti S6 model describes the shape of the backscattered light from nitrogen, oxygen and dry air the best, and within 98% accuracy. The study also confirmed negligible effect of humidity on Rayleigh-Brillouin line shape (figure 2).   Figure 1. Model (Tenti S6 and S7) and measured SRBS profiles, for measurements at 300 mbar, 1 bar and 3 bar (from top to bottom), in nitrogen, oxygen and dry air (from left to right), at ambient temperature, 365 nm wavelength and 90o scattering angle. Local deviations between Tenti S6 model and measured SRBS profiles are within 1-2%.  Figure 2. Left: spontaneous RB profiles measured at 0% humidity (black) and 100% humidity (red), at 1 bar. Right: Difference between 0% humidity and 100% humidity measurements, divided by the maximum of 0% humidity measurement. In addition, the obtained SRBS-CRBS profiles were shown to be the most accurate ever measured and will form the basis for further scientific research. 2.2 Vertical Aeolus Measurement Positioning study The Vertical Aeolus Measurement Positioning (VAMP) study, conducted by the Royal Netherlands Meteorological Institute (KNMI), the Meteorology Department Stockholm Institute (MISU) and the Norwegian Meteorological Institute [7], aims at optimizing the impact of ADM-Aeolus wind observations in NWP and other general circulation model (GCM) applications. In order to do this, strategies for the vertical positioning of the Mie and Rayleigh sampling bins need to be defined. Heterogeneous atmospheric scenes with large optical and dynamical variations are the most challenging for wind retrieval [7]. The Aeolus operations allows for up to 8 changes of the vertical sampling per orbit on  average. This opens the possibility of targeted sampling strategies, e.g. as a function of climate region. This experiment involved the analysis of atmosphere dynamics and atmosphere optics. ECMWF model wind field analyses covering three-month periods and all seasons are used to generate the global statistics of horizontal wind, vertical wind and wind shear, whereas collocated CALIPSO level-1 attenuated backscatter data are used to provide the extinction and backscatter statistics for aerosols and clouds, after conversion to 355 nm. In order to address the well-known underestimation of ECMWF model wind variability on scale smaller than 150 km, a database of high-resolution radiosondes has been created and cloud resolving model simulations have been performed to complete and adjust the derived wind statistics. Figures 3 and 4 gives respectively the horizontal wind and the wind shear statistics as a function of climate zones for the whole month of August 2007. The maximum wind shear (around 0.04 s-1) occurs near the surface and the tropopause. Figure 5 illustrates the derived backscatter statistics for the same climates zones and the same period of time. The retrieved median CALIPSO backscatter is between the reference model atmosphere median profile [8] and the retrieved backscatter from LITE [9] in September 1994, taken during a “dirty” period, shortly after the 1991 Pinatubo eruption. A remarkable increased backscatter is found over the South Pole above 10 km, due to the presence of polar stratospheric clouds in summer.  Figure 3. Horizontal wind statistics as a function of climate zones for the period August 2007.  Left, from to bottom: north-hemisphere mid latitude region 40oN-60oS, tropics 20oS-20oN, and south-hemisphere mid latitude region 40oS-60oS. Right, from top to bottom: north-hemisphere subtropics region 20oN-40oN, south-hemisphere subtropics region 20oS-40oS, and south-hemisphere polar region 60oS-90oS.   Figure 4. Vertical wind shear statistics (horizontal line-of-sight projection) as a function of climate zones for the period August 2007.  Figure 5. Backscatter statistics at 355 nm as a function of climate zones for the period August 2007. The red (mean) and black curves (10%, 25%, 50%, 75%, 90% percentiles) correspond to one month of retrieved backscatter data from CALIPSO. The green solid line denotes the reference model atmosphere (RMA) median profile. The purple solid line corresponds to the median backscatter derived from LITE data (cloud-free scenes only). The blue line is the molecular backscatter. The combine analysis of strong wind dynamics and large optical variability allowed designing optional sampling scenarios while assessing their performance in terms of retrieved quality winds, as a function of altitude, geographic region and season. It allowed also defining quality control methods for the wind retrieval, so that scenes with large variability can be properly treated.  Impacts of pre-selected sampling scenarios on NWP forecasts and stratospheric dynamics will finally be  assess during a simplified vertical one-dimensional assimilation system and a data assimilation ensemble technique [10]  Figure 6. Two sampling scenarios defined in the VAMP study to optimize retrieved wind quality and NWP impact (red is Mie channel, blue is Rayleigh channel). 3. CONCLUSION Status and results of recent studies in support of the ADM-Aeolus mission have been presented in this paper. The Rayleigh-Brillouin Scattering experiment led to a validation and improvement of the Tenti S6 model, used in the operational processing of ADM-Aeolus wind measurements. Some important issues dealing with wavelength, scattering angle and temperatures dependencies of the Rayleigh-Brillouin spectral shape as well as polarisation effects remain open and will be further studies in a follow-on activity.  The Vertical Aeolus Measurement Positioning study aims at defining optional sampling scenarios in order to ensure the retrieval of good quality winds and maximize the impact of ADM-Aeolus wind measurements on NWP and climate modelling. The study analyse critical atmosphere (dynamical and optical) characteristics that will be challenging for ADM-Aeolus, and will provide important inputs to the quality control of the Aeolus wind products. REFERENCES [1] Stoffelen A., J. Pailleux, E. Källén, J.M. Vaughan, L. Isaksen, P. Flamant, W. Wergen, E. Andersson, H. Schyberg, A. Culoma, M. Meynart, M. Endemann, P. Ingmann, 2005: The Atmospheric dynamics mission for global wind measurement, Bull. Am. Meteorol. Soc., 86, pp. 73-87. [2] European Space Agency ESA, 2008: ADM-Aeolus Science Report, ESA SP-1311. [3] World Meteorological organisation (WMO), 2001: Statement of Guidance Regarding How Well Satellite Meet WMO User Requirements in Several Applications Areas, Sat-26, WMO/TD No. 1052. [4] C. D. Boley, R. C. Desai and G. Tenti, 1972:  "Kinetic models and brillouin scattering in a molecular gas," Can. J. Phys., 50, 2158. [5] Dabas A., M.L. Denneulin, P. Flamant, C. Loth, A. Garnier, A. Dofli-Bouteyre, 2007: Correcting winds measured with a Rayleigh Doppler lidar from pressure and temperature effects, Tellus, 60, pp. 206-215. [6] Ubachs W., van Duijn W.-J, Vieitez M.O., Van de Water W., Dam N., ter Meulen J.J., Meijer A.S., de Kloe J., Stoffelen A., Aben E.A.A., 2009: A Spontaneous Rayleigh-Brillouin Scattering Experiment for the Characterization of Atmospheric Lidar Backscatter, Executive Summary, ESA contract no. AO/1-5467/07/NL/HE. [7] Marseille G.J., A. Stoffelen, J. de Kloe, K. Houchi, H. Körnich, H. Schyberg, A.G. Straume, O. Le Rille, 2009: ADM-Aeolus Vertical Sampling scenarios, Proceed 8th International Symposium on Tropospheric Profiling, ISBN 978-90-6960-233-2. [8] Vaughan, J.M., N.J. Geddes, P.H. Flamant and C. Flesia, 1998: Establishment of a backscatter coefficient and atmospheric database, DERA Report, ESA contract no. 12510/97/NL/RE, DERA/EL/ISET/ CR980139 /1.0. [9] Winker, D. M., Couch, R. H., and McCormick, M. P., 1996: An overview of LITE: NASA's Lidar In-space Technology Experiment, Proc. IEEE, 84, 2, pp. 164-180.  [10] Tan D., E. Anderson, M. Fisher and L. Isaksen, 2007: Observing-system impact assessment using a data assimilation ensemble technique: application to the ADM-Aeolus wind profiling mission, Q.J.R. Meteorol. Soc., 133, pp. 381-390.  

https://research.vu.nl/ws/files/2723355/ILRC25.pdf

ESA's wind Lidar mission ADM-AEOLUS; on-going scientific activities related to calibration, retrieval and instrument operation

Abstract

Similar works

Full text

Available Versions

DSpace at VU

Institute of Transport Research:Publications

VU Research Portal