1. Extinction measurements
Solar photometry
Solar occultation
_ Aerosol Optical Depth
_ Extinction profile of stratospheric aerosols

2. Diffusion measurements
Sky radiances
Radiances within the
solid angle(~20°)
Size distribution integrated over the column
AERONET network for example

3. Nadir backscatter diffusion Solar diffusion at limb
Diffusion measurements
Nadir backscatter diffusion
Solar diffusion at limb
AOD
Correction of surface diffusion
_ profil de diffusion des
aérosols stratosphériques

4. IR emission measurements
Measurement of ascending
IR radiations
Limb measurements
of IR radiations
AOD of absorbing aerososl
(mostly dust) – also vertical
profiles
Properties of
stratospheric aerosols

5. Where in the spectra do we measure aerosols ?
 In atmospheric windows where gas absorption is limited
Visible 0.35 – 0.75 µm
Fenêtre atm. à 0.85 µm
Fenêtre atm. à 1.22 µm
Solar Infrared : 0.85 µm, 1.06 µm, 1.22 µm, 2.20 µm, 3.70 µm
Fenêtre atm. à 3.70 µm
transmission
Thermal infrared : 8-12 µm

6. Limitations & precaution
Make a cautious cloud screening to remove cloudy pixels where aerosols
measurement is not possible, only cloud-free observations are available
at the moment !!!
Remove contribution from the surface, take into account surface reflectance
(path radiance) for UV/Vis and emissivity for IR. Models do exist or the multi
angle observations can be used explicitly to identify/quantify surface contribution.
For visible surface it is then much easier to observe observing oceanic surface
And more tricky to get information over continental bright surface (desert, snow)

7. All contributions
Atmospheric contributions
Surface contributions
Environnement contributions

8. Reflectance associated to different surfaces
_ Minimum for vegetalised surface = l~650 nm

9. Global network photometer
The ground based AERONET network (no path radiance)
Measured quantities :
AOD, angstroem coeff., size distribution
Global network photometer
aerosol climatology
validation of satellite products
validation of retriev. Aerosol
models
validation of CTM

10. List/record of aerosol instrument
PARASOL
2006
An important number of instruments are initially dedicated to meteorology or oceanography (older satellite
with longer time series, easier to maintain or continue meteorological missions)
Aerosol dedicated instrument are now present : POLDER, MODIS, CALIOP, MISR, GLORY

11. Aerosol model sensitivity

12. Global AOD observations over Ocean
POLDER-1
Example of AOD retrievals over oceanic
Surface … excluding brighter continental

13. A(qua)-Train a unique set-up for aerosol observations
                                                                                                                      
CALIPSO plateform dedicated to aerosol and clouds properties with a 3-band LISAR and passiv sensors
PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) microsatellite dedicated to measurement radiative properties and cloud microphysic
MODIS (MODerate resolution Imaging Spectroradiometer) microsatellite to radiative properties measurements and cloud parameters

14. Requirement of « Modern » aerosol sensors
 New generation sensors propose multi wave, multi-angle, polarisation set-up
Example of diffusion scattering measurements
POLDER-1; -2; PARASOL
2 l
14 direction of view
Polarisation
 +20 informations + various aerosol models
(with shape hypothesis  retrieval of shape possible)
AOD
size distribution
real part of refraction index for the fine mode
Global data foe 2x8 month of daily datas

15. Example of retrievals for the PARASOL instrument

16. 4. Détection des aérosols
Inversion des propriétés des aérosols avec MODIS
L’épaisseur optique est
dérivée de la radiance à 865 nm
La distribution en taille est
dérivée des radiances spectrales
2 modes sont distingués
Mode d’accumulation
r = 0.1 à 0.25 µm
- Mode grossier
r = 1 à 2.5 µm

17. Mean monthly Distributions of AOD from MODIS
(collection 5 ; Remer et al., 2005 ; Levy et al., 2007a,b )

18. MODIS sampling illustration (Aout 2000)
Total AOD
Fine mode AOD
(Dubovic et al., 2008)

19. Continental AOD from « deep-blue » MODIS
(Hsu et al, 2004)

20. Example of derived composite images
Desert dust aerosol plumes for the yellow sea and
And the Sahara

21. New original information from LIDAR
Caliop (Calipso/A-TRAIN)

22. New original information from LIDAR
Vertical profiles available

23. New original information from LIDAR : A-TRAIN synergy

24. Infrared observations are now strongly emerging
Ability to derive AOD over continental
Very bright surfaces (desert = strongest
Aerosol sources)
Night-time measurements possible
Vertical profiles retrievals also
possible
Comparisons between sensors over
continental areas still shows strong
discrepencies