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

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

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

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

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

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)

All contributions Atmospheric contributions Surface contributions Environnement contributions

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

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

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

Aerosol model sensitivity

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

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

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

Example of retrievals for the PARASOL instrument

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

Mean monthly Distributions of AOD from MODIS http://disc.sci.gsfc.nasa.gov/giovanni (collection 5 ; Remer et al., 2005 ; Levy et al., 2007a,b )

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

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

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

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

New original information from LIDAR Vertical profiles available

New original information from LIDAR : A-TRAIN synergy

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