University of l’Aquila (DFUA [12])
Ecole Polytechnique (EPFL [13])
Observatory of Neuchatel (ON [14])
Meteorol. Inst. Munich (MIM [17]): Matthias Wiegner

1. EARLINET-Contract: Workpackage 8
2. Relevance of WP 8
3. Contributions to WP 8
Definition
Examples
4. Conclusions

EARLINET-Contract:
1. Quantify the sensitivity of radiances at the top of the atmosphere (toa) to variations of the aerosol distribution
[...]. This will be used to provide an estimate of the impact of aerosols on retrievals [...] from spaceborne platforms.
2. Provide aerosol distributions for calibration purposes upon request [...].

This is done by running adequate radiative transfer models using the aerosol data [...]. As a result, inversion algorithms [...] can be critically reviewed and improved.
Additional lidar measurements [...] will be performed at special occasions when satellite overpasses close to an
EARLINET station occurs [...]. For this part to stay within the limits of the available resources it will be done only on request.

multispectral and multiangular radiances from satellites used to retrieve aerosol optical depth critical over land surfaces (albedo, orography) complex retrieval algorithms require validation
„Validation of atmospheric parameters“

multispectral and multiangular radiances from satellites used to retrieve surface properties (e.g. precision farming) determine atmospheric influence (unknown aerosol effect) corrections of atmospheric masking require input and validation
„Validation of surface parameters“

Radiative transfer calculations required to understand satellite data aerosol distribution is one controlling parameter contribution of lidar data to be assessed
„Improvement of aerosol understanding“

Offer our datasets to the satellite community for validation purposes
Demonstrate the benefit of lidar data on the basis of dedicated experiments
Identify cases where lidar data are useful
Note:
WP‘s ordered by „time allocated“:
WP8 is 15. out of 20.

Goal:
Support validation of satellite retrievals by supplying lidar data
(possible candidates: Envisat, MSG community)
Actions proposed:
Supply survey of available aerosol extinction profiles (site, time, wavelength)
Data dissemination:
On request (Webpage)

Results/Conclusions:
Aerosol extinction profiles from more than 20 lidar stations, two times a week and for more than two years, are available.
Validation of aerosol retrievals requires a careful selection of time and place, and averaging over reasonable periods.
Envisat and MSG are still at the beginning of their operation times. Final success requires extra funding (also for the satellite community), time horizon: 2003/04
“Seed is set, but harvesting takes time”

Offer our datasets to the satellite community for validation purposes
Demonstrate the benefit of lidar data on the basis of dedicated experiments
Identify cases where lidar data are useful
Note:
WP‘s ordered by „time allocated“:
WP8 is 15. out of 20.

Goal:
Full characterization of surface and atmosphere of exactly the same scene (for calibration of satellite sensor and algorithms)
Requirements : co-incidence and co-location and very small satellite pixel required.
Time and Place:
May, June, July and August 2002 in Gilching
Acquisition mode:
CHRIS: 18 km swath, 25 m resolution, 19 spectral bands, along track (5 angles)
In co-operation with:

Results/Conclusions:
Satellite PROBA encountered severe problems: no data are available up to now.
First data are announced for fall this year.
A new special field campaign is difficult to be organised.

Offer our datasets to the satellite community for validation purposes
Demonstrate the benefit of lidar data on the basis of dedicated experiments
Identify cases where lidar data are useful
Note:
WP‘s ordered by „time allocated“:
WP8 is 15. out of 20.

Goal:
Support model development by supplying lidar data
Actions:
Performing model calculations with realistic aerosol extinction profiles to investigate the influence of aerosols on toa-radiances

Variation of aerosol optical depth
Variation of aerosol type
Variation of aerosol (vertical) distribution
Variation of surface albedo
Variation of solar zenith angle
Fixed wavelength (532 nm)

Vertical aerosol distribution:
5 cases
(1) (2) (3) (4) (5)

Normalized to isotropic radiance
„ Anisotropy-Function “

Radiance/flux at toa as a function of surface albedo for different aerosol optical depths fixed aerosol type, aerosol profile and solar zenith angle

Radiance/flux at toa different aerosol type

Radiance/flux at toa different aerosol type

Radiance/flux at toa different aerosol type

Radiance/flux at toa different aerosol type

Radiance/flux at toa same as before: 32.5
0

Radiance/flux at toa now: 62.5
0

Radiance/flux at toa as a function of surface albedo for different aerosol types fixed optical depth, aerosol profile and solar zenith angle

Radiance/flux at toa
Different optical depth

Radiance/flux at toa
Different optical depth

Radiance/flux at toa
Different optical depth

Radiance/flux at toa
Different optical depth

Radiance/flux at toa as a function of surface albedo for different aerosol profiles fixed optical depth, aerosol type and solar zenith angle

Radiance/flux at toa
Different aerosol type

Radiance/flux at toa
Different aerosol type

Radiance/flux at toa
Different aerosol type

Radiance/flux at toa
Different aerosol type

Radiance/flux at toa as a function of surface albedo for different aerosol mixtures fixed optical depth, aerosol types and solar zenith angle

Radiance/flux at toa
Different aerosol type

Radiance/flux at toa
Different aerosol type

Radiance/flux at toa
Different aerosol type

Radiance/flux at toa
Different aerosol type

Radiance/flux at toa
Different layer width

Satellite radiances are significantly influenced by aerosols:
-- optical depth
-- aerosol type
-- aerosol profile

Validation campaigns of aerosol parameters with lidar data require extra efforts
Model simulations show that the aerosol vertical distribution is a second order effect for satellite remote sensing, but should be provided together with a aerosol classification („aerosol type“)