WP 8: Impact on Satellite Retrievals University of l’Aquila (DFUA [12]) Ecole Polytechnique (EPFL...
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Transcript of WP 8: Impact on Satellite Retrievals University of l’Aquila (DFUA [12]) Ecole Polytechnique (EPFL...
WP 8: Impact on Satellite Retrievals
University of l’Aquila (DFUA [12])
Ecole Polytechnique (EPFL [13])
Observatory of Neuchatel (ON [14])
Partners (according to Contract):
Meteorol. Inst. Munich (MIM [17]): Matthias Wiegner
Overview over Presentation
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 [...].
Contract: Objectives and input of WP8
Contract: Description of work
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.
Relevance of WP 8
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“
Relevance of WP 8
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“
Relevance of WP 8
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“
Three contributions to WP 8
Demonstrate the benefit of lidar data on the basis of dedicated experiments
Note: WP‘s ordered by „time allocated“:WP8 is 15. out of 20.
Offer our datasets to the satellite communityfor validation purposes
Identify cases where lidar data are useful
First contribution
Actions proposed: Supply survey of available aerosol extinction profiles (site, time, wavelength)
Goal:Support validation of satellite retrievals by supplying lidar data
(possible candidates: Envisat, MSG community)
Data dissemination:On request (Webpage)
First contribution
Results/Conclusions:Aerosol extinction profiles from more than 20 lidar stations, twotimes a week and for more than two years, are available.
Validation of aerosol retrievals requires a careful selectionof 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 satellitecommunity), time horizon: 2003/04
“Seed is set, but harvesting takes time”
Three contributions to WP 8
Demonstrate the benefit of lidar data on the basis of dedicated experiments
Note: WP‘s ordered by „time allocated“:WP8 is 15. out of 20.
Offer our datasets to the satellite communityfor validation purposes
Identify cases where lidar data are useful
Acquisition mode:CHRIS: 18 km swath, 25 m resolution, 19 spectral bands, along track (5 angles)
Second contribution
Time and Place: May, June, July and August 2002 in Gilching
In co-operation with:
Goal:Full characterization of surface and atmosphere of exactlythe same scene (for calibration of satellite sensor and algorithms)
Requirements:
co-incidence and co-location and very small satellite pixel required.
Second contribution
Results/Conclusions:
Satellite PROBA encountered severe problems: no data areavailable up to now.
First data are announced for fall this year.
A new special field campaign is difficult to be organised.
Three contributions to WP 8
Demonstrate the benefit of lidar data on the basis of dedicated experiments
Note: WP‘s ordered by „time allocated“:WP8 is 15. out of 20.
Offer our datasets to the satellite communityfor validation purposes
Identify cases where lidar data are useful
Third contribution
Actions: Performing model calculations with realistic aerosol extinction profiles to investigate the influence of aerosols on toa-radiances
Goal:
Support model development by supplying lidar data
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)
Radiative transfer calculations
Verticalaerosol distribution:
5 cases
(1) (2) (3) (4) (5)
Model calculations
Normalized to isotropic radiance „Anisotropy-Function“
Radiances at top of atmosphere
as a function ofsurface albedofor different aerosoloptical depths
fixed aerosol type,aerosol profile andsolar zenith angle
Radiance/flux at toa
different aerosol type
Radiance/flux at toa
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: 32.50
Radiance/flux at toa
now: 62.50
Radiance/flux at toa
as a function ofsurface albedofor different aerosoltypes
fixed optical depth,aerosol profile andsolar 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 ofsurface albedofor different aerosolprofiles
fixed optical depth,aerosol type andsolar 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 ofsurface albedofor different aerosolmixtures
fixed optical depth,aerosol types andsolar 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
Conclusions from the model simulations
Satellite radiances are significantly influenced by aerosols:
-- optical depth-- aerosol type-- aerosol profile
Conclusions from WP 8
Validation campaigns of aerosol parameterswith lidar data require extra efforts
Model simulations show that the aerosol vertical distribution is a second order effect for satelliteremote sensing, but should be provided together with a aerosol classification („aerosol type“)
Thank you for liste ning