Satellite retreival of AOT over Desert regions

Satellite Retrieval of AOT over Desert Regions : 

Satellite Retrieval of AOT over Desert Regions Wolfgang von Hoyningen-Huene, John P. Burrows, Institute of Environmental Physics, University of Bremen _________ AOD retrieval validation Over deserts – no regular AOD products only TOMS AAI Aim: extension of BAER for desert conditions Validation of retrieved AOD

Determination of AOT : 

Determination of AOT BAER (Bremen AErosol Retritrival) is used for spectral AOT  < 0.67 µm over land Clouds separately treated by the asymptotic theory for optically thick clouds (A. Kokhanovsky) -> COT Angström  derived from spectral AOT AOT(0.412 µm) +  use for the determination of additional aerosol parameters Reff and NAER. Adaptations for desert conditions required

Retrieval Requirements : 

From radiative transfer equation one obtains the aerosol reflectance Aerosol parameters Surface reflectance Retrieval Requirements

Comparison of Phase Functions : 

Comparison of Phase Functions Models underestimate lateral scattering

Surface Reflectance : 

Surface Reflectance Desert cases Now implemented

Status : 

Status Aerosol parameters: Europe: phase function + SSA from LACE-98 Desert: phase function (Senegal 1995) future: phase function + SSA from SAMUM OPAC overestimates AOT Surface reflectance: Europe: vegetation mix tuned by NDVI Desert: now: static bright soil spectrum (F. Baret, INRA) future: a) data base from C. Hsu (NASA) b) model derived from SAMUM

MERIS AOD L3 ACRI : 

MERIS AOD L3 ACRI

Satellite Properties 1 : 

Satellite Properties 1 Observation data

Spectral Channels 1 : 

Spectral Channels 1 UV channels Solar IR

Spectral Channels 2 : 

Spectral Channels 2

Coverage 1 : 

SeaWiFS daily coverage (Clorophyll product, from GAC L1b data ) Swath width: 2400 km Morocco: every 1 - 2 days Coverage 1 ENVISAT Meris: Swath width: 1100 km (only the half) SCIAMACHY: 980 km AATSR: 512 km Coverage about every 2 days

Coverage 2 : 

Coverage 2 TOMS: 2800 km swath, total coverage, every day

Coverage 3 : 

Coverage 3 MODIS: Swath 2330 km

Data Access + Availability : 

Data Access + Availability

Ground Measurements : 

Ground Measurements Cloud free conditions: Sun photometer: AOD(), 7 channels, CIMEL 318 1.020, 0.870, 0.670, 0.500, 0.440, 0.380, 0.340 Cloud free + zo > 60° Skyradiometer: LSky(, zo, ) ALMU, 4 (7 ?) channels, CIMEL (LSky(, z, o) PPL, 4 channels, CIMEL)  p(), o by CIRATRA Old ASP 4 photometer: Surface Reflectance (, zo, ) Totally cloudy or homogeneous Ci: Skyradiometer LSky(, z, o) PPL, 4 channels, CIMEL   cos(z)*Cloud LSky(, zo, ) ALMU, 4 channels, CIMEL  pCi()

Instruments : 

ASP-5 CIMEL 318 Instruments

Data Examples : 

Data Examples

Preparation : 

Preparation Investigation of the temperature influence of the CIMEL Langley-plots, Zugspitze + Bremen Improvment of Calibration check: Calibration campaign at Zugspitze in March 2005 Reference of the sky channels (aureole + sky) to the solar channel (for o required) Additional blocking of channel 7 and 8 (0.380 + 0.340 µm) Leakage light from double wavelength