2008 OMI Science Team Meeting, Helsinki, Finland
Aerosol Direct Radiative Effect from OMI
Concept and First Results
B. Veihelmann, P. Wang, J.P. Veefkind, P.F. Levelt
Royal Netherlands Meteorological Institute
2008 OMI STM, Helsinki, Finland Slide 2
B.Veihelmann, Royal Netherlands Meteorological Institute (KNMI)
Overview
Aerosol Direct Radiative Effect (DRE)
at the top of the atmosphere from OMI Concept Comparison with reference data 2 nice images Conclusions
2008 OMI STM, Helsinki, Finland Slide 3
B.Veihelmann, Royal Netherlands Meteorological Institute (KNMI)
Concept
multi-wavelength algorithm (OMAERO product) radiance in 14 wavelength bands, 340-500 nm Aerosol Optical Thickness (AOT)
best fitting aerosol model (out of 50 models)
refractive index, size distribution, height
model atmosphere of best fitting aerosol model upwelling flux at TOA Direct Radiative Effect DRE = flux() – flux(fit)
2008 OMI STM, Helsinki, Finland Slide 4
B.Veihelmann, Royal Netherlands Meteorological Institute (KNMI)
Concept
fluxes at TOA parameterized
precalculations with Doubling Adding Code KNMI (DAK) spherical albedo S transmission term T flux at top of the atmosphere for black surface Fpath
efficient flux calculations for any given Lambertian surface albedo a sun-satellite geometry elevation
)1( aS
aTFF pathTOA
2008 OMI STM, Helsinki, Finland Slide 5
B.Veihelmann, Royal Netherlands Meteorological Institute (KNMI)
Comparison with reference data EUCAARI intensive observation phase
cloud - aerosol measurement campaign May 2008 at Cabauw, the Netherlands
radiative transfer simulations AOT & SSA from ground-based sun-photometer profiles from radiosondes excellent agreement with ground-based
measurements of broad-band flux
=> reference for DRE from OMI -range 362-452 nm at top of atmosphere
2008 OMI STM, Helsinki, Finland Slide 6
B.Veihelmann, Royal Netherlands Meteorological Institute (KNMI)
Simulations for Cabauw
site
OMI
Nearest pixel
OMI
average 50 km radius
OMI
average 50 km radius
Albedo consitent with Cabauw data
consitent with Cabauw data
consitent with Cabauw data
from climatology
Flux TOA W/m2 30.4 29.7 31.1 30.1
DRE TOA W/m2 -3.6 -3.6 -5.0 -2.2
AOT 0.2 0.2 0.4 0.1
Vertical dist. 0-1 km 0-2 km 0-2 km 0-2 km
SSA 484 nm 0.89 0.95 0.95-0.97 0.95
Comparison with reference data
2008 OMI STM, Helsinki, Finland Slide 7
B.Veihelmann, Royal Netherlands Meteorological Institute (KNMI)
March 2006 aerosol transport event
0 2 4 6 8AOT
-40 -30 -20 -10 0DRE (W/m2)
sun-glint
2008 OMI STM, Helsinki, Finland Slide 8
B.Veihelmann, Royal Netherlands Meteorological Institute (KNMI)
Conclusion DRE at TOA from OMI?
first test indicates that numbers are meaningful relevance of DRE in UV-VIS?
340-500 nm ~15% of irradiant solar energy percentage of DRE larger:
aerosol scattering & absorption ~ -a
Rayleigh scattering enhances absorption by aerosols sensitivity to surface albedo
ocean BRDF implementation envisaged land BRDF?
cloud screening using independent information MODIS cloud mask?