NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Barry Gross (CCNY) Brian Cairns (NASA-GISS) Bill Lawrence (Bowie State) Michael Hagigeorgiou (Ugrad CCNY) Min Min Oo (Grad CCNY) Istvan Laszlo (NOAA-NESDIS) Stephan Ungar (NASA-GSFC) Thomas Brakke (NASA-GSFC) Validation and Refinement of Modis Aerosol Optical Depth Product over Coastal Urban Areas

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Motivation Air Pollution forcasting (Ozone, Aerosols, etc) has become a major NOAA responsibility in support of EPA MODIS AOT algorithms are global in nature. Application to regional areas may be difficult due to local ground albedo anomolies. Colocated matchups show that MODIS optical depth retrievals often overestimate optical depth measurements on the North East coast in urban areas Separate aerosol and land contributions using high spatial resolution data to help –Examine urban ground reflectance to tune MODIS –Retrieve aerosols in urban areas

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Colocated matchup procedure Intercompare MODIS Optical Depth with CIMEL optical depth. (Need to use only spatially homogeneous datasets) CIMEL Optical Depth taken between NYC and Brookhaven (5 hour mean to agree within 10%) MODIS 10km products. 3 x 3 cells to have std < 20% mean Few Points satisfy these conditions

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Intercomparision between CIMEL Sky radiometer and Satellite CART Site CCNY Site

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July MODIS Aerosol algorithms over land Surface correlations

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July MODIS-MISR BRDF Product examining VIS-MIR correlation Red pixels Consistent with MODIS assumptions As we go to Yellow, MODIS Underestimates VIS ground albedo

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Path Radiance (Regression) Approach Many Surfaces have covarying spectral responses between the VIS and MIR If the spectral responses covary in a similar way (one component model), a strong ‘linear’ correlation between the VIS and MIR bands occurs slope Y intercept Single scattering+small Lanbertian surface albedo

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Application and validation of ground reflectance correlations (MODIS over vegetation) Visible / NIR Reflectance Y intercept gives atmospheric reflection while slope (m) is proportional to the ground correlation 1) Correlation between ground reflection for different channels will result in correlations at the TOA 2) This can be used to separate ground and atmosphere components by plotting the MIR and VIS reflectances and determining their regression coefficients MIR Reflectance (2160nm)

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Hyperion as model of Special Events Hyperspectral Imager 30 meter pixel resolution S/N between 60 and 150 (oh well) from blue to red.

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Probing aerosol retrieval and ground correlations over urban scales Regions of interest include vegetation (central park – green), Urban areas (red-black) the river (orange), and lower manhattan Scan Column Scan Line New York observed through Hyperion (30 meter resolution)

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Correlation Coefficient vs wavelength Urban environments have many wavelength independent reflection (geometric) mechanisms that improve the correlations between the VIS and MIR channels Note a sharp difference for lower Manhattan due to shadowing /urban effect Shadow/Urban effect

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Hyperion Retrieval of Aerosol Reflection over heavy urban zone Larger Deviations above 700nm due perhaps to partial Vegetated scenes but Still much smaller than for vegetated scenes themselves Aerosol Reflection based on Aeronet estimates of AOT and Phase Function Total Reflection Single Scattering Rayleigh Scattering Hyperion Retrieval TOA Reflectance %

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July nm (Quite noisy) Hyperion Scene Correlation between VIS and MIR Only keep Aerosol Reflection (bad pixels Masked with navy blue) Increased loading to WTC observed WTC

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Ground reflection correlation frequency histogram No angle dependence (Lambertian) assumption Correlation larger than MODIS assumption of 0.5 This has been Observed elsewhere as seen below Frequency * Source MODIS ATBD Document Light Urban Central Park Heavy Urban

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Gnd ref 0.02 Gnd ref 0.05 Gnd ref 0.1 Gnd ref 0.2 Percentage Of Delata Tau Aerosol optical thickness (Tau) Percentage of Optical depth Overestimation AOT overestimates seem to be fairly consistent with ground albedo ~0.05 MIR albedo Urban

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Conclusions Spatial Regression over urban areas using high spatial resolution sensors can isolate aerosol Path Radiance directly and help decouple ground albedo from atmosphere. MODIS correlation coefficients are too low for urban scenes and leads to an overestimate of optical depth from MODIS. Preliminary Radiative Transfer calculations show that the 30% overestimate of VIS ground reflectance can help explain observed AOD overestimates. More urban data including high aerosol optical depth events needed.

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Additional Slides

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Aeronet Optical Depth Hyperion Fly By From GISS 112 th St

NOAA/NESDIS Cooperative Research Program Second Annual Science Symposium SATELLITE CALIBRATION & VALIDATION July Water leaving radiance using AVIRIS (subtracting ground decoupled atmosphere signal from total water signal) Obtained using high shadowing Better water leaving retrieval Weak shadowing Poor water leaving retrieval Water leaving Radiance (Reflection Units) shadowing Little shadowing water