Environmental Engineering Reference
In-Depth Information
01/25/2008, 04/09/2008, 06/23/2008, 09/06/2008, and 11/20/2008. In total,
1920 AIRS granules are collected.
• For AIRS FOVs, collect scene characteristics, including surface type, solar
angles, view angles, cloud status, etc. These scene characteristics can be
determined using AIRS L1B measurements, AIRS level 2 retrieval data
products, and MODIS land cover data products.
2. Spectral mapping and proxy data generation
• Convolve the spectral response functions of AVHRR band 4 and band 5,
MODIS band 31 and band 32, and VIIRS band M15 and band M16, with
AIRS hyper-spectral thermal infrared measurements to generate global proxy
datasets for various versions of AVHRR, MODIS, and VIIRS.
• MODIS L1B radiance is defined in wavelength domain with unit Wm
2
sr
1
/
μ
m, while AIRS radiance data is defined in wavenumber domain with unit
mWm
2
sr
1
/cm
1
; unit conversion and spectral response function should be
taken into account to simulate broadband radiance with AIRS. After unit
conversion, proxy measurements can be generated by convolving spectral
response functions of various sensors (AVHRR, MODIS, and VIIRS) over
AIRS hyper-spectral measurements.
3. Construction of global testing database
• Combine AIRS-simulated AVHRR/MODIS/VIIRS proxy datasets with AIRS
scene characteristics, including surface type, solar angles, view angles, cloud
status, etc., to construct a global testing database.
4. Regressive analysis to determine band transfer equations
• Select one sensor as template for FCDR.
• Using the testing database, discover the band transfer equations for
converting AVHRR/MODIS/VIIRS bands to the selected template sensor
through regressive analysis.
• Construct the database for coefficients in band transfer equations.
Save the coefficients for band transfer equations for various scene characteristics
in database for later use.
5. Producing global AVHRR FCDR data
• For historical AVHRR measurements, identify scene characteristics and
apply the corresponding band transfer equations to convert SDR of old
AVHRR versions to the template sensor.
• For MODIS measurements, identify scene characteristics and apply the band
transfer equations to get equivalent MODIS SDRs, which can be combined
into AVHRR FCDRs for expansion of temporal coverage.
• After NPP/JPSS lunch, VIIRS SDRs can also be used to expand the thermal
emissive FCDRs.
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