Radiometric Inter-Angle
The non-nadir radiance measured by SPEXone over deep convective clouds (DCCs) is collected and compared to the nadir radiance. The definition of DCCs is given in the table below. As such the Iviewport/Inadir is calculated where Iviewport is the radiance of a non-nadir viewport (-50, -20, 20, 50 degrees) and Inadir is the radiance of the nadir viewport (0 degrees). The monthly mean Iviewport/Inadir
value is plotted. A separate plot is made for each viewport and each plot has a separate line for each chosen wavelength. Besides the measured Iviewport/Inadir, these two values are also theoretically calculated using a radiative transfer (RT) calculation. These values are also averages over a month and thus allow a comparison of the measured Iviewport/Inadir mean and the RT-based calculated
Iviewport/Inadir mean.
| Criteria for DCC | Characteristics | Motivation |
| Reflectivity at 750 nm > 0.7 | Top-of-atmosphere (TOA) signal is dominated by cloud |
TOA signal can be well predicted |
| Inter-tropical locations | Favorable areas for convection | Convective cloud |
| Measurements over ocean |
Negligible surface contribution (outside glint) |
Cloud signal dominates TOA signal |
| Cloud top height > 10 km | Negligible contribution from aerosols |
Cloud signal dominates TOA signal |
| RMS of radiance at 770 nm < 3% (from OCI) |
Homogeneous area | 1D RT calculation is sufficient |
| Solar zenith angle < 30 degrees |
Minimize shadow effects | 1D RT calculation is sufficient |
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Airbus Netherlands B.V.
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NASA
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NSO
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NWO
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TNO
About
SPEXone is being developed by a Dutch consortium consisting of SRON Netherlands Institute for Space Research (SRON) and Airbus Defence and Space Netherlands (Airbus DS NL), supported by optical expertise from the Netherlands Organisation for Applied Scientific Research (TNO). SRON and Airbus DS NL are responsible for the design, manufacturing and testing of the instrument. The scientific lead is in the hands of SRON. SPEXone is a public-private initiative funded by the Netherlands Space Office (NSO), the Netherlands Organization of Scientific Research (NWO), SRON, and Airbus DS NL.
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