January 13, 2009
POLDER 2 - List of Parameters in POLDER "ERB, WV & CLOUDS"
List of Parameters in POLDER "ERB, WV & CLOUDS" level 2 products
The following geophysical parameters are computed from the level 1 product for each superpixel (3x3 pixels), by orbit segment.
For details about the calculation of these parameters, see POLDER2 advanced algorithms.
(a) Level 2 non-directional parameters
| t | GMT time (h mn) |
| Ni | Total number of viewing directions (7 ? Ni ? 14) |
| Nr Np | Number of viewing directions used for the Rayleigh pressure derivation (0 ? Nr ? 14) Number of elementary pixels (5 ? Np ? 12) |
| MinGlitter, MaxGlitter | No of the first / last viewing direction within the expected region of solar specular reflection |
| µs | Cosine of solar zenith angle (defined for the central elementary pixel) |
| Avis | Mean albedo at 670 nm over land and 865 nm over ocean, result from an averaging over pixels and a weighting over directions |
| RSD(Avis) | Relative Spatial standard Deviation of the albedos derived by pixel and by direction at 670/865 nm |
| RAD(Avis) | Relative Angular standard Deviation of the albedos derived by pixel and by direction at 670/865 nm |
| QAvis | Quality index related to the ratio between the relative angular deviation RAD(Avis) and that derived under the Lambertian hypothesis (the lower the better with a 0 ideal case) |
| A*vis | Mean of the albedos calculated under the assumption of an homogeneous scene at 670/865 nm |
| RAD(A*vis) | Relative Angular standard Deviation of the albedos at 670/865 nm calculated under the assumption of an homogeneous scene |
[Amodel( c=0)]vis | Modeled clear-sky albedo at 670/865 nm, that is independent of POLDER measurements |
| ASW | Shortwave albedo derived from the 443, 670 and 865 nm albedos |
| [Amodel(c=0)]SW | Modeled clear-sky shortwave albedo, that is independent of POLDER measurements |
| CC | Cloud Cover, defined as the number of cloudy pixels divided by the total number of pixels. |
 CC+/- | Uncertainty on cloud cover related to re-classification, i.e. number of pixels firstly classified as indeterminate and finally classified as clear (+) /cloudy (-) divided by the total number of pixels |
| QCC | Quality index related to cloud detection (the lower the better with a 0 ideal case) |
| UH2O | Total column precipitable water vapor of the clear part of the superpixel |
| QUH2O | Quality index related to total column precipitable water vapor (the lower the better with a 0 ideal case) |
| Poxy | Mean cloud Oxygen pressure. It is expected to be close to the cloud middle pressure |
| AD(Poxy) | Angular standard Deviation of the cloud Oxygen pressure derived by direction |
| Pray | Mean cloud Rayleigh pressure. It is expected to be close to the cloud top pressure |
| AD(Pray) | Angular standard Deviation of the cloud Rayleigh pressure derived by direction |
| c | Linear mean cloud optical thickness at 670 nm over land and 865 nm over ocean, result from an averaging over cloudy pixels and a weighting over directions |
| RSD(c) | Relative Spatial standard Deviation of the cloud optical thickness at 670/865 nm |
 | Indicator of the radiative variability of the cloud optical thickness distribution. It is defined by = 1 - c* / (CC x c) where c* and CC x c are respectively the radiative and the linear mean cloud optical thickness of the whole superpixel. It is equal to 0 for a homogeneous distribution and increases towards 1 as the variability increases. |
| Sc | Mean cloud spherical albedo (defined over black surface with no atmosphere) at 670/865 nm, result from an averaging over cloudy pixels and a weighting over directions |
| Phase | Cloud thermodynamic phase |
| Micro-index | Microphysical index calculated only for ice clouds. It is expected to be indicative of the ice crystal type |
| strato-aer | Stratospheric aerosol optical thickness (exogeneous data) |
| UO3 | Total column ozone (exogeneous data) |
| Vwind | Meteorological surface wind intensity (in m/s) (exogeneous data) |
 wind | Meteorological surface wind bearing (in degrees) (exogeneous data) |
| Psurface | Meteorological surface pressure (exogeneous data) |
| T(k), k=1,10 | Meteorological temperature profile (exogeneous data) |
| U(k), k=1,10 | Meteorological integrated water vapor profile (exogeneous data) |
(b) Level 2 directional parameters
 v(i) | Viewing zenith angle (defined for the central elementary pixel) in the given direction (i) |
| (i) | Relative azimutal angle (defined for the central elementary pixel) in the given direction (i) |
| Rvis(i) | Mean of the reflectances corrected from gaseous absorption at 670 nm over land and 865 nm over ocean, result from an averaging over cloudy pixels in the given direction (i) |
| Avis(i) | Mean "directional" albedo at 670/865 nm, result from an averaging over cloudy pixels in the given direction (i) |
| RSW(i) | Mean shortwave reflectance estimated from narrowband reflectances |
| ASW(i) | Mean shortwave "directional" albedo estimated from narrowband "directional" albedos |
| LPSMOD865(i) | Modified polarized radiance at 865 nm |
| Ncloud(i), N(i) | Relative number of cloudy / clear pixels (from 0 to 1 by steps of 1/9), i.e. the number of cloudy /clear pixels divided by the total number of pixels. Their sum is less than unity when some pixels are unclassified in the given direction |
| CC(i) | Cloud Cover, defined as the number of cloudy (including "unclassified" relabeled as cloudy) pixels divided by the total number of pixels |
| Sc(i) | Mean cloud spherical albedo (defined over black surface with no atmosphere) at 670/865 nm, result from an averaging over cloudy pixels in the given direction (i) |
List of Parameters in POLDER "ERB, WV & CLOUDS" level 3 products
The following geophysical parameters are computed from the level 2 product for each superpixel (3x3 pixels), by orbit segment.
For details about the calculation of these parameters, see POLDER2 advanced algorithms.
| Ndays | Number of days for which POLDER data are available |
| Norb | Number of orbits for which POLDER data are available |
| Norb-snow | Number of orbits with no snow/ice risk |
| Norb-clear | Number of orbits without cloud |
| Norb-cloudy | Number of orbits with clouds |
| Norb-A | Number of orbits for which albedo is calculated |
| Norb-Poxy | Number of orbits for which cloud Oxygen pressure is calculated |
| Norb-Pray | Number of orbits for which cloud Rayleigh pressure is calculated |
| Norb-Phase | Number of orbits for which cloud phase is calculated |
| Norb-UH2O | Number of orbits for which total column precipitable water vapor is calculated |
| M(µs) | Monthly mean of the cosine of solar zenith angle |
| M(Avis) | Monthly mean of the instantaneous albedo at 670 nm over land and 865 nm over ocean |
| TD(Avis) | Temporal standard Deviation of the instantaneous albedo at 670/865 nm |
| M(Avis)clear | Monthly mean of the instantaneous albedo at 670/865 nm when the superpixel is declared clear |
| TD(Avis)clear | Temporal standard Deviation of the instantaneous albedo at 670/865 nm when the superpixel is declared clear |
| M(Amodel(c=0)vis) | Monthly mean of the modeled clear-sky albedo at 670/865 nm, that is independent of POLDER measurements and must not be confused with M(Avis)clear |
| M(ASW) | Monthly mean of the instantaneous shortwave albedos |
| TD(ASW) | Temporal standard Deviation of the instantaneous shortwave albedo |
| M(ASW)clear | Monthly mean of the instantaneous shortwave albedo when the superpixel is declared clear |
| TD(ASW)clear | Temporal standard Deviation of the instantaneous shortwave albedo when the superpixel is declared clear |
| M(Amodel(c=0)SW) | Monthly mean of the modeled clear-sky shortwave albedo, that is independent of POLDER measurements and must not be confused with M(Avis)SW |
| M(Finc) | Monthly average shortwave incident flux density (expressed in W/m2) |
| M(Frefl) | Monthly average shortwave reflected flux density (expressed in W/m2) ; it must not be confused with the mean of the instantaneous fluxes M(Finc) x M(ASW) |
| M(Frefl)clear | Monthly average clear-sky shortwave reflected flux density (expressed in W/m2) ; it must not be confused with the mean of the instantaneous fluxes M(Finc) x (ASW)clear nor even less with the mean of the modeled clear-sky flux M(Finc) x M(Amodel(c=0)SW) |
| M(CC) | Monthly mean of the cloud cover |
| TD(CC) | Temporal standard Deviation of the cloud cover |
| M(CC+/-) | Monthly mean of the uncertainty on cloud cover related to re-classification |
| M(UH2O) | Monthly mean of the total column precipitable water vapor |
| TD(UH2O) | Temporal standard Deviation of the total column precipitable water vapor |
| M(Poxy) | Monthly mean of the cloud Oxygen pressure |
| TD(Poxy) | Temporal standard Deviation of the cloud Oxygen pressure |
| M(Pray) | Monthly mean of the cloud Rayleigh pressure |
| TD(Pray) | Temporal standard Deviation of the cloud Rayleigh pressure |
| M(c) | Monthly mean of the cloud optical thickness at 670 nm over land and 865 nm over ocean |
| RTD(c) | Relative Temporal standard Deviation of the cloud optical thickness at 670/865 nm |
| M(c)liquid | Monthly mean of the liquid water cloud optical thickness at 670/865 nm |
| M(c)ice | Monthly mean of the ice cloud optical thickness at 670/865 nm |
| M(c)mixed | Monthly mean of the mixed-phase cloud optical thickness at 670/865 nm |
| M(Sc) | Monthly mean of the cloud spherical albedo at 670/865 nm |
| TD(Sc) | Temporal standard Deviation of the cloud spherical albedo at 670/865 nm |
| FREPHASE | Frequency of occurrence of cloud phase in 4 classes (1: liquid, 2: ice, 3: mixed, 4: undetermined) expressed in percent (%) |
| FRECRYSTAL | Frequency of occurrence of ice crystal type in 7 classes (1: undetermined, 2-5: different classes of a priori randomly oriented crystals, 6-7: absolute and relative percentage of horizontally oriented crystals) |
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