| Data Type |
Description |
| Aerosol Optical Depth (AOD) |
|
| Level 1.0 (Raw) |
Unscreened and may not have final calibration applied |
| Level 1.5 (Cloud Screened) |
Automatically cloud cleared but may not have final calibration applied. These data are NOT quality assured. |
| Level 2.0 (Quality Assured) |
Pre- and post-field calibration applied, automatically cloud cleared and manually inspected |
| Precipitable Water |
The total water vapor in the column derived from the 935nm channel. |
| Percent Triplet Variability |
Each AOD measurement is comprised of a triplet measurement: These measurements are taken every 30 seconds for one minute. The variability of this measurement can provide insight on the quality of the data. |
| Angstrom Parameter |
The angstrom parameter is calculated for all available wavelengths within the Angstrom parameter range. For example, the Angstrom 870-440nm includes the 870, 670, 500 and 440 nm AOD data. A special case for a polarized instrument is Angstrom 870-440nm which only includes 870, 670 and 440 nm AOD data (polarized instruments do not have 500nm channel). |
| Instrument Information |
|
| Exact Wavelength |
The exact filter wavelength is used to determine AOD and other parameters. |
| Raw Data |
|
| Polar Principal Planes |
Calibration applied to polarized principal planes scenario data (See Page 31 of the Cimel Sun Photometer User Manual for more information on almucantars) |
| Bidirectional Reflectance Distribution Function (BRDF) |
Calibration applied to BRDF scenario data |
| Almucantars |
Calibration applied to almucantar scenario data (See Page 30 of the Cimel Sun Photometer User Manual for more information on almucantars) |
| Principal Planes |
Calibration applied to principal planes scenario data (See Page (See Page 31 of the Cimel Sun Photometer User Manual for more information on almucantars) |
| Nakajima Almucantar Retrievals |
|
| SKYRAD.PAK |
Derived phase functions, aerosol size distribution and sky optical depth |
| Version 1 Almucantar Retrievals |
|
| Size Distribution |
Volume particle size distribution is retrieved logarithmically equidistant bins from 0.05um to 15um. |
| Refractive Index |
The real refractive index (n from 1.33 to 1.6) and the imaginary part (k from 0.0005 to 0.5) is retrieved for wavelengths corresponding to sky radiance measurements. |
| SSA |
Single scattering albedo (SSA) is retrieved for wavelengths corresponding to sky radiance measurements. Fine and coarse modes are not provided due to the assumption of the retrieval to use the same complex index of refraction for all particle sizes. |
| AOD Coincident |
Calculated by averaging the level 1.5 or 2.0 AOD data values (Level 2.0 has priority) +/- 16 minutes of the almucantar retrieval time (typically uses three to five AOD points for the coincident average) |
| Volume Parameters |
Volume concentration, volume median radius, effective radius, standard deviation (total, fine and coarse modes) |
| AOD Extinction |
Derived values for AOD from almucantar retrieval (total, fine and coarse modes). The total mode is determined by the sum of the fine and coarse modes. |
| Phase Functions |
Phase function is retrieved at 83 scattering angles at wavelengths corresponding to sky radiance measurements (total, fine and coarse modes). |
| Asymmetry Factor |
Integrated value for phase functions (total, fine and coarse modes) where positive values indicate scattering in the forward direction. |
| AOD Absorption |
Equation: (1-SSA)*AOD (where AOD is AOD Extinction)- The single scattering albedo is used for each incidence of an almucantar retrieval. The AOD is calculated by adding the derived almucantar AOD fine and coarse modes. AOD absorption is calculated for the following channels: 1020,870,670 and 440 nm.(total, fine and coarse modes) |
| Combined Retrievals |
Combination of all Dubovik Almucantar Retrievals except phase functions. |
| Version 1 Almucantar Retrieval Settings |
|
| Level 1.5 (Spherical and Spheroid) |
Determined using Level 1.5 (2.0 if available) AOD data
No additional screening |
| Level 2.0 - Spherical and Spheroid (Recommended default options) |
Determined using Level 2.0 AOD; solar zenith angle greater than 25 degrees; number of angles is greater than 20;
Spherical: sky error < 5%
Spheroid: sky error <10% |
| Level 2.0 (User-defined Options) |
Determined using Level 2.0 AOD; activates Advanced Level 2.0 Retrieval Parameters |
| Spherical Level 2.0 |
All of the products provided except when the following conditions are met:
- Solar zenith angle is smaller than 45 degrees, or
- Coincident AOD tau440 is less than 0.4
|
| Condition 1 (Above) |
Condition 2 (Above) |
Not Provided:
Single Scattering Albedo; Real and imaginary parts of refractive index; and AOD Absorption |
Not Provided:
Single Scattering Albedo, Real and imaginary parts of refractive index |
| Non-spherical Level 2.0 |
- Same as Spherical Level 2.0
- Real parts of refractive index for 670 and 440nm are not provided
- The minimum on the size distribution curve on the interval 0.05-1 micron that is closest to 1 micron
3a. Size distribution values are not provided for sizes smaller than where the minimum appears
3b. Fine mode values are not provided for modal products
|
| Spheroid Level 2.0 |
All of the products are provided except when the Angstrom parameter (870-440nm) is greater than 0.6. |
| Combined Spherical and Spheroid Level 2.0 |
All of the products are provided for these retrievals. The selection of spherical and spheroid retrievals follows these rules:
If the spherical model is level 2.0, then the spherical is used; otherwise, if the spheroid model is level 2.0, then the spheroid is used as the recommended level 2.0 retrieval. |
| Version 1 Almucantar Retrieval Filters |
|
| Angles (No.) |
Number of symmetric angles available from the almucantar |
| Solar Zenith Angles (Degrees) |
Minimum and maximum solar zenith angle range in degrees |
| Additional Solar Zenith Angle Limit |
If calculated solar zenith angle is less than solar zenith angle limit, then single scattering albedo and real and imaginary parts of the refractive index are not provided in the download. |
| AOD @ 440 nm |
If the observed AOD at 440 is less than the AOD @ 440nm limit, then single scattering albedo and real and imaginary parts of the refractive index are not provided |
| Angstrom Parameter (440-870nm) Limit |
When non-spherical (spherical model) data type is selected and the sky radiance error is between 5 and 15%, the almucantar will be passed to level 2.0 if the calculated angstrom parameter is smaller than angstrom parameter limit. |
| Sky Error (%) (Spherical and Spheroid) |
Sky radiance error in percent |
