CALIPSO Quality Statements Summary:
Lidar Level 2 Vertical Feature Mask (VFM)
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CALIPSO Quality Statements Summary: |
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| Lidar Level 2 Vertical Feature Mask (VFM) Information Half orbit (Day) geolocated data radiances |
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| Release Date | Version | Data Date Range | Product Quality Statement |
Data Detail Quality Statement |
Maturity Level |
| January 25, 2008 | 2.01 | June 13, 2006 to present | 2.01 Version Summary | QS 2.01 |
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| December 8, 2006 | 1.10 | June 13, 2006 to November 11, 2007 | 1.10 Version Summary | QS 1.10 |
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Data Release Date: January 25, 2008
Version: 2.01
Data Date Range: June 13, 2006 to present
Please refer to the Data Detailed Quality Statement for information about this release.
Data Release Date: December 8, 2006
Version: 1.10
Data Date Range: June 13, 2006 to November 11, 2007
The CALIPSO vertical feature mask (VFM) data product reports a single 16-bit integer for each lidar altitude resolution element in the data stream downlinked from the satellite. Upon decoding each of these bit-mapped integers, users will obtain information describing layer location (both vertically and horizontally), layer type, and the amount of horizontal averaging required for the layer to be detected. Given the accuracy of the CALIPSO altitude registration, the layer locations reported in the VFM appear to be quite accurate. In optically dense layers, the lowest altitude where signal is observed is reported as the base. In actuality, this point may lie well above the true base. In this release, the layers which are reported represent a choice in favor of high reliability over maximum sensitivity. Weakly scattering layers sometimes will go unreported, in the interest of minimizing the number of false positives.
A preliminary version of the algorithm to discriminate cloud and aerosol has been used in this release. Overall, the algorithm performance is fairly good at labeling cloud as cloud and somewhat less successful in labeling aerosol as aerosol. Several types of misclassifications are fairly common and should be watched for. The most common misclassification is portions of dense aerosol layers being labeled as cloud. The algorithm operates on individual profiles, so small regions within an aerosol layer are sometimes labeled as cloud. These misclassifications are often apparent from study of Level 1 browse images. Actual clouds occurring within aerosol layers appear to be correctly classified as cloud most of the time. Additionally, portions of the bases of some cirrus clouds are mislabeled as aerosol, and some tropospheric polar clouds are erroneously labeled as aerosol. Improvements to the cloud/aerosol discrimination algorithm are underway and misclassifications should be greatly reduced in future data releases.
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Page Updated: January 14, 2008
