2B-GEOPROF-LIDAR 001: First Release Issues / Notes

CloudSat DPC — 2007-06-04T18:42:19+01:00

The Cloudsat and Calipso data sets are novel in many respects. Therefore since we are only approximately 1 year into the missions as of this writing, the user of the data must keep in mind the experimental aspect of the data sets and the products derived from them.

Both the Cloudsat and Calipso teams continue to evaluate the data products from which the Radar-Lidar Geometrical Profile Product is derived. Full reprocessing of the data sets is planned by both teams. We summarize here several known issues that users of the Radar-Lidar Geometrical Profile Product should be aware of.

The following is quoted directly from the Calipso Data Quality web site at, http://eosweb.larc.nasa.gov/PRODOCS/calipso/Quality_Summaries/#seeLidarLevel2CloudProfile regarding the Vertical Feature Mask that we use as input to the Radar-Lidar Geometrical Profile Product:

�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. �

Several issues must be kept in mind regarding the Cloudsat Geometrical Profile Product and the Cloudsat data in general. These are discussed in Mace et al. (2007) and Marchand et al. (2007). Additional information can be found at http://www.cloudsat.cira.colostate.edu/dataHome.php

� The minimum detectable signal of the Cloud Profiling Radar is approximately -31 dBZe. Therefore, some fraction of high thin cirrus, and non precipitating water cloud such as altocumulus and continental stratus will be below the detection threshold of the CPR

� Due to reflection from the surface and the 1 km pulse length of the CPR, sensitivities in the lowest 1 km near the surface are reduced. The lowest approximately 500 m of each profile will contain no identifiable hydrometeor signal. Between approximately 500 m and 1 km, hydrometeors can be detected at a reduced sensitivity. Research indicates that the sensitivity between 500 m and 1 km will be largely recovered in reprocessing of the data.

� We make no effort in this product to separate cloud from precipitation.

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Planned resolution: Informational ... no resolution required

2B-GEOPROF-LIDAR 002: CloudFraction missing value is -99

CloudSat DPC — 2007-07-19T20:56:25+01:00

The missing value for CloudFraction is -99. Online documentation and the "missing" attribute in the files incorrectly specify it as -9.

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Planned resolution: TBD

2B-GEOPROF-LIDAR 002: CALIPSO Vertical Feature Mask version change on 1 Mar 2007

CloudSat DPC — 2007-07-19T14:12:58+01:00

On 1 Mar 2007, the CALIPSO lidar vertical feature mask product incremented from version 1.l0 to 1.20. At that time the Goddard Earth Observing System Model Version 5 (GEOS-5) was implemented. GEOS-5 data are used to compute the CALIOP Level 1B data for the 532 nm and 1064 nm calibration constants and their associated uncertainties. See CALIPSO quality statements summary for more detailed information.

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Planned resolution: TBD

2B-GEOPROF-LIDAR issues

2B-GEOPROF-LIDAR 001: First Release Issues / Notes

2B-GEOPROF-LIDAR 002: CloudFraction missing value is -99

2B-GEOPROF-LIDAR 002: CALIPSO Vertical Feature Mask version change on 1 Mar 2007