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Data User’s Guide - Data Product Descriptions - Lidar Level 2 5 km Cloud and Aerosol Profile Products Version 4.20


CALIPSO HOMEUser’s Guide HOMEData Summaries → Lidar Level 2 5 km Cloud and Aerosol Profile Products Version 4.20

Version 4.20 Level 2 Profile Products Description

The CALIPSO Cloud and Aerosol Profile Products report profiles of particle extinction and backscatter and additional profile information (e.g., particulate depolarization ratios) derived from these fundamental products. Layer optical depths are reported in the Cloud and Aerosol Layer Products. The layer optical depths are derived from the same retrievals that are used to compute the extinction and backscatter profiles in the profile products. All of these extinction products are produced using the same basic algorithm (Young and Vaughan, 2009).

The cloud and aerosol profile products are reported at a uniform spatial resolution of 60 m vertically and 5 km horizontally, over a nominal altitude range from 30 km to -0.5 km. Profile data for tropospheric aerosol and stratospheric aerosol are reported in the aerosol profile product, Due to constraints imposed by CALIPSO’s on-board data averaging scheme, the vertical resolution of the aerosol profile data varies as a function of altitude. In the tropospheric region between 20 km to -0.5 km, the aerosol profile products are reported at a resolution of 60 m vertically, and in the stratospheric region (above 20-km), the aerosol profile products are reported at a resolution of 180 m vertically. In the text below we provide brief descriptions of individual data fields reported in the CALIPSO cloud and aerosol profile products. Where appropriate, we also provide an assessment of the quality and accuracy of the data in the current release. Lidar surface retrieval information is reported within the Lidar_Surafce_Detection VGroup.


Data Descriptions

In the text below we provide brief descriptions of individual data fields reported in the CALIPSO cloud and aerosol profile products. Where appropriate, we also provide an assessment of the quality and accuracy of the data in the current release. The data descriptions are grouped into several major categories, as follows:

Additionally all the science data sets (SDSs) are listed in the table to the right, click on the SDS name to go directly to the description.

Science Data Set (SDS)
Latitude
Longitude
Profile_Time
Profile_UTC_Time
Day_Night_Flag
Minimum_Laser_Energy_532
Column_Optical_Depth_Cloud_532
Column_Optical_Depth_Cloud_Uncertainty_532
Column_Optical_Depth_Aerosols_532
Column_Optical_Depth_Aerosols_Uncertainty_532
Column_Optical_Depth_Stratospheric_532
Column_Optical_Depth_Stratospheric_Uncertainty_532
Column_Optical_Depth_Aerosols_1064
Column_Optical_Depth_Aerosols_Uncertainty_1064
Column_Optical_Depth_Stratospheric_1064
Column_Optical_Depth_Stratospheric_Uncertainty_1064
Column_Feature_Fraction
Column_Integrated_Attenuated_Backscatter_532
Column_IAB_Cumulative_Probability
Tropopause_Height
Tropopause_Temperature
Temperature
Pressure
Molecular_Number_Density
Ozone_Number_Density
Relative_Humidity
IGBP_Surface_Type
Surface_Elevation_Statistics
Surface_Top_Altitude_532
Surface_Base_Altitude_532
Surface_532_Integrated_Attenuated_Backscatter
Surface_532_Integrated_Depolarization_Ratio
Surface_532_Integrated_Attenuated_Color_Ratio
Surface_Overlying_Integrated_Attenuated_Backscatter_532
Surface_Peak_Signal_532
Surface_Scaled_RMS_Background_532
Surface_Detection_Flags_532
Surface_Detection_Confidence_532
Surface_Detections_333m_532
Surface_Detections_1km_532
Surface_Top_Altitude_1064
Surface_Base_Altitude_1064
Surface_1064_Integrated_Attenuated_Backscatter
Surface_1064_Integrated_Depolarization_Ratio
Surface_1064_Integrated_Attenuated_Color_Ratio
Surface_Overlying_Integrated_Attenuated_Backscatter_1064
Surface_Peak_Signal_1064
Surface_Scaled_RMS_Background_1064
Surface_Detection_Flags_1064
Surface_Detection_Confidence_1064
Surface_Detections_333m_1064
Surface_Detections_1km_1064
Surface_Winds
Samples_Averaged
Aerosol_Layer_Fraction
Cloud_Layer_Fraction
Atmospheric_Volume_Description
Extinction_QC_Flag_532
Extinction_QC_Flag_1064
CAD_Score
Total_Backscatter_Coefficient_532
Total_Backscatter_Coefficient_Uncertainty_532
Perpendicular_Backscatter_Coefficient_532
Perpendicular_Backscatter_Coefficient_Uncertainty_532
Particulate_Depolarization_Ratio_Profile_532
Particulate_Depolarization_Ratio_Uncertainty_532
Extinction_Coefficient_532
Extinction_Coefficient_Uncertainty_532
Aerosol_Multiple_Scattering_Profile_532
Backscatter_Coefficient_1064
Backscatter_Coefficient_Uncertainty_1064
Extinction_Coefficient_1064
Extinction_Coefficient_Uncertainty_1064
Aerosol_Multiple_Scattering_Profile_1064
Ice_Water_Content_Profile
Ice_Water_Content_Profile_Uncertainty


Column Time Parameters

Profile_Time
Time, expressed in International Atomic Time (TAI). Units are in seconds, starting from January 1, 1993. For the 5 km profile products, three values are reported: the time for the first pulse included in the 15 shot average; the time at the temporal midpoint (i.e., at the 8th of 15 consecutive laser shots); and the time for the final pulse.

Profile_UTC
Similar to Profile Time, but for time expressed in Coordinated Universal Time (UTC), and formatted as 'yymmdd.ffffffff', where 'yy' represents the last two digits of year, 'mm' and 'dd' represent month and day, respectively, and 'ffffffff' is the fractional part of the day.

Day_Night_Flag
Indicates the lighting conditions at an altitude of ~24 km above mean sea level; 0 = day, 1 = night.

Minimum_Laser_Energy_532
This field reports the minimum 532 nm laser pulse energy, in Joules, within each 80 km along-track data segment (80 km = 240 laser pulses). The 80 km distance matches the largest horizontal extent considered in CALIOP’s standard level 2 data analyses. Since layers can be detected at horizontal resolutions as large as 80 km, anomalously low laser energies in coarse resolution upper layers can potentially introduce biases in the spatial and optical property retrievals of underlying layers detected at finer spatial resolutions. The Minimum_Laser_Energy_532 SDS enables ready identification of these problematic situations. See the Data Advisory web page for information on the occurrence of anomalously low laser energy shots, their impact on data quality, and for specific guidance on how to use Minimum_Laser_Energy_532 to identify affected profiles.

Column Geolocation Information

Latitude
Geodetic latitude, in degrees, of the laser footprint. For the 5 km profile products, three values are reported: the footprint latitude for the first pulse included in the 15 shot average; the footprint latitude at the temporal midpoint (i.e., at the 8th of 15 consecutive laser shots); and the footprint latitude for the final pulse.

Longitude
Longitude, in degrees, of the laser footprint. For the 5 km profile products, three values are reported: the footprint longitude for the first pulse included in the 15 shot average; the footprint longitude at the temporal midpoint (i.e., at the 8th of 15 consecutive laser shots); and the footprint longitude for the final pulse.

IGBP_Surface_Type
International Geosphere/Biosphere Programme (IGBP) classification of the surface type at the lidar footprint. The IGBP surface types reported by CALIPSO are the same as those used in the CERES/SARB surface map. The CERES/SARB surface map table is below.

CERES/SARB Surface Map
Surface Index Surface Type   Surface Index Surface Type
1 Evergreen-Needleleaf-Forest   10 Grassland
2 Evergreen-Broadleaf-Forest   11 Wetland
3 Deciduous-Needleleaf-Forest   12 Cropland
4 Deciduous-Broadleaf-Forest   13 Urban
5 Mixed-Forest   14 Crop-Mosaic
6 Closed-Shrublands   15 Permanent-Snow
7 Open-Shrubland (Desert)   16 Barren/Desert
8 Woody-Savanna   17 Water
9 Savanna   18 Tundra

Column Optical Properties

Column_Optical_Depth_Cloud_532
Column_Optical_Depth_Aerosols_532
Column_Optical_Depth_Aerosols_1064
Column_Optical_Depth_Stratospheric_532
Column_Optical_Depth_Stratospheric_1064

Optical depth of all clouds, aerosol, or stratospheric layers within a 5 km column. The optical depths are obtained by integrating the 532 nm cloud/aerosol/stratospheric extinction profile, reported in these profile products. For aerosols and stratospheric layers the optical depth is provided at both 532 and 1064 nm wavelengths.

The column optical depth uncertainties provide the only unique QA indicator for each column optical depth product; no other QA or data quality flags are provided. Therefore, users are strongly encouraged to make use of the Extinction_QC ,CAD_Score, cloud water phase, cloud water phase QA values (both found in the Feature_Classification_Flags in the layer products or the Atmospheric_Volume_Description in the profile products), Column_IAB_Cumulative_Probability, and feature opacity information to make their own quality assessment of the column depths.

The column optical depths are a column integral product. Any large uncertainties or poor extinction retrievals from layers within the column (i.e. clouds, aerosols, or stratospheric features) will propogate downward and may impact the quality of all (i.e. cloud, aerosol, and stratospheric) the column optical depths in the column. The following paragraphs outline notes with regard to specific data products that users should be aware of when using column optical depth data.

Opacity: We remind data users that the CALIPSO lidar is only capable of penetrating to the surface if the total column optical depth is less than ~5. (Note that this value takes into account the contribution of multiple scattering.) If the column is opaque to the lidar, then the reported column optical depths are a measure to the apparent base of the lowest feature observed. Feature opacity can be determined by inspecting the extinction QC flag for the lowest extinction coefficient in any 5-km column; if bit 5 (value = 16) is set then the feature is totally attenuating.

Extinction QC: The extinction QC values in the column should be examined to determine if any of the extinction retrievals were bad. Users are reminded that any poor extinction retrievals in the column may impact the quality of all column optical depths. In general, solutions where the final lidar ratio is unchanged (extinction QC = 0) or the extinction solution is constrained (extinction QC = 1) yield physically plausible solutions more often. Conversely, retrievals tend to be more uncertain in those cases where the lidar ratio for either wavelength must be reduced.

CAD_Score and feature sub-type: Features with low absolute CAD_Scores, "special" CAD_Scores, or uncertain aerosol type classifications may impact the quality of the column optical depths. For example, if the top-most feature in the column has a low absolute CAD_Score it is possible that the assigned lidar ratio may be incorrect; this would impact the extinction retrieval for that feature which would lead to an incorrect rescaling of all the data below that feature.

Cloud phase: If there are clouds in the column that are found to have horizontal oriented ice (HOI) crystals it is likely that the quality of the column optical depths are low. The anomalously high backscatter from HOI clouds generally makes the extinction retrieval more difficult. Because all the data below the HOI cloud is rescaled by the retrieved optical depth, the extinction data below could be suspect.


Column_Optical_Depth_Cloud_Uncertainty_532
Column_Optical_Depth_Aerosols_Uncertainty_532
Column_Optical_Depth_Stratospheric_Uncertainty_532
Column_Optical_Depth_Aerosols_Uncertainty_1064
Column_Optical_Depth_Stratospheric_Uncertainty_1064

Estimated uncertainty in the column optical depth at each wavelength, computed according to the formulas give in the CALIPSO Version 3 Extinction Uncertainty Document (PDF). Ignoring multiple scattering concerns for the moment, errors in column optical depth calculations typically arise from three main sources: signal-to-noise ratio (SNR) within a layer, calibration accuracy, and the accuracy of the lidar ratio specified for use in the solution. Except for constrained solutions, where a lidar ratio estimate can be obtained directly from the attenuated backscatter data, lidar ratio uncertainties are almost always the dominant contributor to optical depth uncertainties, and the relative error in the layer optical depth will always be at least as large as the relative error in the layer lidar ratio.

Calculation of the layer optical depth uncertainty is an iterative process. On some occasions when the SNR is poor, or an inappropriate lidar ratio is being used, the iteration will attempt to converge asymptotically to positive infinity. Whenever this situation is detected, the iteration is terminated, and the layer optical depth uncertainty is assigned a fixed value of 99.99. Any time an uncertainty of 99.99 is reported, the extinction calculation should be considered to have failed. The associated optical depths cannot be considered reliable, and should therefore be excluded from all science studies.

Note: optical depth uncertainties are reported as absolute errors, not relative errors.


Column Integrated Attenuated Backscatter 532
The integral with respect to altitude of the 532 nm total attenuated backscatter coefficients. The limits of integration are from the onset of the backscatter signal at ~40-km, down to the range bin immediately prior to the surface elevation specified by the digital elevation map. This quantity represents the total attenuated backscatter measured within a column. Physically meaningful values of the column integrated attenuated backscatter (hereafter, γ′column) range from ~0.01 sr (completely clear air), to greater than 1.5 sr (e.g., due to anomalous backscatter from horizontally oriented ice crystals; see Hu et al. (Optics Express 15, 2007)).

Column_IAB_Cumulative_Probability
The cumulative probability of measuring a total column integrated attenuated backscatter value equal to the value computed for the current profile. Values in this field range between 0 and 1. The cumulative probability distribution function, shown below in Figure 1, was compiled using all CALIOP total column IAB measurements acquired between 15 June, 2006 and 18 October, 2006.

Figure 3: Distribution of γ′column at 532 nm
Column IAB distribution at 532 nm.

Column Meteorological Data

Tropopause_Height (external)
Mean tropopause height, in kilometers above local mean sea level; derived from the MERRA-2 data product provided to the CALIPSO project by the GMAO Data Assimilation System


Tropopause_Temperature (external)
Mean tropopause temperature, in degrees C; derived from the MERRA-2 data product provided to the CALIPSO project by the GMAO Data Assimilation System


Surface_ Winds (external; aerosol products only)
Provides the mean zonal and meridional component of the surface wind speed computed over the horizontal distance spanned by the averaged profile; units are meters per second.

Profile_Meteorological_Data

Temperature (external)
Mean temperature, in degrees C, reported for the midpoint of each range bin in the profile; derived from the MERRA-2 data product provided to the CALIPSO project by the GMAO Data Assimilation System.


Pressure (external)
Mean pressure, in hectopascals, reported for the midpoint of each range bin in the profile; derived from the MERRA-2 data product provided to the CALIPSO project by the GMAO Data Assimilation System.


Molecular_Number_Density (external)
Mean molecular number density, in molecules per cubic meter, reported for the midpoint of each range bin in the profile; derived from the MERRA-2 data product provided to the CALIPSO project by the GMAO Data Assimilation System.


Ozone_Number_Density (external)
Mean ozone number density, in molecules per cubic meter, reported for the midpoint of each range bin in the profile; derived from the MERRA-2 data product provided to the CALIPSO project by the GMAO Data Assimilation System.


Relative_Humidity (external)
Mean relative humidity, reported for the midpoint of each range bin in the profile; derived from the MERRA-2 data product provided to the CALIPSO project by the GMAO Data Assimilation System

Surface Elevation Statistics

Surface_Elevation_Statistics
Provides the minimum, maximum, mean, and standard deviation of the surface elevation obtained from the GTOPO30 digital elevation map (DEM) for the horizontal distance spanned by the averaged profile; units are kilometers.

Surface_Top_Altitude_532
Surface Top Altitude 1064
Top altitude of the surface return in the 532 nm and 1064 nm channels at the lidar footprint in kilometers above local mean sea level. Contains fill values when surface is not detected. Surface top altitudes are not guaranteed to agree in both channels due to the difference in averaging resolutions at the surface (30 m vs. 60 m at 532 nm and 1064 nm, respectively).

Surface_Base_Altitude_532
Surface_Base_Altitude_1064
Base altitude of the surface return in the 532 nm and 1064 nm channels at the lidar footprint in kilometers above local mean sea level. Contains fill values when surface is not detected. Surface base altitude are not guaranteed to agree in both channels due to the difference in averaging resolutions at the surface (30 m vs. 60 m at 532 nm and 1064 nm, respectively) and also due to the non-ideal detector response in the 532 nm channels which may yield base altitudes much below that of the 1064 nm channel.

Surface Integrated Attenuated Backscatter 532
Vertically integrated Total Attenuated Backscatter 532 nm of the surface return from Surface Top Altitude 532 to Surface Base Altitude 532.

Surface_Integrated_Attenuated_Backscatter_1064
Vertically integrated Attenuated Backscatter 1064 nm of the surface return from Surface Top Altitude 1064 to Surface Base Altitude 1064.

Surface_532_Integrated_Depolarization_Ratio
Depolarization ratio of surface return at 532 nm from Surface Top Altitude 532 to Surface Base Altitude 532, computed as the ratio of vertically integrated Perpendicular Attenuated Backscatter 532 to vertically integrated parallel attenuated backscatter 532 nm.

Surface_1064_Integrated_Depolarization_Ratio
Depolarization ratio of surface return at 532 nm from Surface Top Altitude 1064 to Surface Base Altitude 1064, computed as the ratio of vertically integrated Perpendicular Attenuated Backscatter 532 to vertically integrated parallel attenuated backscatter 532 nm.

Surface_532_Integrated_Attenuated_Color_Ratio
Attenuated color ratio of surface return from Surface Top Altitude 532 to Surface Base Altitude 532, computed as the ratio of vertically integrated Attenuated Backscatter 1064 to vertically integrated Total Attenuated Backscatter 532.

Surface_1064_Integrated_Attenuated_Color_Ratio
Attenuated color ratio of surface return from Surface Top Altitude 1064 to Surface Base Altitude 1064, computed as the ratio of vertically integrated Attenuated Backscatter 1064 to vertically integrated Total Attenuated Backscatter 532.

Surface_Overlying_Integrated_Attenuated_Backscatter_532
Vertically integrated Total Attenuated Backscatter 532 from 40 km to one range bin above Surface Top Altitude 532.

Surface_Overlying_Integrated_Attenuated_Backscatter_1064
Vertically integrated Attenuated Backscatter 1064 from 40 km to one range bin above Surface Top Altitude 1064.

Surface_Detection_Flags_532
Surface_Detection_Flags_1064
Bit-mapped 16-bit integers describing the success of surface detection within the indicated channel, the surface detection method, information about saturated surfaces or surfaces affected by the negative signal anomaly, and diagnostic failure information. Bits are interpreted as follows:
Bit(s) Interpretation
1Surface detected (0 = no, 1 = yes)
2-3Surface detection method; values interpreted as follows
0 = derivative test
1 = multi-shot averaged data test
2 = single shot surface detection fraction test
3 = unused
4-6Is saturated; 532 parallel, 532 perpendicular and 1064, respectively
7-9Has negative signal anomaly; 532 parallel, 532 perpendicular and 1064, respectively
10Derivative method failure: Z(min gradient) < Z(max gradient)
11Derivative method failure: vertical extent exceeds limit
12Derivative method failure: peak signal below threshold
13Failure: vertical separation between 532 and 1064 surface top altitudes exceeds allowable limit
14Failure: surface detected at 1064 nm only, but overlying color ratio below threshold
>15-16Unused

Surface_Detection_Confidence_532
Surface_Detection_Confidence_1064
Not implemented in this release.

Surface_Scaled_RMS_Background_532
Surface_Scaled_RMS_Background_1064
Background noise estimate computed from RMS baseline noise measurements between 65 and 80 km AMSL, rescaled to create a pseudo attenuated backscatter coefficient with units of per kilometer per steradian. The version 4 surface detection algorithm requires the surface signal to exceed the scaled RMS background noise estimate by a multiplicative constant.

Surface_Peak_Signal_532
Surface_Peak_Signal_1064
Maximum attenuated backscatter value of the surface signal within the indicated channel.

Surface_Detections_333m_532
Surface_Detections_333m_1064
Number of single shot profiles (1/3 km resolution) within each 5 km or 1 km resolution profile where surface was detected on the indicated channel.

Surface_Detections_1km_532
Surface_Detections_1km_1064
Number of 1 km resolution profiles within each 5 km resolution profile where surface was detected in the indicated channel.

Feature Spatial Information Within Column

Column_Feature_Fraction
The fraction of the 5-km horizontally averaged profile, between 30-km and the DEM surface elevation, which has been identified as containing a feature (i.e., either a cloud, an aerosol, or a stratospheric layer).

Samples_Averaged
Specifies the number of full resolution samples averaged for each profile range bin; for the purposes of this computation, 'full resolution' is taken to mean 30 meters vertically, and a single shot (~1/3-km) horizontally. Thus a single range bin below an altitude of ~20.2 km (resolution = 60-m vertical, 5-km horizontal) will have at most 480 samples averaged (i.e., for those layers that required 80-km averaging for detection, 240 shots horizontally by two 30-m range bins vertically).

Aerosol_Layer_Fraction
Cloud_Layer_Fraction

Reports the fraction (by area) within each 5 km horizontal * 60 m vertical range bin containing aerosols or clouds in the profile products. The Aerosol and Cloud Layer Fractions are conceptually identical and the same procedure is used to calculate both quantities.

Since the array elements of the profile products can be larger than the native resolution of the extinction retrieval (5 km * 30 m vs. 5 km * 60 m in the lower troposphere), and because atmospheric features can be identified at horizontal resolutions of 1 km and 1/3 km, the atmospheric composition within each profile range bin is not guaranteed to be homogeneous. Thus, the Aerosol and Cloud Layer Fractions report the fraction (by area) of each 5 km * 60 m profile range bin identified as containing aerosols or clouds by the Scene Classification Algorithms. By referencing Cloud Layer Fraction, the fractional amount of cloud clearing performed within each profile range bin of aerosol backscatter and extinction can be determined.

Figure 4: Cloud clearing scenarios for strongly scattering clouds detected at single shot resolution. Red indicates clouds detected at 1/3 km resolution, blue indicates clouds found at 1 km or coarser resolution, yellow indicates an aerosol layer found at 5 km resolution, and white indicates clear air. Scenarios: Clouds embedded in aerosol (upper panel), clouds embedded in clear air (middle panel), and dense clouds embedded in within a weakly scattering cloud layer (lower panel). Each row extends 5 km horizontally and 30 m vertically. Each column extends 1/3 km horizontally.
Cloud/Aerosol Layer fraction example.

Shown in Figure 4 are 3 possible scenarios illustrating how the Cloud Layer Fraction would be reported for each 5 km x 60 m cloud profile range bin. There are at most 30 single shot (1/3 km x 30 m) cloud layers in each 5 km x 60 m cloud profile range bin - fifteen 1/3 km horizontally and two 30 m vertically. In the top panel, red indicates clouds found at 1/3 km resolution and the yellow indicates an aerosol layer found at a 5 km horizontal resolution after the 1/3 km clouds had been removed. In this case, the cloud fraction for the top row would be 11/30 = 0.36. In the middle panel, no features were detected at any coarser spatial resolution after the 1/3 km features were removed. The Atmospheric Volume Description for the 5 km average would report the cell as being "clear air", but the cloud fraction for the top row would still be 11/30 = 0.36. In the lower panel, a cloud was detected in the data remaining after all 1/3 km features had been removed. In this case the cloud fraction would be 1 for all rows shown.

The Aerosol and Cloud Layer Fractions must be values between zero and one, yet both layer fractions are reported as integers between 0 and 30. For example, a value for the Aerosol_Layer_Fraction reported as 11 would indicate a fraction of 11/30 = 0.367.


Atmospheric_Volume_Description

Atmospheric Volume Description is a profile descriptive flag containing the Feature Classification Flags associated with each 5 km x 60 m (or 5 km x 180 m) range bin in the Profile Products. The Feature Classification Flags provide assessments of (a) feature type (e.g., cloud vs. aerosol vs. stratospheric layer); (b) feature subtype; (c) layer ice-water phase (clouds only); and (d) the amount of horizontal averaging required for layer detection. Note that the interpretation of final three bits in the atmospheric volume description (i.e., the averaging required for detection) is slightly different from the interpretation that would be used for the feature classification flags. These differences are summarized in the table below.

Value Atmospheric volume description Feature Classification flag
0 not applicable not applicable
1 5 km 1/3 km
2 20 km 1 km
3 80 km 5 km
4 5 km w/ subgrid feature detected at 1/3 km 20 km
5 20 km w/ subgrid feature detected at 1/3 km 80 km
6 80 km w/ subgrid feature detected at 1/3 km not used
7, 8 not used not used


How profile descriptive flags are stored

Atmospheric Volume Description, CAD Score and Extinction QC [532|1064] are all profile descriptive flags that are stored in the Level 2 Profile Products in the same manner explained here.

Ideally, each profile descriptive flag would be an array of the size [# altitude bins, # profiles] with each array element providing a complete description of the range-resolved atmospheric state. However, because the range resolution of the Level 1 profile data below ~8.3-km is 30 m, and because the feature-finder, scene classification, and extinction algorithms all operate at this finer spatial resolution, providing a genuinely complete description of the atmospheric state for each 60 m Level 2 range bin requires that the profile descriptive flags be stored as 3-D arrays of the size [#profiles, # altitude bins, 2]. The first dimension, [ : , : , 1], corresponds to the standard altitude array of the Profile Products. Thus, below 8.3 km, the first dimension contains the descriptive flags of the higher of the two full resolution (30 m) bins that comprise the single 60 m bin reported in the Profile Products. Meanwhile, below 8.3 km, the second dimension [: , : , 2] contains the descriptive flags for the lower of the two 30 m range bins. Above 8.3 km, where the range resolution of the Level 1 data is 60 m or greater, the descriptive flags for each single 60 m (or 180 m) range bin are replicated in both array elements.

Figure 5: Wholly fictitious but heuristically useful schematic of layer detection results for a data segment extending 80-km horizontally and 480-m vertically. Yellow/orange/brown indicates an aerosol layer detected at horizontal averaging resolutions of, respectively, 80, 20 or 5 km. Shades of blue likewise represent clouds at 80, 20, and 5 km. Red represents a surface detected layer at 5 km, and the white regions are (presumably) clear air, where no features were found. The right-hand side of the figure shows the atmospheric volume descriptor for columns 1 and 16.
Atmospheric volume description example.

Profile QA Information

Extinction_QC_Flag_532
Extinction_QC_Flag_1064

Note that this field is stored in a similar format as the Atmospheric Volume Descriptor.

The extinction QC flags are bit-mapped 16-bit integers, reported for each layer and for each wavelength for which an extinction retrieval was attempted. Aerosol extinction is computed for both wavelengths; cloud extinction is only reported at 532 nm. The information content of each bit is as follows

Bit Value Interpretation
0 0 unconstrained retrieval; initial lidar ratio unchanged during solution process
0 1 constrained retrieval
1 2 Initial lidar ratio reduced to achieve successful full-column solutions
2 4 Suspicious retrieval due to layer or overlying integrated attenuated backscatter being too high or excessive lidar ratio reductions
3 8 Lidar ratio has been reduced and has converged, but backscatter uncertainty solution does not exist
4 16 Layer being analyzed has been identified by the feature finder as being totally attenuating (i.e., opaque)
5 32 Estimated optical depth error exceeds the maximum allowable value
6 64 Negative signal anomaly detected
7 128 Retrieval terminated at maximum iterations for a constrained retrieval
8 256 No solution possible within allowable lidar ratio bounds
9 512 Two-way particulate transmittance has converged but constrained retrieval still not achieved
10 1024 Backscatter coefficients not converging and maximum lidar ratio correction iterations reached
11 2048 Uncertainties not converging and maximum lidar ratio correction iterations achieved
12 4096 Lidar ratio converged but retrieval still not converging
13 8192 Unused
14 16384 Complex retrieval failure (see Young et al., 2009 )
15 32768 Fill value or no solution attempted

The bit assignments are additive, so that (for example) an extinction QC value of 18 represents an unconstrained retrieval (bit 1 is NOT set) for which the lidar ratio was reduced to prevent divergence (+2; bit 2 is set), and for which the feature finder has indicated that the layer is opaque (+16; bit 5 is set). For the version 2.01 release, bits 10-15 are not used. Complete information about the conditions under which each extinction QC bit is toggled can be found in the CALIPSO Extinction Retrieval ATBD (PDF) and in Young et al, 2018.


CAD_Score

Note that this field is stored in a similar format as the Atmospheric Volume Descriptor.

The cloud-aerosol discrimination (CAD) score provides a numerical confidence level for the classification of layers by the CALIOP cloud-aerosol discrimination algorithm. The CAD algorithm separates clouds and aerosols based on multi-dimensional histograms of scattering properties (e.g., intensity and spectral dependence) as a function of geophysical location. In areas where there is no overlap or intersection between these histograms, features can be classified with complete confidence (i.e., |CAD score| = 100). In the current release (version 4) the CAD algorithm uses five-dimensional (5D) probability density functions (PDFs),i.e. layer mean attenuated backscatter at 532 nm, layer-integrated attenuated backscatter color ratio, altitude, latitude and layer-integrated volume depolarization ratio. These PDFs were newly developed to take into account the significantly improved calibration of CALIOP version 4 level 1 data and using a latitude resolution of 5° (as opposed to 10° in earlier versions) leading to an overall improvement in CAD reliability. Detailed descriptions of the CAD algorithm can be found in Sections 4 and 5 of the CALIPSO Scene Classification ATBD (PDF). Further information on the CAD algorithm architecture may be found in Liu et al., 2010, 2009, 2004.

For the profile product, the CAD score for a layer is replicated over the samples spanning the vertical extent of the layer. For a more complete description of CAD score for layers in version 4, the reader is referred to the layer data description.

The standard CAD scores reported in the CALIPSO layer products range between -100 and 100. The sign of the CAD score indicates the feature type: positive values signify clouds, whereas negative values signify aerosols. The absolute value of the CAD score provides a confidence level for the classification. The larger the magnitude of the CAD score, the higher our confidence that the classification is correct. An absolute value of 100 therefore indicates complete confidence. Absolute values less that 100 indicate some ambiguity in the classification; that is, the scattering properties of the feature are represented to some degree in both the cloud PDF and in the aerosol PDF. In this case, a definitive classification cannot be made; that is, although we can provide a "best guess" classification, this guess could be wrong, with a probability of error related to the absolute value of the CAD score. A value of 0 indicates that a feature has an equal likelihood of being a cloud and an aerosol. Users are encouraged to refer to the CAD score when the cloud and aerosol classification results are used and interpreted.

Beginning with the version 2.01 release, several "special" CAD score values have been added. These are listed in the table below. Each of these new values represents a classification result that is based on additional information beyond that normally considered in the standard CAD algorithm.

CAD score Interpretation
-101 Negative mean attenuated backscatter encountered; layer is most likely an artifact, and its spatial and optical properties should be excluded from all science analyses.
101 Initially classified as aerosol, but layer integrated depolarization mandates classifying layer as cloud (version 2 only; obsolete in version 3 and later versions)
102 Layer exhibits very high integrated backscatter and very low depolarization characteristic of oriented ice crystals (version 2 only; obsolete in version 3 and later versions)
103 Layer integrated attenuated backscatter at 532 nm is suspiciously high; feature authenticity and classification are both highly uncertain
104 Boundary layer clouds that were found to be opaque at the initial 5 km horizontal averaging resolution used by the layer detection algorithm; however, these layers are not uniformly filled with high-resolution clouds (i.e., layers detected at a 1/3 km horizontal resolution), and the 532 nm mean attenuated backscatter coefficient of the data that remains after cloud clearing is negative. Studies examining the spatial properties and distributions of clouds can safely include the spatial properties of these layers; however, the associated measured and derived optical properties should be excluded from all science studies.
105 Layer detected at one of the coarser averaging resolutions (20 km or 80 km) for which the initial estimates of measured properties have been negatively impacted by either (a) the attenuation corrections applied to account for the optical depths of overlying layers, or (b) the extension of the layer base altitude are boundary layer clouds that were found to be opaque at the initial 5-km horizontal averaging resolution used by the layer detection algorithm; however, these layers are not uniformly filled with high-resolution clouds (i.e., layers detected at a 1/3 km horizontal resolution), and the 532 nm mean attenuated backscatter coefficient of the data that remains after cloud clearing is negative. Studies examining the spatial properties and distributions of clouds can safely include the spatial properties of these layers; however, the associated measured and derived optical properties should be excluded from all science studies.
106 Suspected fringe of cirrus initially classified as aerosol by the CAD algorithm and subsequently reclassified as no-confidence horizontally oriented ice cloud. These layers are in contact with cirrus (medium or high confidence, randomly or horizontally oriented ice clouds) and have optical properties which make it difficult to distinguish between cloud and aerosol. Due to their proximity to cirrus and low SNR, these "aerosol" layers are more often misclassified cirrus fringes and are thusly reclassified as cloud. Only aerosol layers detected at 20 km and 80 km resolution above 4 km in altitude and having layer centroid temperatures below 0°C are reclassified by the "cirrus fringe amelioration" algorithm.

Profile Extinction and Backscatter Coefficients

Total_Backscatter_Coefficient_532
Backscatter_Coefficient_1064
Particulate total backscatter coefficients reported for each profile range bin in which the appropriate particulates (i.e., clouds or aerosols) were detected; those range bins in which no particulates were detected contain fill values (-9999). Range bins where particulates were detected but the extinction retrieval failed are assigned a fill value of -333.Units are kilometers-1 steradians-1. For the 532 nm data, the particulate total backscatter coefficients are derived from the sum of the parallel and perpendicular backscatter measurements recorded aboard the CALIPSO satellite (i.e., β532 total = β532 parallel + β532 perp).

Total_Backscatter_Coefficient_Uncertainty_532
Total_Backscatter_Coefficient_Uncertainty_1064
Uncertainty in the particulate total backscatter coefficients reported for each profile range bin in which the appropriate particulates were detected; these are absolute uncertainties, not relative, thus the units are identical to the units of the total backscatter coefficients (i.e., kilometers-1 steradians-1); those range bins in which no particulates were detected contain fill values (-9999). Range bins where particulates were detected but the extinction retrieval failed are assigned a fill value of -333. Opaque water cloud uncertainties are assigned fill values of -29. Uncertainties are computed according to the procedures described in the CALIPSO Version 3 Extinction Uncertainty Document (PDF).

Perpendicular_Backscatter_Coefficient_532
Particulate backscatter coefficients derived from the 532 nm perpendicular channel measurements, reported for each profile range bin in which the appropriate particulates (i.e., clouds or aerosols) were detected; those range bins in which no particulates were detected contain fill values (-9999). Range bins where particulates were detected but the extinction retrieval failed are assigned a fill value of -333.Units are kilometers-1 steradians-1.

Perpendicular_Backscatter_Coefficient_Uncertainty_532
Uncertainty in the perpendicular channel backscatter coefficients reported for each profile range bin in which the appropriate particulates were detected; these are absolute uncertainties, not relative, thus the units are identical to the units of the total backscatter coefficients (i.e., kilometers-1 steradians-1); those range bins in which no particulates were detected contain fill values (-9999). Uncertainties are computed according to the procedures described in the CALIPSO Version 3 Extinction Uncertainty Document (PDF).

Extinction_Coefficient_532 (Provisional)
Extinction Coefficient 1064 (Provisional; aerosol products only)
Particulate extinction coefficients reported for each profile range bin in which the appropriate particulates (i.e., clouds or aerosols) were detected; those range bins in which no particulates were detected contain fill values (-9999). Range bins where particulates were detected but the extinction retrieval failed are assigned a fill value of -333. Units are kilometers-1.

Extinction_Coefficient_Uncertainty_532
Extinction_Coefficient_Uncertainty_1064
Uncertainty in the particulate extinction coefficients reported for each profile range bin in which the appropriate particulates were detected; these are absolute uncertainties, not relative, thus the units are identical to the units of the particulate extinction coefficients (i.e., kilometers-1); those range bins in which no particulates were detected contain fill values (-9999). Range bins where particulates were detected but the extinction retrieval failed are assigned a fill value of -333. Opaque water cloud uncertainties are assigned fill values of -29. Uncertainties are computed according to the procedures described in the CALIPSO Version 3 Extinction Uncertainty Document (PDF)

Particulate Depolarization Profiles

Particulate_Depolarization_Ratio_Profile_532
The particulate depolarization ratio, δp(z), is a post-extinction quantity, calculated from ratio of the layer integrated perpendicular and parallel polarization components of particulate backscatter coefficient at a given altitude z, using
Particulate Depol.
Here β⊥,P and β||,P perpendicular and parallel components of particulate backscatter coefficient at 532 nm, respectively. The quality of the estimate for δp is determined not only by the SNR of the backscatter measurements in parallel and perpendicular channels, but also the accuracy of the range-resolved two-way transmittance estimates within the layer. The two-way transmittances due to molecules and ozone can be well characterized via the model data obtained from the GMAO. The two-way transmittances due to particulates, however, are only as accurate as the CALIOP extinction retrieval. Opaque cirrus cloud layers can be particularly prone to errors in the particulate depolarization ratio, as very large attenuation corrections are applied to the weak signals at the base of the layers, and on those occasions where one channel or the other becomes totally attenuated, this situation can generate very large, negative particulate depolarization ratio estimates. For layers that are not opaque, δp is generally reliable. However, in weakly scattering layers, the quality of the daytime estimate can be degraded by a factor of 2-4 due to the larger background noise compared with the nighttime estimate. Range bins where particulates were detected but the extinction retrieval failed are assigned a fill value of -333.

Particulate_Depolarization_Ratio_Uncertainty_532
The uncertainties reported for the particulate depolarization ratios provide an estimate for random error in the particulate depolarization ratio for each range bin (i.e., the ratio of perpendicular and parallel components of retrieved particulate backscatter coefficient within the feature). Based on an assessment of several days of test data (January 1-3, 2007), the uncertainty for aerosol profile products is typically (a median value) ~0.18 and ~0.7 for nighttime and daytime measurements, respectively. For cloud profile products, it is typically ~0.33 and ~0.58 during night and day, respectively. Range bins where particulates were detected but the extinction retrieval failed are assigned a fill value of -333.

Multiple Scattering Profiles

Aerosol_Multiple_Scattering_Profile_532 (aerosol products only)
Aerosol_Multiple_Scattering_Profile_1064 (aerosol products only)
Cloud_Multiple_Scattering_Profile_532 (cloud products only)
The multiple scattering profiles, η532(z) and η1064(z), are specified at each wavelength according to layer type and subtype. Values range between 0 and 1; 1 corresponds to the limit of single scattering only, with smaller values indicating increasing contributions to the backscatter signal from multiple scattering. Multiple scattering effects are different in aerosols, ice clouds, and water clouds. A discussion of multiple scattering factors for ice clouds and several aerosol types can be found in Winker, 2003 (PDF). Multiple scattering in water clouds is discussed in Winker and Poole (1995).

Ice clouds: In Version 3 and earlier, ice clouds were assigned a range-independent multiple scattering factor of η532 = 0.6. In Version 4, the multiple scattering factor is implemented as a sigmoid approximation function of the layer attenuated backscatter centroid temperature, with η532 increasing from 0.46 at 270 K to 0.76 at 190 K. This approximation function was derived from extensive analysis of collocated measurements acquired by the CALIPSO lidar and the CALIPSO IIR, which reconciled observed and theoretical ratios of 532 nm optical depths derived from Version 3 CALIOP measured two-way transmittances to the absorption optical depth retrieved from IIR measurements at 12.05 μm (Garnier et al., 2015). The theoretical ratios are computed assuming severely roughened aggregated columns.

Water clouds: In Version 3 and later versions, ice clouds were assigned a range-independent multiple scattering factor of η532 = 0.6 is used. Based on Monte Carlo simulations of multiple scattering, this value appears to be appropriate for semitransparent water clouds (τ < 1). (It is purely coincidental this is the same value used for ice clouds.) For denser water clouds (τ > 1) the multiply-scattered component of the signal becomes much larger than the single-scattered component, η532 becomes dependent on both cloud extinction and range into the cloud, and the retrieval becomes very sensitive to errors in the multiple scattering factor used. In these cases the multiple scattering cannot be properly accounted for in the current retrieval algorithm and retrieval results are unreliable.

Aerosols: simulations of multiple scattering effects on retrievals of aerosol layer optical depth indicate the effects are small in most cases. There is uncertainty in these estimates, however, due to poor knowledge of aerosol scattering phase functions. Validation comparisons conducted to date do not indicate significant multiple scattering effects on aerosol extinction profile retrievals. Multiple scattering effects may become significant in dense aerosol layers (σ > 1 /km), but in these cases retrieval errors are usually dominated by uncertainties in the lidar ratio or failure to fully penetrate the layer. In version 2 and later, multiple scattering factors for both wavelengths are set to unity.

IWC (Ice Water Content) Profiles

Ice_Water_Content_Profile (cloud products only)

Ice water content (IWC) is reported for all ice clouds with valid extinction retrievals detectedby CALIOP. IWC values of 0.00001.54 gm,-3 account for 99.5% of the values measured by CALIOP, although values up to 10 g/m3 are considered to be physically possible.

Cloud ice water content is a provisional data product that is calculated as a parameterized function of the CALIOP retrieved and interpolated MERRA-2 temperature. This parametrization comes from an emipical relationship derived from aircraft in situ observations, as described in Heymsfield et al., 2014:

(1) IWC(z) = (0.917/3) σ(z) Deff, with Deff = a exp(bT(z))
Here Deff is the effective particle diameter, with empirically derived coefficients a and b are that are derived for three different temperature ranges: For 0 > T > -56 C, a = 308.4 and b = 0.0152; for -56 > T > 71 C, a = 9.1744 x 104 and b = 0.117; and for -71 > T > -85 C, a = 83.3 and b = 0.0184.

Here, σ is the 532 nm volume extinction coefficient in km-1, and c0 = 119 gm-3 and c1 = 1.22 are coefficients derived from an observed empirical relationship between lidar extinction and an extensive set of in situ measurements of cloud particle properties from numerous field campaigns [1]. The relationship between 532 nm extinction and IWC was developed using IWC data between 0-1.0 gm-3 with temperatures between -70 and 0 °C. Cloud ice amount has been shown to vary with temperature, cloud particle size distribution, and by location inside a cloud. A temperature-dependent parameterization is being considered and tested for the next CALIOP data release. The effect of particle size distribution on IWC as seen by CALIOP is also currently being evaluated by comparison with in situ cloud data. Preliminary results show that CALIOP IWC has sufficient spatial resolution and precision to realistically resolve cloud morphology. A more detailed preliminary evaluation of the CALIOP version 3 IWC is available as an ILRC extended abstract [2], which includes CALIOP IWC probability distributions and example browse images. For a brief discussion containing critical information needed to intelligently use CALIOP IWC, please see the "data screening" section, below. Range bins where particulates were detected but the extinction retrieval failed are assigned a fill value of -333.

Resolution
IWC is reported at 60 m vertically, with a horizontal spatial resolution of 5 km along-track, and effectively the width of the laser beam across-track.

Precision
The precision of IWC is directly linked to the precision of the associated extinction retrieval. The precision of the extinction retrieval is ultimately limited by signal-to-noise ratio, and this varies between night and day and according to the overhead two-way 532 nm transmission. Therefore, the precision of CALIOP IWC has to be evaluated for each individual case. The team is currently developing a best-case precision estimate for nighttime high altitude Cirrus clouds.

Accuracy
Because this is a provisional data product, assessment of IWC accuracy is ongoing. This assessment can be approached in two different ways; (1) by establishing the accuracy of the 532 nm extinction and Ice particle area to mass conversion empirical relationship on which it is based, or (2) by assessing the IWC product directly. Direct comparison of CALIOP IWC with other measured IWC values includes evaluates a combination of both the extinction retrieval and the IWC parameterization. The uncertainty reported in the data products is related to the uncertainty in the CALIOP extinction retrieval. If the total IWC uncertainty is needed the user is referred to Heymsfield et al., 2014 for the aircraft data-based uncertainty in the empirical extinction to IWC relationship, and to Molod et al., 2015, for uncertainty in the MERRA-2 interpolated temperature.

Data screening
Users that do not wish to dig more deeply are recommended to use data of type=2 (cloud) and phase=1 (randomly-oriented ice) or 3 (horizontally-oriented ice) with a valid extinction retrieval with extinction QCFlag of 0, 1, 2, 16 or 18, as described above. Valid IWC values are considered to be 0.00001 - 10 g/m3. There is a more detailed discussion of the various factors impacting IWC accuracy, below.

CALIOP IWC is a highly derived data product. Besides the parameterization, it relies on these activities:

Cloud determination (CAD)
Bits 6 and 7 in the atmospheric volume descriptor indicates a feature of type 2=cloud, determined using 5-dimensional probability distribution functions as described above. A CAD "score" higher than 70 indicates "high confidence" in the cloud/aerosol discrimination, although the relationship between "CAD score" and phase confidence is currently under evaluation.

Cloud phase determination
The atmospheric volume descriptor indicates that the cloud phase is 1=randomly oriented ice (ROI) or 3=horizontally oriented ice (HOI) as determined for cloud particles (type=2) primarily using the integrated layer attenuated backscatter coefficient and depolarization. Although extinction is available, IWC is not calculated for cloud particle phase 2=water. Users should use caution with HOI data because the preferred horizontal orientation of ice particles in the 0.3 degree, nadir-viewing data (before November 28, 2007) causes anomalously large backscatter that makes the extinction retrievals more difficult, which in turn may affect the accuracy of the IWC. This problem was much alleviated by tilting the viewing angle to 3 degrees after November, 2007, and also by improvement in the Version 4 extinciton retrievals, so it is not considered to be a problem for the Version 4 data after November 28, 2007.

Extinction retrievals
Users that wish to understand the nuances and details of CALIOP extinction retrievals are referred to the V4 lidar ratio, multiple scattering and extinction discussions, above. The extinction quality flag provides information about the type and reliability of extinction retrievals. Because IWC parameterization relies on accurate extinction retrieval, it is recommended to use IWC only where the extinction retrieval is valid. For this reason, data screening for accurate IWC should follow that for extinction coefficients.


Ice_Water_Content_Profile_Uncertainty (cloud products only)

IWC uncertainty has a range of 0-99.99 gm-3, and is derived directly from the extinction retrieval uncertainty. This is the estimated CALIOP measurement uncertainty, and does not characterize uncertainty in the IWC parameterizationavailable in Heymsfield et al., 2014, or in the interpolated MERRA-2 temperature profile (Molod et al., 2015).

Comparison of CALIOP IWC with direct in situ measurements from various aircraft field campaigns, and is ongoing. A recent evaluation from the ATTREX field campaign is available in Thornberry et al., 2016 (JGR, submitted). Range bins where particulates were detected but the extinction retrieval failed are assigned a fill value of -333.

Future IWC parameterizations may include temperature dependency, based on further in situ data comparisons. Currently suggested temperature-dependant parameterizations do not produce good results for high-altitude tropical clouds [6] and therefore are not used.

File Metadata Parameters

Product_ID
an 80-byte (max) character string specifying the data product name. For all CALIPSO Level 2 lidar data products, the value of this string will be "L2_Lidar".

Date_Time_at_Granule_Start
a 27-byte character string that reports the date and time at the start of the file orbit segment (i.e., granule). The format is yyyy-mm-ddThh:mm:ss.ffffffZ.

Date_Time_at_Granule_End
a 27-byte character string that reports the date and time at the end of the file orbit segment (i.e., granule). The format is yyyy-mm-ddThh:mm:ss.ffffffZ.

Date_Time_at_Granule_Production
This is a 27-byte character string that defines the date at granule production. The format is yyyy-mm-ddThh:mm:ss.ffffffZ.

Number_of_Good_Profiles
This is a 32-bit integer specifying the number of good attenuated backscatter profiles contained in the granule.

Number_of_Bad_Profiles
This is a 32-bit integer specifying the number of bad attenuated backscatter profiles contained in the granule.

Initial_Subsatellite_Latitude
This field reports the first subsatellite latitude of the granule.

Initial_Subsatellite_Longitude
This field reports the first subsatellite longitude of the granule.

Final_Subsatellite_Latitude
This field reports the last subsatellite latitude of the granule.

Final_Subsatellite_Longitude
This field reports the last subsatellite longitude of the granule.

Orbit_Number_at_Granule_Start
This field reports the orbit number at the granule start time.

Orbit_Number_at_Granule_End
This field reports the orbit number at the granule stop time.

Orbit_Number_Change_Time
This field reports the time at which the orbit number changes in the granule.

Path_Number_at_Granule_Start
This field reports the path number at the granule start time.

Path_Number_at_Granule_End
This field reports the path number at the granule stop time.

Path_Number_Change_Time
This field reports the time at which the path number changes in the granule.

Lidar_Level_1_Production_Date_Time
For each CALIOP Lidar Level 2 data product, the Lidar Level 1 Production Date Time field reports the file creation time and date for the CALIOP Level 1 lidar data file that provided the source data used in the Level 2 analyses.

Number_of_Single_Shot_Records_in_File
for internal use only

Number_of_Average_Records_in_File
for internal use only

Number_of_Features_Found
for internal use only

Number_of_Cloud_Features_Found
for internal use only

Number_of_Aerosol_Features_Found
for internal use only

Number_of_Indeterminate_Features_Found
for internal use only

Lidar_Data_Altitude
This field defines the lidar data altitudes (583 range bins) to which Lidar Level 1 profile products are registered.

GEOS_Version
This is a 64-byte character that reports the version of the GEOS data product provided by the GMAO.

Classifier_Coefficients_Version_Number
Version number of the classifier coefficients file that stores the five-dimensional probability distribution functions used by the cloud-aerosol discrimination (CAD) algorithm

Classifier_Coefficients_Version_Date
Creation date of the classifier coefficients file that stores the five-dimensional probability distribution functions used by the cloud-aerosol discrimination (CAD) algorithm

Production_Script
Provides the configuration information and command sequences that were executed during the processing of the CALIOP Lidar Level 2 data products. Documentation for many of the control constants found within this field is contained in the CALIPSO Lidar Level 2 Algorithm Theoretical Basis Documents


Data Quality Statements

Lidar Level 2 Cloud and Aerosol Profile Information
Half orbit (Night and Day) lidar cloud and aerosol profile data and ancillary data
Release Date Version Data Date Range Production Strategy
October 10, 2018
Standard Data
4.20 June 13, 2006 to present Standard
November 8, 2016
Standard Data
4.10 June 13, 2006 to May 31, 2018 Standard

Summary Statement for the release of the CALIPSO LIDAR Level 2 Products Version 4.20, October 10, 2018

View Detailed V4.20 Quality Statement.

Summary Statement for the release of the CALIPSO LIDAR Level 2 Products Version 4.10, November 08, 2016

View Detailed V4.10 Quality Statement.

NASA
Last Updated: October 01, 2021
Curator: Charles R. Trepte
NASA Official: Charles R. Trepte

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