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CALIPSO: Data User's Guide - Data Product Descriptions - Lidar Level 3 Aerosol Profile Monthly Product


CALIPSO HOMECALIPSO User's Guide HOMEData Products Description → Lidar Level 3 Aerosol Profile Monthly Product

Introduction

The CALIPSO lidar level 3 aerosol profile product reports monthly mean profiles of aerosol optical properties on a uniform spatial grid. This is a tropospheric product that reports averaged values at altitudes below 12km. All level 3 parameters are derived from the version 3 CALIOP level 2 aerosol profile product and are quality screened prior to averaging. Eight level 3 data files are generated each month depending on sky condition and lighting condition (night and day are reported separately). Each monthly product set will be available around the middle of the following month.

View the Lidar Level 3 DETAILED for this data product at: http://www-calipso.larc.nasa.gov/resources/calipso_users_guide/data_summaries/l3/CALIOP_L3Products_3-00_v01.php

Organization of Level 3 Files

In order to keep level 3 file sizes manageable, eight different types of level 3 files are produced for eight unique combinations of sky conditions and lighting conditions (i.e., day vs. night).

Aerosol Data Files Produced
Sky Condition Lighting Condition
All Sky Night, Day
Cloud-Free Night, Day
Cloudy-Sky, Transparent Night, Day
Cloudy-Sky Opaque Night, Day

Statistics are reported in separate files corresponding to the relevant sky condition and lighting condition. Sky conditions describe the cloud occurrence frequency and location within the level 2 columns that are aggregated by level 3. There are four varieties of sky condition:

Description of the Four Sky Conditions
Sky Condition Description of Level 2 Data Usage
All Sky All level 2 columns are averaged, regardless of cloud occurrence
Cloud-Free Only cloud-free level 2 columns are averaged
Cloudy-Sky, Transparent Only level 2 columns containing transparent clouds are averaged
Cloudy-Sky Opaque Only level 2 columns containing opaque clouds are averaged

For the purposes of the level 3 aerosol product, clouds detected at 5 km horizontal resolution or greater are used for screening; i.e., cloud-free columns do not contain clouds found at 5 km or coarser resolution, but they may contain clouds found at 1/3 km and 1 km horizontal resolution. These higher resolution clouds have been removed by the boundary layer cloud clearing algorithm prior to computing aerosol layer properties. Note that aerosol properties are never reported within clouds in any CALIPSO data product.

Temporal and Spatial Resolution

Statistics are aggregated with a temporal resolution of one month and are reported on an equal-angle grid with the following specifications.

Temporal and Spatial Resolution
Spatial Coverage Spatial Resolution
360° longitude (180°W to 180°E) 5° longitude
170° latitude (85°N to 85°S) 2° latitude
-0.5 km to 12 km altitude 60 m vertical

Based on the resolution of the grid above, level 3 quantities are reported in arrays having two, three, or four dimensions. The following table lists the sizes of all arrays of 2 dimensions or greater, excluding aerosol type distribution and aerosol spatial distribution arrays. Those arrays have similar dimensionality as the 3-D and 4-D arrays below, except the final dimension length depends on the purpose of the array. See product descriptions of those arrays for size descriptions.

Level 3 Array Sizes
Number of Dimensions Dimension Lengths
2-D num. latitudes x num. longitudes
(85 x 72)
3-D num. latitudes x num. longitudes x num. altitudes
(85 x 72 x 208)
4-D num. latitudes x num. longitudes x num. altitudes x num. percentiles *
(85 x 72 x 208 x 11)
* Number of percentiles is 11 because it contains the minimum, maximum, and the 10th, 20th, 30th, -, 90th percentiles.

Level 2 Input Data

The following table lists the versions of the level 2 data used as input for the version 3.00 level 3 aerosol profile product.

CALIPSO Lidar Level 2 Input Data For Level 3 Aerosol Profile Product, V3.00
Level 2 Version Data Date Range
3.30 March 2013 - present
3.02 November 2011 - February 2013
3.01 June 2006 - October 2011

Quality Screening Strategy

Prior to generating level 3 statistics, all level 2 aerosol profile extinction samples are quality screened using filters designed to eliminate samples and layers that were detected or classified with very low confidence or that have untrustworthy extinction retrievals. Quality filters are described below along with a preliminary assessment of their impact on the reported level 3 statistics. A paper describing the justification of these filters in-depth along with detailed sensitivity analyses is in preparation.

  • CAD Score Filter. Only aerosol layers having cloud-aerosol discrimination (CAD) scores between -100 and -20 are used. Layers with CAD scores between 20 and -20 are often the result of erroneous layer detection triggered by noise.

    The lower confidence boundary of -20 was selected empirically by generating level 3 averages for one month of level 2 data and performing a sensitivity study to assess the dependence of the number of layers rejected, the average extinction, and the propagated extinction uncertainties on the CAD score limit. This study revealed that varying the CAD threshold between -60 and -20 does little to remove large or negative extinction outliers or to reduce the propagated uncertainty. However, allowing aerosol layers with CAD scores closer to 0 does allow large and negative outliers into the extinction averages and increases the uncertainty.

    Examination of the relationship between CAD score and layer IAB QA factor and also the frequency distribution of CAD scores and (Figures 7 and 8 of the level 2 aerosol layer data quality summaries) show that this behavior is expected because low confidence CAD scores typically occur beneath optically thick layers and because there are relatively fewer layers with medium confidence CAD scores (-80 to -20) compared to low and high confidence CAD scores.

    Consequence for level 3: Since dust layers tend to have better CAD scores than other aerosol types, this filter removes fewer aerosol layers over the regions where dust is prevalent compared to regions of the world containing other aerosol types.

  • Extinction QC Flag Filter. Only aerosol layers having extinction QC flag values of 0, 1, 16, or 18 are allowed. Extinction QC flag values of 16 and 18 correspond to layers classified as opaque where, in the former case, the retrieval completes successfully without adjusting the initial lidar ratio, and in the latter case, the lidar ratio is reduced to prevent the retrieval from diverging to infinity. Aerosol layers having extinction QC flag set to any other value are ignored since these retrievals show a greater propensity to exhibit erroneously large or negative values compared to aerosol layers with extinction QC = 0, 1, 16, or 18.
     
  • Aerosol Extinction Uncertainty Filter. Only samples where aerosol extinction uncertainty is less than 99.9 km-1 are allowed. Uncertainty of 99.9 is a flag value assigned by the retrieval algorithm when the extinction uncertainty estimate has begun to diverge to infinity while iterating down the profile. In this case the retrieval results become unreliable and we exclude aerosol samples having extinction uncertainty equal to 99.9 and all aerosol samples at lower altitudes in the same profile since the untrustworthy extinction solution is propagated to lower altitudes as the retrieval proceeds downward.

    Sensitivity studies were conducted to assess if a more restrictive extinction uncertainty threshold is appropriate to reduce the occurrence of extinction outliers. For extinction uncertainty thresholds less than about 5 km-1 (uncertainty is expressed as an absolute uncertainty, not a relative uncertainty), we found that the propagated uncertainty had indeed been reduced, but the shape of level 3 mean extinction profiles had also changed in the lowest altitudes. This is because uncertainty increases at lower altitudes because errors are propagated from above. As a result, samples with relatively large aerosol extinction are selectively removed and the mean extinction is reduced in the lowest altitudes. To avoid changing the shape of the average extinction profile, all aerosol extinction uncertainty values are allowed except the flag value above (uncertainty = 99.9 km-1). Fortunately, just removing these samples reduces the number of extinction and extinction uncertainty outliers existing in level 3 statistics significantly.

  • Isolated 80 km Layer Filter. Detection of layers averaged to 80 km is occasionally triggered by anomalous noise spikes, likely due to high energy particles impacting the lidar detectors. Aerosol layers detected at 80 km horizontal resolution that are not adjacent (either vertically or horizontally) to another aerosol layer and do not contain an embedded aerosol layer are excluded from quality screened level 3 statistics. Requiring that another aerosol layer is adjacent improves the confidence that a real aerosol layer exists in the region. These isolated 80 km layers tend to occur at higher altitudes and to have very low extinction values. Therefore excluding them removes sporadic extinction values which can be significant in the upper troposphere, but have little impact on the column AOD.
     
  • Filter For Misclassified Cirrus. Occasionally, the tenuous edges of cirrus clouds are misclassified as aerosol by the CALIPSO Cloud Aerosol Discrimination algorithm as shown in Figure 1 below. This happens most often for layers detected at 80 km horizontal resolution, and for these tenuous features noise can cause a weak cloud layer to appear to have an aerosol signature. Therefore if an aerosol layer appears adjacent to an ice cloud, the aerosol layer is assumed to be misclassified cloud and is rejected.
    Figure 1: Missclassified Cloud.
    Figure 1. CALIPSO level 2 vertical feature mask example showing where the fringe of cirrus clouds have been misclassified as aerosol. Orange, light blue, and green features have been classified as aerosol, cloud, and surface, respectively.

    In order to remove these from level 3 statistics, aerosol layers above 4 km in altitude that are adjacent to an ice cloud (ice/water phase is randomly oriented or horizontally oriented) having cloud top temperature less than 0°C are excluded prior to computing level 3 statistics. Since this problem seems to occur much more frequently with ice clouds than with water clouds, this test is not applied to aerosol layers adjacent to water clouds.

  • Undetected Surface Attached Aerosol Low Bias Filter. At times the CALIPSO feature detection algorithm may not detect the entire vertical extent of surface attached aerosol layers. Often aerosol bases are assigned at 30 - 90 meters above the local surface due to overlying attenuation. If the aerosol base extension algorithm is invoked, the base is assigned to 90 meters above the local surface by default. This results in a low bias in the mean extinction profiles near the surface since "clear air" extinction is assumed to be 0.0 km-1 and undetected aerosol with non-zero extinction likely exists beneath these assigned bases.

    In order to avoid a low bias in level 3 mean aerosol extinction, for each level 2 profile, samples classified as "clear air" lying beneath the lowest quality screened aerosol layer whose base is below 250 meters are excluded from level 3 statistics; i.e., these values are not assumed to have clear air extinction of 0.0 km-1; they are ignored.

  • Negative Signal Anomaly Mitigation. A phenomenon dubbed a “negative signal anomaly” sometimes occurs when the level 1B attenuated backscatter becomes anomalously negative at the onset of an abrupt target such as the planetary surface or a dense cloud. Aerosol extinction can also become anomalously negative when attenuated backscatter affected by the anomaly is included within the extinction retrieval. Subsequent level 3 mean extinction would therefore exhibit a low bias near the surface where the negative signal anomaly is present. To mitigate the impact of this anomaly, all level 2 aerosol extinction within 60 meters of the planetary surface are excluded from level 3 calculations in version 3. Note that filters 8 and 9 below are carry-overs from version 1 of the level 3 product which were designed to eliminate surface contamination that arises in part due to the negative signal anomaly. Since level 2 aerosol extinction is excluded near the surface in version 3, filters 8 and 9 will have no impact. They are retained in version 3 because they may be useful in future versions of level 3 after level 2 extinction profiles have been corrected for the negative signal anomaly. In the meantime, their impact is benign.
     
  • Large Negative Near-Surface Extinction Filter. Surface contamination in level 2 aerosol extinction can manifest itself as very large negative extinction values for samples adjacent to the local surface. To reduce the effects of surface contamination in level 3 data, all level 2 aerosol extinction samples adjacent to the surface having a value less than -0.2 km-1 are ignored and not used in the computation of level 3 statistics.
     
  • Surface Contamination Beneath Surface-Attached Opaque Layer Filter. Surface contamination can also occur in level 2 aerosol extinction when an opaque layer is adjacent to the surface. For a transparent surface-attached aerosol layer, the feature finder typically assigns the layer base altitude one range bin above the surface as determined by the lidar surface elevation (please consult Section 3.2 of the CALIPSO Feature Detection ATBD (PDF) for a detailed description of how layer base is determined as it is much more sophisticated than is described here). However if the surface attached layer is opaque, then the feature finder assigns the layer base altitude as the nearest range bin in the standard CALIPSO lidar altitude array above the DEM surface elevation. If the nearest CALIPSO range bin is below the true surface altitude, surface contamination occurs. It has been noticed that one occurrence of this error can bias the AOD of an entire level 3 grid cell. Preliminary analysis reveals that this issue occurs primarily over the southern oceans at night, though occurrence over land has not been quantified.

    The following filter was implemented in order to remove these surface contaminated samples: all level 2 aerosol samples belonging to opaque aerosol layers at altitudes beneath the maximum DEM surface elevation having extinction > 2 km-1 that have increased in magnitude by more than 10 times when compared to the extinction at one range bin higher in altitude are excluded when computing level 3 statistics.

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    Data Descriptions

    In the text below we provide brief descriptions of individual data fields reported in the CALIPSO vertical feature mask product. 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) Data Maturity
    Longitude Midpoint NA
    Latitude Midpoint NA
    Altitude Midpoint NA
    Pressure Mean external
    Pressure Standard Deviation external
    Temperature Mean external
    Temperature Standard Deviation external
    Relative Humidity Mean external
    Relative Humidity Standard Deviation external
    Tropopause Height Minimum external
    Tropopause Height Maximum external
    Tropopause Height Median external
    Tropopause Height Mean external
    Tropopause Height Standard Deviation external
    Meteorological Profiles Averaged Provisional
    Surface Elevation Minimum external
    Surface Elevation Maximum external
    Surface Elevation Median external
    Land Samples external
    Water Samples external
    Days of Month Observed Provisional
    Initial Aerosol Lidar Ratio 532 Provisional
    Initial Aerosol Lidar Ratio Uncertainty 532 Provisional
    Extinction 532 Mean [Dust, Polluted Dust, Smoke] Provisional
    Extinction 532 Standard Deviation [Dust, Polluted Dust, Smoke] Provisional
    Extinction 532 Percentiles Provisional
    AOD Mean [Dust, Polluted Dust, Smoke] Provisional
    AOD 63 Percent Below Provisional
    AOD 90 Percent Below Provisional
    Samples Searched Provisional
    Samples Averaged [Dust, Polluted Dust, Smoke] Provisional
    Samples Aerosol Detected Accepted [Dust, Polluted Dust, Smoke] Provisional
    Samples Aerosol Detected Rejected [Dust, Polluted Dust, Smoke] Provisional
    Samples Cloud Detected Provisional
    Aerosol Type Provisional
    Multiple Aerosol Type Count Provisional
    Number Layers Per Column [Dust, Polluted Dust, Smoke] Provisional
    Highest Aerosol Layer Detected [Dust, Polluted Dust, Smoke] Provisional
    Lowest Aerosol Layer Detected [Dust, Polluted Dust, Smoke] Provisional
    Layer Separation Minimum [Dust, Polluted Dust, Smoket] Provisional
    Layer Separation Maximum [Dust, Polluted Dust, Smoke] Provisional
    Layer Separation Median [Dust, Polluted Dust, Smoke] Provisional
    Layer Separation Mean [Dust, Polluted Dust, Smoke] Provisional
    Layer Separation Standard Deviation [Dust, Polluted Dust, Smoke] Provisional


    Spatial Coordinates

    Longitude Midpoint (1-D array)
    Longitude, in degrees, at the latitude/longitude/altitude grid cell midpoint.

    Latitude Midpoint (1-D array)
    Latitude, in degrees, at the latitude/longitude/altitude grid cell midpoint.

    Altitude Midpoint (1-D array)
    Altitude, in kilometers, at the latitude/longitude/altitude grid cell midpoint.

    Meteorological Context

    Pressure Mean (external) (3-D array)
    Pressure Standard Deviation (external) (3-D array)
    Mean and standard deviation of all pressures reported within the latitude/longitude/altitude grid cell in hectopascals; derived from the GEOS-5 data product provided to the CALIPSO project by the GMAO Data Assimilation System.

    Temperature Mean (3-D array)
    Temperature Standard Deviation (external) (3-D array)
    Mean and standard deviation of all temperatures reported within the latitude/longitude/altitude grid cell in degrees C; derived from the GEOS-5 data product provided to the CALIPSO project by the GMAO Data Assimilation System.

    Relative Humidity Mean (3-D array)
    Relative Humidity Standard Deviation (external) (3-D array)
    Mean and standard deviation of all relative humidity reported within the latitude/longitude/altitude grid cell, in percent; derived from the GEOS-5 data product provided to the CALIPSO project by the GMAO Data Assimilation System.

    Tropopause Height Minimum (external) (2-D array)
    Tropopause Height Maximum (external) (2-D array)
    Tropopause Height Median (external) (2-D array)
    Topopause Height Mean (external) (2-D array)
    Tropopause Height Standard Deviation (external) (2-D array)
    Statistics of all tropopause heights reported within the latitude/longitude grid cell in kilometers above local mean sea level; derived from the GEOS-5 data product provided to the CALIPSO project by the GMAO Data Assimilation System.
    Meteorological Profiles Averaged (2-D array)
    Number of 5 km horizontal resolution meteorological profiles averaged within the latitude/longitude grid cell.

    Surface Elevation and Overflight Parameters

    Surface Elevation Minimum (external) (2-D array)
    Surface Elevation Maximum (external) (2-D array)
    Surface Elevation Median (external) (2-D array)
    Surface elevation statistics for all columns reported in the latitude/longitude grid cell in kilometers above local mean sea level, obtained from the GTOPO30 digital elevation map (DEM).

    Land Samples (external) (2-D array)
    Number of columns within the latitude/longitude grid cell having surface type at the lidar footprint classified as land (i.e., not water) by the International Geosphere/Biosphere Programme (IGBP). The IGBP surface types reported by CALIPSO are the same as those used in the CERES/SARB surface map.

    Water Samples (external) (2-D array)
    Number of columns within the latitude/longitude grid cell having surface type at the lidar footprint classified as water by the International Geosphere/Biosphere Programme (IGBP). The IGBP surface types reported by CALIPSO are the same as those used in the CERES/SARB surface map.

    Days of Month Observed (2-D array)
    The days of month observed flags are bit-mapped 32-bit floats indicating which calendar days of the month CALIPSO made observations within a latitude/longitude grid cell. Bits are set to true when CALIPSO makes an observation on that calendar day with the least significant bit corresponding to the first day of the month. Bit 1 is the least significant bit.

    For example, if CALIPSO made an observation within a grid cell on the 1st day of the month, then bit 1 would be set to true and if CALIPSO made an observation on the 2nd day of the month, then bit 2 would be set to true and so on. Based on CALIPSO"s orbit, a grid cell at the equator would have much fewer days set to true than a grid cell near the poles.


    Figure 2: days of month flag interpretation.
    Figure 2. Example of how to interpret Days of Month flag.

    Static Lidar Ratio Parameters

    Initial Aerosol Lidar Ratio 532 (1-D array)
    Initial Aerosol Lidar Ratio Uncertainty 532 (1-D array)
    Indicates estimated initial lidar ratios used in the level 2 retrievals, and their uncertainties, for each aerosol subtype in units of steradians. Retrieving aerosol extinction, backscatter and optical depth from CALIPSO measurements requires an estimate of the particulate extinction-to-backscatter ratio, known as the "lidar ratio". These initial estimates are based on the aerosol subtype of the layer being analyzed. The six values reported correspond to the six aerosol type that the automated classification system identifies: clean marine, dust, polluted continental, clean continental, polluted dust, and smoke, respectively. More information on the rationale for these estimates and their errors is discussed in the Lidar Level 2 Cloud and Aerosol Layer Products Quality Statements.

    Aerosol Optical Parameters

    Extinction 532 Mean [Dust] (3-D array)
    Extinction 532 Standard Deviation [Dust] (3-D array)
    Extinction 532 Median [Dust] (3-D array)
    Extinction 532 Skew [Dust] (3-D array)
    Extinction 532 RMS [Dust] (3-D array)
    Extinction 532 Percentiles [Dust] (4-D array)
    Vertical profiles of mean, standard deviation, median, skew, and RMS error for all quality screened lidar level 2 aerosol profile extinction coefficients reported with the latitude/longitude/altitude grid cell in units of km-1, except skew which is unitless. Percentiles are 11-element arrays with the first value containing the minimum quality screened aerosol extinction coefficient within the grid cell and the last containing the maximum. Intermediate elements specify aerosol extinction coefficients corresponding to percentiles between 10% (element 2) and 90% (element 10). If the parameter name ends with "Dust", then only aerosol layers classified as dust are used to compute statistics. Otherwise, all aerosol species are included in the statistics. Example profiles of level 3 aerosol extinction statistics and percentiles are shown in Figure 3.

    In computing extinction statistics, regions identified as "clear air" by the feature finder are assumed to have an aerosol extinction coefficient of 0.0 km-1. This results in an underestimate of mean extinction, but we believe the low bias is small in most cases at night. During daytime, the low bias may be larger where layers are not detected due to solar noise and high-albedo surfaces. This is being addressed in initial validation studies.

    Figure 3: extinction profile example.
    Figure 3. Example profiles of extinction statistics for a single latitude/longitude grid cell (left) and the percentiles of extinction for the altitude bin at 4 km in the same latitude/longitude grid cell (right). The maximum surface altitude of the grid cell is also labeled in the left panel; grey shading is a reminder that samples within 180 meters of the maximum surface altitude and below should be ignored.

    AOD Mean [Dust, Polluted Dust, Smoke] (2-D array)
    Mean aerosol optical depth (AOD), calculated as the vertical integral of level 3 mean aerosol extinction coefficients.

    AOD 63 Percent Below (2-D array)
    AOD 90 Percent Below (2-D array)
    Altitude in kilometers below which contains 63% or 90% of the total mean aerosol optical depth in the level 3 grid cell.

    Sample Counting Statistics

    Users may want to spatially or temporally aggregate these level 3 data. Therefore, the sample numbers required to correctly aggregate the statistics are included.

    Samples Searched (3-D array)
    Reports the total number of atmospheric measurements made in each latitude/longitude/altitude grid cell, regardless of whether they were accepted, rejected, or ignored. It can be thought of as the number of chances that CALIOP had to measure an atmospheric feature. As such, range bins beneath the surface and range bins beneath opaque layers do not contribute to this number since CALIOP did not have a chance to measure beneath these features. Level 3 sample numbers are reported based on a 5 km horizontal x 30 meter vertical resolution grid to match resolution at which layers are reported in the level 2 aerosol and 5 km cloud layer products.

    Samples Averaged [Dust, Polluted Dust, Smoke] (3-D array)
    Reports the number of samples contributing to the mean, standard deviation, and skew of aerosol extinction coefficients in each latitude/longitude/altitude grid cell. In computing these statistics, regions identified as "clear air" are assumed to have an aerosol extinction coefficient of 0.0 km-1. Therefore, the number of samples averaged includes both the aerosol extinction coefficients passing all quality assurance filtering criteria and the number of "clear air" extinction values in the grid cell. Level 3 sample numbers are reported based on a 5 km horizontal x 30 meter vertical resolution grid to match resolution at which layers are reported in the level 2 aerosol and 5 km cloud layer products.

    Samples Aerosol Detected Accepted [Dust, Polluted Dust, Smoke] (3-D array)
    Reports the number of aerosol samples in each latitude/longitude/altitude grid cell that were detected and passed all quality assurance filtering criteria. However, this is not the number of samples that contributes to extinction and AOD statistics (excluding RMS uncertainty) because clear air extinction samples are included in those calculations (see Samples Averaged, above). For the case of RMS uncertainty, this is the number of samples used because only uncertainties from detected aerosol layers passing all quality assurance filtering criteria are propagated into level 3 RMS uncertainties. Level 3 sample numbers are reported based on a 5 km horizontal x 30 meter vertical resolution grid to match resolution at which layers are reported in the level 2 aerosol and 5 km cloud layer products.

    Samples Aerosol Detected Rejected [Dust, Polluted Dust, Smoke] (3-D array)
    Reports the number of aerosol samples in each latitude/longitude/altitude grid cell that were detected but failed to pass our filtering criteria. These samples are ignored in all statistical calculations. Level 3 sample numbers are reported based on a 5 km horizontal x 30 meter vertical resolution grid to match resolution at which layers are reported in the level 2 aerosol and 5 km cloud layer products.

    Samples Cloud Detected (3-D array)
    Reports the number of 5 km x 30 m resolution range bins that are entirely cloudy (cloud layer fraction equals 100%) occurring in each latitude/longitude/altitude grid cell. Level 3 sample numbers are reported based on a 5 km horizontal x 30 meter vertical resolution grid to match resolution at which layers are reported in the level 2 aerosol and 5 km cloud layer products.

    Aerosol Type Distribution

    Aerosol Type (4-D array)
    Histogram of aerosol type for each latitude/longitude/altitude grid cell. This array of six integers counts the number of aerosol samples having the CALIPSO aerosol type clean marine, dust, polluted continental, clean continental, polluted dust, and smoke, respectively for each latitude/longitude/altitude grid cell. Therefore this array has size num. latitudes x num. longitudes x num. altitudes x num. aerosol types (85 x 72 x 208 x 6).

    Multiple Aerosol Type Count (3-D array)
    Histogram documenting occurrence of multiple aerosol types in each latitude/longitude grid cell. Each element of this 7-element array records the number of instances for which N different aerosol types were detected in the individual level 2 aerosol profiles within each latitude/longitude grid cell. N ranges from 0 (no aerosol detected in a column) to 6 (all six of the CALIPSO aerosol types were detected in a single column). Therefore this array has size num. latitudes x num. longitudes x num. aerosol types detected (85 x 72 x 7).

    Aerosol Spatial Distribution

    Number Layers Per Column [Dust, Polluted Dust, Smoke] (3-D array)
    Histogram of the number of aerosol layers detected in the level 2 data products for each latitude/longitude grid cell. The first element of this 9-element array records the number of columns having zero aerosol layers. Similarly, the second element records the number of columns having one aerosol layer, and so on. The ninth array element records the number of columns having eight or more aerosol layers detected. Therefore this array has size num. latitudes x num. longitudes x num. aerosol detected (85 x 72 x 9).

    Highest Aerosol Layer Detected [Dust, Polluted Dust, Smoke] (3-D array)
    Distribution of highest aerosol layer top altitudes detected within each latitude/longitude grid cell in units of kilometers, reported as percentile arrays. Percentiles are 11-element arrays with the first value containing the minimum layer top altitude within the grid cell and the last containing the maximum. Intermediate elements specify layer top altitudes corresponding to percentiles between 10% (element 2) and 90% (element 10). Therefore this array has size num. latitudes x num. longitudes x num. percentiles (85 x 72 x 11).

    Lowest Aerosol Layer Detected [Dust, Polluted Dust, Smoke] (3-D array)
    Distribution of lowest aerosol layer base altitudes detected within each latitude/longitude grid cell in units of kilometers, reported as percentile arrays. Percentiles are 11-element arrays with the first value containing the minimum layer base altitude within the grid cell and the last containing the maximum. Intermediate elements specify layer base altitudes corresponding to percentiles between 10% (element 2) and 90% (element 10). Therefore this array has size num. latitudes x num. longitudes x num. percentiles (85 x 72 x 11).

    Layer Separation Minimum [Dust, Polluted Dust, Smoke] (3-D array)
    Layer Separation Maximum [Dust, Polluted Dust, Smoke] (3-D array)
    Layer Separation Median [Dust, Polluted Dust, Smoke] (3-D array)
    Layer Separation Mean [Dust, Polluted Dust, Smoke] (3-D array)
    Layer Separation Standard Deviation [Dust, Polluted Dust, Smoke] (3-D array)
    Minimum, maximum, median, mean, and standard deviation of vertical separation distances between all detected aerosol layers in all columns within each latitude/longitude grid cell in units of kilometers. Layer separation is defined as the vertical distance between two aerosol layers that are separated by either clear air or cloud. Since there are can be more than two aerosol layers in a column, layer separation statistics are reported using 7-element arrays where the first element reports the separation statistics for columns where two aerosol layers are detected, the second element reports separation statistics for columns where three aerosol layers are detected, and so on. The seventh and last element reports separation statistics for columns where eight or more layers aerosol layers are detected. Therefore this array has size num. latitudes x num. longitudes x num. layers (85 x 72 x 7).

    File Metadata Parameters

    Product ID
    An 80-byte (max) character string specifying the data product name. For all CALIPSO lidar level 3 aerosol data products, the first portion of this string will be "CAL_LID_L3_APro_" and the final portion of the string will indicate the sky condition, "AllSky" or "CloudFree", "CloudySkyTransparent", or "CloudySkyOpaque".

    Nominal Year Month
    A six digit integer indicating the year and month when data within the level 3 file was measured by CALIPSO in the format yyyymm.

    Number of Level 2 Files Analyzed
    Integer indicating the number of level 2 granules analyzed to generate the level 3 file.

    Earliest Input Filename
    A 160-byte (max) character string specifying the filename of the first (by calendar day and time) level 2 aerosol profile granule analyzed within the month of the level 3 file.

    Latest Input Filename
    A 160-byte (max) character string specifying the filename of the last (by calendar day and time) level 2 aerosol profile granule analyzed within the month of the level 3 file.

    Data Screening Script Filename
    A 160-byte (max) character string specifying the filename of the script containing configuration information and command sequences that were executed during the processing of the CALIPSO lidar level 3 data product.

    Data Screening Script File Contents
    A 5000-byte (max) character string containing configuration information and command sequences that were executed during the processing of the CALIPSO lidar level 3 data product. These commands define spatial boundaries and implement quality filters and are described by in-line documentation.




NASA
Last Updated: November 22, 2021
Curator: Charles R. Trepte
NASA Official: Charles R. Trepte

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