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CALIPSO: Data User's Guide - Data Product Description - Lidar Level 3 Cloud Occurrence Monthly Product Version 1.00


CALIPSO HOMECALIPSO User’s Guide HOMEData Products Descriptions → Lidar Level 3 Cloud Occurrence Monthly Product

Introduction

The lidar level 3 cloud occurrence product reports global distributions of cloud occurrence by counts on a uniform spatial grid. At each grid, the number of detected ice cloud samples is also reported as a histogram of ice cloud layer optical depth. All level 3 parameters are derived from the CALIPSO version 4.10 level 2 5 km merged layer and 5 km cloud profile products, with a temporal arrogation of one month.

Three level 3 data files are generated each month depending on lighting conditions: day time only, night time only, and both day and night.

Resolution and Coverage

The level 3 cloud occurrence product reports monthly aggregation of cloud occurrence. Granules straddling two consecutive months have been examined carefully to make sure each portion has been included in the corresponding month.

Table 1 lists the spatial and coverage of this product. They are specially designed to be compatible with other level 3 cloud and aerosol products. The spatial resolution for level 3 cloud occurrence product is 2.5° longitude by 2.0° latitude and 60 m altitude. For level 3 ice cloud product, it is 2.5° longitude by 2.0° latitude and 120 m altitude. And for level 3 aerosol product, it is 5.0° longitude by 2.0° latitude and 60 m altitude. All products start to count from the same lower altitude boundary. Level 3 cloud occurrence product and ice cloud product have the same altitude coverage. All level 3 ice cloud products have a higher upper altitude boundary than L3 aerosol product does, i.e., 20.2 km vs. 12.0 km. More details could be found in the Detailed Quality Statement web page.

Table 1: The spatial coverage and resolution of L3 ice cloud product.
Spatial Coverage Spatial Resolution
360° longitude (180° W to 180° E) 2.5° longitude
170° latitude (85° S to 85° N) 2.0° latitude
-0.5 km to 20.2 km altitude 60 m vertical

Other than reporting the cloud occurrence in count for different cloud phase and opacity, ice clouds count is also reported as a histogram of the layer optical depth in each three-dimensional (3D) grid. Accordingly, this parameter is described as four-dimensional (4D) array.

Table 2 summarizes the dimensions of the science data sets which are described as two-dimensional (2D), 3D or 4D arrays depending on their purpose.

Table 2: Number of dimensions and dimension lengths of science data sets of L3 cloud occurrence product.
Number of
Dimensions
Dimension Lengths
2-D No. of latitudes bins x No. of longitude bins 85 x 144
3-D No. of latitude bins x No. of longitude bins x No. of altitude bins 85 x 144 x 344
4-D No. of latitude bins x No. of longitude bins x No. of altitude bins x No. of OD bins 85 x 144 x 344 x 7

Level 2 Input Data

The version 1.00 of L3 cloud occurrence product are processed from V4.10 level 2 5 km merged layer and 5 km cloud profile products as shown in the following Table 3.

Table 3: Lidar level 2 input data for level 3 cloud occurrence product V1.00.
Level 2 Version Data Date Range
V4.10 June 2006 - December 2016

Due to an elevated frequency of low energy shots within and near the Southern Atlantic Anomaly region since late May 2017, all level 3 products including this level 3 cloud occurrence product have been stopped processing after December 2016. The lidar science working group is currently working on understanding how this issue might affect all levels of CALIPSO product. The level 3 cloud occurrence products will be updated later.

Data Descriptions

In the text below we provide brief descriptions of individual data fields reported in the CALIPSO Level 3 cloud occurrence 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)
Longitude_Midpoint
Latitude_Midpoint
Altitude_Midpoint
Pressure_Mean
Pressure_Standard_Deviation
Temperature_Mean
Temperature_Standard_Deviation
Relative_Humidity_Mean
Relative_Humidity_Standard_Deviation
Tropopause_Height_Mean
Tropopause_Height_Standard_Deviation
DEM_Surface_Elevation_Minimum
DEM_Surface_Elevation_Maximum
DEM_Surface_Elevation_Median
Snow_Ice_Surface_Mean
Snow_Ice_Surface_Standard_Deviation
Snow_Ice_Surface_Minimum
Snow_Ice_Surface_Maximum
Snow_Ice_Surface_Median
Land_Surface_Samples
Water_Surface_Samples
Days_Of_Month_Observed
Lidar_Surface_Subsurface_Samples
Totally_Attenuated_Samples
Cloud_Free_Samples
Cloud_Samples
Cloud_Rejected_Samples
Cloud_Accepted_Samples
Unknown_Cloud_Transparent_Samples
Unknown_Cloud_Opaque_Samples
Water_Cloud_Transparent_Samples
Water_Cloud_Opaque_Samples
Ice_Cloud_Transparent_Samples
Ice_Cloud_Opaque_Samples
Ice_Cloud_Optical_Depth_Histogram

In the following we provide brief descriptions of individual data fields reported in the cloud occurrence product.



Spatial Coordinates

Longitude_Midpoint (1-D array)
Units: degree (°)
Format: Float_32
Fill Value: -9999.0000
Valid range: -180.0...180.0
Definition: Longitude at the grid cell midpoint.

Latitude_Midpoint (1-D array)
Units: degree (°)
Format: Float_32
Fill Value: -9999.0000
Valid range: -85.0...85.0
Definition: Latitude at the grid cell midpoint.

Altitude_Midpoint (1-D array)
Units: kilometer (km)
Format: Float_32
Fill Value: -9999.0000
Valid range: -0.5...20.2
Definition: Altitude at the grid cell midpoint.

Meteorological Context

Pressure_Mean (external) (3-D array)
Units: hectopascal (hPa)
Format: Float_32
Fill Value: -9999.0000
Valid range: 1.0...1086.0
Definition: Mean of all pressures reported within the latitude/longitude/altitude grid cell derived from the Modern Era Retrospective-Analysis for Research (MERRA-2) reanalysis product provided to the CALIPSO project by the GMAO Data Assimilation System.

Pressure_Standard_Deviation (external) (3-D array)
Units: hPa
Format: Float_32
Fill Value: -9999.0000
Valid range: 0.0...50.0
Definition: Standard deviation of all pressures reported within the latitude/longitude/altitude grid cell derived from the Modern Era Retrospective-Analysis for Research (MERRA-2) reanalysis product provided to the CALIPSO project by the GMAO Data Assimilation System.

Temperature_Mean (3-D array)
Units: degrees C
Format: Float_32
Fill Value: -9999.0000
Valid range: -120.0...60.0
Definition: Mean of all temperature reported within the latitude/longitude/altitude grid cell derived from the Modern Era Retrospective-Analysis for Research (MERRA-2) reanalysis product provided to the CALIPSO project by the GMAO Data Assimilation System.

Temperature_Standard_Deviation (external) (3-D array)
Units: degrees C
Format: Float_32
Fill Value: -9999.0000
Valid range: 0.0...30.0
Definition: Standard deviation of all temperature reported within the latitude/longitude/altitude grid cell derived from the Modern Era Retrospective-Analysis for Research (MERRA-2) reanalysis product provided to the CALIPSO project by the GMAO Data Assimilation System.

Relative_Humidity_Mean (3-D array)
Units: NoUnits
Format: Float_32
Fill Value: -9999.0000
Valid range: 0.0...1.5
Definition: Mean of all relative humidity reported within the latitude/longitude/altitude grid cell derived from the Modern Era Retrospective-Analysis for Research (MERRA-2) reanalysis product provided to the CALIPSO project by the GMAO Data Assimilation System.

Relative_Humidity_Standard_Deviation (external) (3-D array)
Units: NoUnits
Format: Float_32
Fill Value: -9999.0000
Valid range: 0.0...0.80
Definition: Standard deviation of all relative humidity reported within the latitude/longitude/altitude grid cell derived from the Modern Era Retrospective-Analysis for Research (MERRA-2) reanalysis product provided to the CALIPSO project by the GMAO Data Assimilation System.

Tropopause_Height_Mean (external) (2-D array)
Units: km
Format: Float_32
Fill Value: -9999.0000
Valid range: 4.0...22.0
Definition: Mean of all tropopause reported within the latitude/longitude/altitude grid cell derived from the Modern Era Retrospective-Analysis for Research (MERRA-2) reanalysis product provided to the CALIPSO project by the GMAO Data Assimilation System.

Tropopause_Height_Standard_Deviation (external) (2-D array)
Units: km
Format: Float_32
Fill Value: -9999.0000
Valid range: 0.0...5.0
Definition: Standard deviation of all tropopause reported within the latitude/longitude/altitude grid cell derived from the Modern Era Retrospective-Analysis for Research (MERRA-2) reanalysis product provided to the CALIPSO project by the GMAO Data Assimilation System.

Surface and Over-flight Parameters

Science data sets derived from models or data sources other than the CALIPSO are marked as “external”.

DEM_Surface_Elevation_Minimum (external) (2-D array)
Units: kilometer (km)
Format: Float_32
Fill Value: -9999.0000
Valid range: -1.0...9.0
Definition: Minimum of surface elevation for all columns reported in the latitude/longitude grid cell above local mean sea level obtained from the GTOPO30 digital elevation map (DEM).

DEM_Surface_Elevation_Maximum (external) (2-D array)
Units: kilometer (km)
Format: Float_32
Fill Value: -9999.0000
Valid range: -1.0...9.0
Definition: Maximum of surface elevation for all columns reported in the latitude/longitude grid cell above local mean sea level obtained from the GTOPO30 digital elevation map (DEM).

DEM_Surface_Elevation_Median (external) (2-D array)
Units: kilometer (km)
Format: Float_32
Fill Value: -9999.0000
Valid range: -1.0...9.0
Definition: Median of surface elevation for all columns reported in the latitude/longitude grid cell above local mean sea level obtained from the GTOPO30 digital elevation map (DEM).

Snow_Ice_Surface_Mean (external) (2-D array)
Units: percentage (NoUnits)
Format: Float_32
Fill Value: -9999.0000
Valid range: 0.0...100.0
Definition: Mean of snow/sea ice coverage reported within the latitude/longitude grid cell, in percentage; derived from the Near-real-time Ice and Snow Extent data set provided by the National Snow & Ice Data Center. Snow and Permanent ice-covered regions are considered as 100% coverage. For mixed pixels at coastlines which are unable to reliably apply microwave retrieval algorithm, they are ignored. Refer to the Level 3 Cloud Occurrence Detailed Quality Summary for more details.

Snow_Ice_Surface_Standard_Deviation (external) (2-D array)
Units: percentage (NoUnits)
Format: Float_32
Fill Value: -9999.0000
Valid range: 0.0...100.0
Definition: Standard deviation of snow/sea ice coverage reported within the latitude/longitude grid cell, in percentage; derived from the Near-real-time Ice and Snow Extent data set provided by the National Snow & Ice Data Center. Snow and Permanent ice-covered regions are considered as 100% coverage. For mixed pixels at coastlines which are unable to reliably apply microwave retrieval algorithm, they are ignored. Refer to the Level 3 Cloud Occurrence Detailed Quality Summary for more details.

Snow_Ice_Surface_Minimum (external) (2-D array)
Units: percentage (NoUnits)
Format: Float_32
Fill Value: -9999.0000
Valid range: 0.0...100.0
Definition: Minimum of snow/sea ice coverage reported within the latitude/longitude grid cell, in percentage; derived from the Near-real-time Ice and Snow Extent data set provided by the National Snow & Ice Data Center. Snow and Permanent ice-covered regions are considered as 100% coverage. For mixed pixels at coastlines which are unable to reliably apply microwave retrieval algorithm, they are ignored. Refer to the Level 3 Cloud Occurrence Detailed Quality Summary for more details.

Snow_Ice_Surface_Maximum (external) (2-D array)
Units: percentage (NoUnits)
Format: Float_32
Fill Value: -9999.0000
Valid range: 0.0...100.0
Definition: Maximum of snow/sea ice coverage reported within the latitude/longitude grid cell, in percentage; derived from the Near-real-time Ice and Snow Extent data set provided by the National Snow & Ice Data Center. Snow and Permanent ice-covered regions are considered as 100% coverage. For mixed pixels at coastlines which are unable to reliably apply microwave retrieval algorithm, they are ignored. Refer to the Level 3 Cloud Occurrence Detailed Quality Summary for more details.

Snow_Ice_Surface_Median (external) (2-D array)
Units: percentage (NoUnits)
Format: Float_32
Fill Value: -9999.0000
Valid range: 0.0...100.0
Definition: Mean of snow/sea ice coverage reported within the latitude/longitude grid cell, in percentage; derived from the Near-real-time Ice and Snow Extent data set provided by the National Snow & Ice Data Center. Snow and Permanent ice-covered regions are considered as 100% coverage. For mixed pixels at coastlines which are unable to reliably apply microwave retrieval algorithm, they are ignored. Refer to the Level 3 Cloud Occurrence Detailed Quality Summary for more details.

Land_Surface_Samples (external) (2-D array)
Units: count (NoUnits)
Format: Int_32
Fill value: -9999
Valid range: 0...65535
Definition: Number of 5 km profiles within the latitude/longitude grid cell having surface type at the middle-point lidar footprint of each 5 km profile classified as land (all surface types other than 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_Surface_Samples (external) (2-D array)
Units: count (NoUnits)
Format: Int_32
Fill value: -9999
Valid range: 0...65535
Definition: Number of 5 km profiles within the latitude/longitude grid cell having surface type at the middle-point lidar footprint of each 5 km profile classified as land (all surface types other than 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)
Units: NoUnits
Format: UInt_32
Fill value: 0
Valid range: 0...4294967295
Definition: The days of month observed flags are bit-mapped 32-bit floats indicating which calendar days of the month CALIPSO made observations within the 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. Refer to the Level 3 Aerosol Data Product Description for details.

Sampling Counts

Lidar_Surface_Subsurface_Samples (3-D array)
Units: count (NoUnits)
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Number of lidar-detected surface or subsurface samples in the latitude/longitude/altitude grid cell. If the lidar surface is detected, the subsurface goes from the lidar-detected surface down to the lower vertical range which is around -0.5 km.

Totally_Attenuated_Samples (3-D array)
Units: count (NoUnits)
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Number of totally attenuated samples, in counts, in the latitude/longitude/altitude grid cell. If the lidar surface is not detected due to an optically thick cloud in a 333-m column, the region between the base of the bottom cloud layer and lower vertical range (~ -0.5 km) is considered as totally attenuated samples.

Cloud_Free_Samples (3-D array)
Units: count (NoUnits)
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Number of cloud free samples in the latitude/longitude/altitude grid cell. It includes clear sky or aerosol features.

Cloud_Samples (3-D array)
Units: count (NoUnits)
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Number of cloud samples in the latitude/longitude/altitude grid cell.

Cloud_Rejected_Samples (3-D array)
Units: count (NoUnits)
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Number of cloud samples failed to pass the quality control filters in the latitude/longitude/latitude grid cell. Information about the quality filters could be find on the Level 3 Cloud Occurrence Detailed Quality Summary.

Cloud_Accepted_Samples (3-D array)
Units: count (NoUnits)
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Number of cloud samples passed the quality control filters in the latitude/longitude/latitude grid cell. Information about the quality filters could be find on the Level 3 Cloud Occurrence Detailed Quality Summary.

Unknown_Cloud_Transparent_Samples (3-D array)
Units: count (NoUnits)
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Number of transparent unknown phase or not determined cloud samples in the latitude/longitude/altitude grid cell.

Unknown_Cloud_Opaque_Samples (3-D array)
Units: count (NoUnits)
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Number of opaque unknown phase or not determined cloud samples in the latitude/longitude/altitude grid cell.

Water_Cloud_Transparent_Samples (3-D array)
Units: count (NoUnits)
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Number of transparent water cloud samples in the latitude/longitude/altitude grid cell.

Water_Cloud_Opaque_Samples (3-D array)
Units: count (NoUnits)
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Number of opaque water cloud samples in the latitude/longitude/altitude grid cell.

Ice_Cloud_Transparent_Samples (3-D array)
Units: count (NoUnits)
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Number of transparent ice cloud samples in the latitude/longitude/altitude grid cell.

Ice_Cloud_Opaque_Samples (3-D array)
Units: count (NoUnits)
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Number of opaque ice cloud samples in the latitude/longitude/altitude grid cell.

Ice_Cloud_Optical_Depth_Histogram (4-D array)
Units: count (NoUnits)
Boundaries: Optical Depth<0.01; 0.01<=Optical Depth<0.03; 0.03<=Optical Depth<0.10; 0.10<=Optical Depth<0.30; 0.30<=Optical Depth<1.00; Optical Depth>=1.00 & Transparent; Reserved
Format: Int_16
Fill value: -9999
Valid range: 0...32767
Definition: Histogram of ice clouds samples binned by the layer optical depth (OD) in the latitude/longitude/latitude grid cell. It describes numbers of ice clouds at a specific OD range at a specific spatial grid. There are seven optical depth ranges:
  • OD < 0.01
  • 0.01 <= OD < 0.03
  • 0.03 <= OD < 0.10
  • 0.10 <= OD < 0.30
  • 0.30 <= OD < 1
  • OD >= 1 but transparent and opaque
More details about the OD ranges could be find on the Level 3 Cloud Occurrence Detailed Quality Summary.

File Metadata Parameters

Product_ID
Units: no unit (NoUnits)
Format: Char
Valid range: CAL_LID_L3_Cloud_Occurrence
Definition: An 80-byte maximum character string specifying the data product name.

Date_Time_of_Production
Units: no unit (NoUnits)
Format: Char
Valid range: 4/2006 - 12/2026
Definition: A 27-byte character string that defines the date at granule production. The format is yyyy-mm-ddThh:mm:ssZ.

Nominal_Year_Month
Units: no unit (NoUnits)
Format: Char
Valid range: 200606 - present
Definition: A six-digit integer indicating the year and month when data within the level 3 file was measured by CALIPSO in the format yyyymm.

Program_Configuration
Units: no unit (NoUnits)
Format: Char
Valid range: N/A
Definition: This parameter contains the contents of the runtime program configuration file. The file controls the sizes of dimensions used by the program, the cloud quality filter parameters, and an input file check.

Number_of_Level2_Files_Analyzed
Units: no unit (NoUnits)
Format: UInt_16
Valid range: 0...900
Definition: Number of level 2 granules analyzed to generate this level 3 ice cloud file.

Number_of_Bad_333m_Profiles
Units: no unit (NoUnits)
Format: UInt_16
Valid range: 0...65,535
Definition: Number of bad 333 m profiles excluded from aggregation. Due to a single shot feature detection bug in the level 2 algorithm, there are single shots with overlapped feature layers which are not allowed. These single shots including their parent detection have been removed from statistics. Please refer to Level 3 Cloud Occurrence Detailed Quality Statement for more explanations.

Number_of_Bad_5km_Profiles
Units: no unit (NoUnits)
Format: UInt_16
Valid range: 0...65,535
Definition: Number of 5 km bad profiles excluded from aggregation. On rare occasions, there are 5 km feature free or transparent columns (no indication of opacity from Opacity_Flag) but without detected lidar surface from the level 2 algorithm. Please refer to Level 3 Cloud Occurrence Detailed Quality Statement for more explanations.

List_of_Input_MLay_Files
Units: no unit (NoUnits)
Format: Char
Valid range: N/A
Definition: List of included granules of level 2 5 km merged layer product to generate this level 3 cloud occurrence file. In the V1.00 data product, the list of all granules (including both day and night) is incomplete due to a limit on the total number of bytes that could be written to a single VData record. This limit could probably be caused by the Python library or HDF 4 library/specification. The development team is working on solving this issue. If a user would like to knkow the comprehensive list of input files used to produce the *A.hdf, please combine the lists from *D.hdf and *N.hdf of the corresponding month.

List_of_Input_CPro_Files
Units: no unit (NoUnits)
Format: Char
Valid range: N/A
Definition: List of included granules of level 2 5 km cloud profile data product to generate this level 3 cloud occurrence file. In the V1.00 data product, the list of all granules (including both day and night) is incomplete due to a limit on the total number of bytes that could be written to a single VData record. This limit could probably be caused by the Python library or HDF 4 library/specification. The development team is working on solving this issue. If a user would like to knkow the comprehensive list of input files used to produce the *A.hdf, please combine the lists from *D.hdf and *N.hdf of the corresponding month.




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

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