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CALIPSO HOMEUser’s Guide HOMEData Products Description → Lidar Level 2 Blowing Snow - Antarctica Version 1.00 Monthly Product

CALIPSO: Data User’s Guide - Data Product Descriptions - Lidar Level 2 Blowing Snow - Antarctica Version 1.00 Monthly Product


Version 1.00 Lidar Level 2 Blowing Snow - Antarctica Monthly Product Description

The Blowing Snow monthly data product is a new technique for the detection of blowing snow events determined from CALIOP lidar atmospheric attenuated backscatter measurements to obtain the spatial and temporal frequency, layer height, and optical depth of blowing snow events over Antarctica for 2006 through the present.


Data Descriptions

In the text below we provide brief descriptions of individual data fields reported in the CALIPSO blowing snow - Antarctica monthly 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)
Land_Water_Mask
Solar_Zenith_Angle
Surface_Temperature
Surface_Type_IGBP
Surface_Type_NSIDC
Surface_Wind_Direction
Surface_Wind_Speed
Latitude
Longitude
Profile_UTC_Time
Blowing_Snow_Backscatter_Profile
Blowing_Snow_Color_Ratio_Profile
Blowing_Snow_Depol_Profile
Blowing_Snow_Layer_Average_Color_Ratio
Blowing_Snow_Layer_Average_Depolarization
Blowing_Snow_Layer_Confidence_Flag
Blowing_Snow_Layer_Depth
Blowing_Snow_Layer_Optical_Depth
Blowing_Snow_Layer_Strength
Diamond_Dust_Flag
Ground_Bin_Altitude_Index
Ground_Signal_Backscatter
Ground_Signal_Elevation
Max_Blowing_Snow_Layer_Backscatter
Max_Blowing_Snow_Layer_Backscatter_Altitude
Observation_Grid
Blowing_Snow_Frequency_Grid
Surface_Integrated_Attenuated_Backscatter_532
Surface_Overlying_Integrated_Attenuated_Backscatter_532
Surface_Peak_Signal_532
Surface_Top_Altitude_532


Ancillary Fields Parameters


Land_Water_Mask
Units: No Units
Format: Int_16
Fill Value:
Valid Range: 0...7
Definition: This is an 8-bit integer indicating the surface at the laser footprint, with
  • 0 - shallow ocean;
  • 1 = land;
  • 2 = coastlines;
  • 3 = shallow inland water;
  • 4 = intermittent water;
  • 5 = deep inland water;
  • 6 = continental ocean;
  • 7 = deep ocean.

Solar_Zenith_Angle
Units: deg
Format: Float_32
Fill Value:
Valid Range: 0.0...180.0
Definition: This is the angle, in degrees, between the zenith at the lidar footprint on the surface and the line of sight to the sun.

Surface_Temperature
Units: °C
Format: Float_32
Fill Value:
Valid Range: -95.0...13.0
Definition: Temperature, in degrees C, reported for surface altitude recorded in the Met Data Altitudes field. Temperature values are obtained from the ancillary meteorological data provided by the GMAO.

Surface_Type_IGBP
Units: No Units
Format: Int_16
Fill Value:
Valid Range: 1...18
Definition: International Geosphere/Biosphere Programme (IGBP) classification of the surface type at the laser footprint. The IGBP surface types reported by CALIPSO are the same as those used in the CERES/SARB surface map.

Surface_Type_NSIDC
Units: No Units
Format: Int_16
Fill Value:
Valid Range: 0.0...255.0
Definition: Snow and ice coverage for the surface at the laser footprint. This data comes from the Air Force Weather Agency (AFWA). For all releases prior to version 4, data was obtained from the National Snow and Ice Data Center (NSIDC).

Surface_Wind_Direction
Units: deg
Format: Float_32
Fill Value:
Valid Range: 0.0...360.0
Definition: Surface wind direction in degrees are calculated from the ancillary meteorological data provided by the MERR-2.

Surface_Wind_Speed
Units: m·s-1
Format:
Fill Value:
Valid Range: 0.0...33.0
Definition: Surface wind speeds, in meters per second. Surface wind speed values are calculated from the ancillary meteorological data provided by the MERR-2.

Geolocation Fields Parameters


Latitude
Units: deg
Format: Float_32
Fill Value:
Valid Range: -90.0...90.0
Definition: Geodetic latitude, in degrees, of the laser footprint on the Earth’s surface.

Longitude
Units: deg
Format: Float_32
Fill Value:
Valid Range: -180.0...180.0
Definition: Longitude, in degrees, of the laser footprint on the Earth’s surface.

Profile_UTC_Time
Units: No Units
Format: Float_32
Fill Value:
Valid Range: 60,426.0...261,231.0
Definition: This field reports the Coordinated Universal Time (UTC), 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.

Snow Fields Parameters


Blowing_Snow_Backscatter_Profile
Units: sr-1
Format: Float_32
Fill Value:
Valid Range: N/A
Definition: The total attenuated backscatter at 532 nm, Β′532 from one bin below the ground return for 33 altitude bins above (34x#records)

Blowing_Snow_Color_Ratio_Profile
Units: No Units
Format: Float_32
Fill Value:
Valid Range: 0.0...2.0
Definition: The ratio of Attenuated Backscatter 1064 to Total Attenuated Backscatter 532. from one bin below the ground return for 33 altitude bins above (34x#records)

Blowing_Snow_Depol_Profile
Units: No Units
Format: Float_32
Fill Value:
Valid Range: 0.0...1.0
Definition: Depolarization ratio of Perpendicular Attenuated Backscatter 532 to parallel attenuated backscatter 532 nm. from one bin below the ground return for 33 altitude bins above (34x#records)

Blowing_Snow_Layer_Average_Color_Ratio
Units: No Units
Format: Float_32
Fill Value:
Valid Range: 0.0...2.0
Definition: The average color ratio calculated from the color ratio profile (average of 34 bins)

Blowing_Snow_Layer_Average_Depolarization
Units: No Units
Format: Float_32
Fill Value:
Valid Range: 0.0...1.0
Definition: The average depolarization calculated from the depolarization profile (average of 34 bins)

Blowing_Snow_Layer_Confidence_Flag
Units: No Units
Format: Int_16
Fill Value:
Valid Range: -2...7
Definition: The blowing snow confidence flag for each record is the sum of all the non-negative values stored in the blow snow confidence array. The higher the value, the higher the confidence in the blowing snow layer.

The blowing snow confidence array example:

Bsc(0) = -2 - probable diamond dust
Bsc(0) = -1 - probable low cloud
Bsc(0) = 1 - probable blowing snow layer
Bsc(1) = 1 - backscatter ratio of top bin within layer to first bin above ground < 0.5
Bsc(2) = 1 - ratio of average backscatter strength within blowing snow layer to blowing snow threshold > 1.5 and layer depth > 50 m
Bsc(3) = 1 - 10 m wind speed > 6 m/s and layer depth > 50 m
Bsc(4) = 1 - surface elevation (as determined from DEM) > 0.0 and 10 m wind speed > 7 m/s
Bsc(5) = 1 - blowing snow layer depth > 30 m and < 350 m
Bsc(6) = 1 - average layer 532 depolarization > 0.25 and layer average color ratio > 0.8

Blowing_Snow_Layer_Depth
Units: m
Format: Float_32
Fill Value:
Valid Range: 0.0...600.0
Definition: Blowing snow layer depth in meters

Blowing_Snow_Layer_Optical_Depth
Units: No Units
Format: Float_32
Fill Value:
Valid Range: 0.0...18.0
Definition: Estimated optical depth blowing snow layer

Blowing_Snow_Layer_Strength
Units: No Units
Format: Float_32
Fill Value:
Valid Range: 0.0...96.19
Definition: Calculated from the average layer 532nm backscatter / the blowing snow threshold

Diamond_Dust_Flag
Units: No Units
Format: Int_16
Fill Value:
Valid Range: 0...1
Definition: Set to 1 for the following conditions: snow layer greater than 600m thick or layer greater than 400m and the ratio of 532nm backscatter at layer top to ground return less than 0.0 or greather than 0.80

Ground_Bin_Altitude_Index
Units: No Units
Format: Int_16
Fill Value:
Valid Range: 300...582
Definition: Index into the Altitude array for the ground bin

Ground_Signal_Backscatter
Units: sr-1
Format: Float_32
Fill Value:
Valid Range: -0.84...22.15
Definition: Total backscatter at 532nm at ground bin

Ground_Signal_Elevation
Units: km
Format: Float_32
Fill Value:
Valid Range: -0.1568...4.124
Definition: DEM elevation of the ground signal return

Max_Blowing_Snow_Layer_Backscatter
Units: sr-1
Format: Float_32
Fill Value:
Valid Range: -0.022...2.7644
Definition: Maximum 532 nm total backscatter signal within the layer

Max_Blowing_Snow_Layer_Backscatter_Altitude
Units: m
Format: Float_32
Fill Value:
Valid Range: 0.0...570.0
Definition: DEM elevation of the max 532 nm total backscatter signal

Observation_Grid
Units: count
Format: Float_32
Fill Value:
Valid Range: N/A
Definition: 360x180 1 degree grids

Blowing_Snow_Frequency_Grid
Units: count
Format: Float_32
Fill Value:
Valid Range: N/A
Definition: 360x180x9 grid
Contains the monthly blowing snow layer occurrence in each 1x1 degree grid
Blow_Snow_Frequency_Grid(0) = occurrence of blowing snow layers
Blow_Snow_Frequency_Grid(1) = occurrence of blowing snow layers where the backscatter ratio of the top altitude bin within layer to first bin above ground < 0.5
Blow_Snow_Frequency_Grid(2) = occurrence of blowing snow layers where the ratio of average backscatter strength within blowing snow layer to the blowing snow threshold > 1.5 and layer depth > 50 m
Blow_Snow_Frequency_Grid(3) = occurrence of blowing snow layers where the 10 m wind speed > 6 m/s and layer depth > 50 m
Blow_Snow_Frequency_Grid(4) = occurrence of blowing snow layers where the surface elevation (as determined from DEM) > 0.0 and 10 m wind speed > 7 m/s
Blow_Snow_Frequency_Grid(5) = occurrence of blowing snow layers where the layer depth > 30m and < 350 m
Blow_Snow_Frequency_Grid(6) = occurrence of blowing snow layers where the average layer 532 depolarization > 0.25 and layer average color ratio > 0.8
Blow_Snow_Frequency_Grid(7) = occurrence of blowing snow layers where one of the following conditions is true (as stated in (1),(4),&(6)) the backscatter ratio of the top altitude bin within layer to first bin above ground < 0.5 OR the surface elevation (as determined from DEM) > 0.0 and 10 m wind speed > 7 m/s OR the average layer 532 depolarization > 0.25 and layer average color ratio > 0.8
Blow_Snow_Frequency_Grid(8) = occurrence of the Blowing Snow Confidence Flag > 4

Surface_Integrated_Attenuated_Backscatter_532
Units: sr-1
Format: Float_32
Fill Value:
Valid Range: -3.53E-4...1.037
Definition: Vertically integrated Total Attenuated Backscatter 532 nm of the surface return from Surface Top Altitude 532 to Surface Base Altitude 532.

Surface_Overlying_Integrated_Attenuated_Backscatter_532
Units: sr-1
Format: Float_32
Fill Value:
Valid Range: -1.12 ... 3.2
Definition: Vertically integrated Total Attenuated Backscatter 532 from 40 km to one range bin above Surface Top Altitude 532.

Surface_Peak_Signal_532
Units: km·sr-1
Format: Float_32
Fill Value:
Valid Range: -0.210...22.156
Definition: Maximum attenuated backscatter value of the surface signal within the indicated channel.

Surface_Top_Altitude_532
Units: km
Format: Float_32
Fill Value:
Valid Range: -0.246...4.334
Definition: Top altitude of the surface return in the 532 nm channel at the lidar footprint in kilometers above local mean sea level. Contains fill values when surface is not detected.

Metadata Parameters


Production_Time
Units: No Units
Format: Char
Fill Value:
Valid Range: N/A
Definition: This is a 27-byte character string that defines the date at granule production. The format is yyyy-mm-ddThh:mm:ss.ffffffZ.

Input_Files
Units: No Units
Format: Char
Fill Value:
Valid Range: N/A
Definition: Listing of all Lidar Level 1 files used to create monthly product

Region_Boundaries
Units: No Units
Format: Char
Fill Value:
Valid Range: N/A
Definition: Latitude and Longitude boundaries for monthly product

Number_of_Monthly_Ground_Returns
Units: count
Format: Int_32
Fill Value:
Valid Range: 0...40,000,000
Definition: Total number of ground returns detected for the month

Number_of_Monthly_Shots
Units: count
Format: Int_32
Fill Value:
Valid Range: 0...90,000,000
Definition: Total number of profiles processed

Ground_Return_Threshold
Units: No Units
Format: Float_32
Fill Value:
Valid Range: N/A
Definition: Ground return threshold is set to 2.0 during V1.00 processing. This value about 10 times the local value of the molecular attenuated backscatter.

Blowing_Snow_threshold
Units: No Units
Format: Float_32
Fill Value:
Valid Range: N/A
Definition: Wind speed threshold is set to a min of 4.0 m/sec

Wind_Speed_Threshold
Units: No Units
Format: Float_32
Fill Value:
Valid Range: N/A
Definition: Wind speed threshold is set to a min of 4.0 m/sec

Lidar_Data_Altitudes
Units: km
Format: Float_32
Fill Value:
Valid Range: -1.818...-0.382
Definition: The 34 altitude bins that correspond to the profile data



Data Quality Statements

Lidar Level 2 Blowing Snow - Antarctica Information
Monthly file.
Release Date Version Data Date Range Production Strategy
November 14, 2018 1.00 June 13, 2006 to present Standard

Summary Statement for the release of the CALIPSO Lidar Level 2 Blowing Snow - Antarctica Version 1.00 Product, November 14, 2018

View Version 1.00 Detailed Quality Statement.


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

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