Algorithm Theorical Basis Document ( ATBD )

This document contains a detailed description of the algorithm

varcloud - algorithm_description - v1.0



The ice cloud properties are retrieved :

  • at a 60m vertical resolution between [ -1.02 km , 25.08 km ]
  • at CLOUDSAT horizontal footprint resolution i.e. 1.4 km.

DARDAR-CLOUD Ice Water Content browse - orbit subset
Browse of the DARDAR-CLOUD Ice Water Content retrieval - Orbit subset

DARDAR-CLOUD Effective Radius browse - orbit subset
Browse of the DARDAR-CLOUD Effective Radius retrieval - Orbit subset

DARDAR-CLOUD Extinction Coefficient browse - orbit subset
Browse of the DARDAR-CLOUD Extinction Coefficient retrieval - Orbit subset

Naming convention


<Version> A 3 digits dot separated version number as X.X.X
<Timestamp> The timestamp of the orbit, using the CLOUDSAT format YYYYJJJHHMMSS, Year, Julian day, hour, minute, second of the first data contained in the file (UTC)
<Granule> The granule number, on 5 digits


Product Parametres Download
DARDAR-CLOUD - Ice Water Content
- Effective particle radius
- Extinction
Browse Images Ice Water Content DARDAR-CLOUD_v2.1.1_2009001021530_14253_iwc.png
Effective Radius DARDAR-CLOUD_v2.1.1_2009001021530_14253_effective_radius.png
Extinction Coefficient DARDAR-CLOUD_v2.1.1_2009001021530_14253_extinction.png



Name Description Unit Type Fill
time UTC time s float32 -999.0
latitude Latitude degree float32 -999.0
longitude Longitude degree float32 -999.0
CALIOP_Profile_Time Profile time of the first and the last LIDAR shot averaged in the RADAR footprint (TAI93 time convention) secs float64 -9999.0
vis_optical_depth Optical Thickness forwad model None float32 -999.0
vis_optical_depth_error Error in optical thickness forwad model None float32 -999.0
height Height m float32 -999.0
n_iterations Number of iteration to converge None int16 -999
wavelength Wavelength of the centre of radiance channel (infrared) m float32 -999.0
chi2 Value of chi squared for each iteration None float32 1000000000.0
chi2_split Value of chi squared for each iteration and for each instrument (lidar mie, lidar ray, Z, radiance, dradiance) None float32 1000000000.0
radiance Radiance Forward model W m-2 um-1 sr-1 float32 -999.0
radiance_sat Radiance Forward model W m-2 um-1 sr-1 float32 -999.0
radiance_flag Radiance flag (0 = radiance not used, 1 = radiance used) None int16 -999
radiance_difference_flag Radiance difference flag (0 = radiance not used, 1 = radiance used (first radiance), 2 = radiance used (second radiance)) None int16 -999
Z Radar reflectivity mm6 m-3 float32 -999.0
bscat Lidar attenuated backscatter m-1 sr-1 float32 -999.0
DARMASK_Simplified_Categorization -9 -> ground
-1 -> don't know
0 -> clear
1 -> ice
2 -> ice + supercooled
3 ->liquid warm
4 -> supercooled
5 -> rain
6 ->aerosol
7 -> maybe insects
8 -> stratospheric feature
None int16 -9
instrument_flag Instrument flag (0==nothing/1==lidar/2==radar/3==radar+lidar) None int16 -999
Z_fwd Radar reflectivity forward model mm6 m-3 float32 -999.0
bscat_fwd Lidar attenuated backscatter forward model m-1 sr-1 float32 -999.0
extinction Retrieved visible extinction coefficient m-1 float32 -999.0
lidar_ratio Retrieved extinction-to-backscatter ratio sr float32 -999.0
iwc Retrieved Ice Water Content kg m-3 float32 -999.0
effective_radius Retrieved effective radius m float32 -999.0
N0star Retrieved normalized number concentration parameter m-4 float32 -999.0
ln_extinction_error Fractional error in visible extinction coefficient ln(m-1) float32 -999.0
ln_lidar_ratio_error Fractional error in extinction-to-backscatter ratio ln(sr) float32 -999.0
ln_iwc_error Fractional error in IWC ln(kg m-3) float32 -999.0
ln_effective_radius_error Fractional error in effective radius ln(m) float32 -999.0
ln_N0_error Fractional error in normalized number concentration parameter ln(m-4) float32 -999.0
temperature Temperature from ECMWF K float32 -999.0
day_night_flag Day Night Flag for lidar Night (1) Day (0) None int16 -999
land_water_mask Land Water Mask from Calipso files None int16 -999