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.
Browse of the DARDAR-CLOUD Ice Water Content retrieval – Orbit subset
Browse of the DARDAR-CLOUD Effective Radius retrieval – 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



timeUTC timesfloat32-999.0
CALIOP_Profile_TimeProfile time of the first and the last LIDAR shot averaged in the RADAR footprint (TAI93 time convention)secsfloat64-9999.0
vis_optical_depthOptical Thickness forwad modelNonefloat32-999.0
vis_optical_depth_errorError in optical thickness forwad modelNonefloat32-999.0
n_iterationsNumber of iteration to convergeNoneint16-999
wavelengthWavelength of the centre of radiance channel (infrared)mfloat32-999.0
chi2Value of chi squared for each iterationNonefloat321000000000.0
chi2_splitValue of chi squared for each iteration and for each instrument (lidar mie, lidar ray, Z, radiance, dradiance)Nonefloat321000000000.0
radianceRadiance Forward modelW m-2 um-1 sr-1float32-999.0
radiance_satRadiance Forward modelW m-2 um-1 sr-1float32-999.0
radiance_flagRadiance flag (0 = radiance not used, 1 = radiance used)Noneint16-999
radiance_difference_flagRadiance difference flag (0 = radiance not used, 1 = radiance used (first radiance), 2 = radiance used (second radiance))Noneint16-999
ZRadar reflectivitymm6 m-3float32-999.0
bscatLidar attenuated backscatterm-1 sr-1float32-999.0
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
instrument_flagInstrument flag (0==nothing/1==lidar/2==radar/3==radar+lidar)Noneint16-999
Z_fwdRadar reflectivity forward modelmm6 m-3float32-999.0
bscat_fwdLidar attenuated backscatter forward modelm-1 sr-1float32-999.0
extinctionRetrieved visible extinction coefficientm-1float32-999.0
lidar_ratioRetrieved extinction-to-backscatter ratiosrfloat32-999.0
iwcRetrieved Ice Water Contentkg m-3float32-999.0
effective_radiusRetrieved effective radiusmfloat32-999.0
N0starRetrieved normalized number concentration parameterm-4float32-999.0
ln_extinction_errorFractional error in visible extinction coefficientln(m-1)float32-999.0
ln_lidar_ratio_errorFractional error in extinction-to-backscatter ratioln(sr)float32-999.0
ln_iwc_errorFractional error in IWCln(kg m-3)float32-999.0
ln_effective_radius_errorFractional error in effective radiusln(m)float32-999.0
ln_N0_errorFractional error in normalized number concentration parameterln(m-4)float32-999.0
temperatureTemperature from ECMWFKfloat32-999.0
day_night_flagDay Night Flag for lidar Night (1) Day (0)Noneint16-999
land_water_maskLand Water Mask from Calipso filesNoneint16-999

back to the top