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Validation Summary

The Sentinel-5p TROPOMI L2_CLOUD data product (Loyola et al., 2018) contains several cloud-related quantities, retrieved with the Optical Cloud Recognition Algorithm (OCRA) and with the Retrieval of Cloud Information using Neural Networks (ROCINN) either with the Cloud-As-Layers approach (CAL) or the Cloud-as-Reflecting Boundaries approach (CRB) (Lutz et al., 2016, Loyola et al., 2010):

  • OCRA radiometric Cloud Fraction (CF);
  • ROCINN_CAL Cloud Top Height (CTH) and Cloud Optical Thickness (COT);
  • ROCINN_CRB Cloud Height (CH) and Cloud Albedo (CA).

The Sentinel-5p MPC performs in routine the following validation checks:

  • ROCINN_CAL CTH and derived cloud mean height (CMH) and ROCINN_CRB CH are compared to correlative ground-based measurements from the CLOUDNET and ARM networks;
  • OCRA CF, ROCINN_CAL CTH and ROCINN_CRB CH are compared to Sentinel-5p radiometric cloud fraction and cloud height data retrieved with the FRESCO algorithm;


Given their different nature, we look at low (cloud top height below 4km) and high clouds separately. The bias of ROCINN_CAL cloud top height vs. CLOUDNET cloud top height is within the 20% mission requirement for low clouds, but not for high clouds. The bias of CAL cloud mean height vs CLOUDNET cloud mean height is within mission requirements for low and high clouds. The bias of ROCINN_CRB cloud height vs. CLOUDNET cloud mean height is negative and bordering on the 20% mission requirement for high and low clouds. For both ROCINN_CAL and ROCINN_CRB, the dispersion requirement of 0.5 km is met for low clouds but not for high clouds. Given the large difference in sensitivity between the TROPOMI near-infrared observations and the ground-based lidar/radar observations, the agreement is fair.


Product ID Stream Product Bias  Dispersion Special features
 CAL CTH (high)  -36%  1.9 km

Low clouds: CLOUDNET CTH<4km; high clouds: CLOUDNET CTH>4km.
CAL CMH is calculated as the mean of CAL cloud base height and CTH.

 CAL CTH (low)  -15%  0.5 km
 CAL CMH (high)  -12%  1.7 km
 CAL CMH (low)  -16%  0.5 km
 CRB CH (high)  -20%  1.9 km
 CRB CH (low)  -21%  0.5 km


A detailed description of the method and a comprehensive discussion of validation results can be found in the Sentinel-5p Quarterly Validation Report #22: April 2018 - February 2024

  Latest Quarterly Validation Report     Product info     Current Processor Version  
 #22: April 2018 - February 2024  See  




Loyola, D. G. et al., The operational cloud retrieval algorithms from TROPOMI on board Sentinel-5 Precursor, Atmos. Meas. Tech. , 11, 409-427, 2018, doi:10.5194/amt-11-409-2018

Lutz, R. et al., OCRA radiometric cloud fractions for GOME-2 on MetOp-A/B, Atmos. Meas. Tech., 9, 2357-2379,2016, doi:10.5194/amt-9-2357-2016

Loyola, D. al., Global patterns in daytime cloud properties derived from GOME backscatter UV-VIS measurements, Int. J. Remote. Sens., 31, 2010, 4295-4318, doi:10.1080/01431160903246741