For each cloud detection, either cloud thickness or cloud penetration depth is reported. Cloud thickness and cloud penetration depth are reported in meters, corresponding to the distance that the light travelled inside the cloud.
Cloud thickness is reported in cases where a cloud is detected and significant measurement signal is detected above the cloud. Cloud thickness is also always reported in cases of optically thin clouds. Cloud penetration depth is reported in cases of optically thick clouds / precipitation where it is likely that the signal has attenuated completely.
In case of vertical visibility reporting, neither cloud thickness nor cloud penetration depth is reported.