Abstrakt:
The four year FSO link attenuation measurement concurrently with most important meteorological parameters was performed at our mountain observatory Milesovka. In this contribution we summarize and classify different atmospheric phenomena after the FSO link attenuation quantity. For all particular phenomena the CD curves, typical events and simple dependences on relevant atmospheric parameter(s) are presented. We consider the following phenomena (approximate attenuation in dB in brackets): 1. Fog and cloud (hundreds dB) 2. Rain and snow (tens dB) 3. Atmospheric turbulence (unit dB) 4. Clear air attenuation due to water vapour (unit dB or less)