Prediction of monthly attenuation statistics due to clouds and water vapor: Performance assessment

This contribution investigates the accuracy in predicting attenuation statistics due to water vapour (P(A_V)) and clouds (P(A_C)) achieved by the methodologies included in recommendations ITU-R (International Telecommunication Union - Radiocommunication sector) P.676-10 and P.840-6, respectively, whose applicability has been recently extended from yearly to monthly basis, but is yet to be properly assessed. To this aim, we make use of an extensive long-term dataset of RAdiosonde OBServations (RAOBS), collected in 14 sites spread across Europe, to calculate the reference monthly attenuation statistics due to clouds and water vapour. Results indicate that the prediction of P(A_C) degrades both with the increase in frequency and switching from yearly to monthly basis, while on the other hand, ITU-R P.676-10 offers a much more accurate estimate of P(A_V), being almost independent of the frequency and the temporal scale. In addition, while Recommendation P.676-10 provides a fairly stable performance regardless of the month, P.840-6 tends to offer slightly more accurate predictions for May to July.