Advancement on Cloud Attenuation Modelling in Tropical Ota Climatic Zone

This is a further study on development of the cloud attenuation model for improvement of the availability of satellite services in tropical Ota (6.7oN, 3.23oE) climatic zone. The radiometric data analysis has been re-evaluated for better accuracy through the Matlab embedded into the data processing electronic spreadsheets. The collection of station data such as the spectrum analyser beacon measurements of the total attenuation at re-established elevation angle 59.9° to Astra 2(E-G) satellites located at 28.2°E; the station weather parameters and the clouds parameters visual measurements; as well as the acquisition of station climatic zone radiosonde data were carried out. Then the station spectrum analyser data for 2014 - 2017 were analysed to obtain cloud attenuation contributions from the total attenuation measurement. Cloud attenuation distributions outputs of these data analyses were used to obtain the station integrated cumulative distribution for each of the existing cloud models and the 2014 – 2017 integrated data. The results at the station beacons frequency of 12.245 GHz show wide gap between the 3.40 dB maximum cloud attenuation by the Ota spectrum analyser integrated data cumulative distribution to the 0.81 dB maximum cloud attenuation predicted by its closest ITU-R model, while next in closeness is the Liebe model, followed by Slobin model. This recommends a new cloud attenuation model be developed for the tropical region. The earlier published cloud attenuation algorithm is further developed with simulation program written to run its simulations cycles over possible range of maximum signal amplitudes, using the Ota climatic zone radiosonde empirical data (1953-2011) for computations of each cloud layer's liquid water content and specific cloud attenuation coefficient. The cumulative distribution curves obtained were compared with those for each generated simulation distribution and the closest match to the station integrated data cumulative distribution became the new cloud attenuation model for Ota climatic zone. The new model predicted 4.0 dB margin for signals to pass through clouds attenuation effect in the Ota climatic zone, revealing that the prediction for cloud attenuation by the earlier models largely under estimate the margin for the tropical region. (paper)