Cloud Attenuation Model Research Articles

Performance Evaluation and Analysis of Cloud Attenuation Prediction Models for Satellite Transmission Quality Improvement

Abstract The reliability of social and business interactions on communication infrastructure determines the technological advancement of a nation. In the disclaimer notices of our financial institution’s transaction forms, they declared that they are not liable for communication channels malfunction that may lead to transaction interruption, transmission blackout and delayed services. Thus, effective hydrometeors attenuation margins are needed from accurate models to have reliable signal transmissions. Earlier research works established that increase in transmission frequency is directly proportional to attenuation on the signal, and that satellite communication unavailability in most tropical regions is above the allowed 1% outage percentage, significantly due to cloud attenuation contribution at satellite bands. The existence of clouds in tropical climates is almost perpetual, making cloud models all the more fundamental in tropical regions – which include Africa and about half of the rest of the world. The published new tropical cloud attenuation algorithm and its accompanying new tropical cloud attenuation model (NTM) - derived from it, is hereby further analysed with respect to wider frequency range. In the primary research to this work, data were collected from spectrum analyzer, weather-link and radiosonde equipment. The data were used to calculate values of projected attenuation by each major existing cloud model in the propagation range of 12 to 50 GHz. The predicted cloud attenuation values were spectrally processed and analysed. These results in the observation that the NTM’s predictions generally average the characteristics prediction values of existing models as shown by the graphical outputs. Also, the predicted attenuation values by each of the cloud models converge increasingly with frequency.

Predictions of cloud attenuation models for uplink and downlink margins at ku, ka and v bands in tropical regions

To achieve effective wireless transmission margin and larger bandwidth at lower cost, hydrometeor models roles are of primary importance. The almost perpetual existence of clouds in tropical climates makes cloud models all the more fundamental. Details of four years station spectrum analyzer data, five years climatological data and fifty – eight years radiosonde data used in this research were earlier published. The radiosonde data was used to obtain existing primary cloud models’ predicted cloud attenuation cumulative distributions for the station and it was also used to deduce the new algorithm’s parameters for the station. The every minute measured and logged station cloud attenuation data using spectrum analyzer was used to deduce the station cloud attenuation cumulative distribution for comparison with that of other existing cloud models. The simulation program was run to generate the new cloud attenuation algorithm’s parameters, which defines the cloud attenuation model for the station. Thus the new model only fundamentally requires station radiosonde data. The cloud cover data and all others are needed only for graphical comparisons and corroboration. Thus the new tropical cloud attenuation algorithm can be used to develop the cloud attenuation model for any station climatic zone by using the methodology earlier published. Collected spectrum analyzer data, climatological data and acquired radiosonde data were used to compute projected attenuation values for each cloud attenuation model at propagation signal frequencies between 12 GHz to 50 GHz. The predicted values were extracted and analysed statistically. With respect to frequency, the new cloud attenuation model’s cumulative distribution proportionally averaged the characteristics of the cumulative distributions deduced from the station radiosonde data and that of the spectrum analyzer data as shown by the graphical figures. The results show that convergence of the range of predicted attenuation values by each of the cloud models increases directly with frequency.

Climatic Bases and Analysis of Proposed Cloud Attenuation Model for Satellite Links Application

Consistently required lager bandwidth at lower cost induce increases in magnitude of transmission frequency for satellite signal. This is phenomenally accompanied by proportional hydrometeors attenuation. Hence, there is need to evaluate cloud attenuation impact in every climatic region periodically. This report is one of the outcomes of experimental communication research carried out at tropical Ota (6.7oN, 3.23oE) station, southwest, Nigeria. The station spectrum analyzer measures its received beacons total attenuation at 12.245 GHz and elevation angle 59.9o to Astra satellites located at 28.2oE. Daily maximum, minimum and mean temperatures; rain amount, wind speed and direction as well as time of occurrence of each of these weather parameters were also measured. Then the radiometric data including acquired radiosonde data were analysed under rainy and non-rainy conditions, to obtain cloud attenuation contribution from the total attenuation measured per minute. The various data used range in measurement periods between four and fifty-eight years. The outputs were used to compute the station cumulative distributions for the existing cloud models and for the integrated station’s data. Statistical analysis comparing the two cumulative distributions show a high difference between the measured data and existing models’ predicted values. Hence a cloud attenuation computation algorithm and its simulation program were developed and used to derive a new tropical cloud attenuation model. The results of climatic data and analysis were used to justify the well corroborated new cloud attenuation model.

High-Resolution ITU-R Cloud Attenuation Model for Satellite Communications in Tropical Region

In this paper, the precipitable water vapor (PWV) data from Global Navigation Satellite System (GNSS) is introduced into ITU-R cloud attenuation model for higher temporal and spatial resolution for a tropical region. The revised model incorporates PWV value for estimation of cloud integrated liquid water content (ILWC) and then determines the cloud attenuation. In this study, ILWC along the propagation path is obtained by processing radiosonde vertical profile using the combination of a water vapor pressure cloud detection model and the Salonen and Uppala liquid water density model. From the analysis of 2 years of radiosonde data from eight sites within the tropical region, the results show that the ILWC along the path can be approximated by a power function relationship with the PWV. The estimated cloud attenuation using the improved model is compared with the values calculated using the ITU-R model and the cloud attenuation derived from a Ka-band beacon data. The results show that the proposed model is in good agreement with the ITU-R model at high percentage of time exceedance for the thin layer of stratus clouds and matches well with cloud attenuation suffered from beacon signal at low percentage of time exceedance for the thick layer of cumulonimbus clouds.

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.

Cloud attenuation modelling for satellite network links performance improvement

All local climate zones need to develop relevant climatic models such as cloud attenuation model which can serve as correlative resources to global satellites applications and a means of determining local link margins for satellite networks services in localities. Effects of suspended water droplets (SWD) and suspended ice crystals (SIC) which constitute clouds are major concern in the design and successful operation of satellite communication system at frequencies above 3GHz because the hydrometeors reduces the services availability critically as frequency increases. This work is a review of cloud attenuation modelling, using as a case study typical research work been carried out, to develop cloud attenuation model for tropical Ota (6.7oN, 3.23oE), southwest Nigeria. Cloud attenuation modelling for a station involve obtaining clouds parametric system equation from their numerical representations, taking into consideration the climatic initial and boundary conditions. The numerical representations are collected climatological and radiometric data, derived from well-designed experiments in which cloud parameters measurements are carried out using radiances change measured by satellites and visual observations from the surface station(s) on land and ships in the ocean. The on-going research work begin with the study of performance of eight foundation cloud models at the station, through their detailed evaluation from cloud cover data and radiosonde data analysis, followed by analysis of collected over three years spectrum analyser signal attenuation data. Then modelling analysis of the station spectrum analyser data collected at computed elevation angle 56.18o to Astra 2(E-G) Satellite located at 28.2oE, which involve comparisons of the derived attenuation distribution curves, both of the spectrum analyser data and those of the existing cloud models for the station, with the derived attenuation distribution curves of output data generated by each run session of the station simulation equation program. The general representation of the station cloud attenuation model is stated and the specific model equation is been worked on.

The microwave properties of the jovian clouds: A new model for the complex dielectric constant of aqueous ammonia

A new model for the complex dielectric constant of aqueous ammonia (NH4OH) under conditions characteristic of the jovian clouds has been developed. The new model is based on laboratory measurements in the frequency range between 2 and 8.5GHz for ammonia concentrations of 0–8.5% by volume and temperatures between 274 and 297K. The new model is based on the Meissner and Wentz (Meissner, T., Wentz, F.J. [2004]. IEEE Trans. Geosci. Rem. Sens. 42, 1836–1849) model of the complex dielectric constant of pure water but contains corrections for dissolved ammonia. Assuming Raleigh scattering, these measurements are applied to a cloud attenuation model to calculate the range of opacity of the jovian aqueous ammonia clouds. These measurements will improve our understanding of the data collected by the Juno microwave radiometer (MWR) by better characterizing the absorption properties of the aqueous ammonia present in the jovian atmosphere.The new model has been validated for temperatures up to 313K, and may be consistently used for the expected conditions for aqueous clouds in all of the outer planets. The model fits 60.26% of all laboratory measurements within 2-sigma uncertainty. Descriptions of the experimental setups, uncertainties associated with the laboratory measurements, the model fitting process, the new model, and its application to approximating jovian cloud opacity are provided.

Cloud attenuation modelling for SHF and EHF applications

AbstractTropospheric propagation impairments that affect earth–space communication signals increase in severity with the increase of frequency. Introduction of satellite services using higher frequency bands such as Ka‐ and V‐band requires the characterization of propagation factors that are normally considered negligible at lower frequency bands. Cloud attenuation is considered one such factor. Clouds are present during a large fraction of an average year and cloud attenuation, together with gaseous absorption, will determine the system performance under non‐rainy conditions. A cloud attenuation model that has global applicability is presented in this paper. The model is based on average properties of four cloud types and their occurrence probabilities. The occurrence probabilities are derived from long‐term observations of cloud cover carried out by several thousand meteorological stations throughout the world. Predictions made with the model are compared with cloud attenuation data gathered using Ka‐band beacon signals and radiometers. Copyright © 2001 John Wiley & Sons, Ltd.

Measurement and modelling of cloud attenuation atmillimetre wavelengths

Results are presented from a 93 GHz radiometer over a one-year period. A cloud attenuation model, which uses measurements from radiosonde profiles, has been used to provide a comparison. The effects of rain, water vapour and oxygen have been removed from the radiometer total attenuation record through the use of GPS observations and meteorological measurements at ground level. Agreement between the radiometer and cloud model is good, indicating that the cloud model is able to give an accurate prediction of attenuation due to liquid water clouds.