Application of synthetic storm technique to predict time series of rain attenuation from rain rate measurement for a tropical location

Abstract: We have developed and discussed the theory and applications of a physical-mathematical model of the dynamics of rain attenuation and have tested it as a rain attenuation prediction model in slant paths. Other parameters, however, such as fade durations and rates of change of fades, can be calculated. The main physical input is the 1-min rain rate time series of a site, which is converted to a rain rate space series along horizontal or slant paths by using an estimate of the storm translation speed v method known as “synthetic storm technique.” However, the long-term predictions are found to be insensitive to v. The vertical structure of precipitation is modeled with two layers. The model was tested against the probability distributions of rain long-term 11.6-GHz attenuation collected at the three Italian stations (Fucino, Gera Lario, and Spino d'Adda) during the SIRIO propagation experiment (13 years of data) for which concurrent rain rate time series are available. In the outage probability range 10−1 to 5×10−3% defined the prediction error e = ( Ap − Am) / Am (where Am and Ap are respectively, the measured and predicted rain attenuations, dB), = −10.6%, σ=7.6% and rms=13%. Compared to nine other well-known prediction methods, the present model surmounts all of them in the three sites tested.

Abstract: The paper discusses the prediction of long-term fade duration statistics in slant paths, obtained from rain attenuation time series simulated with the synthetic storm technique (with input from 1-min rain rate time series). The results of the prediction were tested against the experimental fade duration statistics collected at three sites of the Sirio experiment in Italy at 11.6 GHz. Predicted and measured statistics are very similar for fade durations longer than about 64–128 s, which represent a fundamental lower limit to fade duration prediction using 1-min rain rate time series. The short durations have not been reproduced because they are mainly caused by tropospheric turbulence, not by the space-time structure of rain, well described statistically by the synthetic storm technique. The prediction is not sensitive to rainstorm speed.

Abstract: Many prediction methods of long term complementary distribution function (CDF) of rain attenuation based on rain intensity CDF, when tested against concurrent beacon measurements show very similar large errors. In our opinion, these tests may indicate that the real concurrency of rain attenuation and rain intensity CDFs is not sure. The scope of the paper is to show that this can happen even in a well designed and controlled experiment. To this end, we have used the measurements collected at Spino d'Adda of Italsat 18.7-GHz beacon in a 37.7/spl deg/ slant path, and the independent predictions of the synthetic storm technique (SST) for the same radio link, to search the most reliable long term rain attenuation CDF of the slant path, that we found given by the SST CDF. Since the search is based on concurrent and independent rain intensity measurements, we think that our conclusion is sound. We have also discussed how to complete, statistically, a rain attenuation data bank with the SST prediction (such as the large and valuable Italsat data bank) to provide a secure experimental set of concurrent rain attenuation and rain intensity statistics to test prediction methods under controlled conditions, like in a laboratory.

Abstract: We present annual/seasonal rainfall rate statistics derived from a 29-month data bank of 1 sample/min, measured by a disdrometer located inside the National Technical University of Athens Campus. We discuss both the inaccuracy and the unavailability of the measuring equipment, as well as the statistical reliability of the rainfall rate sample. Additionally, after applying the Synthetic Storm Technique on the measured rainfall rate time series, we present the first long term simulated annual/seasonal and diurnal rain attenuation statistics, at 12 GHz for a hypothetical downlink from Hellas Sat 2 to Athens. According to the results, we predict that communication downlinks working in the afternoon and early evening hours must be given an extra power margin, to compensate for high rain attenuation