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.

Physical-mathematical model of the dynamics of rain attenuation based on rain rate time series and a two-layer vertical structure of precipitation

https://narac.llnl.gov/content/mods/publications/research-and-development/UCRL-JC-155010.pdf

Precipitation scavenging of atmospheric aerosols for emergency response applications: testing an updated model with new real-time data

Simulation of NOx and ultrafine particles in a street canyon in Stockholm, Sweden

Statistics of rain rate increments are obtained from a 10-year record of a tipping-bucket rain gage. These statistics are analyzed for various effects: smoothing of data, sampling of data, noise in the data, and their consequences on the evidence for the fractal structure of rain. Furthermore, it is shown that rain becomes effectively decorrelated after ∼20 min. No evidence for scaling of rain rate increments in time is apparent from this analysis.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/JD092iD08p09586%4010.1002/%28ISSN%292169-8996.RAINFALL1

Fractal structure and exponential decorrelation in rain

The concept of employing synthetic storm data to evaluate simpler attenuation prediction techniques based on cumulative distributions of point rain rate is introduced. As examples, several versions of the «path average rain rate technique» and a new method developed by Crane are tested using 10-year rain rate data bases from several Canadian locations. The results indicate that there is no universal relationship for the ratio of the path average to the point rain rate in terms of either rain rate or percentage of time. However, Crane’s new method appears to be an improvement over earlier versions of the path average rain rate technique.

R.R. Rogers

Papers

Statistics of rainfall over paths from 1 to 50 km

Rainfall statistics for application to plume rainout models