A. Burgueño

Spectral analysis of 49 years of rainfall rate and relation to fade dynamics

The nature of the rainfall rate R(t) as a transient random process is presented in the context of microwave attenuation and fade dynamics. Using 49 years of data recorded in Barcelona, the spectral densities of energy and power and the autocorrelation function are presented, together with their analytical model. Examples for specific rain events are also presented. Several regimes covering a wide range of intensities have been investigated, and it is found that the spectral densities all exhibit a similar form which is independent of the average regime of R considered. This leads to a mean frequency and a spectral width which appear to be universal constants and independent of the regime. Similar features are found for the autocorrelation function. The mathematical models and numerical values found are compared to the Maseng-Bakken model (1981) proposed in earlier work of fade dynamics, and the agreement is good. The method is proposed for modeling the denormalized autocorrelation, and hence the spectrum, using only the measured average rainfall rate during a period of interest. Finally, the average number of crossings per unit of time is modeled and compared to the experimental results, and the agreement is satisfactory. >

Analysis and modeling of time intervals between rain rate exceedances in the context of fade dynamics

Using a 49 year point rainfall rate databank the authors present the analysis and statistical modeling of the interval of time between exceedances of rainfall rate thresholds within the context of rain fade dynamics and system availability. The study distinguishes between successive exceedances occurring at different rain events. The global study of both return periods or intervals is also presented together with a comparison with the statistics of durations of exceedances. A comparative study is presented with published results, both on rain and on fade after conversion to point rain rate, together with the dependence of the annual average number of return periods upon the rainfall rate thresholds. >

Influence of rain gauge integration time on the rain rate statistics used in microwave communications

An investigation into the effect of the integration time T on the rain rate distribution P(R) is presented using a rainfall rate data bank of 49 years recorded at Barcelona (CCIR - Zone L), using a rapid response Jardi rain rate gauge. T extends from 1 to 60 min and P(R) extends to less than 10-3 %. The relation between the various T-distributions P(RT) is presented as well as the values of RT and R1 which give the same probability. The ratio RT/R1 and the potential expression R1 = aRbT are studied. Comparison with recent results from Canada confirms both the numerical value presented and the climatic dependence of the equi-probable ratio RT/R1.RésuméOn présente une étude de l’effet du temps d’intégration T sur la distribution statistique P(R) de l’intensité de précipitation utilisant des données obtenues pendant 49 ans à Barcelone (zone CCIR-L), à l’aide d’un pluviomètre d’intensité Jardí. T s’étend entre 1 et 60 min, et P(R) va jusqu’à moins de 10-3 %. On présente la relation entre les différentes distributions obtenues lorsque T varie, P(RT), ainsi que les valeurs de RT et R1 qui conduisent à la même probabilité. On étudie le rapport RT/R1 et l’expression potentielle R1 = aRbT. On compare les résultats pour RT/R1 avec ceux obtenus récemment pour le Canada, ce qui confirme les valeurs numériques du rapport RT/R1 aussi bien que sa dépendance climatologique.

Analysis of Moderate and Intense Rainfall Rates Continuously Recorded Over Half a Century and Influence on Microwave Communications Planning and Rain-Rate Data Acquisition

This paper is concerned with the statistical investigation of a massive data bank of 49 years of rainfall rate R continuously recorded in Barcelona using a rain-rate gauge with ten seconds response time. With radio communications in mind, the paper addresses and reviews in detail: 1) reliable statistical model for R , 2) number of years required to obtain a database from which to derive a reliable R -distribution, and 3) the CCIR worst-month concept. The research has shown that the generalized Pareto a exp (-\muR)/R^{b} gives nearly perfect fit for all ranges of R followed closely by the gamma distribution, and the simpler square root ( R^{1/2} ) normal distribution gives excellent fit too. The log-normal distribution was unsatisfactory for R \geq 60 mm/h. The spread of the yearly distribution of P(R) is cube root normally distributed ([P(R)]^{1/3}) and between 7 and 10 years are required before a reliable average distribution P(R) can be obtained. The study of the P(R) return time in years is also presented. High resolution of P(R) is presented looking at the evolution of the annual P(R) in terms of the hourly and monthly contributing parts revealing statistical features such as the location in time of rain rates above 50 mm/h. Finally, the study shows that the calendar month contribution to P(R) remains at all times well below the synthetic CCIR worst month and recommendations are then given about its use.

Analysis of joint rainfall rate and duration statistics: microwave system design implications

The joint statistical analysis of duration D and intensity R of rain exceedances relevant to the design of microwave communication systems is considered. The data analyzed are derived from point precipitation-rate observations recorded over a period of 49 years in the city of Barcelona, Spain, using a Jardi gauge. The concept of event and the duration of a single exceedance of a threshold R within that event is introduced. The analysis shows the parametric R dependence of the annual average number of exceedances and of the average duration. >

Return period maps of dry spells for Catalonia (northeastern Spain) based on the Weibull distribution / Périodes de retour des périodes sèches en Catalogne (nord-est de l'Espagne) à partir de la distribution de Weibull

Abstract A detailed description of the spatial distribution of dry spell lengths in Catalonia (northeastern Spain) for the years 1950–2000 is obtained from a statistical analysis. The database is derived from the daily records of 75 raingauges, and a dry spell is defined as a set of consecutive days with daily rainfall amounts below thresholds of 0.1, 1.0, 5.0 and 10.0 mm/d. The Weibull model fits the distribution of dry spell lengths well, whatever the raingauge and threshold. The Weibull parameters estimated by L-moments and the L-skewness—kurtosis diagrams allow quantification of the goodness of fit between the model and the empirical distribution. Dry spell lengths for return periods of 2, 5, 10, 25 and 50 years indicate the areas where drought phenomena might be more severe, as well as how often they might occur. A regional homogeneity method is used to test whether a single set of Weibull parameters could describe the series of dry spells for the whole region.

Statistical properties of 49 years of rainfall rate events

SummaryThe paper presents a detailed investigation of magnitudes and properties pertaining to the large population of rainfall events recorded during 49 years at the Fabra Observatory in Barcelona. The study includes a statistical analysis of event durationT and rainfall quantityQ together with the statistical rainfall rate parameters:

Preliminary aspects of rainfall rates in the north east of Spain

\bar R,\overline {R^2 }