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Real-Time Rain Rate Evaluation via Satellite Downlink Signal Attenuation Measurement

Authors:
Filippo Giannetti at University of Pisa
Filippo Giannetti
Ruggero Reggiannini at University of Pisa
Ruggero Reggiannini
Marco Moretti at University of Pisa
Marco Moretti
Elisa Adirosi at Italian National Research Council
Elisa Adirosi
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Abstract and Figures

We present the NEFOCAST project (named by the contraction of "Nefele", which is the Italian spelling for the mythological cloud nymph Nephele, and "forecast"), funded by the Tuscany Region, about the feasibility of a system for the detection and monitoring of precipitation fields over the regional territory based on the use of a widespread network of new-generation Eutelsat "SmartLNB" (smart low-noise block converter) domestic terminals. Though primarily intended for interactive satellite services, these devices can also be used as weather sensors, as they have the capability of measuring the rain-induced attenuation incurred by the downlink signal and relaying it on an auxiliary return channel. We illustrate the NEFOCAST system architecture, consisting of the network of ground sensor terminals, the space segment, and the service center, which has the task of processing the information relayed by the terminals for generating rain field maps. We discuss a few methods that allow the conversion of a rain attenuation measurement into an instantaneous rainfall rate. Specifically, we discuss an exponential model relating the specific rain attenuation to the rainfall rate, whose coefficients were obtained from extensive experimental data. The above model permits the inferring of the rainfall rate from the total signal attenuation provided by the SmartLNB and from the link geometry knowledge. Some preliminary results obtained from a SmartLNB installed in Pisa are presented and compared with the output of a conventional tipping bucket rain gauge. It is shown that the NEFOCAST sensor is able to track the fast-varying rainfall rate accurately with no delay, as opposed to a conventional gauge.
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Real-Time Rain Rate Evaluation via Satellite Downlink Signal Attenuation Measureme
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... These novel techniques focus on quantifying rain-induced attenuation in existing radio communication networks, which include both cellular backhaul connections and satelliteto-earth microwave links (SMLs), particularly those operating in Ku and Ka frequency bands [11][12][13][14][15]. While commercial microwave links (CMLs) for rain estimation are wellstudied [16][17][18][19][20][21][22][23][24], the field of Earth-to-satellite links is still nascent, and further research is warranted given the limitations due to their scarce coverage [4]. ...
... Standard techniques, often based on physical models and heuristic methods, can estimate local RR at the receiver site if certain meteorological and geometric parameters are known. Such techniques can also partner with traditional tools, e.g., pairing SMLs to back regional rain gauges (RGs) and weather radar monitoring systems [11,25]. ...
... Since the ML methods proposed in this paper are strictly related to the mechanism and the methodologies applied in the traditional opportunistic rainfall estimations, we summarize here the key points, referring to the work in [11,37]. ...
Deep Learning for Opportunistic Rain Estimation via Satellite Microwave Links
Article
Full-text available
  • Oct 2024
  • SENSORS-BASEL
Accurate precipitation measurement is critical for managing flood and drought risks. Traditional meteorological tools, such as rain gauges and remote sensors, have limitations in resolution, coverage, and cost-effectiveness. Recently, the opportunistic use of microwave communication signals has been explored to improve precipitation estimation. While there is growing interest in using satellite-to-earth microwave link (SMLs) for machine learning-based precipitation estimation, direct rainfall estimation from raw signal-to-noise ratio (SNR) data via deep learning remains underexplored. This study investigates a range of machine learning (ML) approaches, including deep learning (DL) models and traditional methods like gradient boosting machine (GBM), for estimating rainfall rates from SNR data collected by interactive satellite receivers. We develop real-time models for rainfall detection and estimation using downlink SNR signals from satellites to user terminals. By leveraging a year-long dataset from multiple locations—including SNR measurements paired with disdrometer and rain-gauge data—we explore and evaluate various ML models. Our final models include ensemble approaches for both rainfall detection and cumulative rainfall estimation. The proposed models provide a reliable solution for estimating precipitation using Earth–satellite microwave links, potentially improving precipitation monitoring. Compared to the state-of-the-art power-law-based models applied to similar datasets reported in the literature, our ML models achieve a 46% reduction in the RMSE
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... The authors of [23] pioneered opportunistic sensing with GEO satellites, proposing the collection of RSSI measurements through time and comparing them to a baseline RSSI value from historical data. In [24], the authors employ two Kalman filters tracking slow and fast variations of the RSSI, respectively, and a rain event is detected when the difference between the outcomes exceed a threshold. In [25], the bit error rate (BER) is constantly measured and logistic regression is used to detect rain periods; the rain intensity is evaluated similarly as before. ...
... Each satellite s ∈ S i operates at a given frequency band with carrier frequency f s , bandwidth B s , antenna gain G s , are deployed at an altitude h s , which is equal for all s ∈ S i , and has a footprint covering up to C s cells. At least one orbital shell operates at a carrier frequency in the K-band or higher, as operating in such high frequencies enables atmospheric sensing [24]. Furthermore, the satellites in each orbital plane orbit are evenly spaced across the orbit and orbit the Earth with a given inclination angle δ s at an orbital velocity ...
... Let α r (k) ∈ {0, 1} be an indicator variable that takes the value of 1 if rain cell r is active at frame k and 0 otherwise. Consequently, the probability that an active rain cell at time k − 1 becomes inactive at frame k is 1 We remark that many solutions are available to retrieve the rainfall attenuation from the total atmospheric attenuation, e.g., [20], [24], [28]. 2 We implicitly assume that the rainfall is approximately constant in a cell, and that the slanted path of the GSL does not pass over other cells below the rain height. These two assumption are not required for the proposed design to work, but are used to simplify the implementation of the simulations. ...
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Preprint
Full-text available
  • Jul 2024
The integration of Non-Terrestrial Networks (NTNs) with Low Earth Orbit (LEO) satellite constellations into 5G and Beyond is essential to achieve truly global connectivity. A distinctive characteristic of LEO mega-constellations is that they constitute a global infrastructure with predictable dynamics, which enables the pre-planned allocation of the radio resources. However, the different bands that can be used for ground-to-satellite communication are affected differently by atmospheric conditions such as precipitation, which introduces uncertainty on the attenuation of the communication links at high frequencies. Based on this, we present a compelling case for applying integrated sensing and communications (ISAC) in heterogeneous and multi-layer LEO satellite constellations over wide areas. Specifically, we present an ISAC framework and frame structure to accurately estimate the attenuation in the communication links due to precipitation, with the aim of finding the optimal serving satellites and resource allocation for downlink communication with users on ground. The results show that, by dedicating an adequate amount of resources for sensing and solving the association and resource allocation problems jointly, it is feasible to increase the average throughput by 59% and the fairness by 600% when compared to solving these problems separately.
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... Where H 0 is the altitude of zero degree isotherm, H S the altitude of the ground sensor and θ the elevation angle of the ground 220 -satellite link. It would be unreasonable to use a unique climatological freezing level height, especially in mid-latitudes where the mean freezing level ranges for instance in northern Italy from 1.5 km in January to 4 km in August (Giannetti et al., 2017). ...
... Another phenomena, probably more frequent and affecting mostly convective rain is the fact that the freezing level is not 625 always a clear limit (see for instance Giannetti et al. (2017) notably their Figure 6 and associated text): there can be liquid rain above the freezing height and solid ice below due to strong vertical winds. This could lead to systematic errors, especially in areas subject to heavy rainfall like the tropics. ...
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Preprint
Full-text available
  • Jun 2024
Earth – satellite microwave links such as TV-SAT can help for rainfall monitoring and could be a complement or an alternative to ground-based weather radars, rain gauges or satellites dedicated to Earth observation. Rain induced attenuation which is harmful for telecommunication is exploited here as an opportunistic way to estimate rain rate along the path link. This technique makes it possible to obtain rain measurements at a fine temporal resolution (a few tens of seconds) and with a spatial resolution of few kilometers, which is a good compromise for human activities such as civil security (watershed monitoring, flash flood), agriculture or transport. Among the advantages of this technique, one can note the low cost of the hardware used (which can be commercial) as well as that of its maintenance on site. However, measured attenuation does not directly provide rain intensity and some parameters have to be estimated. Among these, it is necessary to take into account the contribution of the natural radiation of the atmosphere. In this paper, we detail a theoretical framework allowing to estimate rainfall from the measurements of a low-cost sensor operating simultaneously over two parts of the Ku-frenquency band. Then this framework is assessed in a densely instrumented area in south of France, where it is shown that very good results are obtained when compared to rain gauges measurements, both in terms of overall rain accumulation and in terms of rainfall rate distribution. Then we apply this dual channel method in Ivory Coast, in the metropolitan area of Abidjan, where such an approach is very promising. It is shown that this technique when compared to rain gauge measurements give results far better than a single-channel naive approach neglecting natural radiation of atmosphere, but that there are still significant errors in the rain assessment, leading to a persistent underestimation of rain accumulation. Finally we discuss various effects that could lead to this remaining underestimation, opening the door to further studies.
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... During NEFOCAST project a rain retrieval algorithm has been developed to obtain rainfall rate from commercial interactive digital video broadcasting (DVB) receivers called SmartLNB (Smart Low-Noise Block converter), and a platform to collect, process and store SmartLNB data, the NEFOCAST Service Center (NSC), was developed. Main results of the project are reported in [15] and [17]. During INSIDERAIN a new technique for the acquisition of SmartLNB data and several updates of the retrieval algorithm have been developed. ...
... For instance, most commercial receivers for satellite broadcasting yield a measurement of the signal-to-noise ratio (SNR), expressed as η = E s /N 0 , where E s is the average RF energy per modulation symbol and N 0 is the one-sided power spectral density (PSD) of the overall noise affecting the received signal. The total additional attenuation A experienced by the MW signal during the rain event (wet condition) with respect to the pre-rain value (dry condition) can be obtained as [15] ...
Enhanced Estimation of Rainfall From Opportunistic Microwave Satellite Signals
Article
Full-text available
  • Jan 2024
Physical characteristics of precipitation, like temporal and spatial variability, jointly with coverage and costs of conventional meteorological devices for quantitative rainfall estimation (i.e., rain gauges, disdrometers, weather radars) make the precipitation monitoring a complex task. However, real time rainfall maps are an important tool for many applications, dealing with environment, social activities, and business. Recently, the use of “opportunistic” methods to estimate rainfall has been investigated, highlighting the possibility to exploit inexpensive opportunities to augment information about precipitation. This paper deals with SmartLNBs (Smart Low-Noise Block converters), which are commercially available interactive digital video broadcasting (DVB) receivers designed to be used as bidirectional modems for commercial interactive TV applications. In the last few years an algorithm that converts the SmartLNB raw data into attenuation values, from which the rainfall rate is obtained, has been developed and evaluated. The aim of this paper is to describe the improvements of the rainfall estimation from SmartLNBs brought by significant changes in the data acquisition from SmartLNB and by algorithms’ update. One year of data collected in Rome and Tuscany (Italy) are analyzed to test the performance of SmartLNB in estimating rainfall accumulation with respect to co-located rain gauges and disdrometer in the new configuration. Comparing SmartLNB and disdrometer data in Rome we obtained Root Mean Square Error equal to 7.7 mm, Normalized Mean Absolute Error equal to 44%, with a correlation coefficient of 0.91, that can point out the maturity of the technique.
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... For the calculation of signal losses during transmission, the specific signal attenuation (in the following referred to as attenuation) is calculated in accordance to the recommendation ITU-R P.676-10 (09/2013) of the International Telecommunication Union (ITU, 2013). For the calculation, a mathematical model is used to consider signal intensity losses due to electromagnetic gases (Giannetti et al., 2017). In this calculation, the environmental factors pressure, temperature and humidity as well as the distance between the point of transmission and the receiver and the frequency of the transmission have to be known (ITU, 2013). ...
System Reliability Assessment Of Component-Integrated Wireless Sensor Networks With Consideration Of Data Accuracy
Chapter
Full-text available
  • Jun 2024
The system reliability of wireless sensor networks (WSN) is an important issue to ensure robust data acquisition. Especially when sensor networks are directly integrated into components, for example inside the composite layup of composite parts, the non-repairability has to be considered for sensor placement. Since the quality of the acquired data is as important as the reliability of the network itself to fulfill the main function of data acquisition, a combined perspective on data and hardware is needed. Therefore, an algorithmic approach for data path-based reliability assessment is enhanced to the estimation of data accuracy regarding signal quality losses during transmission. This approach uses signal attenuation along data paths to estimate changes in the Signal-to-Noise ratio (SNR) and therefore in the accuracy of acquired data. To demonstrate the algorithmic effectiveness, a case study is presented that analyzes an exemplary WSN from both a data and a hardware perspective. Resulting from the demonstrated effectiveness and applicability, the approach presented in this paper aids engineers in designing WSNs for reliable data acquisition.
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... The rain cell is an area of space made up of con-nected locations when the rainfall rate exceeds a certain threshold [71][72][73][74][75][76][77][78]. A variety of studies have employed radar to assess the size and shape of rain cells [79][80][81][82][83][84][85][86]. Signal attenuation in FSO communication can also be caused by rain. ...
A Precise Review on Different Aspects of Free Space Optical Communication (FSOC) Systems
Article
Full-text available
  • Jul 2024
  • WIRELESS PERS COMMUN
Radio frequency (RF) is perceived as one of the most popular wireless transmission candidate in the last decade however due to ever-increasing current generation bandwidth demands; it becomes incompetent to fulfil the requirements. A futuristic and high speed data transmission technique is replacing RF nowadays i.e. Free space optical communication (FSOC) because of its great potentials. Future generation communication systems require competent FSOC technology to sustain wireless traffic in 5G and 6G services. Because the features of FSOC and RF are complimentary, combining the two technologies is seen as a potential way to enable future communication systems. Hybrid RF/FSOC is a good way to overcome the limits of separate systems while still taking use of the beneficial aspects of each technology. Wireless systems use e.g. in hybrid RF/FSOC can increase individual network performance in terms of performance, dependability, and economical operations. In this work, a detailed review on FSOC systems is presented by doing the extensive literature review of reported research. Review covered key ideas consisting all sorts of FSOC systems, FSOC design with multiple and single beams, as part of the evaluation. The examination of rainfall and hazy effects on FSO signal transmission is also included in the review. The key benefits, future potential, and obstacles that must be addressed in order to successfully implement FSOC for 5G paradigms are presented.
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... The parameterization of DSD can obtain the distribution model parameters of DSD in different rain types, which is significant in advancing microphysics parameterization in numerical weather prediction (NWP) models (Wainwright et al., 2014;McFarquhar et al., 2015;Zhao et al., 2019). In addition, understanding the DSD is crucial in many applied fields concerning hydrology, agriculture, soil erosion, and microwave communication (Rincon and Lang, 2002;Smith et al., 2009;Angulo-Martínez and Barros, 2015;Lim et al., 2015;Yang et al., 2016;Giannetti et al., 2017). ...
Statistical characteristics of raindrop size distribution during rainy seasons in complicated mountain terrain
Article
Full-text available
In order to improve our understanding of the characteristics of raindrop size distribution (DSD) over complex mountainous terrain, the differences in DSD over the southern slopes, northern slopes, and interior of the Qilian Mountains were analyzed using 6 months of observations. For all rainfall events, the number concentrations of small and large raindrops in the interior and on the southern slopes were greater than on the northern slopes, but midsize raindrops were less. The DSD spectrum of the interior was more variable and differed significantly from that of the northern slopes. The differences in the normalized intercept parameters of the DSD for stratiform and convective rainfall were 8.3 % and 10.4 %, respectively, and those of the mass-weighted mean diameters were 10.0 % and 23.4 %, respectively, while the standard deviations of DSD parameters at interior sites were larger. The differences in the coefficient and exponent of the Z–R relationship were 2.5 % and 10.7 %, respectively, with an increasing value of the coefficient from the southern to the northern slopes for stratiform rainfall but the opposite for convective rainfall. In addition, the DSD characteristics and Z–R relationships were more similar at the ipsilateral sites and had smaller differences between the southern slopes and interior of the mountains.
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Rainfall Classification in Genoa: Machine Learning vs. Adaptive Statistical Models Using Satellite Microwave Links
Article
Full-text available
  • Jan 2024
Monitoring rainfall is becoming increasingly important due to the impacts of climate change. In this context, opportunistic sensing based on satellite microwave links (SMLs) is gaining significant interest for its potential to provide real-time, low-cost, and valuable information. In this work, we deployed a network of 26 SML sensors over a survey territory corresponding to a catchment area of 140 km 2 , and the data collected from it were used to train two machine learning (ML) algorithms and a statistical method to predict wet/dry conditions. Additionally, a voting mechanism based on the majority vote of the three classifiers enhances the performance of the individual methods. The results show that ML algorithms are valuable solutions for real-time monitoring of rainfall, even in an extended sensor network. The voting mechanism improves the prediction of low precipitation at the expense of a higher false positive rate.
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Recording Rainfall Intensity: Has an Optimum Method Been Found?
Article
Full-text available
  • Sep 2023
Many design principles for rain gauges that have the capacity to record rainfall intensity have been proposed or developed. These are here grouped into 15 categories, and the abilities and limitations of each are discussed. No standard or optimum method has emerged, despite more than 80 years of effort in the last two centuries, together with prior work from the 17th C onwards. Indeed, new methods continue to be explored for both point-based and area-wide collections of intensity data. Examples include the use of signal attenuation by rain along the tower-to-tower links of cellular phone networks, monitoring the speed of vehicle windscreen wipers, and exploiting the sound or vision from security and traffic-monitoring cameras. Many of these approaches have the potential to provide vastly more observation sites than conventional meteorological stations equipped with rain gauges. Some of these contemporary approaches seek to harness the potential of crowdsourced or citizen-science data. It is hoped that the present overview of methods will provide a guide for those wishing to collect or analyses rainfall intensity data for application in areas such as soil erosion processes, ecohydrology, agrochemical washoff, or urban flash flooding. Because rainfall intensity is one of the key aspects of the hydrologic cycle likely to respond as climate change and variability proceed, the choice of appropriate data collection methods has additional contemporary importance for the monitoring of regional and global precipitation changes.
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Investigation of Weather Radar Quantitative Precipitation Estimation Methodologies in Complex Orography
Article
Full-text available
  • Feb 2017
Near surface quantitative precipitation estimation (QPE) from weather radar measurements is an important task for feeding hydrological models, limiting the impact of severe rain events at the ground as well as aiding validation studies of satellite-based rain products. To date, several works have analyzed the performance of various QPE algorithms using actual and synthetic experiments, possibly trained by measurement of particle size distributions and electromagnetic models. Most of these studies support the use of dual polarization radar variables not only to ensure a good level of data quality but also as a direct input to rain estimation equations. One of the most important limiting factors in radar QPE accuracy is the vertical variability of particle size distribution, which affects all the acquired radar variables as well as estimated rain rates at different levels. This is particularly impactful in mountainous areas, where the sampled altitudes are likely several hundred meters above the surface. In this work, we analyze the impact of the vertical profile variations of rain precipitation on several dual polarization radar QPE algorithms when they are tested in a complex orography scenario. So far, in weather radar studies, more emphasis has been given to the extrapolation strategies that use the signature of the vertical profiles in terms of radar co-polar reflectivity. This may limit the use of the radar vertical profiles when dual polarization QPE algorithms are considered. In that case, all the radar variables used in the rain estimation process should be consistently extrapolated at the surface to try and maintain the correlations among them. To avoid facing such a complexity, especially with a view to operational implementation, we propose looking at the features of the vertical profile of rain (VPR), i.e., after performing the rain estimation. This procedure allows characterization of a single variable (i.e., rain) when dealing with vertical extrapolations. In this work, a definition of complex orography is also given, introducing a radar orography index to objectively quantify the degree of terrain complexity when dealing with radar QPE in heterogeneous environmental scenarios. Three case studies observed by the research C-band polarization agility Doppler radar named Polar 55C, managed by the Institute of Atmospheric Sciences and Climate (ISAC) at the National Research Council of Italy (CNR), were used to prove the concept of VPR. Our results indicate that the combined algorithm, which merges together differential phase shift (Kdp), single polarization reflectivity factor (Zhh), and differential reflectivity (Zdr), once accurately processed, in most cases performs better among those tested and those that make use of Zhh alone, Kdp alone, and Zhh, and Zdr. Improvements greater than 25% are found for the total rain accumulations in terms of normalized bias when the VPR extrapolation is applied.
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Rainfall measurement from the opportunistic use of an Earth–space link in the Ku band
Article
Full-text available
  • Aug 2013
The present study deals with the development of a low-cost microwave device devoted to the measurement of average rain rates observed along Earth–satellite links, the latter being characterized by a tropospheric path length of a few kilometres. The ground-based power measurements, which are made using the Ku-band television transmissions from several different geostationary satellites, are based on the principle that the atmospheric attenuation produced by rain encountered along each transmission path can be used to determine the path-averaged rain rate. This kind of device could be very useful in hilly areas where radar data are not available or in urban areas where such devices could be directly placed in homes by using residential TV antenna. The major difficulty encountered with this technique is that of retrieving rainfall characteristics in the presence of many other causes of received signal fluctuation, produced by atmospheric scintillation, variations in atmospheric composition (water vapour concentration, cloud water content) or satellite transmission parameters (variations in emitted power, satellite pointing). In order to conduct a feasibility study with such a device, a measurement campaign was carried out over a period of five months close to Paris. The present paper proposes an algorithm based on an artificial neural network, used to identify dry and rainy periods and to model received signal variability resulting from effects not related to rain. When the altitude of the rain layer is taken into account, the rain attenuation can be inverted to obtain the path-averaged rain rate. The rainfall rates obtained from this process are compared with co-located rain gauges and radar measurements taken throughout the full duration of the campaign, and the most significant rainfall events are analysed.
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Rain Drop Measurement Techniques: A Review
Article
Full-text available
  • Jan 2016
Abstract:For over a century there have been many studies that describe the use of rain dropmeasurement techniques. Initial manual measurement methods evolved due to improved technologyto include photographic and, more recently, automated disdrometer and laser measurementtechniques. Despite these numerous studies, there have been few comparative reviews of the rangeof methodologies, and their relative performance. This review explores the raindrop measurementtechniques available, and summarizes and classifies the techniques according to the method orprinciple involved. The requirements of a robust raindrop measurement technique are suggested,and these are reviewed against existing rain drop measurement techniques to provide a comparativeguide to the use of the range of techniques available for any research study. This review revealedthat while advances in technology have allowed many of the deficiencies of early techniques to beeliminated, challenges remain in relation to the precision of the measurement of the size, shape,and velocity of rain drops.Keywords:raindrop measurement techniques; impact and optical disdrometers; laser precipitationmonitor; pluviometer Rain Drop Measurement Techniques: A Review. Available from: https://www.researchgate.net/publication/291345845_Rain_Drop_Measurement_Techniques_A_Review [accessed Jan 22, 2016].
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WMO Field Intercomparison of Rainfall Intensity Gauges
Article
Full-text available
  • Jan 2009
The WMO Field Intercomparison of Rainfall Intensity (RI) Gauges was conducted from 1 October 2007 to 30 April 2009, in the Centre of Meteorological Experimentations (ReSMA) of the Italian Meteorological Service, in Vigna di Valle, Italy. It was organized following the request of users and the recommendation of CIMO-XIV. Heavy rainfall is generally the origin of flash floods. In view of the very high variability of the rainfall intensity, measurements at a 1-minute time scale are crucial to enable proper measures be taken to mitigate the impact of such events and save lives, property and infrastructures. As the return period of heavy rainfall events is large, long-term records of rainfall intensity data are needed to estimate the probability of occurrence of heavy rainfall at a given location and time. Such measurements would also be used for better design of structures (building, construction works) and infrastructure (drainage) to mitigate severe weather impact. This intercomparison hosted 25 different rainfall intensity gauges. The majority of these instruments were catching type gauges comprising tipping-bucket gauges, weighing gauges and one water level gauge. Non-catching rain gauges were represented by optical and impact disdrometers, one optical/capacitive gauge and one microwave radar gauge. This intercomparison was unique as to the number of instruments and variability of techniques used. The main objective of this intercomparison was to intercompare the performance of in-situ rainfall intensity instruments of different measuring principles, with special consideration given to high rainfall intensities. Further objectives were to offer advice on improvements of instruments and precipitation measurements. Prior to installation in the field all reference gauges and the catching type instruments were calibrated in the WMO recognized laboratory at the University of Genoa. Calibration procedures were based on recommendations of the previous WMO Laboratory Intercomparison of RI Gauges (2004-2005) which were further developed to allow an assessment of the 1-minute measurement uncertainty under constant flow conditions. Additionally all catching gauges were subject to a step response test to assess their dynamic response. In the field, all gauges were compared with a RI composite working reference consisting of a set of three reference rain gauges in a standard pit. The results of the intercomparison confirmed the feasibility to measure and compare rainfall intensities on a one minute time scale and provided information on the achievable measurement uncertainties. Due to the very high variability of rainfall intensity, the time synchronization of the instruments is crucial to compare their measurements and to design the measurement systems, as two successive 1-minute rainfall intensity measurements can differ much more than the measurements of two well synchronized instruments. The uncertainty of the RI composite working reference in the pit was evaluated to be 4.3 mm/h, leading to a relative uncertainty below 5% above 90 mm/h and higher than the 5% measurement uncertainty required by WMO below 90 mm/h. It is recommended that rainfall intensity measurements be further standardized at an international level and based on knowledge obtained from this intercomparison to allow the users to obtain homogeneous and compatible data sets. The procedure adopted for performing calibration tests in the laboratory should become a standard method to be used for assessing the instruments’ performance. Acceptance tests could be based on the adopted laboratory procedures and standards. A classification of instrument performance should also be developed to help users in selecting the proper instrument for their applications. The intercomparison results confirmed that uncorrected tipping bucket rain gauges should be corrected. Very good results can be achieved by software correction methods. Catching gauges that do not use a funnel are sensitive to environmental factors, affecting the measurements of some instruments. It was found that proper techniques can be used to reduce the noise in the measurements. It was found that manufacturers need to improve their documentation, and users should contact manufacturers for additional guidance, as how to best operate their instruments for various applications. The Intercomparison high quality data set (1-min rainfall intensity data) constitutes an important scientific resource that should be further exploited beyond the objectives of the present data analysis. It is also recommended that the developed expertise and the infrastructure of the sites, both the field and the laboratory facilities, be further exploited within WMO.
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From S-band mobile interactive multimedia to fixed satellite interactive multimedia: Making satellite interactivity affordable at Ku-band and Ka-band
Article
Full-text available
  • Nov 2015
This paper describes the evolution of the ETSI S-band Mobile Interactive Multimedia (S-MIM) protocol to support Fixed Interactive Multimedia Services (F-SIM) exploiting existing Ku and Ka-band satellites. The key F-SIM protocol differences for both physical and upper layers are described and justified. The F-SIM protocol has been adopted by the recently deployed Eutelsat Broadcast Interactive System (EBIS) whose architecture, key system parameters, link budget examples and key composing elements are also described. Finally, a summary of laboratory and field trials results over the Eutelsat Ka-Ssat multi-beam satellite are illustrated.
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Polarimetric Doppler Weather Radar: Principles and Applications
Book
  • Aug 2001
This 2001 book provides a detailed introduction to the principles of Doppler and polarimetric radar, focusing in particular on their use in the analysis of weather systems. The design features and operation of practical radar systems are highlighted throughout the book in order to illustrate important theoretical foundations. The authors begin by discussing background topics such as electromagnetic scattering, polarization, and wave propagation. They then deal in detail with the engineering aspects of pulsed Doppler polarimetric radar, including the relevant signal theory, spectral estimation techniques, and noise considerations. They close by examining a range of key applications in meteorology and remote sensing. The book will be of great use to graduate students of electrical engineering and atmospheric science as well as to practitioners involved in the applications of polarimetric radar systems.
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A Field Study of Pixel-Scale Variability of Raindrop Size Distribution in the Mid-Atlantic Region
Article
  • Jan 2016
The spatial variability of parameters of the raindrop size distribution and its derivatives is investigated through a field study where collocated Particle Size and Velocity (Parsivel2) and two-dimensional video disdrometers were operated at six sites at Wallops Flight Facility, Virginia, from December 2013 to March 2014. The three-parameter exponential function was employed to determine the spatial variability across the study domain where the maximum separation distance was 2.3 km. The nugget parameter of the exponential function was set to 0.99 and the correlation distance d0 and shape parameter s0 were retrieved by minimizing the root-mean-square error, after fitting it to the correlations of physical parameters. Fits were very good for almost all 15 physical parameters. The retrieved d0 and s0 were about 4.5 km and 1.1, respectively, for rain rate (RR) when all 12 disdrometers were reporting rainfall with a rain-rate threshold of 0.1 mm h-1 for 1-min averages. The d0 decreased noticeably when one or more disdrometers were required to report rain. The d0 was considerably different for a number of parameters (e.g., mass-weighted diameter) but was about the same for the other parameters (e.g., RR) when rainfall threshold was reset to 12 and 18 dBZ for Ka- and Ku-band reflectivity, respectively, following the expected Global Precipitation Measurement mission's spaceborne radar minimum detectable signals. The reduction of the database through elimination of a site did not alter d0 as long as the fit was adequate. The correlations of 5-min rain accumulations were lower when disdrometer observations were simulated for a rain gauge at different bucket sizes.
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Rainfall measurements using satellite downlink attenuation
Conference Paper
  • Jul 2014
The attenuation of a commercial satellite link signal at Ku-band is used for estimating rainfall rate along the link path. Comparisons with rainfall accumulations obtained using simultaneous radar measurements along the same path show good agreement. This method can potentially be used to complement other rainfall accumulation measurements obtained with radar and rain gauges in urban settings and areas with complex terrain.
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Improvement of vertical profiles of raindrop size distribution from micro rain radar using 2D video disdrometer measurements
Article
  • Jul 2015
  • ATMOS RES
A measurement scheme aimed at investigating precipitation properties based on collocated disdrometer and profiling instruments is used in many experimental campaigns. Raindrop size distribution (RSD) estimated by disdrometer is referred to the ground level; the collocated profiling instrument is supposed to provide complementary estimation at different heights of the precipitation column above the instruments. As part of the Special Observation Period 1 of the HyMeX (Hydrological Cycle in the Mediterranean Experiment) project, conducted between 5 September and 6 November 2012, a K-band vertically pointing micro rain radar (MRR) and a 2D video disdrometer (2DVD) were installed close to each other at a site in the historic center of Rome (Italy). The raindrop size distributions collected by 2D video disdrometer are considered to be fairly accurate within the typical sizes of drops. Vertical profiles of raindrop sizes up to 1085mare estimated fromthe Doppler spectra measured by themicro rain radarwith a height resolution of 35 m. Several issues related to verticalwinds, attenuation correction, Doppler spectra aliasing, and range-Doppler ambiguity limit the performance of MRR in heavy precipitation or in convection, conditions that frequently occur in late summer or in autumn in Mediterranean regions. In this paper,MRR Doppler spectra are reprocessed, exploiting the 2DVDmeasurements at ground to estimate the effects of vertical winds at 105 m (the most reliable MRR lower height), in order to provide a better estimation of vertical profiles of raindrop size distribution fromMRR spectra. Results showthat the reprocessing procedure leads to a better agreement between the reflectivity computed at 105 m from the reprocessed MRR spectra and that obtained fromthe 2DVD data. Finally, vertical profiles ofMRR-estimated RSDs and their relevant moments (namely median volume diameter and reflectivity) are presented and discussed in order to investigate the microstructure of rain both in stratiform and convective conditions.
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