On the Use of a 77 GHz Automotive Radar as a Microwave Rain Gauge

The European Telecommunications Standards Institute (ETSI) defines the frequency band of 77 GHz (W-band) as the one dedicated to automatic cruise control long-range radars. A car can be thought as a moving integrated weather sensor since it can provide meteorological information exploiting the sensors installed on board. This work presents the preliminary analysis of how a 77 GHz mini radar can be used as a short range microwave rain gauge. After the discussion of the Mie scattering formulation applied to a microwave rain gauge working in the W-band, the proposal of a new Z-R equation to be used for correct rain estimation is given. Atmospheric attenuation and absorption are estimated taking into account the ITU-T recommendations. Functional requirements in adapting automatic cruise control long-range radar to a microwave rain gauge are analyzed. The technical specifications are determined in order to meet the functional requirements

Ultra-light disposable radio probes for atmospheric monitoring

Representation of clouds remains a latent ambiguity for weather forecasting and climate models since their characteristics depends on multidisciplinary processes in a wide range of natural scales, from the collision of micron-sized droplets and particles to the thousand-of-meters scale of airflow dynamics. Within the Horizon 2020 Innovative Training Network Cloud-MicroPhysics-Turbulence-Telemetry (ITN-COMPLETE), the development of ultra-small light disposable radio probes for fluctuation-inside-cloudsmonitoring is promoted and financed. Being light-weighted (less than 20 grams), the probes will have a fluid-dynamic behavior to allow them to “float” inside warm clouds after been released by an aircraft or an Unmanned Aerial Vehicle (UAV). Each disposable probe is equipped with compact size microprocessors (presently the first prototype uses Arduino© Nano), controllers and a set of sensors for the measurement of atmospheric parameters such as velocity, acceleration, pressure, temperature and humidity variations. All probes are part of the Internet-of-Things (IoT) world. In fact, while floating, they collect, store and then send the coded information to a base station located at the ground through a dedicated radio transmission link. It is to be noted that long-range communication link (10 km) should be assured with low power consumption technology: a network based on the Long Range Wide Area Network (LoRaWAN© protocol) to connect and exchange data within the end-modules and the base station is the potential adopted solution. As far as possible biocompatible elements within the mini ultra-light radio probes will be used to avoid any environmental pollution

Progress on the realization of innovative low cost disposable hail sensing probes

Detailed studies and researches about hail characterization are considered to play a key role both in weather prediction and potentially also in damage assessment after a strong hail event occurred. Most monitoring instruments perform indirect monitoring operations, sensing the parameters from a remote position and not being directly inside a hailstorm. Since 2015 the CINFAI (Italian National Consortium for the Physic of Atmospheres and Hydrospheres) with its local operative research unit at the DET (Department of Electronic and Telecommunications) of Politecnico di Torino, Italy, realized a first preliminary study concerning the realization of artificial disposable sensing probes to study and monitor hail (conducted within a project called HaSP, founded by Regione Piemonte, Italy) [1]. The study was continued in cooperation with EST (Envisens Technologies s.r.l.), a small Italian engineering company, in order to realize the first small prototypes. Introducing the appropriate modifications, a similar version of the probes can be also suitable for monitoring atmospheric parameters [2]. Aim of this work is to present the progress on the realization of low cost disposable hail sensing probes for remote sensing and the study of the properties of hail. The probes are designed as artificial hailstones in order to study both the physical properties of the portion of atmosphere where the formation of hail occurs and the modification of atmospheric conditions while the hailstones are falling to the ground. For this reason, the probes and the hailstones should have the most similar as possible fluid-dynamic properties. The artificial probes can be dropped by a plane, or potentially by a UAV (Unmanned Aircraft Vehicle) if permitted by specific legislation, which fly above and through the clouds where the hail formation occurs. Each probe is equipped with different sensors and during their falling to the ground, they directly measure different physical parameters (e.g humidity, temperature, pressure, acceleration…). All data are sent to a receiver located on the ground exploiting a specific communication link realized at a frequency not affected by the presence of hail and water in the atmosphere. The hail sensing probes can be used for efficient monitoring operations and studies of hail formation dynamics and conditions, thus increasing the set of instruments used for monitoring, remotely sensing and study the physical properties of hail, and possibly also to improve the hail forecasting models

Real Time Monitoring of Extreme Rainfall Events with Simple X-Band Mini Weather Radar

Real time rainfall events monitoring is very important for a large number of reasons: Civil Protection, hydrogeological risk management, hydroelectric power purposes, road and traffic regulation, and tourism. Efficient monitoring operations need continuous, high-resolution and large-coverage data. To monitor and observe extreme rainfall events, often much localized over small basins of interest, and that could frequently causing flash floods, an unrealistic extremely dense rain gauge network should be needed. On the other hand, common large C-band or S-band long range radars do not provide the necessary spatial and temporal resolution. Simple short-range X-band mini weather radar can be a valid compromise solution. The present work shows how a single polarization, non-Doppler and non-coherent, simple and low cost X-band radar allowed monitoring three very intense rainfall events occurred near Turin during July 2014. The events, which caused damages and floods, are detected and monitored in real time with a sample rate of 1 minute and a radial spatial resolution of 60 m, thus allowing to describe the intensity of the precipitation on each small portion of territory. This information could be very useful if used by authorities in charge of Civil Protection in order to avoid inconvenience to people and to monitor dangerous situations

Derivation of Z-R equation using Mie approach for a 77 GHz radar

The ETSI (European Telecommunications Standards Institute) defines the frequency band around 77 GHz as dedicated to automatic cruise control long-range radars. This work aims to demonstrate that, with specific assumption and the right theoretical background it is also possible to use a 77 GHz as a mini weather radar and/or a microwave rain gauge. To study the behavior of a 77 GHz meteorological radar, since the raindrop size are comparable to the wavelength, it is necessary to use the general Mie scattering theory. According to the Mie formulation, the radar reflectivity factor Z is defined as a function of the wavelength on the opposite of Rayleigh approximation in which is frequency independent. Different operative frequencies commonly used in radar meteorology are considered with both the Rayleigh and Mie scattering theory formulation. Comparing them it is shown that with the increasing of the radar working frequency the use of Rayleigh approximation lead to an always larger underestimation of rain. At 77 GHz such underestimation is up to 20 dB which can be avoided with the full Mie theory. The crucial derivation of the most suited relation between the radar reflectivity factor Z and rainfall rate R (Z-R equation) is necessary to achieve the best Quantitative Precipitation Estimation (QPE) possible. Making the use of Mie scattering formulation from the classical electromagnetic theory and considering different radar working frequencies, the backscattering efficiency and the radar reflectivity factor have been derived from a wide range of rain rate using specific numerical routines. Knowing the rain rate and the corresponding reflectivity factor it was possible to derive the coefficients of the Z-R equation for each frequency with the least square method and to obtain the best coefficients for each frequency. The coefficients are then compared with the ones coming from the scientific literature. The coefficients of a 77 GHz weather radar are then obtained. A sensitivity analysis of a 77 GHz weather radar using such Z-R relation is also studied. The work shows that the right knowledge of Z-R equation is absolutely essential to use such a specific radar for the estimation of rainfall. The use Mie scattering theory is absolutely necessary for a 77 GHz radar in order to avoid the heavy underestimation of rainfall

A LoRaWAN based network for monitoring operation of environmental pollution and meteorological parameters using public transport

The LoRa (Long Range Low Power) technology and in particular the LoRaWAN (LoRa Wireless Area Network) is a Low Power Wide Area Network (LPWAN) is used to connect different sensors in a regional, national or global network and making sensed data available on the Internet of Things (IoT). LoRaWAN provides secure bi-directional data transfer and communication. Equipment using such technology can work over for years without a battery change. LoRaWAN specification provides seamless interoperability among IoT without the need of complex local installations and gives back the freedom to the user. At the same time, the number of fields of application of LoRa sensors is continuously increasing. Among them, LoRa technology can be used in meteorology. LoRa uses adaptive data rate, which allows receiving messages from a high number of devices. Considering that a node can send unlimited messages per day, a set of meteorological sensors (e. g. rain gauges, disdrometers, hygrometers, thermometers, etc.) can be thought as nodes of a star topology network in order to capillary monitor a portion of territory, improving also weather forecasting, services and operations. The present work aims to realize a control network for pollutant emissions including sound emissions) and meteorological purpose by exploiting the vehicular traffic of public transport. A specific detection system is placed on a fleet of public transport vehicles to measure both the level of emissions and meteorological parameters along the tracks of the vehicles, thus defining hourly and daily trends. Concerning pollution, it is possible to identify where levels are higher than what required by the law. In order to connect the individual sensors to the central data collection and processing server, a LoRaWAN is implemented. The network is made up of individual slave nodes, corresponding to the sensors mounted on each vehicle. Each slave node is connected with a cluster node (placed at a maximum distance of 10 km) installed on the poles present at public transport stops. All the cluster nodes receives and re-transmits the information until reaching the final cluster represented by a centralized server. The presented project is intended to be sustainable from both environmental and economic point of view and allows to acquire information with high spatial and temporal resolution

High resolution KE-maps with X-band mini weather radar

The erosion of the terrain starts with the process of soil detachment by raindrop impact. The Kinetic Energy (KE)of a single raindrop can represent the basic and most commonly used unit of raindrop erosivity. KE is functions of the drop size, drop shape and its terminal velocity. It can be expressed as the rain kinetic energy per unit area and per unit time (KEtime, time-specific kinetic energy) or, alternatively, as the amount of rain kinetic energy per unit volume of rain (KEmm volume-specific kinetic energy). The total KE of rainfall is evaluated by summing up the individual kinetic energies of all the raindrops. Therefore, KE can be calculated directly for any rainfall event by knowing its intensity (I) and by using one of the so-called KE–I relationships, which are present in large number in the scientific landscape, relations that in turn derive from an assumed Drop Size Distribution (DSD). Alternatively, it would be more pertinent to relate KE with data obtained by a disdrometer: however, such instruments are costly, complex (and therefore critics to use) and, consequently not generally available. Short-range X band weather radars are a good alternative solution to estimate KE. They can provide measure of radar reflectivity factor (Z) taking into account that indeed Z is related to the drops kinetic energy than the rain intensity itself. By using the weather radar, it is possible to measure KE exploiting the KE-Z relationships. In this work, we consider a pulsed X-band radar, non-coherent, non-Doppler, with vertical polarization, acquiring reflectivity maps each minute with radial resolution of 60 meters, up to a maximum range of 30 km. By using the high temporal and spatial resolution radar maps it is possible to realize high-resolution KE maps exploiting one of the KE-Z relations available in the literature, in particular the one by Yu et. al. in 2012. Starting from the maps acquired by the radar in the form of digital number, the radar reflectivity maps are obtained exploiting signal processing algorithms and the consequent KE maps are evaluated. A significant correlation between a strong rain event and some landslides in the nearby hills is presented. The high-resolution KE maps can put in evidence the spatial and temporal variability of the kinetic energy of rainfall. Used in conjunction with GIS layers concerning topography, soil properties and land use, such KE maps have a strong potential for geosciences applications

77 GHz radar for meteorological purposes: preliminary results

The European Telecommunications Standards Institute defines the frequency band around 77 GHz as dedicated to automatic cruise control long-range radars, but recent works demonstrated that, under specific assumption and with the right theoretical background, it is also possible to use a W-band radar as a short range microwave rain gauge. Working at 77 GHz, raindrop size are comparable to the used wavelength and therefore it is necessary to use the general Mie scattering theory. In order to avoid underestimation of rain (up to -20 dB), the proper relation between the radar reflectivity factor Z and the rainfall rate R (the so-called Z-R equation) should be used, specifically determined for such frequency with the Mie scattering theory. A possible Z-R equation for 77 GHz radar has been presented by Bertoldo et. al. in 2017, during the EGU General Assembly. An overview of functional requirements to adapt an automatic cruise control long-range radar (of particular interests for its low cost) to a short-range microwave rain gauge is given qualified for achieving rainfall measurements. Using a commercial prototype of W-band radar some preliminary measurements were made and will be presented. It is shown that it is possible to use W-band radar for monitoring weather events. A good Quantitative Precipitation Estimation (QPE) can be achieved with an acceptable approximation

Radar meteo ad alta risoluzione spaziale per studio di eventi estremi

L'analisi degli eventi estremi di pioggia, insieme ai relativi studi statistici, costituisce un campo di ricerca che riveste una grande importanza al giorno d’oggi, dato che avvengono sempre più frequentemente fenomeni molto intensi, di breve durata e localizzati, che possono avere anche grandi ripercussioni sulla società. In letteratura scientifica sono presenti un gran numero di modelli e una grande varietà di analisi che suggeriscono e mettono in relazione le variazioni della frequenza e l’intensità stessa degli eventi estremi con i cambiamenti climatici che avvengono su brevi intervalli temporali o su piccola scala, fatto che rende ancora più importante lo studio di tali eventi. Gran parte delle analisi di eventi estremi è effettuata utilizzando i dati pluviometrici. Solo poche di esse sono state eseguite sfruttando le potenzialità dei radar meteo. A. Overeem [1] presenta un lavoro molto importante condotto studiando una regione olandese con orografia in gran parte omogenea. Viene presentata un'analisi climatologica basata su 10 anni di dati radar Doppler a banda C con una risoluzione spaziale di 2.4 km. Vengono anche valutate sia la Generalized Extreme Value (GEV) distribution e le Depth-Duration-Frequency curve su piccoli bacini appositamente selezionati, dimostrando che i sistemi radar possono essere uno strumento molto utile per analizzare gli eventi estremi. Spesso l’analisi degli eventi estremi deve essere condotta in aree in cui le precipitazioni presentano una grande variabilità anche a distanze ridotte, come può essere, ad esempio, un’area montana o comunque con una orografia complessa. Su tali zone è necessario un dataset di misure di pioggia allargato in modo da tenere conto della variabilità spaziale del territorio monitorato. Tali dati possono essere ottenuti con una rete pluviometrica molto fitta oppure utilizzando radar meteorologici ad alta risoluzione spaziale come possono essere quelli in banda X. Tali radar consentono infatti di ottenere mappe di pioggia con risoluzione spaziale di qualche decina di metri e frequenza temporale di un minuto. Nel presente lavoro sono stati considerati circa tre anni di mappe radar acquisite dal radar in banda X installato sul tetto del Politecnico di Torino che presentano una risoluzione spaziale di 60 m. L'intera area monitorata è stata suddivisa in quattro zone considerandone la complessa orografia, i problemi dovuti al clutter e, in parte, anche la distanza dal radar stesso: zone pianeggianti, montagne, colline e area urbane. Sulle quattro zone sono stati analizzati gli eventi estremi utilizzando le mappe radar e i pluviometri dell’ARPA Piemonte i cui dati sono liberamente accessibili e scaricabili da internet. Definendo come estremo un giorno con una quantità di pioggia caduta cumulata superiore ad una determinata soglia, e considerando aree di diversa estensione centrare sui pluviometri, si vuole mostrare come il numero di eventi estremi identificati utilizzando le mappe radar, opportunamente processate per evitare l’utilizzo di informazioni errate, è sempre maggiore o uguale rispetto a quelli identificati utilizzando un insieme di pluviometri stessi. Ciò conferma come un mini radar meteorologico può essere adatto per lo studio degli eventi estremi [2]. Si vuole anche mettere in evidenza che un sistema radar può essere utilizzato in cooperazione con le reti pluviometriche già esistenti, soprattutto in aree ad orografia complessa, come quelle montane e collinari, dove l’alta risoluzione spaziale delle mappe di un radar meteo può permettere di accrescere notevolmente la statistica degli eventi estremi identificati, soprattutto in considerazione della loro risoluzione spaziale. Utilizzando congiuntamente i dati è possibile validare e ricostruire in maniera accurata la statistica degli eventi estremi su una specifica area e risalire a serie storiche molto lunghe, considerando che maggiore è la disponibilità di informazioni, maggiore sarà l’attendibilità della statistica stessa