Statistical analysis and modelling of weather radar beam propagation conditions in the Po Valley (Italy)

Ground clutter caused by anomalous propagation (anaprop) can affect seriously radar rain rate estimates, particularly in fully automatic radar processing systems, and, if not filtered, can produce frequent false alarms. A statistical study of anomalous propagation detected from two operational C-band radars in the northern Italian region of Emilia Romagna is discussed, paying particular attention to its diurnal and seasonal variability. The analysis shows a high incidence of anaprop in summer, mainly in the morning and evening, due to the humid and hot summer climate of the Po Valley, particularly in the coastal zone. Thereafter, a comparison between different techniques and datasets to retrieve the vertical profile of the refractive index gradient in the boundary layer is also presented. In particular, their capability to detect anomalous propagation conditions is compared. Furthermore, beam path trajectories are simulated using a multilayer ray-tracing model and the influence of the propagation conditions on the beam trajectory and shape is examined. High resolution radiosounding data are identified as the best available dataset to reproduce accurately the local propagation conditions, while lower resolution standard TEMP data suffers from interpolation degradation and Numerical Weather Prediction model data (Lokal Model) are able to retrieve a tendency to superrefraction but not to detect ducting conditions. Observing the ray tracing of the centre, lower and upper limits of the radar antenna 3-dB half-power main beam lobe it is concluded that ducting layers produce a change in the measured volume and in the power distribution that can lead to an additional error in the reflectivity estimate and, subsequently, in the estimated rainfall rate

Clutter and rainfall discrimination by means of doppler-polarimetric measurements and vertical reflectivity profile analysis

The estimation of rainfall rate and other parameters from radar scattering volume is heavily affected by the presence of intense sea and ground clutter and echoes which appears in anomalous propagation condition. To deal with these non meteorological echoes we present a new clutter removal algorithm which combines the results of previous works. The algorithm fully exploits both the Doppler and polarimetric capabilities of the radar used and the analysis of vertical reflectivity profile in order to achieve the better identification of the meteorological and non-meteorological targets. The algorithm has been applied to the C-band radar of Monte Settepani (Savona, Italy), which runs in a high-topography environment. Preliminary results are presented

Effects of propagation conditions on radar beam-ground interaction: impact on data quality

International audienceA large part of the research in the radar meteorology is devoted to the evaluation of the radar data quality and to the radar data processing. Even when, a set of absolute quality indexes can be produced (like as ground clutter presence, beam blockage rate, distance from radar, etc.), the final product quality has to be determined as a function of the task and of all the processing steps. In this paper the emphasis lies on the estimate of the rainfall at the ground level taking extra care for the correction for ground clutter and beam blockage, that are two main problems affecting radar reflectivity data in complex orography. In this work a combined algorithm is presented that avoids and/or corrects for these two effects. To achieve this existing methods are modified and integrated with the analysis of radar signal propagation in different atmospheric conditions. The atmospheric refractivity profile is retrieved from the nearest in space and time radiosounding. This measured profile is then used to define the `dynamic map' used as a declutter base-field. Then beam blockage correction is applied to the data at the scan elevations computed from this map. Two case studies are used to illustrate the proposed algorithm. One is a summer event with anomalous propagation conditions and the other one is a winter event. The new algorithm is compared to a previous method of clutter removal based only on static maps of clear air and vertical reflectivity continuity test. The improvement in rain estimate is evaluated applying statistical analysis and using rain gauges data. The better scores are related mostly to the ``optimum" choice of the elevation maps, introduced by the more accurate description of the signal propagation. Finally, a data quality indicator is introduced as an output of this scheme. This indicator has been obtained from the general scheme, which takes into account all radar data processing steps

Spatial and temporal biochemical variation in the Norther Adriatic Sea during summer 2001

Nel giugno e nel settembre del 2001 sono state effettuate due crociere oceanografiche nel nord Adriatico, da Numana (An) a Chioggia (Ve), dall\u27Italia alla Croazia, con misurazioni di temperatura, salinit?, fluorescenza, irradianza, ossigeno disciolto e nutrienti. Nel lavoro vengono posti in relazione tra loro l\u27ossigeno disciolto, la fluorescenza, i nutrienti, l\u27irradianza e le portate del Po, con lo scopo di osservare le loro variazioni biochimiche nello spazio e nel tempo. Dallo studio risulta che gli inputs del Po e l\u27irradianza sono fattori importanti nella distribuzione della clorofilla a e dell\u27ossigeno disciolto in superficie, e che i processi di mineralizzazione determinano una marcata ipossia in un\u27ampia area al largo della foce del Po.Nel giugno e nel settembre del 2001 sono state effettuate due crociere oceanografiche nel nord Adriatico, da Numana (An) a Chioggia (Ve), dall\u27Italia alla Croazia, con misurazioni di temperatura, salinit?, fluorescenza, irradianza, ossigeno disciolto e nutrienti. Nel lavoro vengono posti in relazione tra loro l\u27ossigeno disciolto, la fluorescenza, i nutrienti, l\u27irradianza e le portate del Po, con lo scopo di osservare le loro variazioni biochimiche nello spazio e nel tempo. Dallo studio risulta che gli inputs del Po e l\u27irradianza sono fattori importanti nella distribuzione della clorofilla a e dell\u27ossigeno disciolto in superficie, e che i processi di mineralizzazione determinano una marcata ipossia in un\u27ampia area al largo della foce del Po

Effect of exclusion net timing of deployment and color on Halyomorpha halys (Hemiptera: Pentatomidae) infestation in pear and apple orchards

The brown marmorated stink bug, Halyomorpha halys (Stål, 1855) (Hemiptera: Pentatomidae), is an invasive pest species native to East Asia that has become the major pest for many crops, causing serious economic damage. The occurrence of this invasive pest leads to an increase in broad-spectrum insecticides applications, often with limited results in H. halys management. Exclusion netting based on insect-proof nets is considered an environmentally friendly tactic that may potentially reduce H. halys infestation and damage. In a first experiment, during two growing seasons we investigated whether the timing of exclusion netting deployment affected season-long H. halys infestation and impact on apple and pear production. A second experiment considered the effect of netting color. Our results confirm that insect-proof nettings are effective in controlling H. halys infestations in fruit orchards, also observing an effect of timing of netting deployment on H. halys adult infestation, especially in apple orchards. Netting deployment could be delayed until the growing fruit phase on pear orchards, while on apple orchards it should be performed at flower fading phase. Brown marmorated stink bug infestation and damage were also influenced by the netting color, with black nets having higher infestation levels and fruit damage than white ones. Within an integrated pest management framework, early net deployment and the use of clear color nettings should be considered to reduce H. halys infestation and its damage in pome fruit crops

Challenges and prospects of plasmonic metasurfaces for photothermal catalysis

Solar-thermal technologies for converting chemicals using thermochemistry require extreme light concentration. Exploiting plasmonic nanostructures can dramatically increase the reaction rates by providing more efficient solar-to-heat conversion by broadband light absorption. Moreover, hot-carrier and local field enhancement effects can alter the reaction pathways. Such discoveries have boosted the field of photothermal catalysis, which aims at driving industrially-relevant chemical reactions using solar illumination rather than conventional heat sources. Nevertheless, only large arrays of plasmonic nano-units on a substrate, i.e., plasmonic metasurfaces, allow a quasi-unitary and broadband solar light absorption within a limited thickness (hundreds of nanometers) for practical applications. Through moderate light concentration (∼10 Suns), metasurfaces reach the same temperatures as conventional thermochemical reactors, or plasmonic nanoparticle bed reactors reach under ∼100 Suns. Plasmonic metasurfaces, however, have been mostly neglected so far for applications in the field of photothermal catalysis. In this Perspective, we discuss the potentialities of plasmonic metasurfaces in this emerging area of research. We present numerical simulations and experimental case studies illustrating how broadband absorption can be achieved within a limited thickness of these nanostructured materials. The approach highlights the synergy among different enhancement effects related to the ordered array of plasmonic units and the efficient heat transfer promoting faster dynamics than thicker structures (such as powdered catalysts). We foresee that plasmonic metasurfaces can play an important role in developing modular-like structures for the conversion of chemical feedstock into fuels without requiring extreme light concentrations. Customized metasurface-based systems could lead to small-scale and low-cost decentralized reactors instead of large-scale, infrastructure-intensive power plants

Clutter and rainfall discrimination by means of doppler-polarimetric measurements and vertical reflectivity profile analysis

International audienceThe estimation of rainfall rate and other parameters from radar scattering volume is heavily affected by the presence of intense sea and ground clutter and echoes which appears in anomalous propagation condition. To deal with these non meteorological echoes we present a new clutter removal algorithm which combines the results of previous works. The algorithm fully exploits both the Doppler and polarimetric capabilities of the radar used and the analysis of vertical reflectivity profile in order to achieve the better identification of the meteorological and non-meteorological targets. The algorithm has been applied to the C-band radar of Monte Settepani (Savona, Italy), which runs in a high-topography environment. Preliminary results are presented