scholarly journals On the use of radar reflectivity for estimation of the areal reduction factor

2006 ◽  
Vol 6 (3) ◽  
pp. 377-386 ◽  
Author(s):  
F. Lombardo ◽  
F. Napolitano ◽  
F. Russo
Keyword(s):  
Reduction Factor ◽  
Radar Reflectivity ◽  
Medium Size ◽  
Small Scale ◽  
Natural Phenomena ◽  
Radar Rainfall ◽  
Areal Reduction Factor ◽  
Empirical Relations ◽  
Urban Catchments ◽  
Areal Rainfall

Abstract. In order to estimate the rainfall fields over an entire basin raingauge, pointwise measurements need to be interpolated and the small-scale variability of rainfall fields can lead to biases in the rain rate estimation over an entire basin, above all for small or medium size mountainous and urban catchments. For these reasons, several raingauges should be installed in different places in order to determine the spatial rainfall distribution during the evolution of the natural phenomena over the selected area. In technical applications, many empirical relations are used in order to deduce heavy areal rainfall, when just one raingauge is available. In this work, we studied the areal reduction factor (ARF) using radar reflectivity maps collected with the Polar 55C, a C-band Doppler dual polarized coherent weather radar with polarization agility and with a 0.9° beamwidth. The radar rainfall estimates, for an area of 1 km2, were integrated for heavy rainfall with an upscaling process, until we had rainfall estimate for an area of 900 km2. The results obtained for a significant amount of data by using this technique are compared with the most important relations of the areal reduction factor reported in the literature.

scholarly journals Scaling Characteristics of Storm-Centered ARF Using Radar Rainfall

10.29007/hmzf ◽  
2018 ◽  
Author(s):  
Eunji Kim ◽  
Boosik Kang
Keyword(s):  
Return Period ◽  
Reduction Factor ◽  
Exceedance Probability ◽  
Storm Events ◽  
Reference Area ◽  
Radar Rainfall ◽  
Areal Reduction Factor ◽  
Fixed Area ◽  
Spatio Temporal ◽  
Areal Rainfall

In the hydraulic design practices, it is necessary to apply areal reduction factor to convert the point rainfall into the areal rainfall in the reference area. The fixed-area ARF (ARFf), which is commonly used, can be considered unrealistic because it is estimated through independent frequency analysis of the point rainfall and the areal rainfall. In this study, storm-centred ARF (ARFs) was estimated using radar rainfall data to reflect the spatial distribution characteristics of storm events effectively. ARFs representing the duration and the return period was extracted by 95% non-exceedance probability of the Weibull distribution to derive envelope covering all values from various storm events. ARFs has a correlation with not only the reference area but also the duration and the return period. Their relationships are defined as the scaling factors. A new ARFs equation that reflects the spatio-temporal characteristics of actual rainfall is presented.

scholarly journals Temperature effects on heavy rainfall modify catchment hydro-morphological response

2019 ◽  
Author(s):  
Nadav Peleg ◽  
Chris Skinner ◽  
Simone Fatichi ◽  
Peter Molnar
Keyword(s):  
Spatial Structure ◽  
Heavy Rainfall ◽  
Rainfall Intensity ◽  
Climate Impacts ◽  
Medium Size ◽  
Small Scale ◽  
Morphological Response ◽  
Sediment Yields ◽  
Central Switzerland ◽  
Areal Rainfall

Abstract. Heavy rainfall is expected to intensify with increasing temperatures, which will likely affect the rainfall spatial characteristics. The spatial variability of rainfall can affect streamflow and sediment transport volumes and peaks. Yet, the effect of climate change on the small-scale spatial structure of heavy rainfall and how those impacts hydrology and geomorphology remains largely unexplored. In this study, the sensitivity of the hydro-morphological response to heavy rainfall at the small-scale of minutes and hundreds of meters was investigated. A numerical experiment was conducted, in which synthetic rainfall fields representing heavy rainfall events of two types, stratiform and convective, were simulated using a space-time rainfall generator model. The rainfall fields were modified to follow different spatial rainfall scenarios, associated with increasing temperatures, and used as inputs into a landscape evolution model. The experiment was conducted over a complex topography medium-size (477 km2) Alpine catchment in central Switzerland. The results highlight that the response of the streamflow and sediment yields are highly sensitive to changes in the rainfall structure at the small-scale, in particular to changes in the areal rainfall intensity and in the area of heavy rainfall, which alters the total rainfall volume, and to a lesser extent to changes in the peak rainfall intensity. The hydro-morphological response is enhanced (reduced) when the local peak rainfall intensified and the area of heavy rainfall increased (decreased). The hydro-morphological response was found to be more sensitive to convective rainfall than stratiform rainfall because of localized runoff and erosion production. It is further shown that assuming heavy rainfall to intensify with increasing temperatures without introducing changes in the rainfall spatial structure might lead to over-estimation of future climate impacts on basin hydro-morphology.

Space-time heterogeneities of rainfalls on runoff over urban catchments

1995 ◽  
Vol 32 (1) ◽  
pp. 209-215 ◽  
Author(s):  
Christian Roux ◽  
Anne Guillon ◽  
Anne Comblez
Keyword(s):  
Peak Flow ◽  
Reduction Factor ◽  
Rainfall Series ◽  
Urban Watershed ◽  
Design Rainfall ◽  
Areal Reduction Factor ◽  
Outlet Flow ◽  
Urban Catchments ◽  
Areal Precipitation

Simulated outlet flow series are compared downstream of a 14 sq. km. urban watershed. They are generated either with design rainfall, with long-term point rainfall series, or with long-term space distributed rainfall series (measured with 3 raingauges or with radar). The use of the double-triangle shaped hyetograph as design rainfall provides the same T-year flow as the long term 3 raingauge series, if it is used with a areal reduction factor and uniformly applied to the watershed. For the same T-year mean areal precipitation depth during the time of concentration, the rainfall spatial and temporal heterogenities may induce differences up to +/− 30% on the peak flow, compared to the T-year peak flow.

scholarly journals Effect of the Assimilation Frequency of Radar Reflectivity on Rain Storm Prediction by Using WRF-3DVAR

2021 ◽  
Vol 13 (11) ◽  
pp. 2103
Author(s):  
Yuchen Liu ◽  
Jia Liu ◽  
Chuanzhe Li ◽  
Fuliang Yu ◽  
Wei Wang
Keyword(s):  
Data Assimilation ◽  
Northern China ◽  
Horizontal Resolution ◽  
Radar Reflectivity ◽  
Small Scale ◽  
Time Interval ◽  
Outer Domain ◽  
Storm Prediction ◽  
The Impact ◽  
Assimilation Time

An attempt was made to evaluate the impact of assimilating Doppler Weather Radar (DWR) reflectivity together with Global Telecommunication System (GTS) data in the three-dimensional variational data assimilation (3DVAR) system of the Weather Research Forecast (WRF) model on rain storm prediction in Daqinghe basin of northern China. The aim of this study was to explore the potential effects of data assimilation frequency and to evaluate the outputs from different domain resolutions in improving the meso-scale NWP rainfall products. In this study, four numerical experiments (no assimilation, 1 and 6 h assimilation time interval with DWR and GTS at 1 km horizontal resolution, 6 h assimilation time interval with radar reflectivity, and GTS data at 3 km horizontal resolution) are carried out to evaluate the impact of data assimilation on prediction of convective rain storms. The results show that the assimilation of radar reflectivity and GTS data collectively enhanced the performance of the WRF-3DVAR system over the Beijing-Tianjin-Hebei region of northern China. It is indicated by the experimental results that the rapid update assimilation has a positive impact on the prediction of the location, tendency, and development of rain storms associated with the study area. In order to explore the influence of data assimilation in the outer domain on the output of the inner domain, the rainfall outputs of 3 and 1 km resolution are compared. The results show that the data assimilation in the outer domain has a positive effect on the output of the inner domain. Since the 3DVAR system is able to analyze certain small-scale and convective-scale features through the incorporation of radar observations, hourly assimilation time interval does not always significantly improve precipitation forecasts because of the inaccurate radar reflectivity observations. Therefore, before data assimilation, the validity of assimilation data should be judged as far as possible in advance, which can not only improve the prediction accuracy, but also improve the assimilation efficiency.

scholarly journals Monitoring Lakes Surface Water Velocity with SAR: A Feasibility Study on Lake Garda, Italy

2021 ◽  
Vol 13 (12) ◽  
pp. 2293
Author(s):  
Marina Amadori ◽  
Virginia Zamparelli ◽  
Giacomo De Carolis ◽  
Gianfranco Fornaro ◽  
Marco Toffolon ◽  
...  
Keyword(s):  
Surface Water ◽  
Wind Waves ◽  
Test Site ◽  
Water Velocity ◽  
Surface Velocity ◽  
Medium Size ◽  
Small Scale ◽  
Lake Garda ◽  
Marine Applications

The SAR Doppler frequencies are directly related to the motion of the scatterers in the illuminated area and have already been used in marine applications to monitor moving water surfaces. Here we investigate the possibility of retrieving surface water velocity from SAR Doppler analysis in medium-size lakes. ENVISAT images of the test site (Lake Garda) are processed and the Doppler Centroid Anomaly technique is adopted. The resulting surface velocity maps are compared with the outputs of a hydrodynamic model specifically validated for the case study. Thermal images from MODIS Terra are used in support of the modeling results. The surface velocity retrieved from SAR is found to overestimate the numerical results and the existence of a bias is investigated. In marine applications, such bias is traditionally removed through Geophysical Model Functions (GMFs) by ascribing it to a fully developed wind waves spectrum. We found that such an assumption is not supported in our case study, due to the small-scale variations of topography and wind. The role of wind intensity and duration on the results from SAR is evaluated, and the inclusion of lake bathymetry and the SAR backscatter gradient is recommended for the future development of GMFs suitable for lake environments.

scholarly journals The standard characterization of the Romanian onion landrace ‘Roșie de Făgăraș’

2016 ◽  
Vol 73 (2) ◽  
pp. 101
Author(s):  
Mihaela Antofie ◽  
Camelia Sand Sava
Keyword(s):  
In Situ Conservation ◽  
Political Support ◽  
Medium Size ◽  
Small Scale ◽  
The European Union ◽  
Market Place ◽  
Food And Agriculture ◽  
Land Cultivation

‘Roșie de Făgăraș’ is a red onion landrace originating from the old region Făgăraș Country situated in South East Transylvania. It was officially included in the National Official Catalogue for cultivars and hybrids in 1952, for almost 50 years, and erased before 2004 without applying in situ conservation measures. However, food security depends on the appropriate management of all genetic resources for food and agriculture (PGRFA). Thus they have to be conserved and sustainable used and efforts have to be done for the recognition of this landrace as a PGRFA and therefore to be maintained "under conservation" into the Official Catalogue. The study focused on analysing data from three localities recognized for cultivating ‘Roșie de Făgăraș’, in order to evaluate morphometric characteristics of mature onion bulbs according to the UPOV Standard TG/46/7, productivity, land cultivation and socio-economic vulnerabilities. The analysis of morphometric measurements results support that ‘Roșie de Făgăraș’ is a medium size red onion that may have the chance to enter the market place, at least at the small scale, according to the current regulatory framework of the European Union regarding the conservation of landraces and provided by: Directive 2008/62/EC, Directive 2009/145/EC and Directive 2010/60/EU. The analysis of productivity, and land cultivation revealed dramatic land use change associated with the decline of cultivated area as following: 76.27% in Mândra, 50% in Recea and 33.34% in Beclean. With an increasing aging population, lack of political support for entering the market place, decrease of landowners cultivating ‘Roșie de Făgăraș’ for trade will increase vulnerability of traditional knowledge related to the conservation of this landrace.

scholarly journals Multifractal analysis of radar rainfall fields over the area of Rome

2005 ◽  
Vol 2 ◽  
pp. 293-299 ◽  
Author(s):  
G. Calenda ◽  
E. Gorgucci ◽  
F. Napolitano ◽  
A. Novella ◽  
E. Volpi
Keyword(s):  
Scale Invariance ◽  
Large Scale ◽  
Doppler Radar ◽  
Risk Mitigation ◽  
Small Scale ◽  
Radar Rainfall ◽  
Invariance Properties ◽  
Meteorological Radar ◽  
Using Data ◽  
Precipitation Events

Abstract. A scale-invariance analysis of space and time rainfall events monitored by meteorological radar over the area of Rome (Italy) is proposed. The study of the scale-invariance properties of intense precipitation storms, particularly important in flood forecast and risk mitigation, allows to transfer rainfall information from the large scale predictive meteorological models to the small scale hydrological rainfall-runoff models. Precipitation events are monitored using data collected by the polarimetric Doppler radar Polar 55C (ISAC-CNR), located 15 km Southeast from downtown. The meteorological radar provides the estimates of rainfall intensity over an area of about 10 000 km2 at a resolution of 2×2 km2 in space and 5 min in time. Many precipitation events have been observed from autumn 2001 up to now. A scale-invariance analysis is performed on some of these events with the aim at exploring the multifractal properties and at understanding their dependence on the meteorological large-scale conditions.

High Pressure Vertical Axis Wind Pump

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
D. Keisar ◽  
B. Eilan ◽  
D. Greenblatt
Keyword(s):  
High Pressure ◽  
Vertical Axis ◽  
Cross Sectional Area ◽  
Liquid Volume ◽  
Medium Size ◽  
Small Scale ◽  
Sectional Area ◽  
Peak Efficiency ◽  
Cross Sectional ◽  
Positive Displacement

Abstract A novel positive displacement, high pressure, vertical axis wind pump (HP-VAWP) was evaluated for the application of stand-alone high-pressure reverse-osmosis desalination and drip irrigation systems. The direct interface between a vertical axis wind turbine (VAWT) and a positive displacement pump that delivers a constant liquid volume per revolution has never been studied before. Understanding the interaction between turbine and pump efficiencies, where delivery pressure is determined by back-pressure alone, is critical for efficient design. Wind tunnel experiments were conducted on a small-scale two-bladed turbine (0.4 m2 cross-sectional area) that operated on a dynamic stall principle. At these small laboratory scales, the turbine and pump peak efficiencies were relatively low (15% and 28%, respectively); nevertheless, the system produced nearly constant pressures in excess of 1.5 bar for a broad operational range. Moreover, the system exhibited a basic self-priming capability, and the turbine could easily be braked by overloading the pump. A conservative field-scale analysis of an HP-VAWP system indicated that a medium-size turbine (12.5 m2 cross-sectional area) could attain a peak efficiency of 12.9%. Realistic efficiencies greater than 20% are attainable, significantly exceeding the 4%–8% typical peak efficiency of the widely used American multibladed wind pumps. Indeed, our research indicates that an HP-VAWP system is viable and requires further development. The benefits of zero carbon emissions during operation, high relative efficiency, and easy manufacturing and maintenance render the HP-VAWP ideal for stand-alone or off-grid environments.

scholarly journals Radar Rainfall Estimation in Morocco: Quality Control and Gauge Adjustment

Hydrology ◽  
2019 ◽  
Vol 6 (2) ◽  
pp. 41 ◽  
Author(s):  
Zahra Sahlaoui ◽  
Soumia Mordane
Keyword(s):  
Positive Impact ◽  
Radar Reflectivity ◽  
Radar Rainfall ◽  
Rain Gauges ◽  
Impact Bias ◽  
African Rainfall ◽  
Precipitation Structure ◽  
Radar Rainfall Estimate ◽  
The Impact

This study focused on investigating the impact of gauge adjustment on the rainfall estimate from a Moroccan C-band weather radar located in Khouribga City. The radar reflectivity underwent a quality check before deployment to retrieve the rainfall amount. The process consisted of clutter identification and the correction of signal attenuation. Thereafter, the radar reflectivity was converted into rainfall depth over a period of 24 h. An assessment of the accuracy of the radar rainfall estimate over the study area showed an overall underestimation when compared to the rain gauges (bias = −6.4 mm and root mean square error [RMSE] = 8.9 mm). The adjustment model was applied, and a validation of the adjusted rainfall versus the rain gauges showed a positive impact (bias = −0.96 mm and RMSE = 6.7 mm). The case study conducted on December 16, 2016 revealed substantial improvements in the precipitation structure and intensity with reference to African Rainfall Climatology version 2 (ARC2) precipitations.

scholarly journals The derivation of areal reduction factor of storm rainfall from its scaling properties

2001 ◽  
Vol 37 (12) ◽  
pp. 3247-3252 ◽  
Author(s):  
Carlo De Michele ◽  
Nathabandu T. Kottegoda ◽  
Renzo Rosso
Keyword(s):  
Reduction Factor ◽  
Scaling Properties ◽  
Areal Reduction Factor ◽  
Storm Rainfall
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