scholarly journals Radar subpixel-scale rainfall variability and uncertainty: a lesson learned from observations of a dense rain-gauge network

2013 ◽  
Vol 10 (1) ◽  
pp. 1-32
Author(s):  
N. Peleg ◽  
M. Ben-Asher ◽  
E. Morin

Abstract. Hydrological models for runoff estimations and flash-flood predictions are very sensitive to rainfall's spatial and temporal variability. The increasing use of radar and satellite data in hydrological applications, due to the sparse distribution of rain gauges over most catchments worldwide, requires improving our knowledge of the uncertainties of these data. In 2011, a new super-dense network of rain gauges, containing 27 gauges covering an area of about 4 km2, was installed near Kibbutz Galed in northern Israel. This network was established for a detailed exploration of the uncertainties and errors regarding rainfall variability in remote-sensing at subpixel-scale resolution. In this paper, we present the analysis of the first year's record collected from this network and from the Shacham weather radar. The gauge–rainfall spatial correlation and uncertainty were examined along with the estimated radar error. The zero-distance correlation between rain gauges was high (0.92 on the 1-min scale) and increased as the time scale increased. The variance of the differences between radar pixel rainfall and averaged point rainfall (the variance reduction factor – VRF) was 1.6%, as measured for the 1-min scale. It was also found that at least four uniformly distributed rain stations are needed to represent the rainfall on the radar pixel scale. The radar–rain gauge error was mainly derived from radar estimation errors as the gauge sampling error contributed up to 22% to the total error. The radar rainfall estimations improved with increasing time scale and the radar-to-true rainfall ratio decreased with increasing time scale. Rainfall measurements collected with this network of rain gauges in the coming years will be used for further examination of rainfall's spatial and temporal variability.

2013 ◽  
Vol 17 (6) ◽  
pp. 2195-2208 ◽  
Author(s):  
N. Peleg ◽  
M. Ben-Asher ◽  
E. Morin

Abstract. Runoff and flash flood generation are very sensitive to rainfall's spatial and temporal variability. The increasing use of radar and satellite data in hydrological applications, due to the sparse distribution of rain gauges over most catchments worldwide, requires furthering our knowledge of the uncertainties of these data. In 2011, a new super-dense network of rain gauges containing 14 stations, each with two side-by-side gauges, was installed within a 4 km2 study area near Kibbutz Galed in northern Israel. This network was established for a detailed exploration of the uncertainties and errors regarding rainfall variability within a common pixel size of data obtained from remote sensing systems for timescales of 1 min to daily. In this paper, we present the analysis of the first year's record collected from this network and from the Shacham weather radar, located 63 km from the study area. The gauge–rainfall spatial correlation and uncertainty were examined along with the estimated radar error. The nugget parameter of the inter-gauge rainfall correlations was high (0.92 on the 1 min scale) and increased as the timescale increased. The variance reduction factor (VRF), representing the uncertainty from averaging a number of rain stations per pixel, ranged from 1.6% for the 1 min timescale to 0.07% for the daily scale. It was also found that at least three rain stations are needed to adequately represent the rainfall (VRF < 5%) on a typical radar pixel scale. The difference between radar and rain gauge rainfall was mainly attributed to radar estimation errors, while the gauge sampling error contributed up to 20% to the total difference. The ratio of radar rainfall to gauge-areal-averaged rainfall, expressed by the error distribution scatter parameter, decreased from 5.27 dB for 3 min timescale to 3.21 dB for the daily scale. The analysis of the radar errors and uncertainties suggest that a temporal scale of at least 10 min should be used for hydrological applications of the radar data. Rainfall measurements collected with this dense rain gauge network will be used for further examination of small-scale rainfall's spatial and temporal variability in the coming years.


2017 ◽  
Vol 21 (7) ◽  
pp. 3859-3878 ◽  
Author(s):  
Elena Cristiano ◽  
Marie-Claire ten Veldhuis ◽  
Nick van de Giesen

Abstract. In urban areas, hydrological processes are characterized by high variability in space and time, making them sensitive to small-scale temporal and spatial rainfall variability. In the last decades new instruments, techniques, and methods have been developed to capture rainfall and hydrological processes at high resolution. Weather radars have been introduced to estimate high spatial and temporal rainfall variability. At the same time, new models have been proposed to reproduce hydrological response, based on small-scale representation of urban catchment spatial variability. Despite these efforts, interactions between rainfall variability, catchment heterogeneity, and hydrological response remain poorly understood. This paper presents a review of our current understanding of hydrological processes in urban environments as reported in the literature, focusing on their spatial and temporal variability aspects. We review recent findings on the effects of rainfall variability on hydrological response and identify gaps where knowledge needs to be further developed to improve our understanding of and capability to predict urban hydrological response.


2007 ◽  
Vol 24 (9) ◽  
pp. 1598-1607 ◽  
Author(s):  
Jeremy D. DeMoss ◽  
Kenneth P. Bowman

Abstract During the first three-and-a-half years of the Tropical Rainfall Measuring Mission (TRMM), the TRMM satellite operated at a nominal altitude of 350 km. To reduce drag, save maneuvering fuel, and prolong the mission lifetime, the orbit was boosted to 403 km in August 2001. The change in orbit altitude produced small changes in a wide range of observing parameters, including field-of-view size and viewing angles. Due to natural variability in rainfall and sampling error, it is not possible to evaluate possible changes in rainfall estimates from the satellite data alone. Changes in TRMM Microwave Imager (TMI) and the precipitation radar (PR) precipitation observations due to the orbit boost are estimated by comparing them with surface rain gauges on ocean buoys operated by the NOAA/Pacific Marine Environment Laboratory (PMEL). For each rain gauge, the bias between the satellite and the gauge for pre- and postboost time periods is computed. For the TMI, the satellite is biased ∼12% low relative to the gauges during the preboost period and ∼1% low during the postboost period. The mean change in bias relative to the gauges is approximately 0.4 mm day−1. The change in TMI bias is rain-rate-dependent, with larger changes in areas with higher mean precipitation rates. The PR is biased significantly low relative to the gauges during both boost periods, but the change in bias from the pre- to postboost period is not statistically significant.


2010 ◽  
Vol 10 (1) ◽  
pp. 149-158 ◽  
Author(s):  
L. Alfieri ◽  
P. Claps ◽  
F. Laio

Abstract. The operational use of weather radars has become a widespread and useful tool for estimating rainfall fields. The radar-gauge adjustment is a commonly adopted technique which allows one to reduce bias and dispersion between radar rainfall estimates and the corresponding ground measurements provided by rain gauges. This paper investigates a new methodology for estimating radar-based rainfall fields by recalibrating at each time step the reflectivity-rainfall rate (Z-R) relationship on the basis of ground measurements provided by a rain gauge network. The power-law equation for converting reflectivity measurements into rainfall rates is readjusted at each time step, by calibrating its parameters using hourly Z-R pairs collected in the proximity of the considered time step. Calibration windows with duration between 1 and 24 h are used for estimating the parameters of the Z-R relationship. A case study pertaining to 19 rainfall events occurred in the north-western Italy is considered, in an area located within 25 km from the radar site, with available measurements of rainfall rate at the ground and radar reflectivity aloft. Results obtained with the proposed method are compared to those of three other literature methods. Applications are described for a posteriori evaluation of rainfall fields and for real-time estimation. Results suggest that the use of a calibration window of 2–5 h yields the best performances, with improvements that reach the 28% of the standard error obtained by using the most accurate fixed (climatological) Z-R relationship.


2019 ◽  
Vol 20 (9) ◽  
pp. 1941-1959 ◽  
Author(s):  
Yagmur Derin ◽  
Emmanouil Anagnostou ◽  
Marios Anagnostou ◽  
John Kalogiros

Abstract The difficulty of representing high rainfall variability over mountainous areas using ground-based sensors is an open problem in hydrometeorology. Observations from locally deployed dual-polarization X-band radar have the advantage of providing multiparameter measurements near ground that carry significant information useful for estimating drop size distribution (DSD) and surface rainfall rate. Although these measurements are at fine spatiotemporal scale and are less inhibited by complex topography than operational radar network observations, uncertainties in their estimates necessitate error characterization based upon in situ measurements. During November 2015–February 2016, a dual-polarized Doppler on Wheels (DOW) X-band radar was deployed on the Olympic Peninsula of Washington State as part of NASA’s Olympic Mountain Experiment (OLYMPEX). In this study, rain gauges and disdrometers from a dense network positioned within 40 km of DOW are used to evaluate the self-consistency and accuracy of the attenuation and brightband/vertical profile corrections, and rain microphysics estimation by SCOP-ME, an algorithm that uses optimal parameterization and best-fitted functions of specific attenuation coefficients and DSD parameters with radar polarimetric measurements. In addition, the SCOP-ME precipitation microphysical retrievals of median volume diameter D0 and normalized intercept parameter NW are evaluated against corresponding parameters derived from the in situ disdrometer spectra observations.


Author(s):  
Dr. Vasudev S. Salunke ◽  
Pramila. P. Zaware

Rainfall is one of the vital form of precipitation which affects not only agricultural activity but also entire ecology in any region. Hence rainfall distribution and its trends in district is important to understand water availability and to take decisions for the agricultural activities in area. This research paper is an effort to assess the spatial and temporal rainfall variability of Ahmednagar district of Maharashtra State. Ahmednagar is popularly known as the largest district of Maharashtra with fourteen Talukas. The average annual rainfall of this district is 621 mm with an average of 46 rainy days. In this study the spatial and temporal rainfall distribution of this district is taken in to account. Short-term annual rainfall data are considered from 1998 to 2014. The daily rainfalls of monsoon months of all the fourteen Taluka are analyzed for the year 2015.It was found that spatial and temporal variability is high in the District.


Author(s):  
Romário Rosa de Sousa

LOW COST RAIN GAUGES AND RAINFALL VARIABILITY IN BARRA DO GARÇAS – MT (OCTOBER 2015 TO APRIL 2016)PLUVIÓMETRO DE BAJO COSTO Y LA VARIACIÓN DE LA LLUVIA EN EL MUNICIPIO DE BARRA DO GARÇAS – MT (OCTUBRE DE 2015 A ABRIL 2016)Este trabalho teve como objetivo principal confeccionar e distribuir vinte pluviômetros de baixo custo de PVC, dentro do município de Barra do Garças-MT, onde posteriormente a partir dos dados coletados, gerou-se um mapa pluviométrico da irregularidade da chuva. Os trabalhos metodológicos foram desenvolvidos em onze etapas distintas. Após toda a fase de aquisição dos materiais de baixo custo, na sequência realizou-se os seguintes procedimentos: confecção dos pluviômetros, aferição, instalação, treinamento dos produtores rurais, coleta de dados a campo, organização dos dados em planilha eletrônica com geração de relatório de tabela dinâmica, realização do processo de interpolação dos dados, geração do mapa pluviométrico, ajustes e finalização do mapa gerado, análise e discussão dos dados. É importante ressaltar que o processo de interpolação dos dados foi realizado no software ArcGis, 10.1. Ressalta-se que o processo de construção do pluviômetro de baixo custo, demonstrou que foi de grande ajuda, no sentido de baixar custos com um instrumento de grande importância para o meio rural e urbano. Também ficou comprovado que o pluviômetro de baixo custo, é um aparelho de credibilidade e confiabilidade nos registros dos dados pluviométricos. Quanto a distribuição pluviométrica da chuva no município de Barra do Garças-MT, foi bem diversificada e irregular para o período estudado, onde averiguou-se que o maior acumulo pluviométrico foi registrado no extremo sul do município com 986,1mm de chuva. E encontra partida um núcleo seco com um baixo volume de precipitação foi confirmado na porção leste com 146,2 mm de chuva.Palavras-chave: Pluviômetros; Chuva; PVC; Baixo Custo.ABSTRACTThis study aims to design, assemble and distribute twenty low cost PVC rain gauges in Barra do Garças-MT, where afterwards a rainfall map was generated from the collected data. The methodological works were developed in eleven distinct stages. Following the entire acquisition phase of the low cost materials, the following procedures were carried out: preparation of the rain gauges, gauging, installation, training of rural producers, data collection in the field, data organization in electronic spreadsheet making a dynamic table report, data interpolation, creating a rainfall map, adjustment and finalization of the created map, data analysis and discussion. It is important to note the data interpolation process was performed in ArcGis software, 10.1. It should be noted that the process of construction of the low cost rain gauge showed that it was of great help in order to reduce costs with an instrument of great importance for the rural and urban environments. It has also been proven that the low cost rain gauge is an apparatus of credibility and reliability in rainfall records. As for the rainfall distribution in Barra do Garças-MT, it was well diversified and irregular for the period studied, where it was verified that the highest rainfall accumulation was recorded in the southern end of the municipality with 986.1mm of rain. However, finding a dry core with a low volume of precipitation was confirmed in the eastern portion with 146.2mm of rain.Keywords: Rain Gauges; Rain; PVC; Low Cost.RESUMENEste trabajo tuvo como objetivo principal elaborar, montar y distribuir veinte pluviómetros de bajo costo de PVC, dentro del municipio de Barra do Garças-MT, posteriormente, a partir de los datos colectados, se originó un mapa pluviométrico de la irregularidad de la lluvia. Los trabajos metodológicos fueron desarrollados en once etapas distintas. Después de toda la fase de adquisición de los materiales de bajo costo, en seguida se realizaron los siguientes procedimientos: confección de los pluviómetros, calibración, instalación, entrenamiento de los productores rurales, colecta de datos a campo, organización de los datos en planilla electrónica con elaboración de un informe de tabla dinámica, realización del proceso de interpolación de los datos, producción del mapa pluviométrico, ajustes y finalización del mapa generado, análisis y discusión de los datos. Es importante realzar que el proceso de interpolación de los datos fueron realizados en el software ArcGis, 10.1. Se resalta que el proceso de construcción del pluviómetro de bajo costo, demostró que fue de gran ayuda, en el sentido de bajar costos con un instrumento de gran importancia para el medio rural y urbano. También quedó demostrado que el pluviómetro de bajo costo, es un aparato de credibilidad y confiabilidad en los registros de los datos pluviométricos. Cuanto a la distribución pluviométrica en el municipio de Barra do Garças-MT, fue bien diversificada e irregular para el periodo estudiado, donde se comprobó que el mayor acúmulo pluviométrico fue registrado en el extremo Sur del municipio con 986,1mm de lluvia. En contra partida un núcleo seco con un bajo volumen de precipitación fue confirmado en la región Este con 146,2 mm de lluvia.Palabras-clave: Pluviómetros; Lluvia; PVC; Bajo Costo.


2011 ◽  
Vol 15 (12) ◽  
pp. 3651-3658 ◽  
Author(s):  
M. Ćurić ◽  
D. Janc

Abstract. Convective clouds generate extreme rainfall events and flash floods in small areas with both large spatial and temporal variability. For this reason, the monitoring of the total accumulated precipitation fields at the surface with rain gauges and meteorological radars has both strengths and weakness. Alternatively, a numerical cloud model may be a useful tool to simulate convective precipitation for various analyses and predictions. The main objective of this paper is to show that the cloud-resolving model reproduces well the accumulated convective precipitation obtained from the rain gauge network data in the area with frequent split storms. We perform comparisons between observations and model samples of the areal accumulated convective precipitation for a 15-year period over treated area. Twenty-seven convective events have been selected. Statistical analyses reveal that the model areal accumulated convective precipitation closely match their observed values with a correlation coefficient of 0.80.


1997 ◽  
Vol 36 (6) ◽  
pp. 735-747 ◽  
Author(s):  
Grzegorz J. Ciach ◽  
Witold F. Krajewski ◽  
Emmanouil N. Anagnostou ◽  
Mary L. Baeck ◽  
James A. Smith ◽  
...  

Abstract This study presents a multicomponent rainfall estimation algorithm, based on weather radar and rain gauge network, that can be used as a ground-based reference in the satellite Tropical Rainfall Measuring Mission (TRMM). The essential steps are constructing a radar observable, its nonlinear transformation to rainfall, interpolation to rectangular grid, constructing several timescale accumulations, bias adjustment, and merging of the radar rainfall estimates and rain gauge data. Observations from a C-band radar in Darwin, Australia, and a local network of 54 rain gauges were used to calibrate and test the algorithm. A period of 25 days was selected, and the rain gauges were split into two subsamples to apply cross-validation techniques. A Z–R relationship with continuous range dependence and a temporal interpolation scheme that accounts for the advection effects is applied. An innovative methodology was used to estimate the algorithm controlling parameters. The model was globally optimized by using an objective function on the level of the final products. This is equivalent to comparing hundreds of Z–R relationships using a uniform and representative performance criterion. The algorithm performance is fairly insensitive to the parameter variations around the optimum. This suggests that the accuracy limit of the radar rainfall estimation based on power-law Z–R relationships has been reached. No improvement was achieved by using rain regime classification prior to estimation.


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