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1

Weather Radar and Hydrology 1 Influence of rainfall spatial variability on hydrological modelling: a  

E-print Network

Weather Radar and Hydrology 1 Influence of rainfall spatial variability on hydrological modelling variability as well as characteristics and hydrological behavior of catchments, we have proceeded simulator and a distributed hydrological model (with four production functions and a distributed transfer

Paris-Sud XI, Université de

2

Quantization analysis of weather radar data with synthetic rainfall  

Microsoft Academic Search

Quantization is a process by where continuous signals are transformed into discrete values. It is an important part of the\\u000a signal processing involved in using weather radar. Technological advances have made it easier to increase the number of quantization\\u000a levels, as witnessed by the replacement of a 3 bit system by an 8 bit system by the UK Meteorological Office. Research has

M. Hammond; D. Han

2008-01-01

3

Estimates of cumulative rainfall over a large area by weather radar  

NASA Astrophysics Data System (ADS)

In this work we propose a technique for 15-minutes cumulative rainfall mapping, applied over Tuscany, using Italian weather radar networks together with the regional rain gauge network. In order to assess the accuracy of the radar-based rainfall estimates, we have compared them with spatial coincident rain gauge measurements. Precipitation at ground is our target observable: rain gauge measurements of such parameter have a so small error that we consider it negligible (especially if compared from what retrievable from radars). In order to make comparable the observations given from these two types of sensors, we have collected cumulative rainfall over areas a few tens of kilometres wide. The method used to spatialise rain gauges data has been the Ordinary Block Kriging. In this case the comparison results have shown a good correlation between the cumulative rainfall obtained from the rain gauges and those obtained by the radar measurements. Such results are encouraging in the perspective of using the radar observations for near real time cumulative rainfall nowcasting purposes. In addition the joint use of satellite instruments as SEVIRI sensors on board of MSG-3 satellite can add relevant information on the nature, spatial distribution and temporal evolution of cloudiness over the area under study. For this issue we will analyse several MSG-3 channel images, which are related to cloud physical characteristics or ground features in case of clear sky.

Mazza, Alessandro; Antonini, Andrea; Melani, Samantha; Ortolani, Alberto

2014-10-01

4

Polarimetric rainfall retrieval from a C-Band weather radar in a tropical environment (The Philippines)  

NASA Astrophysics Data System (ADS)

We evaluated the potential of polarimetric rainfall retrieval methods for the Tagaytay C-Band weather radar in the Philippines. For this purpose, we combined a method for fuzzy echo classification, an approach to extract and reconstruct the differential propagation phase, ? DP , and a polarimetric self-consistency approach to calibrate horizontal and differential reflectivity. The reconstructed ? DP was used to estimate path-integrated attenuation and to retrieve the specific differential phase, K DP . All related algorithms were transparently implemented in the Open Source radar processing software wradlib. Rainfall was then estimated from different variables: from re-calibrated reflectivity, from re-calibrated reflectivity that has been corrected for path-integrated attenuation, from the specific differential phase, and from a combination of reflectivity and specific differential phase. As an additional benchmark, rainfall was estimated by interpolating the rainfall observed by rain gauges. We evaluated the rainfall products for daily and hourly accumulations. For this purpose, we used observations of 16 rain gauges from a five-month period in the 2012 wet season. It turned out that the retrieval of rainfall from K DP substantially improved the rainfall estimation at both daily and hourly time scales. The measurement of reflectivity apparently was impaired by severe miscalibration while K DP was immune to such effects. Daily accumulations of rainfall retrieved from K DP showed a very low estimation bias and small random errors. Random scatter was, though, strongly present in hourly accumulations.

Crisologo, I.; Vulpiani, G.; Abon, C. C.; David, C. P. C.; Bronstert, A.; Heistermann, Maik

2014-11-01

5

ESTIMATING RAINFALL INTENSITIES FROM WEATHER RADAR DATA: THE SCALE DEPENDENCY PROBLEM 1490  

Technology Transfer Automated Retrieval System (TEKTRAN)

Meteorological radar is a remote sensing system that provides rainfall estimations at high spatial and temporal resolution. The radar-based rainfall intensities (R) are calculated from the observed radar reflectivities (Z). In this paper we explore scale-dependency of the power-law Z-R parameters w...

6

Radar hydrology: rainfall estimation  

Microsoft Academic Search

Radar observations of rainfall and their use in hydrologic research provide the focus for the paper. Radar-rainfall products are crucial for input to runoff and flood prediction models, validation of satellite remote sensing algorithms, and for statistical characterization of extreme rainfall frequency. In this context we discuss the issues of radar-rainfall product development, and the theoretical and practical requirements of

W. F. Krajewski; J. A. Smith

2002-01-01

7

Weather Radar Fundamentals  

NSDL National Science Digital Library

This 2-hour module presents the fundamental principles of Doppler weather radar operation and how to interpret common weather phenomena using radar imagery. This is accomplished via conceptual animations and many interactive radar examples in which the user can practice interpreting both radar reflectivity and radar velocity imagery. Although intended as an accelerated introduction to understanding and using basic Doppler weather radar products, the module can also serve as an excellent refresher for more experienced users.

COMET

2012-03-21

8

Benefits and limitations of using the weather radar for the definition of rainfall thresholds for debris flows. Case study from Catalonia (Spain).  

NASA Astrophysics Data System (ADS)

Torrential processes such as debris flows or hyperconcentrated flows are fast movements formed by a mix of water and different amounts of unsorted solid material. They occur in steep torrents and suppose a high risk for the human settlements. Rainfall is the most common triggering factor for debris flows. The rainfall threshold defines the rainfall conditions that, when reached or exceeded, are likely to provoke one or more events. Many different types of empirical rainfall thresholds for landslide triggering have been defined. Direct measurements of rainfall data are normally not available from a point next to or in the surroundings of the initiation area of the landslide. For this reason, most of the thresholds published for debris flows have been established by data measured at the nearest rain gauges (often located several km far from the landslide). Only in very few cases, the rainfall data to analyse the triggering conditions of the debris flows have been obtained by weather (Doppler) radar. Radar devices present certain limitations in mountainous regions due to undesired reboots, but their main advantage is that radar data can be obtained for any point of the territory. The objective of this work was to test the use of the weather radar data for the definition of rainfall thresholds for debris-flow triggering. Thus, rainfall data obtained from 3 to 5 rain gauges and from radar were compared for a dataset of events occurred in Catalonia (Spain). The goal was to determine in which cases the description of the rainfall episode (in particular the maximum intensity) had been more accurate. The analysed dataset consists of: 1) three events occurred in the Rebaixader debris-flow monitoring station (Axial Pyrenees) including two hyperconcentrated flows and one debris flow; 2) one debris-flow event occurred in the Port Ainé ski resort (Axial Pyrenees); 3) one debris-flow event in Montserrat (Mediterranean Coastal range). The comparison of the hyetographs from the different devices showed that the reliability of the radar is higher for short, high intensity storms more than for long lasting, medium intensity ones. Additionally, the best fit corresponds to the situations where the storm nucleus is located near the source area of the debris flow. The results of the comparison between different rain gauges show similar trends. The ones located in the same valley as the debris flow usually show good results, but if there are orographic elements in-between the debris-flow torrent and the rain gauge or the distance is large, the results can imply a great error in the definition of rainfall intensity. Therefore, we can state that the reliability of the use of the weather radar to define rainfall thresholds is strongly depending on the type of the storm and the distance between the source area and the nucleus of the storm.

Abancó, C.; Hürlimann, M.; Sempere, D.; Berenguer, M.

2012-04-01

9

Weather Radar and Instrumentation: Laboratory Modules  

NSDL National Science Digital Library

These 16 radar education modules, developed for the Weather Radar and Instrumentation Curriculum at the University of Oklahoma, provide hands-on instruction for beginning, intermediate, or advanced students to learn about radar systems, especially weather radar. Topics include hardware, weather radar, adaptive systems, advanced hydrometeors, applications of weather radar, and atmospheric interpretations. The modules may be downloaded.

10

INTEGRATED CONTROL OF COMBINED SEWER REGULATORS USING WEATHER RADAR  

EPA Science Inventory

Integrated operation was simulated of ten dynamic combined sewer regulators on a Montreal interceptor. Detailed review of digital recording weather radar capabilities indicated that it is potentially the best rainfall estimation means for accomplishing the runoff prediction that ...

11

Rainfall regionalization on the basis of the precipitation convective features using a raingauge network and weather radar observations  

Microsoft Academic Search

The main objective of the present paper is to show a methodology for undertaking rainfall regionalization of a region taking into account the convective features of the precipitation, and useful for establishing homogeneous zones for improving the alert system. This methodology has been applied to a hydrographic region located in northeast Spain, with an area of 16000 km2 and characterized by

Maria-Carmen Llasat; Manuel Ceperuelo; Tomeu Rigo

2007-01-01

12

Sensitivity of urban hydrodynamic modelling to high resolution radar rainfall  

NASA Astrophysics Data System (ADS)

Since the early 90's, the need to improve the spatial and temporal resolution of rainfall estimates has been emphasised. Urban hydrological applications require high resolution rainfall inputs matching rapid response times of such catchments. With the advent of new radar technology, urban hydrologists nowadays have access to highly accurate rainfall estimates to drive their models. High resolution rainfall products are provided by dual polarimetric X-band radars, which retrieve rainfall rates at 1 min temporal resolution and 30 m spatial resolution. This study attempts to characterise sensitivity of hydrologic response to high resolution weather radar rainfall input for hydrodynamic models at urban scale. Spatial resolutions of both rainfall input and hydrologic units are of the order of 100 meters. Rainfall rates derived from X-band polarimetric weather radar are used as input into a detailed hydrodynamic sewer model for an urban catchment in Rotterdam, The Netherlands. Rainfall data of two storms, one convective and one stratiform, at different spatial resolutions, are used to analyse the effect of precipitation data resolution on simulated in-sewer water levels as well as runoff peaks. Dimensionless parameters are derived to analyse the effect of rainfall resolution in relation to storm and catchment properties. Simulation results are first analysed in relation to 'storm redistribution' induced by spatial precipitation sampling: storm correlation distance is compared to rainfall resolution and the effect on hydrodynamic model results is discussed. Sensitivity of hydrodynamic model results to storm redistribution will be discussed for varying positions throughout the catchment and dependent on localisation of convective storm cells.

Bruni, Guendalina; Reinoso, Ricardo; van de Giesen, Nick; Clemens, Francois; ten Veldhuis, Marie-Claire

2014-05-01

13

Improved radar rainfall estimation at ground level  

Microsoft Academic Search

A technique has been developed to provide an estimate of the rainfall reaching the earth's surface by extrapolating radar data contained aloft to ground level, simultaneously estimating unknown data in the radar volume scan. The technique has been developed so as to be computationally fast, to work in real time and comprises the following steps. A rainfall classification algorithm is

S. M. Wesson; G. G. S. Pegram

2006-01-01

14

A 10-year radar-based climatology of rainfall Aart Overeem, Iwan Holleman, Adri Buishand  

E-print Network

A 10-year radar-based climatology of rainfall Aart Overeem, Iwan Holleman, Adri Buishand Royal@knmi.nl I. INTRODUCTION Weather radars give quantitative precipitation estimates (QPE) over large areas radar data sets become available (e.g. Allen and DeGaetano, 2005; Germann et al., 2006), radar data

Stoffelen, Ad

15

Simple Radar Rainfall Bias Correction Using Rain Gauges  

NASA Astrophysics Data System (ADS)

The purpose of this research is to generate a bias-adjusted radar rainfall product, which is required as a reference data for calibration of GOES Multi-Spectral Rainfall Algorithm (GMSRA). For this goal, radar rainfall estimates were compared to the gauge estimates, and the ratio of gauge estimates to those for radars (G/R ratio) were computed. The radar estimates were then adjusted to the equivalent values of rain gauges by using the G/R ratios. Finally, the results were compared against the NEXRAD Stage III rainfall estimates. For this study, the US composite reflectivity data from National Weather Service Radars, which were obtained from the Global Hydrology Resource Center (GHRC), and hourly rain gauge data from NCEP/NOAA were used. Sixty days of precipitation events over Arkansas-Basin River Forecast Center (ABRFC) region were chosen during 1998-1999. The resulting mean G/R ratio for those sixty days was about 0.40. Radar estimates were corrected simply by multiplying the radar estimates by the G/R ratio. Comparisons of unadjusted/adjusted radar estimates against NEXRAD Stage III rainfall estimates show that adjusted radar estimates have good agreement with Stage III estimates. The mean RMSD and mean ratio of Stage III to uncorrected radar estimates were 19.9 mm/day and 0.45 respectively. After correction, they were 7.5 mm/day and 1.11 respectively. These simple statistics show that this correction method can be applied to generate reference rainfall data for calibration of GMSRA over the ABRFC region.

Jeong, M.; Syed, K. H.; Gruber, A.

2002-05-01

16

ATS 351, Spring 2010 Weather Radar -55 points  

E-print Network

ATS 351, Spring 2010 Lab #9 Weather Radar - 55 points 1. (5 points) If a radar has a maximum) Explain the presence of a bright band. 3. (5 points) What are the differences between the Clear Air Mode Collins during a 5-hour period. This heavy rainfall caused the Spring Creek to spill over its banks, which

Rutledge, Steven

17

Aggregation and disaggregation of radar rainfall rates  

NASA Astrophysics Data System (ADS)

Spatially distributed, high-resolution precipitation rates are key ingredients for modeling soil-vegetation processes, water and solute transports in mesoscale catchments, and for short-range weather prediction. The ultimate goal of our study is to develop a space-time, multilevel statistical model that merges rain radar measurements with other observations of precipitation. This is a challenging task since it aims at combining data sources with a variety of error structures, and temporal resolutions. E.g., in-situ measurements are quite accurate, but available only at sparse and irregularly distributed locations, whereas remote measurements cover complete areas but suffer from spatially and temporally inhomogeneous systematic errors. The first step towards such a space-time precipitation model is to develop a statistical model for precipitation based on radar measurements. Precipitation rates over a region of about 230× 230 km2 are provided by a composite of the two polarimetric X-band radars in Germany. The two radars are located in a distance of about 60 km in Bonn and Jülich, respectively. For the statistical model formulation we use a Gaussian Markov random field as underlying process. A Markov random field is a suitable model to account for spatial dependencies if the neighborhood can be reduced to a small region without losing information. This makes large data problems computationally feasible, since the neighborhood structure is given by a sparse precision matrix. Markov random fields are closely related to a graphical models. In processing the unadjusted radar rainfall rates, we follow D. Allcroft and C. Glasbey (2003)footnote{?bel{foot:1}David Allcroft and Chris Glasbey (2003). A latent Gaussian Markov Random Field model for spatiotemporal rainfall disaggregationJournal of the Royal Statistical Society: Series C (Applied Statistics), 52:487-498}. We start with a transformation of the precipitation rates to a truncated Gaussian distribution. The advantage of such a latent variable approach is that the occurrence as well as the intensity of rainfall are modeled by a single spatial process. The correlation function is then estimated as a function of the lag distance in space (and time) using the maximum likelihood method. Finally the Gaussian Markov random field is fitted such that its inverse is close to the empirical covariance matrix in some matrix norm. Therefore we use a minimum least squares method and implement a penalty term to assure the positive definiteness of the resulting covariance matrix. Note, that throughout our calculations we assume stationarity. The statistical model then allows for a disaggregation and aggregation of precipitation rates.

Krebsbach, K.; Friederichs, P.

2012-12-01

18

Investigating rainfall estimation from radar measurements using neural networks  

NASA Astrophysics Data System (ADS)

Rainfall observed on the ground is dependent on the four dimensional structure of precipitation aloft. Scanning radars can observe the four dimensional structure of precipitation. Neural network is a nonparametric method to represent the nonlinear relationship between radar measurements and rainfall rate. The relationship is derived directly from a dataset consisting of radar measurements and rain gauge measurements. The performance of neural network based rainfall estimation is subject to many factors, such as the representativeness and sufficiency of the training dataset, the generalization capability of the network to new data, seasonal changes, and regional changes. Improving the performance of the neural network for real time applications is of great interest. The goal of this paper is to investigate the performance of rainfall estimation based on Radial Basis Function (RBF) neural networks using radar reflectivity as input and rain gauge as the target. Data from Melbourne, Florida NEXRAD (Next Generation Weather Radar) ground radar (KMLB) over different years along with rain gauge measurements are used to conduct various investigations related to this problem. A direct gauge comparison study is done to demonstrate the improvement brought in by the neural networks and to show the feasibility of this system. The principal components analysis (PCA) technique is also used to reduce the dimensionality of the training dataset. Reducing the dimensionality of the input training data will reduce the training time as well as reduce the network complexity which will also avoid over fitting.

Alqudah, A.; Chandrasekar, V.; Le, M.

2013-03-01

19

Radar Rainfall Estimation for Ground Validation Studies of the Tropical Rainfall Measuring Mission.  

NASA Astrophysics Data System (ADS)

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.

Ciach, Grzegorz J.; Krajewski, Witold F.; Anagnostou, Emmanouil N.; Baeck, Mary L.; Smith, James A.; McCollum, Jeffrey R.; Kruger, Anton

1997-06-01

20

SUB-PIXEL RAINFALL VARIABILITY AND THE IMPLICATIONS FOR UNCERTAINTIES IN RADAR RAINFALL ESTIMATES  

EPA Science Inventory

Radar estimates of rainfall are subject to significant measurement uncertainty. Typically, uncertainties are measured by the discrepancies between real rainfall estimates based on radar reflectivity and point rainfall records of rain gauges. This study investigates how the disc...

21

SUB-PIXEL RAINFALL VARIABILITY AND THE IMPLICATIONS FOR UNCERTAINTIES IN RADAR RAINFALL ESTIMATES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Radar estimates of rainfall are subject to significant measurement uncertainty. Typically, uncertainties are measured by the discrepancies between area rainfall estimates based on radar reflectivity and point rainfall records of rain gauges. This study investigates how the discrepancies can potent...

22

Radar rainfall estimation for the identification of debris-flow occurrence thresholds  

NASA Astrophysics Data System (ADS)

This work aims to evaluate the potential benefits and limitations of radar rainfall estimates for the identification of debris flow occurrence rainfall thresholds. Observations from a C-band weather radar and raingauge data are analyzed for seven convective rainfall events that triggered 117 debris flows in the Upper Adige river basin (Eastern Italian Alps). Four radar rainfall scenarios characterized by incrementally increasing accuracy are used for the estimation of rainfall intensity-duration thresholds. Error sources considered in the radar correction chain include beam blockage, attenuation and vertical profile of reflectivity. The impact of rainfall accuracy on the estimation of the intensity-duration thresholds is analyzed by comparing the thresholds derived from the various radar rainfall scenarios, using the rainfall estimates obtained from the application of the complete correction algorithm as a reference scenario. Results show that the application of the complete correction algorithm improves significantly the accuracy of radar rainfall estimates: Fractional Standard Error is decreased by 20%, Correlation Coefficient is increased by 24% relative to uncorrected data. Correction for atmospheric attenuation is the most important step in the correction chain. The use of uncorrected radar estimates leads to substantially underestimated thresholds with respect to the reference scenario; adjusting radar data for bias is not sufficient to overcome this problem. Radar rainfall estimates which are corrected but not adjusted with raingauge data are able to provide intensity-duration thresholds which are almost indistinguishable from the reference scenario. The derivation of the radar-based threshold is shown to be very sensitive to spatial location errors of rainfall and debris flows. Raingauge-based thresholds are severely underestimated with respect to the reference scenario. This clearly demonstrates the severity of the raingauge-based estimation problem for the derivation of debris flow triggering rainfall and highlights the benefits of using weather radar observations, at least for the case of short duration convective storms.

Marra, Francesco; Nikolopoulos, Efthymios I.; Creutin, Jean Dominique; Borga, Marco

2014-11-01

23

TRMM precipitation radar helps address problems of ground-based weather radar systems  

Microsoft Academic Search

The launch of the first spaceborne precipitation radar (PR) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite provides a unique opportunity to address the ground-based weather radar system's calibration problem. The PR measures the same variable as ground-based systems---radar reflectivity--- and is proven to be consistent with respect to calibration accuracy. PR calibration tests, conducted by the Space Agency of

Emmanouil N. Anagnostou; Carlos A. Morales

2000-01-01

24

Efficient Ways to Learn Weather Radar Polarimetry  

ERIC Educational Resources Information Center

The U.S. weather radar network is currently being upgraded with dual-polarization capability. Weather radar polarimetry is an interdisciplinary area of engineering and meteorology. This paper presents efficient ways to learn weather radar polarimetry through several basic and practical topics. These topics include: 1) hydrometeor scattering model…

Cao, Qing; Yeary, M. B.; Zhang, Guifu

2012-01-01

25

Australian Weather Watch Radar Home Page  

NSDL National Science Digital Library

The Commonwealth Bureau of Meteorology's Weather Watch Radar website provides up-to-date radar images of the locations of rain in Australia in relation to local features such as coast lines. The newly developed Loops provide four consecutive radar images so that users can view how the weather has been changing in the last forty to fifty minutes. The website provides radar images of past cyclone events as well as updates on severe weather throughout Australia. Those interested in radar systems can discover how the weather radars work and how to interpret the maps. [RME

26

Enhanced Weather Radar (EWxR) System  

NASA Technical Reports Server (NTRS)

An airborne weather radar system, the Enhanced Weather Radar (EWxR), with enhanced on-board weather radar data processing was developed and tested. The system features additional weather data that is uplinked from ground-based sources, specialized data processing, and limited automatic radar control to search for hazardous weather. National Weather Service (NWS) ground-based Next Generation Radar (NEXRAD) information is used by the EWxR system to augment the on-board weather radar information. The system will simultaneously display NEXRAD and on-board weather radar information in a split-view format. The on-board weather radar includes an automated or hands-free storm-finding feature that optimizes the radar returns by automatically adjusting the tilt and range settings for the current altitude above the terrain and searches for storm cells near the atmospheric 0-degree isotherm. A rule-based decision aid was developed to automatically characterize cells as hazardous, possibly-hazardous, or non-hazardous based upon attributes of that cell. Cell attributes are determined based on data from the on-board radar and from ground-based radars. A flight path impact prediction algorithm was developed to help pilots to avoid hazardous weather along their flight plan and their mission. During development the system was tested on the NASA B757 aircraft and final tests were conducted on the Rockwell Collins Sabreliner.

Kronfeld, Kevin M. (Technical Monitor)

2003-01-01

27

Vertical and Temporal Variability of Rainfall Using a K-band Radar  

NASA Astrophysics Data System (ADS)

A vertically pointing Micro Rain Radar (MRR) was installed along a tipping bucket rain gauge at a site within a distance of 58.54 km from the nearest local National Weather Service weather radar, which have an average beam height of 552 m above ground level at the collocated gauge and MRR site. The MRR data were collected at two different gate height resolutions, 35 and 100 meters. The results showed that weather radar underestimated rainfall by 30 to 40% with respect to the gauge. And the MRR rainfall derived as function of Drop Size Distribution (DSD) and fall velocity (RR) was much closer to the gauge rainfall than MRR rainfall measurements derived from the same Z-R relationship used by the National Weather Service (Rz), which significantly underestimated rainfall in both height resolutions. The examination of the rainfall statistics suggested that the height resolution of 100 m produces better estimates especially at the third gate (centered at 300 m). MRR rain rates were highly variable during the same rainfall event or across different events. Few rainfall events showed very high rain rates at higher gates, but no bright band signature was found; thus a detailed inspection of DSDs variability with height and time is being conducted along with analysis of other MRR derived rainfall parameters to understand and capture the MRR rainfall variability and abnormalities.

Mazari, N.; Sharif, H. O.; Xie, H.; Tekeli, A. E.; Habib, E. H.; Zeitler, J.

2012-12-01

28

Radar rainfall estimation for the identification of debris-flow precipitation thresholds  

NASA Astrophysics Data System (ADS)

Identification of rainfall thresholds for the prediction of debris-flow occurrence is a common approach for warning procedures. Traditionally the debris-flow triggering rainfall is derived from the closest available raingauge. However, the spatial and temporal variability of intense rainfall on mountainous areas, where debris flows take place, may lead to large uncertainty in point-based estimates. Nikolopoulos et al. (2014) have shown that this uncertainty translates into a systematic underestimation of the rainfall thresholds, leading to a step degradation of the performances of the rainfall threshold for identification of debris flows occurrence under operational conditions. A potential solution to this limitation lies on use of rainfall estimates from weather radar. Thanks to their high spatial and temporal resolutions, these estimates offer the advantage of providing rainfall information over the actual debris flow location. The aim of this study is to analyze the value of radar precipitation estimations for the identification of debris flow precipitation thresholds. Seven rainfall events that triggered debris flows in the Adige river basin (Eastern Italian Alps) are analyzed using data from a dense raingauge network and a C-Band weather radar. Radar data are elaborated by using a set of correction algorithms specifically developed for weather radar rainfall application in mountainous areas. Rainfall thresholds for the triggering of debris flows are identified in the form of average intensity-duration power law curves using a frequentist approach by using both radar rainfall estimates and raingauge data. Sampling uncertainty associated to the derivation of the thresholds is assessed by using a bootstrap technique (Peruccacci et al. 2012). Results show that radar-based rainfall thresholds are largely exceeding those obtained by using raingauge data. Moreover, the differences between the two thresholds may be related to the spatial characteristics (i.e., spatial variogram) of the triggering rainfall. These results show that weather radar has the potential to effectively increase the accuracy of rainfall thresholds for debris flow occurrence. However, these benefits may only be achieved if the same monitoring instrumentation is used both to derive the rainfall thresholds and for use of thresholds for real-time identification of debris flows occurrence. References Nikolopoulos, E.I., Borga M., Crema S., Marchi L, Marra F. & Guzzetti F., 2014. Impact of uncertainty in rainfall estimation on the identification of rainfall thresholds for debris-flow occurrence. Geomorphology (conditionally accepted) Peruccacci, S., Brunetti, M.T., Luciani, S., Vennari, C., and Guzzetti, F., 2012. Lithological and seasonal control of rainfall thresholds for the possible initiation of landslides in central Italy, Geomorphology, 139-140, 79-90, 2012.

Marra, Francesco; Nikolopoulos, Efthymios I.; Creutin, Jean-Dominique; Borga, Marco

2014-05-01

29

Imperfect scaling in distributions of radar-derived rainfall fields  

NASA Astrophysics Data System (ADS)

Fine-scale rainfall observations for modelling exercises are often not available, but rather coarser data derived from a variety of sources are used. Effectively using these data sources in models often requires the probability distribution of the data at the applicable scale. Although numerous models for scaling distributions exist, these are often based on theoretical developments, rather than on data. In this study, we develop a model based on the ?-stable distribution of rainfall fields, and tested on 5 min radar data from a Belgian weather radar. We use these data to estimate functions that describe parameters of the distribution over various scales. Moreover, we study how the mean of the distribution and the intermittency change with scale, and validate and design functions to describe the shape parameter of the distribution. This information was combined into an effective model of the distribution.

van den Berg, M. J.; Delobbe, L.; Verhoest, N. E. C.

2014-12-01

30

Comparison of rain gauge and radar data as input to an urban rainfall-runoff model  

Microsoft Academic Search

This paper presents an application of radar data (DX-product of the German Weather Service) with a high resolution in space (1º ¥ 1 km) and time (Dt = 5 minutes) in urban hydrology. The radar data and data of rain gauges with different locations in the test catchment were compared concerning their suitability as input into an urban rainfall-runoff model.

M. Quirmbach; G. A. Schultz

31

Analyses of the temporal and spatial structures of heavy rainfall from a catalog of high-resolution radar rainfall fields  

NASA Astrophysics Data System (ADS)

In this paper, we develop a storm catalog of heavy rainfall events for a region centered on the Milwaukee, Wisconsin WSR-88D (Weather Surveillance Radar - 1988 Doppler) radar. The study region includes portions of southern Wisconsin, northern Illinois and Lake Michigan. The long-term objective of this study is to develop rainfall frequency analysis methods based on a storm catalog of major rain events. The specific objectives of this study are to develop a long-term catalog of high-resolution radar rainfall fields and characterize key features of the space-time variability of rainfall. The research questions that underlie these objectives are: 1) What are the spatial heterogeneities of rainfall over the study region for major flood-producing storm systems? 2) What are the key elements of storm evolution that control the scale-dependent properties of extreme rainfall? The storm catalog contains a record of the 50 “largest” storm days during the 1996-2011 observation period. We show that mean rainfall for the 50 largest storm days exhibits pronounced spatial heterogeneity with a broad maximum in western Wisconsin and a minimum in the eastern portion of the study region over Lake Michigan. We also show that there is a narrow line of maximum mean rainfall extending from west to east along the Wisconsin-Illinois border. This feature is tied to a maximum in the probability of daily rainfall exceeding 100 mm. There are characteristic elements to the storm life cycle of heavy rainfall days that relate to size, structure and evolution of heavy rainfall. Extreme rainfall is also linked with severe weather (tornados, large hail and damaging wind). The diurnal cycle of rainfall for heavy rain days is characterized by an early peak in the largest rainfall rates, an afternoon-evening peak in rain area exceeding 25 mm h- 1 and development of a large stratiform rain area during the night and early morning.

Thorndahl, Søren; Smith, James A.; Baeck, Mary Lynn; Krajewski, Witold F.

2014-07-01

32

Tests of Radar Rainfall Retrieval Algorithms  

NASA Technical Reports Server (NTRS)

The NASA/JPL Airborne Rain Mapping Radar (ARMAR) operates at 14 GHz. ARMAR flew on the NASA DC-8 aircraft during Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean Atmosphere Response Experiment (COARE), collecting data in oceanic mesoscale convective systems, similar to those now being observed by the Tropical Rainfall Measuring Mission (TRMM) satellite, which includes a 14-GHz precipitation radar. Several algorithms for retrieving rain rate from downward looking radars are in existence. These can be categorized as deterministic and stochastic. Deterministic algorithms use the path integrated attenuation (PIA), measured by the surface reference technique, as a constraint. One deterministic algorithm corrects the attenuation-rainfall (k-R) relation, while another corrects the reflectivity rainfall (ZR) relation. Stochastic algorithms apply an Extended Kalman Filter to the reflectivity profile. One employs radar reflectivity only; the other additionally uses the PIA. We find that the stochastic algorithm with PIA is the most robust algorithm with regard to incorrect assumptions about the drop-size distribution (DSD). The deterministic algorithm that uses the PIA to adjust the Z-R relation is also fairly robust and produces rain rates similar to the stochastic algorithm that uses the PIA. The deterministic algorithm that adjusts only the k-R relation and the stochastic radar-only algorithm are more sensitive to assumptions about the DSD. It is likely that they underestimate convective rainfall, especially if the DSD is erroneously assumed to be appropriate for stratiform rain conditions. The underestimation is illustrated in the diagram. The algorithm labeled D IS initially assumes a DSD that is appropriate for stratiform. rain, while the rain is most likely convective. The PIA constraint causes the k-R relation to be adjusted, resulting in a much lower rain rate than the other algorithms. Additional information is contained in the original.

Durden, Stephen L.

1999-01-01

33

Airborne Differential Doppler Weather Radar  

NASA Technical Reports Server (NTRS)

The Precipitation Radar aboard the Tropical Rain Measuring Mission (TRMM) Satellite has shown the potential for spaceborne sensing of snow and rain by means of an incoherent pulsed radar operating at 13.8 GHz. The primary advantage of radar relative to passive instruments arises from the fact that the radar can image the 3-dimensional structure of storms. As a consequence, the radar data can be used to determine the vertical rain structure, rain type (convective/stratiform) effective storm height, and location of the melting layer. The radar, moreover, can be used to detect snow and improve the estimation of rain rate over land. To move toward spaceborne weather radars that can be deployed routinely as part of an instrument set consisting of passive and active sensors will require the development of less expensive, lighter-weight radars that consume less power. At the same time, the addition of a second frequency and an upgrade to Doppler capability are features that are needed to retrieve information on the characteristics of the drop size distribution, vertical air motion and storm dynamics. One approach to the problem is to use a single broad-band transmitter-receiver and antenna where two narrow-band frequencies are spaced apart by 5% to 10% of the center frequency. Use of Ka-band frequencies (26.5 GHz - 40 GHz) affords two advantages: adequate spatial resolution can be attained with a relatively small antenna and the differential reflectivity and mean Doppler signals are directly related to the median mass diameter of the snow and raindrop size distributions. The differential mean Doppler signal has the additional property that this quantity depends only on that part of the radial speed of the hydrometeors that is drop-size dependent. In principle, the mean and differential mean Doppler from a near-nadir viewing radar can be used to retrieve vertical air motion as well as the total mean radial velocity. In the paper, we present theoretical calculations for the differential reflectivity and Doppler as functions of the center frequency, frequency difference, and median mass diameter. For a fixed pair of frequencies, the detectability of the differential signals can be expressed as the number of independent samples required to detect rain or snow with a particular median mass diameter. Because sampling numbers on the order of 1000 are needed to detect the differential signal over a range of size distributions, the instrument must be confined to a near-nadir, narrow swath. Radar measurements from a zenith directed radar operated at 9.1 GHz and 10 GHz are used to investigate the qualitative characteristics of the differential signals. Disdrometer and rain gauge data taken at the surface, just below the radar, are used to test whether the differential signals can be used to estimate characteristics of the raindrop size distribution.

Meneghini, R.; Bidwell, S.; Liao, L.; Rincon, R.; Heymsfield, G.; Hildebrand, Peter H. (Technical Monitor)

2001-01-01

34

14 CFR 135.175 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 false Airborne weather radar equipment requirements. 135.175 ...Equipment § 135.175 Airborne weather radar equipment requirements. (a) No...operations unless approved airborne weather radar equipment is installed in the...

2011-01-01

35

14 CFR 121.357 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Airborne weather radar equipment requirements. 121.357 ...Requirements § 121.357 Airborne weather radar equipment requirements. (a) No...1964, unless approved airborne weather radar equipment has been installed in the...

2013-01-01

36

14 CFR 135.175 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Airborne weather radar equipment requirements. 135.175 ...Equipment § 135.175 Airborne weather radar equipment requirements. (a) No...operations unless approved airborne weather radar equipment is installed in the...

2013-01-01

37

14 CFR 135.175 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Airborne weather radar equipment requirements. 135.175 ...Equipment § 135.175 Airborne weather radar equipment requirements. (a) No...operations unless approved airborne weather radar equipment is installed in the...

2010-01-01

38

14 CFR 121.357 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2014 CFR

...2014-01-01 false Airborne weather radar equipment requirements. 121.357 ...Requirements § 121.357 Airborne weather radar equipment requirements. (a) No...1964, unless approved airborne weather radar equipment has been installed in the...

2014-01-01

39

14 CFR 135.175 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2014 CFR

...2014-01-01 false Airborne weather radar equipment requirements. 135.175 ...Equipment § 135.175 Airborne weather radar equipment requirements. (a) No...operations unless approved airborne weather radar equipment is installed in the...

2014-01-01

40

14 CFR 121.357 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 false Airborne weather radar equipment requirements. 121.357 ...Requirements § 121.357 Airborne weather radar equipment requirements. (a) No...1964, unless approved airborne weather radar equipment has been installed in the...

2011-01-01

41

14 CFR 121.357 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 false Airborne weather radar equipment requirements. 121.357 ...Requirements § 121.357 Airborne weather radar equipment requirements. (a) No...1964, unless approved airborne weather radar equipment has been installed in the...

2012-01-01

42

14 CFR 125.223 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 false Airborne weather radar equipment requirements. 125.223 ...Requirements § 125.223 Airborne weather radar equipment requirements. (a) No person...operations unless approved airborne weather radar equipment is installed in the...

2011-01-01

43

14 CFR 125.223 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 false Airborne weather radar equipment requirements. 125.223 ...Requirements § 125.223 Airborne weather radar equipment requirements. (a) No person...operations unless approved airborne weather radar equipment is installed in the...

2012-01-01

44

14 CFR 125.223 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Airborne weather radar equipment requirements. 125.223 ...Requirements § 125.223 Airborne weather radar equipment requirements. (a) No person...operations unless approved airborne weather radar equipment is installed in the...

2010-01-01

45

14 CFR 125.223 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2014 CFR

...2014-01-01 false Airborne weather radar equipment requirements. 125.223 ...Requirements § 125.223 Airborne weather radar equipment requirements. (a) No person...operations unless approved airborne weather radar equipment is installed in the...

2014-01-01

46

14 CFR 135.175 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 false Airborne weather radar equipment requirements. 135.175 ...Equipment § 135.175 Airborne weather radar equipment requirements. (a) No...operations unless approved airborne weather radar equipment is installed in the...

2012-01-01

47

14 CFR 121.357 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Airborne weather radar equipment requirements. 121.357 ...Requirements § 121.357 Airborne weather radar equipment requirements. (a) No...1964, unless approved airborne weather radar equipment has been installed in the...

2010-01-01

48

14 CFR 125.223 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Airborne weather radar equipment requirements. 125.223 ...Requirements § 125.223 Airborne weather radar equipment requirements. (a) No person...operations unless approved airborne weather radar equipment is installed in the...

2013-01-01

49

Improved rainfall estimates in convective storms using polarisation diversity radar  

Microsoft Academic Search

Errors arise when using conventional radar reflectivity, Z, to estimate rainfall rate, R, and these can be particularly severe during severe convective storms; the very events when accurate estimates are needed so that action can be taken to mitigate the effects of flooding. Concentration is on three problems associated with heavy rainfall: hail, attenuation and absolute calibration of the radar,

A. J. Illingworth; T. M. Blackman; J. W. F. Goddard

2000-01-01

50

Use of weather radar for flood forecasting in the Sieve River Basin: A sensitivity analysis  

Microsoft Academic Search

Weather radar, in combination with a distributed rainfall-runoff model, promises to significantly improve real-time flood forecasting. This paper investigates the value of radar-derived precipitation in forecasting streamflow in the Sieve River basin, near Florence, Italy. The basin is modeled with a distributed rainfall-runoff model that exploits topographic information available from digital elevation maps. The sensitivity of the flood forecast to

Marcos L. Pessoa; Rafael L. Bras; Earle R. Williams

1993-01-01

51

High-resolution rainfall estimation for Helsinki urban area using Helsinki radar network  

NASA Astrophysics Data System (ADS)

High resolution precipitation data is a crucial factor for hydrological applications in urban areas. Small fluctuations in precipitation fields are of great importance considering the fast response of urban catchments due to the dominance of impervious surfaces. High resolution precipitation observations are needed in order to characterize these fluctuations. Weather radar provides high spatial resolution precipitation estimations. However, the quality of its observations in an urban environment is significantly degraded, among other things, by ground clutter and beam-blockage. A solution for this problem is to use a radar network, where the data gaps of one radar will be filled by using observations from the others. Very few cities have dedicated weather radar networks. In some cities, like Helsinki, there are several weather radars covering the metropolitan area, but they are operated by different organizations. In this study, we show how such systems can be used to build a network and what is the advantage of using radarnetworks for estimating precipitation in urban catchments. The urban Helsinki area is covered by observations from three individual-purpose C-band weather radars (Helsinki University's Kumpula (KUM), Vaisala Oy's Kerava (KER) and Finnish Meteorological Institute's Vantaa (VAN)). We used the data from these radars to form a network and we design a similar task which runs at the same time in each radar couple of times per day. Nonetheless, it is challenging to make them observe at the same area at exactly the same time, which could lead to fast changing, short precipitation events being missed. Hence, synchronization and temporal resolution are the main concerns when building a network. Consequently, to decrease the impact of these restrictions in the Helsinki radar network we propose the use of the optic flow interpolation algorithm to retrieve information in between two radar observations and use the retrieved dataset from the three radars to estimate rainfall. The accuracy of this method is studied by comparing the composite rainfall estimation with both single radar observations and ground measurements.

Rojas, Laura; Nordling, Kalle; Cremonini, Roberto; Moisseev, Dmitri; Chandrasekar, Venkatachalam

2014-05-01

52

A New Approach For Reducing The Uncertainty In Radar Rainfall Estimation Procedures  

NASA Astrophysics Data System (ADS)

The weather radar provides a convenient means for measuring rainfall in space and time. However, its use as a rainfall measuring device is limited due to the poor accu- racy of algorithms used to convert the measured reflectivity to ground rainfall. While this accuracy can be acceptable in situations where the catchment is large and ground measurements few, the use of radar based rainfall observations can lead to signifi- cant errors in small catchments located far from the radar site. This study aims to identify some of the reasons behind the limited accuracy of radar rainfall estimation algorithms, and proposes a method that addresses some of the factors responsible. The accuracy of weather radars is effected by a number of factors, not all of which are considered in the algorithms used. Some of these are: (a) mis-specification of the relationship between reflectivity and rainfall through the use of an improperly speci- fied equation, (b) nonstationarity in measured reflectivity values due to changes in the rainfall drop size distribution, (c) an inability to convert the reflectivity measured at an elevation above ground to the rainfall at ground level, and, (d) a reduction in the reli- ability associated with measured reflectivity with increase in distance from the radar, a result of the radar emitted power being shared over an increasing volume of air. The above factors can be addressed by either formulating a relationship that is stable and consistent, or using a quantile matching approach called the Probability Matching Method (PMM) which is helpful when the relationship is difficult to specify. How- ever, for either method to be useful, the measured reflectivity must be stationary, or, must bear the same relation with rainfall irrespective of factors such as changes in storm type or distance from the radar. Another cause of nonstationarity in the mea- sured reflectivity values is use of measurements that vary in accuracy depending on their distance from the radar site. As conventional methods do not attempt to take ac- count of the factors mentioned, the resulting algorithms are uncertain and unstable, and perform poorly especially when applied to storms not used in the calibration ex- ercise. Presented here is an approach that attempts to identify and correct for known sources of nonstationarity in radar reflectivity observations, and establish a procedure that explicitly takes into account the variations in reliability associated with the ob- servations used. This approach is applied to six months of reflectivity values from the Kurnell radar in Sydney, Australia.

Chumchean, S.; Sharma, A.

53

Bayesian Integration of Radar Rainfall Data with Rain Gauge Measurements  

NASA Astrophysics Data System (ADS)

Accurate representation of the spatial and temporal distribution of rainfall intensity is crucial to development of robust calibrated hydrologic models. Rainfall data are commonly collected using rain gauges and Doppler radar. Rain gauge data are more accurate but they only yield information at point locations. Radar data provide continuous spatial information but they are less accurate. We present a Bayesian approach for integrating gauge and radar data to develop more accurate and continuous rainfall interpretation. In a Bayesian framework, the resulting probability distribution of rainfall intensity (posterior distribution) at a location at a time step is computed from a prior distribution and a likelihood function. Here, the prior distribution is estimated from the rain gauge data by applying geostatistical methods. The likelihood function is calculated based on the mismatch errors between the rainfall radar and rainfall gauge data where they overlap. We shortly discuss an earlier applied model based on a lognorm-transform of a Gaussian random field, but then focus on a novel non-parameteric approach. Therein, at each time step, a range of rainfall threshold levels is considered. For each threshold level, rain gauge and radar data are encoded into indicator values with 1 denoting rainfall intensity greater than the threshold level, 0 otherwise. Radar data are used to characterize the correlation structure of the indicator field. We study and compare several characterization approaches. Indicator Kriging using the resulting correlation model is applied to gauge indicator data to compute the prior estimate of the probability of exceeding the rainfall threshold. A fault table based on comparison of gauge and radar indicator values is used to compute the likelihood at each location. The resulting posterior estimate of the probability of exceeding the rainfall threshold is equal to the value of the posterior cumulative probability distribution function value. We applied this Bayesian approach to the gauge and radar rainfall data collected between January 1, 1995 to June 30, 2003 in the Tampa Bay region in Florida, US. The inconsistency between the radar rainfall estimation and rain gauge point measurements were evaluated. Results show that Bayesian Integration of radar rainfall with rain gauge measurements using the proposed non-parametric threshold approach holds the potential to improve rainfall estimations. Posterior rainfall estimations obtained from Bayesian Integration show higher accuracy than rainfall estimations obtained from Kriging along and are consistent with all rain gauge data. We also have experimented with a Bayesian Integration based on the lognorm-transform of a Gaussian approach. Although the log-transformation approach is computationally more efficient than the proposed non-parametric approach, it can lead to unrealistically large rainfall. The non-parametric approach does not have this problem.

Heimann, Marian; Straub, Daniel; Mok, Chin Man Bill

2013-04-01

54

Weather Radar Control System Seidu Ibrahim; Advisor: Eric J. Knapp  

E-print Network

Weather Radar Control System Seidu Ibrahim; Advisor: Eric J. Knapp Dept. of Electrical and Computer Engineering University of Massachusetts, Amherst Abstract Weather radar is an important part of the national radars such as the National Weather Service WSR88D Doppler radars are limited in their ability to provide

Mountziaris, T. J.

55

Weather Radar and Hydrology (Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2011).  

E-print Network

Weather Radar and Hydrology (Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2011). Copyright © 2011 IAHS Press 1 Getting higher resolution rainfall estimates: X-band radar Hydrologists have been waiting for some time to have radar data with a resolution higher than the kilometre

Lovejoy, Shaun

56

Uncertainty Analysis of Radar and Gauge Rainfall Estimates in the Russian River Basin  

NASA Astrophysics Data System (ADS)

Radar Quantitative Precipitation Estimation (QPE) has been a very important application of weather radar since it was introduced and made widely available after World War II. Although great progress has been made over the last two decades, it is still a challenging process especially in regions of complex terrain such as the western U.S. It is also extremely difficult to make direct use of radar precipitation data in quantitative hydrologic forecasting models. To improve the understanding of rainfall estimation and distributions in the NOAA Hydrometeorology Testbed in northern California (HMT-West), extensive evaluation of radar and gauge QPE products has been performed using a set of independent rain gauge data. This study focuses on the rainfall evaluation in the Russian River Basin. The statistical properties of the different gridded QPE products will be compared quantitatively. The main emphasis of this study will be on the analysis of uncertainties of the radar and gauge rainfall products that are subject to various sources of error. The spatial variation analysis of the radar estimates is performed by measuring the statistical distribution of the radar base data such as reflectivity and by the comparison with a rain gauge cluster. The application of mean field bias values to the radar rainfall data will also be described. The uncertainty analysis of the gauge rainfall will be focused on the comparison of traditional kriging and conditional bias penalized kriging (Seo 2012) methods. This comparison is performed with the retrospective Multisensor Precipitation Estimator (MPE) system installed at the NOAA Earth System Research Laboratory. The independent gauge set will again be used as the verification tool for the newly generated rainfall products.

Cifelli, R.; Chen, H.; Willie, D.; Reynolds, D.; Campbell, C.; Sukovich, E.

2013-12-01

57

Spatial-temporal mesoscale modelling of rainfall intensity using gage and radar data  

E-print Network

Spatial-temporal mesoscale modelling of rainfall intensity using gage and radar data Montserrat fields. Doppler radar data offer better spatial and temporal coverage, but Doppler radar measures effective radar reflectivity (Ze) rather than rainfall rate (R). Thus, rainfall estimates from radar data

Reich, Brian J.

58

Automation of Cn2 profile extraction from weather radar images  

NASA Astrophysics Data System (ADS)

A novel method for measuring the structure constant of the atmospheric turbulence on an arbitrary path has recently been demonstrated by the Air Force Institute of Technology (AFIT). This method provides a unique ability to remotely measure the intensity of turbulence, which is important for predicting beam spread, wander, and scintillation effects on High Energy Laser (HEL) propagation. Because this is a new technique, estimating A novel method for measuring the structure constant of the atmospheric turbulence on an arbitrary path has recently been demonstrated by the Air Force Institute of Technology (AFIT). This method provides a unique ability to remotely measure the intensity of turbulence, which is important for predicting beam spread, wander, and scintillation effects on High Energy Laser (HEL) propagation. Because this is a new technique, estimating Cn2 using radar is a complicated and time consuming process. This paper presents a new software program which is being developed to automate the calculation of Cn2 over an arbitrary path. The program takes regional National Weather Service NEXRAD radar reflectivity measurements and extracts data for the path of interest. These reflectivity measurements are then used to estimate Cn2 over the path. The program uses the Radar Software Library (RSL) produced by the Tropical Rainfall Measuring Mission (TRMM) at the NASA/Goddard Flight Center. RSL provides support for nearly all formats of weather radar data. The particular challenge to extracting data is in determining which data bins the path passes through. Due to variations in radar systems and measurement conditions, the RSL produces data grids that are not consistent in geometry or completeness. The Cn2 program adapts to the varying geometries of each radar image. Automation of the process allows for fast estimation of Cn2 and supports a goal of real-time remote turbulence measurement. Recently, this software was used to create comparison data for RF scintillation measurements. In this task it performed well, extracting thousands of measurements in only a few minutes.using radar is a complicated and time consuming process. This paper presents a new software program which is being developed to automate the calculation of Cn2 over an arbitrary path. The program takes regional National Weather Service NEXRAD radar reflectivity measurements and extracts data for the path of interest. These reflectivity measurements are then used to estimate Cn2 over the path. The program uses the Radar Software Library (RSL) produced by the Tropical Rainfall Measuring Mission (TRMM) at the NASA/Goddard Flight Center. RSL provides support for nearly all formats of weather radar data. The particular challenge to extracting data is in determining which data bins the path passes through. Due to variations in radar systems and measurement conditions, the RSL produces data grids that are not consistent in geometry or completeness. The Cn2 program adapts to the varying geometries of each radar image. Automation of the process allows for fast estimation of Cn2 and supports a goal of real-time remote turbulence measurement. Recently, this software was used to create comparison data for RF scintillation measurements. In this task it performed well, extracting thousands of measurements in only a few minutes.

Burchett, Lee R.; Fiorino, Steven T.; Buchanan, Matthew

2012-06-01

59

Storm Scale Rainfall Estimation and Quantifying Uncertainty from Ground-based Dual-Polarimetric Radar  

NASA Astrophysics Data System (ADS)

Ground-based radar and gauge rainfall estimates will be vital components in both statistical and physical validation of Global Precipitation Measurement (GPM) constellation satellite rainfall retrievals, and the quantification of uncertainty of the ground-based measurements is a key requirement of the GPM Ground Validation (GV) program. Legacy Tropical Rainfall Measuring Mission (TRMM) GV radar reflectivity - rain rate (Z-R) lookup tables are determined by matching reflectivity and rain gauge distributions via the probability matching method (PMM) over a minimum time period of one month, thereby constraining the radar-derived accumulations to match the gauge accumulations. However, the usage of climatological PMM tables for rain rate estimation is not representative for the storm scale accumulations relevant to GPM science hydrology applications. The availability of S-band dual-polarimetric data from the KPOL radar at Kwajalein Atoll, RMI and KMLB (WSR-88D) radar at Melbourne, FL provides opportunity to evaluate alternative rainfall estimation methods with error quantification derived via comparison with independent rain gauges. In this study, statistical comparisons of rainfall accumulation from legacy PMM and two multi-parameter methods are evaluated on a GPM relevant storm scale (~3 hours). The first multi-parameter approach considers rain rate equations derived from several years of Joss-Waldvogel disdrometer data near both radars (JW method), while the second involves a polarimetrically-based Z-R relation with a continuously adjusted coefficient tuned to the evolving drop size distribution (Bringi method). The primary objective is to generate rainfall accumulations and associated error estimates with fidelity at a storm scale relevant to GPM goals. Of further interest will be the difference in results between the two regimes; the KPOL environment being a tropical oceanic climate, while the KMLB environment is influenced by continental, coastal, and maritime weather systems.

Marks, D. A.; Wolff, D. B.

2012-12-01

60

Multiresolution Precipitation Visualization of Weather Radar Volume Scans  

NASA Astrophysics Data System (ADS)

Weather radars measure the backscatter from atmospheric hydrometeors. The three-dimensional structure of a complete radar scan contains information which can improve rainfall rate estimates which is crucial for hydrological modeling and simulations. For the understanding and conveyance of the data, interactive volume visualization tools within visual geographic information systems are required. However, due to the large size of the data it is difficult to achieve real-time visualization performance. Furthermore, the data has to be put in a context for better comprehension, e.g. by additionally rendering the local terrain or satellite image data which further increases the amount of data which has to be displayed. In addition, the simultaneous display of volume and surface data leads to algorithmic visualization difficulties. In this talk, we address these problems by adaptive multiresolution algorithms (see [1]). Multiresolution methods allow a fast coarse display of the data for overview images or interaction, while higher resolution is used when zooming into the data or for detail images. The algorithms are adaptive in the sense that the resolution does not have to be uniform everywhere but may be variable in space. For example, in smooth areas a lower resolution can be sufficient to provide a good representation of the data while in areas with greater variation a higher resolution is used. The adaptive refinement is controlled by suitable error indicators which can be specified by the user. The employed volume visualization algorithm is based on the simultaneous extraction of several transparent isosurfaces. In this way, interactive visualization performance of time-varying three-dimensional radar data can be achieved without the usage of special-purpose hardware (apart from a standard graphics card). [1] T. Gerstner, D. Meetschen, S. Crewell, M. Griebel, and C. Simmer. A Case Study on Multiresolution Visualization of Local Rainfall from Weather Radar Measurements. In H. Pfister and M. Bailey, editors, Proceedings IEEE Visualization 2002, pages 533-536. IEEE Computer Society Press, 2002.

Gerstner, T.; Meetschen, D.; Simmer, C.

2004-12-01

61

SUBPIXEL-SCALE RAINFALL VARIABILITY AND THE EFFECTS ON SEPARATION OF RADAR AND GAUGE RAINFALL ERRORS  

EPA Science Inventory

One of the primary sources of the discrepancies between radar-based rainfall estimates and rain gauge measurements is the point-area difference, i.e., the intrinsic difference in the spatial dimensions of the rainfall fields that the respective data sets are meant to represent. ...

62

Multi-scale evaluation of the IFloodS radar-rainfall products  

NASA Astrophysics Data System (ADS)

Rainfall products estimated using ground-based radars are often used as reference to assess capabilities and limitations of using satellite rainfall estimates in hydrologic modeling and prediction. During the spring of 2013, NASA conducted a hydrology-oriented field campaign called Iowa Flood Studies (IFloodS) in the central and northeastern Iowa in the United States, as a part of the Ground Validation (GV) program for the Global Precipitation Measurement (GPM) mission. The purpose of IFloodS was to enhance the understanding of flood-related rainfall processes and the predictability in flood forecasting. While there are multiple types of rainfall data sets (e.g., satellite, radar, rain gauge, and disdrometer) available as the observational assets of IFloodS, the authors focus on the evaluation of multi-scale rainfall products observed from ground-based radars. The radar-only products used in the evaluation are the NEXRAD single polarization products (i.e., Stage IV, NMQ Q2, and Iowa Flood Center rainfall maps) and products generated using dual-polarization procedures (i.e., the U.S. National Weather Service operational and Colorado State University experimental blended precipitation processing algorithms) with comparable space and time resolution. The NASA NPOL S-band radar products are also evaluated and compared with the aforementioned NEXRAD products. The uncertainty for different temporal and spatial resolution products is characterized using ground reference data of dense rain gauge and disdrometer networks. This multi-scale characterization is required for hydrologic modeling frameworks that assess model predictive abilities as a function of space and time scales.

Seo, Bong-Chul; Krajewski, Witold; Cunha, Luciana; Dolan, Brenda; Smith, James; Rutledge, Steven; Petersen, Walter

2014-05-01

63

Weather models as virtual sensors to data-driven rainfall predictions in urban watersheds  

NASA Astrophysics Data System (ADS)

Weather and climate predictions are a key element of urban hydrology where they are used to inform water management and assist in flood warning delivering. Indeed, the modelling of the very fast dynamics of urbanized catchments can be substantially improved by the use of weather/rainfall predictions. For example, in Singapore Marina Reservoir catchment runoff processes have a very short time of concentration (roughly one hour) and observational data are thus nearly useless for runoff predictions and weather prediction are required. Unfortunately, radar nowcasting methods do not allow to carrying out long - term weather predictions, whereas numerical models are limited by their coarse spatial scale. Moreover, numerical models are usually poorly reliable because of the fast motion and limited spatial extension of rainfall events. In this study we investigate the combined use of data-driven modelling techniques and weather variables observed/simulated with a numerical model as a way to improve rainfall prediction accuracy and lead time in the Singapore metropolitan area. To explore the feasibility of the approach, we use a Weather Research and Forecast (WRF) model as a virtual sensor network for the input variables (the states of the WRF model) to a machine learning rainfall prediction model. More precisely, we combine an input variable selection method and a non-parametric tree-based model to characterize the empirical relation between the rainfall measured at the catchment level and all possible weather input variables provided by WRF model. We explore different lead time to evaluate the model reliability for different long - term predictions, as well as different time lags to see how past information could improve results. Results show that the proposed approach allow a significant improvement of the prediction accuracy of the WRF model on the Singapore urban area.

Cozzi, Lorenzo; Galelli, Stefano; Pascal, Samuel Jolivet De Marc; Castelletti, Andrea

2013-04-01

64

Weather types and rainfall in the Amazon basin  

NASA Astrophysics Data System (ADS)

A neuronal method (Self Organizing Maps or SOMs) is used to identify weather types over tropical South America from total wind at 850 hPa in ERA-40 reanalysis. Weather types are associated with daily rainfall in two regions of the Amazon basin where the long term hydrologic variability is the strongest. In the south-western basin, important rainfall is associated with a weather type characterized by negative geopotential anomalies over the Chaco region and positive ones behind, that promote the convergence of north-western wind anomalies (monsoon flux around summer) and southern anomalies over the Bolivian lowlands. In the north-western Amazon basin, important rainfall is associated with a weather regime characterized by positive geopotential anomalies over the Chaco region that promote strong southern wind anomalies over western Amazon and their convergence with the trade winds. We show that the progression of extra tropical perturbations and their incursion toward low latitude, favoured by the N-S orientation of the Andes, partly control the characteristics of weather types over tropical South America. The frequency of weather regimes allows explaining partially rainfall variability at interannual and pluriannual time scales. In addition, weather type's frequency is able to explain the occurrence of exceptional floods in the Amazonian Basin Rivers.

Espinoza, J. C.; Lengaigne, M.; Ronchail, J.; Janicot, S.; Guyot, J. L.

2009-04-01

65

SUB-PIXEL SCALE RAINFALL VARIABILITY AND THE EFFECTS ON SEPARATION OF RADAR AND GAUGE RAINFALL ERRORS  

Technology Transfer Automated Retrieval System (TEKTRAN)

As long recognized, one of the primary sources of the discrepancies in the radar-based rainfall estimates and rain gauge measurements is the point-area difference, i.e., the intrinsic difference in the spatial dimensions of the rainfall fields that radar rainfall estimates and gauge measurements are...

66

Radar-based rainfall estimation: Improving Z/R relations through comparison of drop size distributions, rainfall rates and radar reflectivity patterns  

NASA Astrophysics Data System (ADS)

The relation between the measured radar reflectivity factor Z and surface rainfall intensity R - the Z/R relation - is profoundly complex, so that in general one speaks about radar-based quantitative precipitation estimation (QPE) rather than exact measurement. Like in Plato's Allegory of the Cave, what we observe in the end is only the 'shadow' of the true rainfall field through a very small backscatter of an electromagnetic signal emitted by the radar, which we hope has been actually reflected by hydrometeors. The meteorological relevant and valuable Information is gained only indirectly by more or less justified assumptions. One of these assumptions concerns the drop size distribution, through which the rain intensity is finally associated with the measured radar reflectivity factor Z. The real drop size distribution is however subject to large spatial and temporal variability, and consequently so is the true Z/R relation. Better knowledge of the true spatio-temporal Z/R structure therefore has the potential to improve radar-based QPE compared to the common practice of applying a single or a few standard Z/R relations. To this end, we use observations from six laser-optic disdrometers, two vertically pointing micro rain radars, 205 rain gauges, one rawindsonde station and two C-band Doppler radars installed or operated in and near the Attert catchment (Luxembourg). The C-band radars and the rawindsonde station are operated by the Belgian and German Weather Services, the rain gauge data was partly provided by the French, Dutch, Belgian, German Weather Services and the Ministry of Agriculture of Luxembourg and the other equipment was installed as part of the interdisciplinary DFG research project CAOS (Catchment as Organized Systems). With the various data sets correlation analyzes were executed. In order to get a notion on the different appearance of the reflectivity patterns in the radar image, first of all various simple distribution indices (for example the Gini index, Rosenbluth index) were calculated and compared to the synoptic situation in general and the atmospheric stability in special. The indices were then related to the drop size distributions and the rain rate. Special emphasis was laid in an objective distinction between stratiform and convective precipitation and hereby altered droplet size distribution, respectively Z/R relationship. In our presentation we will show how convective and stratiform precipitation becomes manifest in the different distribution indices, which in turn are thought to represent different patterns in the radar image. We also present and discuss the correlation between these distribution indices and the evolution of the drop size distribution and the rain rate and compare a dynamically adopted Z/R relation to the standard Marshall-Palmer Z/R relation.

Neuper, Malte; Ehret, Uwe

2014-05-01

67

Propagation of radar rainfall uncertainty in urban flood simulations  

NASA Astrophysics Data System (ADS)

This work discusses the results of the implementation of a novel probabilistic system designed to improve ensemble sewer flow predictions for the drainage network of a small urban area in the North of England. The probabilistic system has been developed to model the uncertainty associated to radar rainfall estimates and propagate it through radar-based ensemble sewer flow predictions. The assessment of this system aims at outlining the benefits of addressing the uncertainty associated to radar rainfall estimates in a probabilistic framework, to be potentially implemented in the real-time management of the sewer network in the study area. Radar rainfall estimates are affected by uncertainty due to various factors [1-3] and quality control and correction techniques have been developed in order to improve their accuracy. However, the hydrological use of radar rainfall estimates and forecasts remains challenging. A significant effort has been devoted by the international research community to the assessment of the uncertainty propagation through probabilistic hydro-meteorological forecast systems [4-5], and various approaches have been implemented for the purpose of characterizing the uncertainty in radar rainfall estimates and forecasts [6-11]. A radar-based ensemble stochastic approach, similar to the one implemented for use in the Southern-Alps by the REAL system [6], has been developed for the purpose of this work. An ensemble generator has been calibrated on the basis of the spatial-temporal characteristics of the residual error in radar estimates assessed with reference to rainfall records from around 200 rain gauges available for the year 2007, previously post-processed and corrected by the UK Met Office [12-13]. Each ensemble member is determined by summing a perturbation field to the unperturbed radar rainfall field. The perturbations are generated by imposing the radar error spatial and temporal correlation structure to purely stochastic fields. A hydrodynamic sewer network model implemented in the Infoworks software was used to model the rainfall-runoff process in the urban area. The software calculates the flow through the sewer conduits of the urban model using rainfall as the primary input. The sewer network is covered by 25 radar pixels with a spatial resolution of 1 km2. The majority of the sewer system is combined, carrying both urban rainfall runoff as well as domestic and trade waste water [11]. The urban model was configured to receive the probabilistic radar rainfall fields. The results showed that the radar rainfall ensembles provide additional information about the uncertainty in the radar rainfall measurements that can be propagated in urban flood modelling. The peaks of the measured flow hydrographs are often bounded within the uncertainty area produced by using the radar rainfall ensembles. This is in fact one of the benefits of using radar rainfall ensembles in urban flood modelling. More work needs to be done in improving the urban models, but this is out of the scope of this research. The rainfall uncertainty cannot explain the whole uncertainty shown in the flow simulations, and additional sources of uncertainty will come from the structure of the urban models as well as the large number of parameters required by these models. Acknowledgements The authors would like to acknowledge the BADC, the UK Met Office and the UK Environment Agency for providing the various data sets. We also thank Yorkshire Water Services Ltd for providing the urban model. The authors acknowledge the support from the Engineering and Physical Sciences Research Council (EPSRC) via grant EP/I012222/1. References [1] Browning KA, 1978. Meteorological applications of radar. Reports on Progress in Physics 41 761 Doi: 10.1088/0034-4885/41/5/003 [2] Rico-Ramirez MA, Cluckie ID, Shepherd G, Pallot A, 2007. A high-resolution radar experiment on the island of Jersey. Meteorological Applications 14: 117-129. [3] Villarini G, Krajewski WF, 2010. Review of the different sources of uncertainty in single polarization radar-based estimate

Liguori, Sara; Rico-Ramirez, Miguel

2013-04-01

68

USING METEOROLOGICAL RADAR TO LINK LANDSLIDES AND RAINFALL IN THE OREGON COAST RANGE  

E-print Network

USING METEOROLOGICAL RADAR TO LINK LANDSLIDES AND RAINFALL IN THE OREGON COAST RANGE by AMANDA JANE #12;ii "Using Meteorological Radar to Link Landslides and Rainfall in the Oregon Coast Range METEOROLOGICAL RADAR TO LINK LANDSLIDES AND RAINFALL IN THE OREGON COAST RANGE Approved

Roering, Joshua J.

69

Numerical simulations of radar rainfall error propagation Hatim O. Sharif1  

E-print Network

Numerical simulations of radar rainfall error propagation Hatim O. Sharif1 and Fred L. Ogden model of convective rainfall with an active microwave radiative transfer model to simulate radar of that storm and used them to evaluate the propagation of radar rainfall errors through distributed hydrologic

Xue, Ming

70

Rainfall estimation using raingages and radar — A Bayesian approach: 1. Derivation of estimators  

Microsoft Academic Search

Procedures for estimating rainfall from radar and raingage observations are constructed in a Bayesian framework. Given that the number of raingage measurements is typically very small, mean and variance of gage rainfall are treated as uncertain parameters. Under the assumption that log gage rainfall and log radar rainfall are jointly multivariate normal, the estimation problem is equivalent to lognormal co-kriging

D.-J. Seo; J. A. Smith

1991-01-01

71

Radar Signatures for Severe Convective Weather  

NSDL National Science Digital Library

This resource is intended for use as a job aid by operational weather forecasters in live warning situations and as a reference tool to better understand some aspects of severe thunderstorm warning events. Thumbnail images show typical representatives for sixteen radar reflectivity and velocity signatures as well as three primary severe storm types. Each signature links to content describing detection techniques and conceptual and diagnostic information to help determine storm severity. The majority of the examples shown are southern hemisphere storms in Australia; examples from the northern hemisphere are noted.

2014-09-14

72

Simulation of radar reflectivity and surface measurements of rainfall  

NASA Technical Reports Server (NTRS)

Raindrop size distributions (RSDs) are often estimated using surface raindrop sampling devices (e.g., disdrometers) or optical array (2D-PMS) probes. A number of authors have used these measured distributions to compute certain higher-order RSD moments that correspond to radar reflectivity, attenuation, optical extinction, etc. Scatter plots of these RSD moments versus disdrometer-measured rainrates are then used to deduce physical relationships between radar reflectivity, attenuation, etc., which are measured by independent instruments (e.g., radar), and rainrate. In this paper RSDs of the gamma form as well as radar reflectivity (via time series simulation) are simulated to study the correlation structure of radar estimates versus rainrate as opposed to RSD moment estimates versus rainrate. The parameters N0, D0 and m of a gamma distribution are varied over the range normally found in rainfall, as well as varying the device sampling volume. The simulations are used to explain some possible features related to discrepancies which can arise when radar rainfall measurements are compared with surface or aircraft-based sampling devices.

Chandrasekar, V.; Bringi, V. N.

1987-01-01

73

Exploration of discrepancy between radar and gauge rainfall estimates driven by wind fields  

NASA Astrophysics Data System (ADS)

to the fact that weather radar is prone to several sources of errors, it is acknowledged that adjustment against ground observations such as rain gauges is crucial for radar measurement. Spatial matching of precipitation patterns between radar and rain gauge is a significant premise in radar bias corrections. It is a conventional way to construct radar-gauge pairs based on their vertical locations. However, due to the wind effects, the raindrops observed by the radar do not always fall vertically to the ground, and the raindrops arriving at the ground may not all be caught by the rain gauge. This study proposes a fully formulated scheme to numerically simulate the movement of raindrops in a three-dimensional wind field in order to adjust the wind-induced errors. The Brue catchment (135 km2) in Southwest England covering 28 radar pixels and 49 rain gauges is an experimental catchment, where the radar central beam height varies between 500 and 700 m. The 20 typical events (with durations of 6-36 h) are chosen to assess the correlation between hourly radar and gauge rainfall surfaces. It is found that for most events, the improved rates of correlation coefficients are greater than 10%, and nearly half of the events increase by 20%. With the proposed method, except four events, all the event-averaged correlation values are greater than 0.5. This work is the first study to tackle both wind effects on radar and rain gauges, which could be considered as one of the essential components in processing radar observational data in its hydrometeorological applications.

Dai, Qiang; Han, Dawei

2014-11-01

74

Study on Rainfall Forecasting by Using Weather Satellite Imagery in a Small Watershed Located at Mountainous Area of Central Taiwan  

NASA Astrophysics Data System (ADS)

Using meteorological radar and satellite imagery had become an efficient tool for rainfall forecasting However few studies were aimed to predict quantitative rainfall in small watersheds for flood forecasting by using remote sensing data Due to the terrain shelter and ground clutter effect of Central Mountain Ridges the application of meteorological radar data was limited in mountainous areas of central Taiwan This study devises a new scheme to predict rainfall of a small upstream watershed by combing GOES-9 geostationary weather satellite imagery and ground rainfall records which can be applied for local quantitative rainfall forecasting during periods of typhoon and heavy rainfall Imagery of two typhoon events in 2004 and five correspondent ground raingauges records of Chitou Forest Recreational Area which is located in upstream region of Bei-Shi river were analyzed in this study The watershed accounts for 12 7 square kilometers and altitudes ranging from 1000 m to 1800 m Basin-wide Average Rainfall BAR in study area were estimated by block kriging Cloud Top Temperature CTT from satellite imagery and ground hourly rainfall records were medium correlated The regression coefficient ranges from 0 5 to 0 7 and the value decreases as the altitude of the gauge site increases The regression coefficient of CCT and next 2 to 6 hour accumulated BAR decrease as the time scale increases The rainfall forecasting for BAR were analyzed by Kalman Filtering Technique The correlation coefficient and average hourly deviates between estimated and observed value of BAR for

Wei, C.; Cheng, K. S.

75

Spatial rainfall estimation by linear and non-linear co-kriging of radar-rainfall and raingage data  

Microsoft Academic Search

The feasibility of linear and nonlinear geostatistical estimation techniques for optimal merging of rainfall data from raingage and radar observations is investigated in this study by use of controlled numerical experiments. Synthetic radar and raingage data are generated with their hypothetical error structures that explicitly account for sampling characteristics of the two sensors. Numerically simulated rainfall fields considered to be

A. Azimi-Zonooz; W. F. Krajewski; D. S. Bowles; D. J. Seo

1989-01-01

76

Reconfigurable Data Acquisition System for Weather Radar Applications  

E-print Network

powerful signal processing algorithms on the raw data collected by the radars. Following processing, data, Amherst MA Abstract-- Tornado, hazardous weather and flood detection radars demand high-throughput, high-based system has been successfully integrated with a radar optimized for tornado detection and deployed

Tessier, Russell

77

Sensitivity of power functions to aggregation: Bias and uncertainty in radar rainfall retrieval  

NASA Astrophysics Data System (ADS)

retrieval using weather radar relies on power functions between radar reflectivity Z and rain rate R. The nonlinear nature of these relations complicates the comparison of rainfall estimates employing reflectivities measured at different scales. Transforming Z into R using relations that have been derived for other scales results in a bias and added uncertainty. We investigate the sensitivity of Z-R relations to spatial and temporal aggregation using high-resolution reflectivity fields for five rainfall events. Existing Z-R relations were employed to investigate the behavior of aggregated Z-R relations with scale, the aggregation bias, and the variability of the estimated rain rate. The prefactor and the exponent of aggregated Z-R relations systematically diverge with scale, showing a break that is event-dependent in the temporal domain and nearly constant in space. The systematic error associated with the aggregation bias at a given scale can become of the same order as the corresponding random error associated with intermittent sampling. The bias can be constrained by including information about the variability of Z within a certain scale of aggregation, and is largely captured by simple functions of the coefficient of variation of Z. Several descriptors of spatial and temporal variability of the reflectivity field are presented, to establish the links between variability descriptors and resulting aggregation bias. Prefactors in Z-R relations can be related to multifractal properties of the rainfall field. We find evidence of scaling breaks in the structural analysis of spatial rainfall with aggregation.

Sassi, M. G.; Leijnse, H.; Uijlenhoet, R.

2014-10-01

78

Evaluation of Various Radar Data Quality Control Algorithms Based on Accumulated Radar Rainfall Statistics  

NASA Technical Reports Server (NTRS)

The primary function of the TRMM Ground Validation (GV) Program is to create GV rainfall products that provide basic validation of satellite-derived precipitation measurements for select primary sites. A fundamental and extremely important step in creating high-quality GV products is radar data quality control. Quality control (QC) processing of TRMM GV radar data is based on some automated procedures, but the current QC algorithm is not fully operational and requires significant human interaction to assure satisfactory results. Moreover, the TRMM GV QC algorithm, even with continuous manual tuning, still can not completely remove all types of spurious echoes. In an attempt to improve the current operational radar data QC procedures of the TRMM GV effort, an intercomparison of several QC algorithms has been conducted. This presentation will demonstrate how various radar data QC algorithms affect accumulated radar rainfall products. In all, six different QC algorithms will be applied to two months of WSR-88D radar data from Melbourne, Florida. Daily, five-day, and monthly accumulated radar rainfall maps will be produced for each quality-controlled data set. The QC algorithms will be evaluated and compared based on their ability to remove spurious echoes without removing significant precipitation. Strengths and weaknesses of each algorithm will be assessed based on, their abilit to mitigate both erroneous additions and reductions in rainfall accumulation from spurious echo contamination and true precipitation removal, respectively. Contamination from individual spurious echo categories will be quantified to further diagnose the abilities of each radar QC algorithm. Finally, a cost-benefit analysis will be conducted to determine if a more automated QC algorithm is a viable alternative to the current, labor-intensive QC algorithm employed by TRMM GV.

Robinson, Michael; Steiner, Matthias; Wolff, David B.; Ferrier, Brad S.; Kessinger, Cathy; Einaudi, Franco (Technical Monitor)

2000-01-01

79

1. Introduction The use of radar rainfall data for hydrological model-  

E-print Network

for the supply of potable water and the treatment of wastewater in the north- west of England. The primary radar rainfall data was as an input to rainfall­runoff models of rural river systems. Building drainage system (storm) flows using radar rainfall data as a model input has seen an upsurge in interest

Fox, Neil I.

80

Simulation of a weather radar display for over-water airborne radar approaches  

NASA Technical Reports Server (NTRS)

Airborne radar approach (ARA) concepts are being investigated as a part of NASA's Rotorcraft All-Weather Operations Research Program on advanced guidance and navigation methods. This research is being conducted using both piloted simulations and flight test evaluations. For the piloted simulations, a mathematical model of the airborne radar was developed for over-water ARAs to offshore platforms. This simulated flight scenario requires radar simulation of point targets, such as oil rigs and ships, distributed sea clutter, and transponder beacon replies. Radar theory, weather radar characteristics, and empirical data derived from in-flight radar photographs are combined to model a civil weather/mapping radar typical of those used in offshore rotorcraft operations. The resulting radar simulation is realistic and provides the needed simulation capability for ongoing ARA research.

Clary, G. R.

1983-01-01

81

Weather radar research at the USA's storm laboratory  

NASA Technical Reports Server (NTRS)

Radar research that is directed toward improving storm forecasts and hazard warnings and studying lightning is discussed. The two moderately sensitive Doppler weather radars in central Oklahoma, with their wide dynamic range, have demonstrated the feasibility of mapping wind fields in all weather conditions from the clear skies of quiescent air and disturbed prestorm air near the earth's surface to the optically opaque interior of severe and sometimes tornadic thunderstorms. Observations and analyses of Doppler weather radar data demonstrate that improved warning of severe storm phenomena and improved short-term forecast of storms may be available when Doppler techniques are well integrated into the national network of weather radars. When used in combination with other sensors, it provides an opportunity to learn more about the complex interrelations between the wind, water, and electricity in storms.

Doviak, R. J.

1982-01-01

82

Radar volume reflectivity estimation using an array of ground-based rainfall drop size detectors  

NASA Astrophysics Data System (ADS)

Rainfall drop size distribution (DSD) measurements made by single disdrometers at isolated ground sites have traditionally been used to estimate the transformation between weather radar reflectivity Z and rainfall rate R. Despite the immense disparity in sampling geometries, the resulting Z-R relation obtained by these single point measurements has historically been important in the study of applied radar meteorology. Simultaneous DSD measurements made at several ground sites within a microscale area may be used to improve the estimate of radar reflectivity in the air volume surrounding the disdrometer array. By applying the equations of motion for non-interacting hydrometers, a volume estimate of Z is obtained from the array of ground based disdrometers by first calculating a 3D drop size distribution. The 3D-DSD model assumes that only gravity and terminal velocity due to atmospheric drag within the sampling volume influence hydrometer dynamics. The sampling volume is characterized by wind velocities, which are input parameters to the 3D-DSD model, composed of vertical and horizontal components. Reflectivity data from four consecutive WSR-88D volume scans, acquired during a thunderstorm near Melbourne, FL on June 1, 1997, are compared to data processed using the 3D-DSD model and data form three ground based disdrometers of a microscale array.

Lane, John; Merceret, Francis; Kasparis, Takis; Roy, D.; Muller, Brad; Jones, W. Linwood

2000-08-01

83

Real-time rainfall forecasting using weather satellite imagery  

NASA Astrophysics Data System (ADS)

Taiwan locates at the center of the western Pacific Rim and is particularly vulnerable to threat by typhoons. In average, there are 3.5 typhoons pass through Taiwan annually. Typhoons often draw huge amount and high intensity rainfalls, resulting in high casualties and severe property damages. For example, during the passage of Typhoon Nari in September 2002, more than 700mm rainfall was recorded near the capital city Taipei, causing extensive inundation and tremendous property damages in the city. Recent events and studies indicate that accurate real-time rainfall forecasting is crucial for flood forecasting since most watersheds in Taiwan have short time-of-concentrations (Tc). In this study we propose a real-time rainfall forecasting approach using GMS weather satellite imagery. The approach composes a multi-spectral spatial convolution (MSSC) scheme that yields a 3-hour lead rainfall forecast and a Kalman filtering algorithm for real-time parameter update. Using a single GMS thermal infrared band, the spatial convolution scheme can be expressed by the following equation: [ R(x,y)=sumlimits{x'=x-?}x+? {sumlimits{y'=y-?}y+? {T({x}',{y}')f(x-{x}',y-{y}')} } =sumlimitsi=1^N {T(i;x,y)f(i;x,y)} ] where R(x,y), T(x,y) and f(x,y) represent rainfall, cloud-top- temperature and kernel function weight at location (x, y). The spatial convolution is carried out within a(2?-1)× (2?-1) moving window. Using rainfall measurements of a network of 37 raingauge stations within the study area and cloud-top-temperatures derived from GMS images, the kernel function weights can be solved by a least square estimator: [ {R(1)} {R(2)} ?ots {R(n)} ]=[ {T(1,1)} & {T(1,2)} & \\cdots & {T(1,N)} {T(2,1)} & {T(2,2)} & \\cdots & {T(2,N)} ?ots & ?ots & ddots & ?ots {T(n,1)} & {T(n,2)} & \\cdots & {T(n,N)} ] [ {f(1)} {f(2)} ?ots {f(N)} ] where N is the total number of pixels in the moving window and n is the number of raingauge stations. The above equation can also be expressed as R=T\\cdot F, and the least square estimator of the kernel function is TRIAL RESTRICTION. In order to yield rainfall forecast, 3-hour lead accumulative rainfalls are used in the above equation. A multiple bands version of the above matrix equation is also developed using three thermal IR bands of the GMS satellite. During a typhoon event the kernel function may change with time and Kalman filtering is implemented using kernel function weight TRIAL RESTRICTION as the state vector. Results of a cross validation scheme reveal that the correlation between rainfall measurements and real-time forecasted rainfalls by spatial convolution and Kalman filtering ranging from 0.74 to 0.93 in most raingauges, indicating a great potential of real-time rainfall forecasting using weather satellite imagery.

Cheng, K. S.; Wei, C.

84

Analysis of a polarization diversity weather radar design  

Microsoft Academic Search

This report focuses not only on a design for a pulse to pulse polarization diversity modification of the Air Force Geophysics Laboratory (AFGL) S-band Doppler weather radar, but also upon the meteorological and technical requirements of such a radar. The theoretical aspects of and physical limitations imposed by the polarization diversity requirement are presented independently of this design and as

J. S. Ussailis; L. A. Leiker; R. M. Goodman IV; J. I. Mecalf

1982-01-01

85

The Use of Radar to Improve Rainfall Estimation over the Tennessee and San Joaquin River Valleys  

NASA Technical Reports Server (NTRS)

This slide presentation provides an overview of the collaborative radar rainfall project between the Tennessee Valley Authority (TVA), the Von Braun Center for Science & Innovation (VCSI), NASA MSFC and UAHuntsville. Two systems were used in this project, Advanced Radar for Meteorological & Operational Research (ARMOR) Rainfall Estimation Processing System (AREPS), a demonstration project of real-time radar rainfall using a research radar and NEXRAD Rainfall Estimation Processing System (NREPS). The objectives, methodology, some results and validation, operational experience and lessons learned are reviewed. The presentation. Another project that is using radar to improve rainfall estimations is in California, specifically the San Joaquin River Valley. This is part of a overall project to develop a integrated tool to assist water management within the San Joaquin River Valley. This involves integrating several components: (1) Radar precipitation estimates, (2) Distributed hydro model, (3) Snowfall measurements and Surface temperature / moisture measurements. NREPS was selected to provide precipitation component.

Petersen, Walter A.; Gatlin, Patrick N.; Felix, Mariana; Carey, Lawrence D.

2010-01-01

86

Chemical weathering of granite under acid rainfall environment, Korea  

NASA Astrophysics Data System (ADS)

Chemical weathering was investigated by collecting samples from five selected weathering profiles in a high elevation granitic environment located in Seoul, Korea. The overall changes of chemistry and mineralogical textures were examined reflecting weathering degrees of the samples, using polarization microscopy, X-ray diffraction (XRD), electron probe micro analysis (EPMA), X-ray fluorescence spectroscopy (XRF), and inductively coupled plasma-mass spectroscopy (ICP-MS). The chemical distribution in the weathering profiles shows that few trace elements are slightly immobile, whereas most major (particularly Ca and Na) and trace elements are mobile from the beginning of the granite weathering. On the other hand, there were mineralogical changes initiated from a plagioclase breakdown, which shows a characteristic circular dissolved pattern caused by a preferential leaching of Ca cation along grain boundaries and zoning. The biotite in that region is also supposed to be sensitive to exterior environmental condition and may be easily dissolved by acidic percolated water. As a result, it seems that some rock-forming minerals in the granitic rock located in Seoul are significantly unstable due to the environmental condition of acidic rainfall and steep slopes, where they are susceptible to be dissolved incongruently leading some elements to be highly depleted.

Lee, Seung Yeop; Kim, Soo Jin; Baik, Min Hoon

2008-08-01

87

New Approaches to Rainfall and Flood Frequency Analysis Using High Resolution Radar Rainfall Fields and Stochastic Storm Transposition  

NASA Astrophysics Data System (ADS)

Conventional techniques for rainfall and flood frequency analysis in small watersheds involve a variety of assumptions regarding the spatial and temporal structure of extreme rainfall systems as well as how resulting runoff moves through the drainage network. These techniques were developed at a time when observational and computational resources were limited. They continue to be used in practice though their validity has not been fully examined. New observational and computational resources such as high-resolution radar rainfall estimates and distributed hydrologic models allow us to examine these assumptions and to develop alternative methods for estimating flood risk. We have developed a high-resolution (1 square km, 15-minute resolution) radar rainfall dataset for the 2001-2010 period using the Hydro-NEXRAD processing system, which has been bias corrected using a dense network of 71 rain gages in the Charlotte metropolitan area. The accuracy of the bias-corrected radar rainfall estimates compare favorably with rain gage measurements. The radar rainfall dataset is used in a stochastic storm transposition framework to estimate the frequency of extreme rainfall for urban watersheds ranging the point/radar pixel scale up to 240 square km, and can be combined with the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model to estimate flood frequency analysis. The results of these frequency analyses can be compared against the results of conventional methods such as the NOAA Atlas 14 precipitation frequency estimates and peak discharge estimates prepared by FEMA and the North Carolina state government.

Wright, D. B.; Smith, J. A.; Villarini, G.; Baeck, M. L.

2012-12-01

88

Optimizing weather radar observations using an adaptive multiquadric surface fitting algorithm  

NASA Astrophysics Data System (ADS)

Real time forecasting of river flow is an essential tool in operational water management. Such real time modelling systems require well calibrated models which can make use of spatially distributed rainfall observations. Weather radars provide spatial data, however, since radar measurements are sensitive to a large range of error sources, often a discrepancy between radar observations and ground-based measurements, which are mostly considered as ground truth, can be observed. Through merging ground observations with the radar product, often referred to as data merging, one may force the radar observations to better correspond to the ground-based measurements, without losing the spatial information. In this paper, radar images and ground-based measurements of rainfall are merged based on interpolated gauge-adjustment factors (Moore et al., 1998; Cole and Moore, 2008) or scaling factors. Using the following equation, scaling factors (C(x?)) are calculated at each position x? where a gauge measurement (Ig(x?)) is available: Ig(x?)+-? C (x?) = Ir(x?)+ ? (1) where Ir(x?) is the radar-based observation in the pixel overlapping the rain gauge and ? is a constant making sure the scaling factor can be calculated when Ir(x?) is zero. These scaling factors are interpolated on the radar grid, resulting in a unique scaling factor for each pixel. Multiquadric surface fitting is used as an interpolation algorithm (Hardy, 1971): C*(x0) = aTv + a0 (2) where C*(x0) is the prediction at location x0, the vector a (Nx1, with N the number of ground-based measurements used) and the constant a0 parameters describing the surface and v an Nx1 vector containing the (Euclidian) distance between each point x? used in the interpolation and the point x0. The parameters describing the surface are derived by forcing the surface to be an exact interpolator and impose that the sum of the parameters in a should be zero. However, often, the surface is allowed to pass near the observations (i.e. the observed scaling factors C(x?)) on a distance a?K by introducing an offset parameter K, which results in slightly different equations to calculate a and a0. The described technique is currently being used by the Flemish Environmental Agency in an online forecasting system of river discharges within Flanders (Belgium). However, rescaling the radar data using the described algorithm is not always giving rise to an improved weather radar product. Probably one of the main reasons is the parameters K and ? which are implemented as constants. It can be expected that, among others, depending on the characteristics of the rainfall, different values for the parameters should be used. Adaptation of the parameter values is achieved by an online calibration of K and ? at each time step (every 15 minutes), using validated rain gauge measurements as ground truth. Results demonstrate that rescaling radar images using optimized values for K and ? at each time step lead to a significant improvement of the rainfall estimation, which in turn will result in higher quality discharge predictions. Moreover, it is shown that calibrated values for K and ? can be obtained in near-real time. References Cole, S. J., and Moore, R. J. (2008). Hydrological modelling using raingauge- and radar-based estimators of areal rainfall. Journal of Hydrology, 358(3-4), 159-181. Hardy, R.L., (1971) Multiquadric equations of topography and other irregular surfaces, Journal of Geophysical Research, 76(8): 1905-1915. Moore, R. J., Watson, B. C., Jones, D. A. and Black, K. B. (1989). London weather radar local calibration study. Technical report, Institute of Hydrology.

Martens, Brecht; Cabus, Pieter; De Jongh, Inge; Verhoest, Niko

2013-04-01

89

Effects of Radar-Rainfall Uncertainties on Statistical Structure of Floods  

NASA Astrophysics Data System (ADS)

Peak flows in a basin are a result of complex nonlinear interactions among rainfall and various processes in the landscape. Studies based on simulations and data have explored the role of rainfall characteristics on the statistical structure of peak flows. However, it is widely acknowledged that the rainfall products are affected by uncertainties from various sources. In this study, we investigated the role of radar-rainfall errors on the peak flow scaling structure. For this purpose, we selected several radar-rainfall events over the 1100 km2 study area of Whitewater River basin in Kansas. We employed recently proposed product-error-driven rainfall generator to obtain an ensemble of probable true rainfall events conditional on selected radar-rainfall event. We obtained the hydrographs for all the channel links in the basin using hillslope and channel network based hydrologic model. The role of radar-rainfall errors is then investigated by comparing the statistical structure of peak flows from radar-rainfall fields and probable true rainfall events.

Mandapaka, P.; Krajewski, W.; Mantilla, R.

2009-04-01

90

Rainfall estimation using raingages and radar — A Bayesian approach: 2. An application  

Microsoft Academic Search

In Seo and Smith (this issue), a set of estimators was built in a Bayesian framework to estimate rainfall depth at an ungaged location using raingage measurements and radar rainfall data. The estimators are equivalent to lognormal co-kriging (simple co-kriging in the Gaussian domain) with uncertain mean and variance of gage rainfall. In this paper, the estimators are evaluated via

D.-J. Seo; J. A. Smith

1991-01-01

91

Development and Planned Operational Applications Of A Conditional Error Model For Radar Rainfall Estimates  

NASA Astrophysics Data System (ADS)

A model for the statistical distribution of radar rainfall estimate errors has been developed empirically from WSR 88D and rain gauge data. The model expresses the expected value of actual rainfall and the mean and standard deviation of the multiplicative error in the radar estimate as functions of the radar estimate itself and several power law parameters derived from an historic sample of rain gauge/radar pairs. The model enables an end user of the radar estimates to determine the expected value of point rainfall, the probability that rainfall is less than or greater than a given value, and the probability that the true rainfall is within a given interval. Experiments with data from several WSR 88D umbrellas indicate that the basic form of the model is valid at most or all locations within the conterminous United States, though parameter adjustments for long-term radar bias and rainfall climatology must be made. The error model has several potential applications in radar hydrology, such as determining the probability that rainfall exceeds flash flood-producing thresholds, quality control of real-time rain gauge estimates, and construction of ensembles of rainfall fields. The development methodology and examples of operational applications will be presented.

Kitzmiller, D.; Fulton, R.; Guan, S.; Ding, F.; Krajewski, W. F.; Villarini, G.; Ciach, G. J.

2006-05-01

92

Mapping wintering waterfowl distributions using weather surveillance radar  

USGS Publications Warehouse

The current network of weather surveillance radars within the United States readily detects flying birds and has proven to be a useful remote-sensing tool for ornithological study. Radar reflectivity measures serve as an index to bird density and have been used to quantitatively map landbird distributions during migratory stopover by sampling birds aloft at the onset of nocturnal migratory flights. Our objective was to further develop and validate a similar approach for mapping wintering waterfowl distributions using weather surveillance radar observations at the onset of evening flights. We evaluated data from the Sacramento, CA radar (KDAX) during winters 1998–1999 and 1999–2000. We determined an optimal sampling time by evaluating the accuracy and precision of radar observations at different times during the onset of evening flight relative to observed diurnal distributions of radio-marked birds on the ground. The mean time of evening flight initiation occurred 23 min after sunset with the strongest correlations between reflectivity and waterfowl density on the ground occurring almost immediately after flight initiation. Radar measures became more spatially homogeneous as evening flight progressed because birds dispersed from their departure locations. Radars effectively detected birds to a mean maximum range of 83 km during the first 20 min of evening flight. Using a sun elevation angle of -5° (28 min after sunset) as our optimal sampling time, we validated our approach using KDAX data and additional data from the Beale Air Force Base, CA (KBBX) radar during winter 1998–1999. Bias-adjusted radar reflectivity of waterfowl aloft was positively related to the observed diurnal density of radio-marked waterfowl locations on the ground. Thus, weather radars provide accurate measures of relative wintering waterfowl density that can be used to comprehensively map their distributions over large spatial extents.

Buler, Jeffrey J.; Randall, Lori A.; Fleskes, Joseph P.; Barrow, Wylie C.; Bogart, Tianna; Kluver, Daria

2012-01-01

93

A Variational Scheme for Retrieving Rainfall Rate and Hail Reflectivity Fraction from Polarization Radar  

E-print Network

Radar ROBIN J. HOGAN Department of Meteorology, University of Reading, Reading, United Kingdom (Manuscript received 30 June 2006, in final form 17 January 2007) ABSTRACT Polarization radar offers the promise of much more accurate rainfall-rate R estimates than are possible from radar reflectivity factor Z

Hogan, Robin

94

Development of Weather Radar Mosaic Products in the U.S. National Weather Service  

Microsoft Academic Search

The Weather Surveillance Radar 1988 (Doppler) (WSR-88D) network contains 142 units within the conterminous United States, 7 units in Alaska, and 4 units in Hawaii. The units are maintained by several agencies of the federal government, including the National Weather Service, the Federal Aviation Administration, and the Department of Defense. Many users of the data require access to observations from

D. H. Kitzmiller; S. Guan; C. Mello; J. Dai

2002-01-01

95

Radar-based rainfall thresholds for debris flow warning: A review of opportunities, effect of estimation uncertainties, and assessment of key challenges  

NASA Astrophysics Data System (ADS)

The increasing availability of weather radar precipitation products provides new opportunities to improve upon existing methods for debris flow warning. The aim of this work is to examine how different characteristics of precipitation products, derived either from raingauges or from weather radar, may impact on the identification and use of precipitation thresholds that are used for debris flow warning. Precipitation exhibits space and time variability at all scales leading to high uncertainty in raingauge-based rain estimation. One distinct feature of the precipitation estimation problem for raingauge-based threshold relationship identification and use, is that the triggering precipitation to be estimated at the debris flow location exceeds an actual threshold which is likely not to be exceeded at the measuring raingauges. Recent results has shown that these characteristics may lead to biased precipitation threshold identification and low warning efficiency. Weather radar monitoring represent an interesting alternative for precipitation threshold identification, overcoming the sampling problem of point measurements. However, despite long-standing efforts, radar derived estimates are still affected by considerable uncertainties, particularly in the rough topography terrain typical of debris flows. It is therefore important to understand how uncertainties due to either rainfall sampling (typical of raingauges) or to rainfall estimation (typical of weather radar) propagates through the precipitation threshold identification methodology. Results are presented for a set of 10 high intensity debris-flow triggering storms that impacted the Southern Tyrol Region (Eastern Italian Alps) during the last decade. The region is characterized by rough orography, with elevation ranging from 300 to 4000 m asl, and it is monitored by a raingauge network with an average density of 1/70 km2 and a well calibrated and maintained C-band Doppler radar. High quality radar rainfall estimations are obtained taking into account both vertical (VPR) and radial (attenuation, screening) sources of error, and are adjusted with raingauges to provide reference rainfall estimates at the ground. Radar- and raingauge- based precipitation thresholds are identified and are compared, showing that a bias arises when using raingauge measurements for threshold assessment. The bias is related to the spatial variability characteristics of the considered storms and to the relative geometry of raingauges and debris flows. Even though the weather radar estimation uncertainty also impact the precipitation threshold identification methodology, no bias is reported for this last case. This provides a basis to identify opportunities in the use of radar-based estimates for debris flow warning in alpine regions. Key challenges are also identified, including the requirement for high quality, high resolution radar-based precipitation reanalyses and problems in areas with mixed or poor radar-coverage.

Marra, F.; Nikolopoulos, E.; Borga, M.; Creutin, J. D.

2013-12-01

96

ASSIMILATION OF DOPPLER RADAR DATA INTO NUMERICAL WEATHER MODELS  

SciTech Connect

During the year 2008, the United States National Weather Service (NWS) completed an eight fold increase in sampling capability for weather radars to 250 m resolution. This increase is expected to improve warning lead times by detecting small scale features sooner with increased reliability; however, current NWS operational model domains utilize grid spacing an order of magnitude larger than the radar data resolution, and therefore the added resolution of radar data is not fully exploited. The assimilation of radar reflectivity and velocity data into high resolution numerical weather model forecasts where grid spacing is comparable to the radar data resolution was investigated under a Laboratory Directed Research and Development (LDRD) 'quick hit' grant to determine the impact of improved data resolution on model predictions with specific initial proof of concept application to daily Savannah River Site operations and emergency response. Development of software to process NWS radar reflectivity and radial velocity data was undertaken for assimilation of observations into numerical models. Data values within the radar data volume undergo automated quality control (QC) analysis routines developed in support of this project to eliminate empty/missing data points, decrease anomalous propagation values, and determine error thresholds by utilizing the calculated variances among data values. The Weather Research and Forecasting model (WRF) three dimensional variational data assimilation package (WRF-3DVAR) was used to incorporate the QC'ed radar data into input and boundary conditions. The lack of observational data in the vicinity of SRS available to NWS operational models signifies an important data void where radar observations can provide significant input. These observations greatly enhance the knowledge of storm structures and the environmental conditions which influence their development. As the increase in computational power and availability has made higher resolution real-time model simulations possible, the need to obtain observations to both initialize numerical models and verify their output has become increasingly important. The assimilation of high resolution radar observations therefore provides a vital component in the development and utility of numerical model forecasts for both weather forecasting and contaminant transport, including future opportunities to improve wet deposition computations explicitly.

Chiswell, S.; Buckley, R.

2009-01-15

97

Comparison of soft computing systems for the post-calibration of weather radar  

NASA Astrophysics Data System (ADS)

The most usual tools to monitor rainfall events are raingauges and weather radar. Networks of raingauges provide accurate point estimates of rainfall, when appropriately set, but their usual low density restricts considerably the spatial resolution of the gathered information. Such networks, with rain gauges at distinct points, do not reflect the spatial distribution of rainfall. The quality of raingauge observations is also susceptible to some error sources, for example wind effects around the raingauges and poor raingauge reports due to hardware problems. Radar systems offer high spatial and temporal resolution observation which is much more efficient at providing the space-time evolution of a rainfall event in comparison with raingauge networks. However the radar measurements are not free of errors due to a variety of factors including ground clutter, bright bands, anomalous propagation, beam blockages, and attenuation. The effectiveness of weather radar operation is strongly linked to rigorous calibration. Various methods have been proposed to calibrate radar data. They can be classified into two main categories: deterministic and statistical. The deterministic approach involves the calibration of radar rainfall estimations against raingauge observations. The statistical approach includes multivariate analysis and cokriging. Geostatistical approaches are known as the best methods for radar-raingauge data integration but they are usually inefficient in real time, especially when dealing with the sampling rates of one hour or less necessary for urban and small watershed applications. Such methods also rely on a strong human expertise which can lead to user-dependent results. The objectives of this research are to introduce and to investigate the feasibility of soft computing systems for the post-calibration of weather radar in comparison with the best existing method based on geostatistics. In this work, the soft computing systems include artificial neural networks and Adaptive Neuro-Fuzzy Inference System (ANFIS) and the geostatistical approach includes residual kriging. The residual kriging calibration results are satisfying however this method is based on stationary hypotheses and requires variogram modeling, making it difficult in an operational context. This method has the advantage of providing a mean squared errors map based on variogram modeling for the estimations. For the artificial neural network, thirteen variants of the multilayer feedforward networks and two variants of radial basis functions are tested in this work. The neural calibration results showed that the Levenberg-Marquardt algorithm using Bayesian regularization is robust and reliable for radar-raingauge data integration. The ANFIS offers the precision and learning capability of artificial neural networks combined with the advantages of fuzzy logic. This method based on the Jackknife approach allows the use of all the available data for training and checking the neuro-fuzzy inference system, and provides a degree of reliability of the post-calibration. The training and the interpolation results of proposed methods can be obtained within just a few seconds using an ordinary personal computer, which is incomparably faster than geostatistical approaches. The proposed algorithms would be very efficient for real time post-calibration.

Hessami Kermani, Masoud Reza

98

Quality Assessment of Weather Radar Wind Profiles during Bird Migration IWAN HOLLEMAN  

E-print Network

Quality Assessment of Weather Radar Wind Profiles during Bird Migration IWAN HOLLEMAN Royal profiles from an operational C-band Doppler radar have been combined with data from a bird tracking radar to assess the wind profile quality during bird migration. The weather radar wind profiles (WRWPs

Stoffelen, Ad

99

High-resolution Radar Rainfall Records for Assessment of Hydroclimatology of the Christina River Basin  

NASA Astrophysics Data System (ADS)

A high-resolution 15-minute, 1 km2 radar rainfall data set for the warm season during the period of 2001-2010 was developed for the 1440 km2 Christina River Basin. Daily rainfall observations from rain gauges were used to bias correct radar fields derived from volume scan reflectivity observations from the NEXRAD WSR-88D radar at Fort Dix, NJ. The bias-corrected radar rainfall data were used to assess the spatial and temporal structure of rainfall over the Christina River Basin and its four sub-watersheds: White Clay Creek (277 km2), Red Clay Creek (140 km2), Brandywine Creek (842 km2), and the tidal Christina River (202 km2). High-quality rain gauge data from within the intensively studied 7.5 km2 3rd order east fork of the east branch of White Clay Creek were supplemented with the additional spatial rainfall distribution information provided by the radar rainfall product to create a more complete picture of prescription patterns over this long-term highly-instrumented research watershed. The high-resolution long-term bias-corrected radar rainfall data set will also be used in hydrologic modeling for the Christina River Basin Critical Zone Observatory.

Bates, N. S.; Baeck, M. L.; Smith, J. A.; Damiano, S. G.; Aufdenkampe, A. K.

2013-12-01

100

The next generation airborne polarimetric Doppler weather radar  

NASA Astrophysics Data System (ADS)

Results from airborne field deployments emphasized the need to obtain concurrently high temporal and spatial resolution measurements of 3-D winds and microphysics. A phased array radar on an airborne platform using dual-polarization antenna has the potential for retrieving high-resolution, collocated 3-D winds and microphysical measurements. Recently, ground-based phased array radar (PAR) has demonstrated the high time-resolution estimation of accurate Doppler velocity and reflectivity of precipitation and clouds when compared to mechanically scanning radar. PAR uses the electronic scanning (e-scan) to rapidly collect radar measurements. Since an airborne radar has a limited amount of time to collect measurements over a specified sample volume, the e-scan will significantly enhance temporal and spatial resolution of airborne radar observations. At present, airborne weather radars use mechanical scans, and they are not designed for collecting dual-polarization measurements to remotely estimate microphysics. This paper presents a possible configuration of a novel airborne phased array radar (APAR) to be installed on an aircraft for retrieving improved dynamical and microphysical scientific products. The proposed APAR would replace the aging, X-band Electra Doppler radar (ELDORA). The ELDORA X-band radar's penetration into precipitation is limited by attenuation. Since attenuation at C-band is lower than at X-band, the design specification of a C-band airborne phased array radar (APAR) and its measurement accuracies are presented. Preliminary design specifications suggest the proposed APAR will meet or exceed ELDORA's current sensitivity, spatial resolution and Doppler measurement accuracies of ELDORA and it will also acquire dual-polarization measurements.

Vivekanandan, J.; Lee, W.-C.; Loew, E.; Salazar, J. L.; Grubiši?, V.; Moore, J.; Tsai, P.

2014-07-01

101

Demonstration of radar reflector detection and ground clutter suppression using airborne weather and mapping radar  

NASA Technical Reports Server (NTRS)

A navigation system which utilizes minimum ground-based equipment is especially advantageous to helicopters, which can make off-airport landings. Research has been conducted in the use of weather and mapping radar to detect large radar reflectors overland for navigation purposes. As initial studies have not been successful, investigations were conducted regarding a new concept for the detection of ground-based radar reflectors and eliminating ground clutter, using a device called an echo processor (EP). A description is presented of the problems associated with detecting radar reflectors overland, taking into account the EP concept and the results of ground- and flight-test investigations. The echo processor concept was successfully demonstrated in detecting radar reflectors overland in a high-clutter environment. A radar reflector target size of 55 dBsm was found to be adequate for detection in an urban environment.

Anderson, D. J.; Bull, J. S.; Chisholm, J. P.

1982-01-01

102

Impact of radar data assimilation for the simulation of a heavy rainfall case in central Italy using WRF-3DVAR  

NASA Astrophysics Data System (ADS)

The aim of this study is to investigate the role of the assimilation of Doppler weather radar (DWR) data in a mesoscale model for the forecast of a heavy rainfall event that occurred in Italy in the urban area of Rome from 19 to 22 May 2008. For this purpose, radar reflectivity and radial velocity acquired from Monte Midia Doppler radar are assimilated into the Weather Research Forecasting (WRF) model, version 3.4.1. The general goal is to improve the quantitative precipitation forecasts (QPF): with this aim, several experiments are performed using the three-dimensional variational (3DVAR) technique. Moreover, sensitivity tests to outer loops are performed to include non-linearity in the observation operators. In order to identify the best initial conditions (ICs), statistical indicators such as forecast accuracy, frequency bias, false alarm rate and equitable threat score for the accumulated precipitation are used. The results show that the assimilation of DWR data has a large impact on both the position of convective cells and on the rainfall forecast of the analyzed event. A positive impact is also found if they are ingested together with conventional observations. Sensitivity to the use of two or three outer loops is also found if DWR data are assimilated together with conventional data.

Maiello, I.; Ferretti, R.; Gentile, S.; Montopoli, M.; Picciotti, E.; Marzano, F. S.; Faccani, C.

2014-09-01

103

Radar Scan Strategies for the Patrick Air Force Base Weather Surveillance Radar, Model-74C, Replacement  

NASA Technical Reports Server (NTRS)

The 45th Weather Squadron (45 WS) is replacing the Weather Surveillance Radar, Model 74C (WSR-74C) at Patrick Air Force Base (PAFB), with a Doppler, dual polarization radar, the Radtec 43/250. A new scan strategy is needed for the Radtec 43/250, to provide high vertical resolution data over the Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS) launch pads, while taking advantage of the new radar's advanced capabilities for detecting severe weather phenomena associated with convection within the 45 WS area of responsibility. The Applied Meteorology Unit (AMU) developed several scan strategies customized for the operational needs of the 45 WS. The AMU also developed a plan for evaluating the scan strategies in the period prior to operational acceptance, currently scheduled for November 2008.

Short, David

2008-01-01

104

Investigation of Advanced Radar Techniques for Atmospheric Hazard Detection with Airborne Weather Radar  

NASA Technical Reports Server (NTRS)

In 2013 ProSensing Inc. conducted a study to investigate the hazard detection potential of aircraft weather radars with new measurement capabilities, such as multi-frequency, polarimetric and radiometric modes. Various radar designs and features were evaluated for sensitivity, measurement range and for detecting and quantifying atmospheric hazards in wide range of weather conditions. Projected size, weight, power consumption and cost of the various designs were also considered. Various cloud and precipitation conditions were modeled and used to conduct an analytic evaluation of the design options. This report provides an overview of the study and summarizes the conclusions and recommendations.

Pazmany, Andrew L.

2014-01-01

105

The impact of reflectivity correction and accounting for raindrop size distribution variability to improve precipitation estimation by weather radar for an extreme low-land mesoscale convective system  

NASA Astrophysics Data System (ADS)

Between 25 and 27 August 2010 a long-duration mesoscale convective system was observed above the Netherlands, locally giving rise to rainfall accumulations exceeding 150 mm. Correctly measuring the amount of precipitation during such an extreme event is important, both from a hydrological and meteorological perspective. Unfortunately, the operational weather radar measurements were affected by multiple sources of error and only 30% of the precipitation observed by rain gauges was estimated. Such an underestimation of heavy rainfall, albeit generally less strong than in this extreme case, is typical for operational weather radar in The Netherlands. In general weather radar measurement errors can be subdivided into two groups: (1) errors affecting the volumetric reflectivity measurements (e.g. ground clutter, radar calibration, vertical profile of reflectivity) and (2) errors resulting from variations in the raindrop size distribution that in turn result in incorrect rainfall intensity and attenuation estimates from observed reflectivity measurements. A stepwise procedure to correct for the first group of errors leads to large improvements in the quality of the estimated precipitation, increasing the radar rainfall accumulations to about 65% of those observed by gauges. To correct for the second group of errors, a coherent method is presented linking the parameters of the radar reflectivity-rain rate (Z - R) and radar reflectivity-specific attenuation (Z - k) relationships to the normalized drop size distribution (DSD). Two different procedures were applied. First, normalized DSD parameters for the whole event and for each precipitation type separately (convective, stratiform and undefined) were obtained using local disdrometer observations. Second, 10,000 randomly generated plausible normalized drop size distributions were used for rainfall estimation, to evaluate whether this Monte Carlo method would improve the quality of weather radar rainfall products. Using the disdrometer information, the best results were obtained in case no differentiation between precipitation type (convective, stratiform and undefined) was made, increasing the event accumulations to more than 80% of those observed by gauges. For the randomly optimized procedure, radar precipitation estimates further improve and closely resemble observations in case one differentiates between precipitation type. However, the optimal parameter sets are very different from those derived from disdrometer observations. It is therefore questionable if single disdrometer observations are suitable for large-scale quantitative precipitation estimation, especially if the disdrometer is located relatively far away from the main rain event, which was the case in this study. In conclusion, this study shows the benefit of applying detailed error correction methods to improve the quality of the weather radar product, but also confirms the need to be cautious using locally obtained disdrometer measurements.

Hazenberg, Pieter; Leijnse, Hidde; Uijlenhoet, Remko

2014-11-01

106

Rainfall estimation using raingages and radar — A Bayesian approach: 2. An application  

NASA Astrophysics Data System (ADS)

In Seo and Smith (this issue), a set of estimators was built in a Bayesian framework to estimate rainfall depth at an ungaged location using raingage measurements and radar rainfall data. The estimators are equivalent to lognormal co-kriging (simple co-kriging in the Gaussian domain) with uncertain mean and variance of gage rainfall. In this paper, the estimators are evaluated via cross-validation using hourly radar rainfall data and simulated hourly raingage data. Generation of raingage data is based on sample statistics of actual raingage measurements and radar rainfall data. The estimators are compared with lognormal co-kriging and nonparametric estimators. The Bayesian estimators are shown to provide some improvement over lognormal co-kriging under the criteria of mean error, root mean square error, and standardized mean square error. It is shown that, if the prior could be assessed more accurately, the margin of improvement in predicting estimation variance could be larger. In updating the uncertain mean and variance of gage rainfall, inclusion of radar rainfall data is seen to provide little improvement over using raingage data only.

Seo, D.-J.; Smith, J. A.

1991-03-01

107

A space-time multifractal analysis on radar rainfall sequences from central Poland  

NASA Astrophysics Data System (ADS)

Rainfall downscaling belongs to most important tasks of modern hydrology. Especially from the perspective of urban hydrology there is real need for development of practical tools for possible rainfall scenarios generation. Rainfall scenarios of fine temporal scale reaching single minutes are indispensable as inputs for hydrological models. Assumption of probabilistic philosophy of drainage systems design and functioning leads to widespread application of hydrodynamic models in engineering practice. However models like these covering large areas could not be supplied with only uncorrelated point-rainfall time series. They should be rather supplied with space time rainfall scenarios displaying statistical properties of local natural rainfall fields. Implementation of a Space-Time Rainfall (STRAIN) model for hydrometeorological applications in Polish conditions, such as rainfall downscaling from the large scales of meteorological models to the scale of interest for rainfall-runoff processes is the long-distance aim of our research. As an introduction part of our study we verify the veracity of the following STRAIN model assumptions: rainfall fields are isotropic and statistically homogeneous in space; self-similarity holds (so that, after having rescaled the time by the advection velocity, rainfall is a fully homogeneous and isotropic process in the space-time domain); statistical properties of rainfall are characterized by an "a priori" known multifractal behavior. We conduct a space-time multifractal analysis on radar rainfall sequences selected from the Polish national radar system POLRAD. Radar rainfall sequences covering the area of 256 km x 256 km of original 2 km x 2 km spatial resolution and 15 minutes temporal resolution are used as study material. Attention is mainly focused on most severe summer convective rainfalls. It is shown that space-time rainfall can be considered with a good approximation to be a self-similar multifractal process. Multifractal analysis is carried out assuming Taylor's hypothesis to hold and the advection velocity needed to rescale the time dimension is assumed to be equal about 16 km/h. This assumption is verified by the analysis of autocorrelation functions along the x and y directions of "rainfall cubes" and along the time axis rescaled with assumed advection velocity. In general for analyzed rainfall sequences scaling is observed for spatial scales ranging from 4 to 256 km and for timescales from 15 min to 16 hours. However in most cases scaling break is identified for spatial scales between 4 and 8, corresponding to spatial dimensions of 16 km to 32 km. It is assumed that the scaling break occurrence at these particular scales in central Poland conditions could be at least partly explained by the rainfall mesoscale gap (on the edge of meso-gamma, storm-scale and meso-beta scale).

Licznar, Pawe?; Deidda, Roberto

2014-05-01

108

Rainfall Generator for the Rhine Basin Multi-site generation of weather variables  

E-print Network

Rainfall Generator for the Rhine Basin Multi-site generation of weather variables for the entire generator for the Rhine Basin 38 3 #12;Summary This is the final report of a project on the development of a rainfall generator for the Rhine basin. The request for this generator arose from the need to study

Stoffelen, Ad

109

Estimation of rainfall field by combining radar data and raingauge observations: the modified conditional merging technique  

NASA Astrophysics Data System (ADS)

Estimation of rainfall field by combining radar data and raingauge observations: the modified conditional merging technique N. Rebora, F. Pignone, F. Silvestro The estimation of rainfall fields, especially its spatial distribution and position is a crucial task both for rainfall nowcasting and for modeling catchment response to rainfall. Some studies of literature about multisensor datafusion prove that combining data from raingauges and radar represents the best way to obtain an enhanced ad more reliable estimation of QPE and of the associated river discharge. Sinclair and Peagram (2004) have proposed the Conditional Merging (CM) technique, a merging algorithm which extract the information content from the observed data and use it within an interpolation method to obtain the rainfall maps. The raingauges provide a punctual measure of the observed "real" rainfall while the remote sensors (radar network or satellite constellation) supply rainfall estimation maps which give an idea of the correlation and structure of covariance of the observed field. In this work is studied an enhanced algorithm based on CM, called Modified Conditional Merging, which can be used in real-time to produce the optimal rainfall maps. The area of interest is Italy, where are both available a dense network of raingauge measurements (about 2000 stations) and a QPE estimated by the Italian Radar composite. The main innovation respect to classical CM is to estimate the structure of covariance and the length of spatial correlation ?, for every raingauge, directly from the cumulated radar rainfall fields. The advantages of this method is to estimate the local characteristic of the domain to obtain information at smaller scale, very useful for convective events. An operative use and a validation are presented and discussed.

Pignone, Flavio; Rebora, Nicola

2014-05-01

110

Prediction of a Flash Flood in Complex Terrain. Part I: A Comparison of Rainfall Estimates from Radar, and Very Short Range Rainfall Simulations from a Dynamic Model and an Automated Algorithmic System.  

NASA Astrophysics Data System (ADS)

Operational prediction of flash floods caused by convective rainfall in mountainous areas requires accurate estimates or predictions of the rainfall distribution in space and time. The details of the spatial distribution are especially critical in complex terrain because the watersheds generally are small in size, and position errors in the placement of the rainfall can distribute the rain over the wrong watershed. In addition to the need for good rainfall estimates, accurate flood prediction requires a surface-hydrologic model that is capable of predicting stream or river discharge based on the rainfall-rate input data. In part 1 of this study, different techniques for the estimation and prediction of convective rainfall are applied to the Buffalo Creek, Colorado, flash flood of July 1996, during which over 75 mm of rain from a thunderstorm fell on the watershed in less than 1 h. The hydrologic impact of the rainfall was exacerbated by the fact that a considerable fraction of the watershed experienced a wildfire approximately two months prior to the rain event.Precipitation estimates from the National Weather Service Weather Surveillance Radar-1988 Doppler and the National Center for Atmospheric Research S-band, dual-polarization radar, collocated east of Denver, Colorado, were compared. Very short range simulations from a convection-resolving dynamic model that was initialized variationally using the radar reflectivity and Doppler winds were compared with simulations from an automated algorithmic forecast system that also employs the radar data. The radar estimates of rain rate and the two forecasting systems that employ the radar data have degraded accuracy by virtue of the fact that they are applied in complex terrain. Nevertheless, the dynamic model and automated algorithms both produce simulations that could be useful operationally for input to surface-hydrologic models employed for flood warning. Part 2 of this study, reported in a companion paper, describes experiments in which these radar-based precipitation estimates and dynamic model-and automated algorithm-based precipitation simulations are used as input to a surface-hydrologic model for simulation of the stream discharge associated with the flood.

Warner, Thomas T.; Brandes, Edward A.; Sun, Juanzhen; Yates, David N.; Mueller, Cynthia K.

2000-06-01

111

"A Functional Design and System Architecture of a Control System for a Weather Radar"  

E-print Network

"A Functional Design and System Architecture of a Control System for a Weather Radar" Seidu Ibrahim Faculty Mentor: Eric Knapp Weather radars operate by transmitting pulses of very high microwave energy radiation through an antenna which reflects off objects such as rain drops and hail stones. As the radar

Mountziaris, T. J.

112

METR 4624--Radar Meteorology SPRING 2014  

E-print Network

METR 4624--Radar Meteorology SPRING 2014 Dr. Michael I. Biggerstaff; drdoppler@ou.edu (best method Principles of weather radar and storm observations including: radar system design, em wave propagation, radar&Q, moments of the power spectrum, ground clutter, attenuation, rainfall measurements using radar reflectivity

Droegemeier, Kelvin K.

113

METR 4624--Radar Meteorology SPRING 2012  

E-print Network

METR 4624--Radar Meteorology SPRING 2012 Dr. Michael I. Biggerstaff; drdoppler@ou.edu (best method Principles of weather radar and storm observations including: radar system design, em wave propagation, radar&Q, moments of the power spectrum, ground clutter, attenuation, rainfall measurements using radar reflectivity

Droegemeier, Kelvin K.

114

Attenuation of Weather Radar Signals Due to Wetting of the Radome by Rainwater or Incomplete Filling of the Beam Volume  

NASA Technical Reports Server (NTRS)

A search of scientific literature, both printed and electronic, was undertaken to provide quantitative estimates of attenuation effects of rainfall on weather radar radomes. The emphasis was on C-band (5 cm) and S-Band (10 cm) wavelengths. An empirical model was developed to estimate two-way wet radome losses as a function of frequency and rainfall rate for both standard and hydrophobic radomes. The model fits most of the published data within +/- 1 dB at both target wavelengths for rain rates from less than ten to more than 200 mm/hr. Rainfall attenuation effects remain under 1 dB at both frequencies regardless of radome type for rainfall rates up to 10 mm/hr. S-Band losses with a hydrophobic radome such as that on the WSR-88D remain under 1 dB up to 100 mm/hr. C-Band losses on standard radomes such as that on the Patrick AFB (Air Force Base) WSR-74C can reach as much as 5 dB at 50 mm/hr. In addition, calculations were performed to determine the reduction in effective reflectivity, Z, when a radar target is smaller than the sampling volume of the radar. Results are presented for both the Patrick Air Force Base WSR-74C and the WSR-88D as a function of target size and range.

Merceret, Francis J.; Ward, Jennifer G.

2000-01-01

115

Rainfall estimation using raingages and radar — A Bayesian approach: 1. Derivation of estimators  

NASA Astrophysics Data System (ADS)

Procedures for estimating rainfall from radar and raingage observations are constructed in a Bayesian framework. Given that the number of raingage measurements is typically very small, mean and variance of gage rainfall are treated as uncertain parameters. Under the assumption that log gage rainfall and log radar rainfall are jointly multivariate normal, the estimation problem is equivalent to lognormal co-kriging with uncertain mean and variance of the gage rainfall field. The posterior distribution is obtained under the assumption that the prior for the mean and inverse of the variance of log gage rainfall is normal-gamma 2. Estimate and estimation variance do not have closed-form expressions, but can be easily evaluated by numerically integrating two single integrals. To reduce computational burden associated with evaluating sufficient statistics for the likelihood function, an approximate form of parameter updating is given. Also, as a further approximation, the parameters are updated using raingage measurements only, yielding closed-form expressions for estimate and estimation variance in the Gaussian domain. With a reduction in the number of radar rainfall data in constructing covariance matrices, computational requirements for the estimation procedures are not significantly greater than those for simple co-kriging. Given their generality, the estimation procedures constructed in this work are considered to be applicable in various estimation problems involving an undersampled main variable and a densely sampled auxiliary variable.

Seo, D.-J.; Smith, J. A.

1991-03-01

116

Assimilation of Doppler Weather Radar Data in WRF Model for Simulation of Tropical Cyclone Aila  

NASA Astrophysics Data System (ADS)

For the accurate and effective forecasting of a cyclone, it is critical to have accurate initial structure of the cyclone in numerical models. In this study, Kolkata Doppler weather radar (DWR) data were assimilated for the numerical simulation of a land-falling Tropical Cyclone Aila (2009) in the Bay of Bengal. To study the impact of radar data on very short-range forecasting of a cyclone's path, intensity and precipitation, both reflectivity and radial velocity were assimilated into the weather research and forecasting (WRF) model through the ARPS data assimilation system (ADAS) and cloud analysis procedure. Numerical experiment results indicated that radar data assimilation significantly improved the simulated structure of Cyclone Aila. Strong influences on hydrometeor structures of the initial vortex and precipitation pattern were observed when radar reflectivity data was assimilated, but a relatively small impact was observed on the wind fields at all height levels. The assimilation of radar wind data significantly improved the prediction of divergence/convergence conditions over the cyclone's inner-core area, as well as its wind field in the low-to-middle troposphere (600-900 hPa), but relatively less impact was observed on analyzed moisture field. Maximum surface wind speed produced from DWR-Vr and DWR-ZVr data assimilation experiments were very close to real-time values. The impact of radar data, after final analysis, on minimum sea level pressure was relatively less because the ADAS system does not adjust for pressure due to the lack of pressure observations, and from not using a 3DVAR balance condition that includes pressure. The greatest impact of radar data on forecasting was realized when both reflectivity and wind data (DWR-ZVr and DWR-ZVr00 experiment) were assimilated. It is concluded that after final analysis, the center of the cyclone was relocated very close to the observed position, and simulated cyclone maintained its intensity for a longer duration. Using this analysis, different stages of the cyclone are better captured, and cyclone structure, intensification, direction of movement, speed and location are significantly improved when both radar reflectivity and wind data are assimilated. As compared to other experiments, the maximum reduction in track error was noticed in the DWR-ZVr and DWR-ZVr00 experiments, and the predicted track in these experiments was very close to the observed track. In the DWR-ZVr and DWR-ZVr00 experiments, rainfall pattern and amount of rainfall forecasts were remarkably improved and were similar to the observation over West Bengal, Orissa and Jharkhand; however, the rainfall over Meghalaya and Bangladesh was missed in all the experiments. The influence of radar data reduces beyond a 12-h forecast, due to the dominance of the flow from large-scale, global forecast system models. This study also demonstrates successful coupling of the data assimilation package ADAS with the WRF model for Indian DWR data.

Srivastava, Kuldeep; Bhardwaj, Rashmi

2014-08-01

117

Image processing for hazard recognition in on-board weather radar  

NASA Technical Reports Server (NTRS)

A method of providing weather radar images to a user includes obtaining radar image data corresponding to a weather radar image to be displayed. The radar image data is image processed to identify a feature of the weather radar image which is potentially indicative of a hazardous weather condition. The weather radar image is displayed to the user along with a notification of the existence of the feature which is potentially indicative of the hazardous weather condition. Notification can take the form of textual information regarding the feature, including feature type and proximity information. Notification can also take the form of visually highlighting the feature, for example by forming a visual border around the feature. Other forms of notification can also be used.

Kelly, Wallace E. (Inventor); Rand, Timothy W. (Inventor); Uckun, Serdar (Inventor); Ruokangas, Corinne C. (Inventor)

2003-01-01

118

Development of High Altitude UAV Weather Radars for Hurricane Research  

NASA Technical Reports Server (NTRS)

A proposed effort within NASA called (ASHE) over the past few years was aimed at studying the genesis of tropical disturbances off the east coast of Africa. This effort was focused on using an instrumented Global Hawk UAV with high altitude (%Ok ft) and long duration (30 h) capability. While the Global Hawk availability remains uncertain, development of two relevant instruments, a Doppler radar (URAD - UAV Radar) and a backscatter lidar (CPL-UAV - Cloud Physics Lidar), are in progress. The radar to be discussed here is based on two previous high-altitude, autonomously operating radars on the NASA ER-2 aircraft, the ER-2 Doppler Radar (EDOP) at X-band (9.6 GHz), and the Cloud Radar System (CRS) at W- band (94 GHz). The nadir-pointing EDOP and CRS radars profile vertical reflectivity structure and vertical Doppler winds in precipitation and clouds, respectively. EDOP has flown in all of the CAMEX flight series to study hurricanes over storms such as Hurricanes Bonnie, Humberto, Georges, Erin, and TS Chantal. These radars were developed at Goddard over the last decade and have been used for satellite algorithm development and validation (TRMM and Cloudsat), and for hurricane and convective storm research. We describe here the development of URAD that will measure wind and reflectivity in hurricanes and other weather systems from a top down, high-altitude view. URAD for the Global Hawk consists of two subsystems both of which are at X-band (9.3-9.6 GHz) and Doppler: a nadir fixed-beam Doppler radar for vertical motion and precipitation measurement, and a Conical scanning radar for horizontal winds in cloud and at the surface, and precipitation structure. These radars are being designed with size, weight, and power consumption suitable for the Global Hawk and other UAV's. The nadir radar uses a magnetron transmitter and the scanning radar uses a TWT transmitter. With conical scanning of the radar at a 35" incidence angle over an ocean surface in the absence of precipitation, the surface return over a single 360 degree sweep over -25 h-diameter region provides information on the surface wind speed and direction within the scan circle. In precipitation regions, the conical scan with appropriate mapping and analysis provides the 3D structure of reflectivity beneath the plane and the horizontal winds. The use of conical scanning in hurricanes has recently been demonstrated for measuring inner core winds with the IWRAP system flying on the NOAA P3's. In this presentation, we provide a description of the URAD system hardware, status, and future plans. In addition to URAD, NASA SBIR activity is supporting a Phase I study by Remote Sensing Solutions and the University of Massachusetts for a dual-frequency IWRAP for a high altitude UAV that utilizes solid state transmitters at 14 and 35 GHz, the same frequencies that are planned for the radar on the Global Precipitation System satellite. This will be discussed elsewhere at the meeting.

Heymsfield, Gerald; Li, Li-Hua

2005-01-01

119

Terminal Doppler weather radar operational test and evaluation, Orlando 1990  

NASA Astrophysics Data System (ADS)

Lincoln Laboratory conducted an evaluation of the Federal Aviation Administration (FAA) Terminal Doppler Weather Radar (TDWR) system in Orlando, Florida during the summer of 1990. In previous years, evaluations have been conducted at airports in Kansas City, MO (1989) and Denver, CO (1988). Since the testing at the Kansas City International Airport, the radar was modified to operate in C-band, which is the intended frequency band for the production TDWR systems. The objectives of the 1990 evaluation period were to evaluate TDWR system performance in detecting low-altitude wind shear, specifically microbursts and gust fronts, at the Orlando International Airport and in the surrounding area; to refine the system's wind shear detection capabilities; and to evaluate elements of the system developed by the contractor, which were new for the C-band system and therefore not available for evaluation in previous years. Some performance comparisons are made among results from the vastly different weather environments of Denver, Kansas City, and Orlando. Statistics are presented and discussed for the performance of the system in detecting and predicting microbursts and gust fronts. A significant use of the prediction capability is its potential use for air traffic control (ATC) personnel to plan airport operations when hazardous weather is predicted. Issues such as low velocity ground clutter (from tree leaves, road traffic, and dense urban areas) that affect prediction performance are discussed along with possible software modification to account for them.

Bernella, David M.

1991-04-01

120

Analysis of a polarization diversity weather radar design  

NASA Astrophysics Data System (ADS)

This report focuses not only on a design for a pulse to pulse polarization diversity modification of the Air Force Geophysics Laboratory (AFGL) S-band Doppler weather radar, but also upon the meteorological and technical requirements of such a radar. The theoretical aspects of and physical limitations imposed by the polarization diversity requirement are presented independently of this design and as a result are applicable towards the development of any similar system. The antenna modification could also be applied towards the general case, excepting the condition imposed in this design that the present 24 foot diameter reflector be retained. Formulae are developed to demonstrate the various uncertainties for the system as a whole and the antenna in particular. Tradeoffs between the various meteorological measurement goals vs available and constructible radio frequency components are presented.

Ussailis, J. S.; Leiker, L. A.; Goodman, R. M., IV; Mecalf, J. I.

1982-07-01

121

Disdrometer measurements during a unique rainfall event in central Illinois and their implication for differential reflectivity radar observations  

NASA Technical Reports Server (NTRS)

Understanding of the natural variability of rainfall is essential in order to assess radar's ability to estimate rainfall characteristics such as rainfall rate, rainfall water content and drop size distribution parameters. The two most useful measurements of rainfall for this purpose derive from ground-based disdrometers and aircraft-borne drop size spectrometers. Accordingly, this paper examines a time series of disdrometer measurements obtained during a unique rainfall event which occurred in central Illinois on October 6, 1982. The measurements are used to predict the behavior of radar observables (reflectivity factor and differential reflectivity) for application to the estimation of rainfall parameters. The results support previous theoretical predictions (Seliga and Bringi, 1976) and experimental results (Seliga et al., 1979, 1981; Bringi et al., 1982; Hall et al., 1980; Goddard et al., 1982) based upon the differential reflectivity (ZDR) radar technique.

Seliga, T. A.; Aydin, K.; Direskeneli, H.

1983-01-01

122

The Utility of X-Band Polarimetric Radar for Quantitative Estimates of Rainfall Parameters  

Microsoft Academic Search

The utility of X-band polarimetric radar for quantitative retrievals of rainfall parameters is analyzed using observations collected along the U.S. west coast near the mouth of the Russian River during the Hy- drometeorological Testbed project conducted by NOAA's Environmental Technology and National Severe Storms Laboratories in December 2003 through March 2004. It is demonstrated that the rain attenuation effects in

Sergey Y. Matrosov; David E. Kingsmill; Brooks E. Martner; F. Martin Ralph

2005-01-01

123

Very high resolution precipitation climatologies from the Tropical Rainfall Measuring Mission precipitation radar  

E-print Network

Very high resolution precipitation climatologies from the Tropical Rainfall Measuring Mission precipitation radar Stephen W. Nesbitt1 and Alison M. Anders2 Received 4 March 2009; revised 6 July 2009 of topography and precipitation, a tropics-wide (±36° latitude) high resolution (0.1°) ten year (1998

Nesbitt, Steve

124

Frequency of tropical precipitating clouds as observed by the Tropical Rainfall Measuring Mission Precipitation Radar and  

E-print Network

as surface heating over the continents; by definition, these clouds precipitate at some stageFrequency of tropical precipitating clouds as observed by the Tropical Rainfall Measuring Mission Precipitation Radar and ICESat/Geoscience Laser Altimeter System Sean P. F. Casey,1 Andrew E. Dessler,1

125

P11B.1 A VARIATIONAL SCHEME FOR RETRIEVING RAINFALL RATE AND HAIL REFLECTIVITY FRACTION FROM POLARIZATION RADAR  

E-print Network

POLARIZATION RADAR ROBIN J. HOGAN Department of Meteorology, University of Reading, United Kingdom ABSTRACT Polarization radar offers the promise of much more accurate rainfall rate (R) estimates than possible from radar reflectivity factor (Z) alone, not only by better characterization of the drop size distribution

Hogan, Robin

126

Dual polarized staggered PRT scheme for weather radars: analysis and applications  

Microsoft Academic Search

Weather radars require long unambiguous ranges, high Nyquist sampling rates and good clutter suppression. In addition, polarization diversity is also used extensively, switching polarization of the transmit pulse on a pulse by pulse basis. This paper presents a dual polarized staggered pulse repetition scheme that can be used for Doppler and polarization diversity measurements in a weather radar. Processing algorithms

K. Golestani; T. Chandrasekar; R. J. Keeler

1995-01-01

127

Operational Monitoring of Weather Radar Receiving Chain Using the Sun IWAN HOLLEMAN  

E-print Network

Operational Monitoring of Weather Radar Receiving Chain Using the Sun IWAN HOLLEMAN Royal, is presented. The ``online'' method is entirely based on the analysis of sun signals in the polar volume data- termining the weather radar antenna pointing at low elevations using sun signals, and it is suited

Stoffelen, Ad

128

Thunderstorm lightning and radar characteristics: insights on electrification and severe weather forecasting  

E-print Network

THUNDERSTORM LIGHTNING AND RADAR CHARACTERISTICS: INSIGHTS ON ELECTRIFICATION AND SEVERE WEATHER FORECASTING A Dissertation by SCOTT MICHAEL STEIGER Submitted to the Office of Graduate Studies of Texas A&M University in partial... fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY December 2005 Major Subject: Atmospheric Sciences THUNDERSTORM LIGHTNING AND RADAR CHARACTERISTICS: INSIGHTS ON ELECTRIFICATION AND SEVERE WEATHER...

Steiger, Scott Michael

2007-04-25

129

ERADERAD 20062006Proceedings ofProceedings of Detecting weather radar clutter  

E-print Network

ERADERAD 20062006Proceedings ofProceedings of Detecting weather radar clutter using satellite results from investigations into detection of weather radar clutter by data fusion with satellite from low-level signal processing methods over higher level pattern recognition to data fusion methods

130

Multi-PRI Signal Processing for the Terminal Doppler Weather Radar. Part I: Clutter Filtering  

E-print Network

Multi-PRI Signal Processing for the Terminal Doppler Weather Radar. Part I: Clutter Filtering JOHN and processing algorithm being developed to aggressively combat range­velocity ambiguity in weather radars-elevation scans and yield low biases of velocity estimates so that accurate velocity dealiasing is possible

Cho, John Y. N.

131

The space-time structure of radar rainfall in complex terrain  

NASA Astrophysics Data System (ADS)

The space-time structure in rainfall fields is affected by topography to the extent that topography influences the multitude of processes that lead to precipitation on the ground, e.g., orographic forcing of moist air flow, condensation, convective activity, wind speeds and directions, etc. One way to analyse the structure in space-time precipitation fields is to study the time evolution of cumulated rainfall fields from radar data. Rainfall organization leads to a scaling relationship between the spatial variance and time with a characteristic scaling exponent H which is indicative of the nature of the memory (short or long) in the data. Rodriguez-Iturbe et al. (1998) developed this technique to show that space-time rainfall from radar at a daily time resolution exhibited consistent scaling and long-term memory (H>0.5) over a rather flat area of the Arkansas-Red River Basin in the U.S. In this paper we investigate whether the time evolution of cumulated rainfall fields from radar data may be used in topographically complex terrain to study if topography has a measurable effect on the space-time structure of rainfall and to quantify this effect. We apply the method of Rodriguez-Iturbe et al. (1998) to determine the scaling relationship and characteristic scaling exponent H between the spatial variance and mean of rainfall measured by radar on a 120x120 km domain centered on the main Alpine divide around Kl. Matterhorn, covering parts of Switzerland and Italy. The radar product we use is the 30-min precipitation depth estimated at the ground at a 1 km grid resolution from MeteoSwiss C-band radar for a continuous period of about one year. The altitude within the study domain ranges from 140 to 4520 m. As a first step the exponent H was evaluated by subdividing the study domain into 5x5 sub-domains, each with a resolution of 24x24 km, and averaging. We found that the scaling relationship is consistent and that long-term memory is present (H=0.84). We then evaluated H separately for each realization in each sub-domain and correlated it with topographic attributes of the sub-domain, such as mean altitude, relief, dominant aspect, etc. We found that H was statistically significantly correlated with mean altitude, with higher H present at higher altitudes where local topographic features lead to singularities in the rainfall field which increase the variance. However, at the same time the total rainfall amount was not well correlated with altitude, which suggests that it is the organization of the space-time structure in rainfall, not simply rainfall amount that is affected by topography. This study contributes observational evidence to the effect of orography on rainfall and the utility of radar data to study the space-time structure of rainfall.

Savina, M.; Molnar, P.; Burlando, P.

2009-04-01

132

Comparing two radar rainfall products with the help of Multifractal Analysis  

NASA Astrophysics Data System (ADS)

Distributed rainfall radar data are commonly used in hydrology and increasingly used in urban hydrology. However radar validation and comparison still commonly relies on standard scores such as Nash-Sutcliffe coefficient, Correlation and Quadratic Error, which enable to grasp neither the underlying spatio-temporal structure of the studied rainfall field nor meaningful statistics, i.e. of order larger than two. We implement an innovative methodology that relies on Universal Multifractal (UM) to compare two operational radar products covering the Paris region. The UM framework has been extensively used to characterize and simulate geophysical fields extremely variable over a wide range of scales such as rainfall with the help of only three parameters, which are furthermore physically meaningful. Both Météo-France operational radar mosaic and the CALAMAR radar product use the same single polarization C-band radar data. However their QPE algorithms are different, as well as the calibration with rain gauges. Cartesian fields of final resolution 1 km in space and 5 min in time are used in this study. Three rainfall events that occurred in 2010 and 2011 are used, in order to quantify the quality of the adjustment process we add to this comparison a non-adjusted CALAMAR radar product. As a first step, we compare these radar products to the Val de Marne County network of 27 rain gauges distributed over a 245 Km2 area. Standard scores at various resolutions (5min, 15min, 30min and 1h) are computed. The Météo France radar product is better correlated with these rain gauges data than both CALAMAR products at 5min scale, but we observe the opposite when we increase the time scale. We also observe that the CALAMAR adjustment process improves the correlation with rain gauges. In a second step, both spatial (2D maps) and temporal (1D time series for each pixel) multifractal analyses are performed and the UM parameters computed. Preliminary results suggest that both products do not yield the same parameters in terms of spatial distribution and temporal evolution. CALAMAR product seems to significantly under-estimates rainfall singularities and yields a higher percentage of zero values. This may results from the fact CALAMAR replaces the ground clutters by zero values. Authors acknowledge the European INTERREG IV NEW RainGain project (http://raingain.eu) for partial financial support.

Ichiba, Abdellah; Gires, Auguste; Tchiguirinskaia, Ioulia; Bompard, Philippe; Schertzer, Daniel

2014-05-01

133

Rainfall estimation from TOGA radar observations during LBA field campaign  

NASA Astrophysics Data System (ADS)

The TRMM Large Scale Biosphere-Atmosphere (LBA) experiment, conducted between January and February of 1999 in Southwest Amazon, deployed among other instruments NASA's C-band Doppler radar (TOGA) and four dense rain gauge networks. This paper presents a procedure devised to derive surface rainfall rate estimates from combination of TOGA observations and the in situ rain gauge rainfall measurements. The spatial and temporal scales considered are 2 × 2 km2 grids of instantaneous to hourly rain accumulations. The procedure includes evaluation of TOGA calibration through comparisons with TRMM Precipitation Radar (PR) data and implementation of an optimal quantitative precipitation estimation (QPE) algorithm. Comparisons with PR indicated a 4-dB calibration offset occurring in the later two thirds of the observation period. The implemented QPE algorithm applies a parameter that differentiates the Z-R conversion in convective and stratiform regimes and a stochastic filtering approach for estimation of mean-field bias on the basis of radar-rain gauge comparisons at the hourly timescale. The calibration of the algorithm parameter values is formulated as a global optimization problem, which is solved by minimizing the radar-rain gauge rainfall accumulation root-mean-square (rms) difference at the hourly timescale. A random resampling calibration/validation exercise is performed to evaluate the algorithm performance and its sensitivity to parameter values. Validation against gauges shows that the algorithm produces unbiased estimates with ˜57% relative RMS difference at the hourly scale. Comparison with S-POL rain estimates showed good correlation (0.9) but some overestimation (9%). Rainfall products are used to derive rainfall statistics for two distinct meteorological low-level wind regimes (easterly and westerly) that occurred during LBA. Finally, instantaneous rain estimates are compared against TRMM PR rainfall profiles for six coincident storm cases showing high correlation (0.9) and low (7%) systematic difference (PR overestimation).

Anagnostou, Emmanouil N.; Morales, Carlos A.

2002-10-01

134

wradlib - an Open Source Library for Weather Radar Data Processing  

NASA Astrophysics Data System (ADS)

Even though weather radar holds great promise for the hydrological sciences, offering precipitation estimates with unrivaled spatial and temporal resolution, there are still problems impeding its widespread use, among which are: almost every radar data set comes with a different data format with public reading software being available only rarely. standard products as issued by the meteorological services often do not serve the needs of original research, having either too many or too few corrections applied. Especially when new correction methods are to be developed, researchers are often forced to start from scratch having to implement many corrections in addition to those they are actually interested in. many algorithms published in the literature cannot be recreated using the corresponding article only. Public codes, providing insight into the actual implementation and how an approach deals with possible exceptions are rare. the radial scanning setup of weather radar measurements produces additional challenges, when it comes to visualization or georeferencing of this type of data. Based on these experiences, and in the hope to spare others at least some of these tedious tasks, wradlib offers the results of the author's own efforts and a growing number of community-supplied methods. wradlib is designed as a Python library of functions and classes to assist users in their analysis of weather radar data. It provides solutions for all tasks along a typical processing chain leading from raw reflectivity data to corrected, georeferenced and possibly gauge adjusted quantitative precipitation estimates. There are modules for data input/output, data transformation including Z/R transformation, clutter identification, attenuation correction, dual polarization and differential phase processing, interpolation, georeferencing, compositing, gauge adjustment, verification and visualization. The interpreted nature of the Python programming language makes wradlib an ideal tool for interactive data exploration and analysis. Based on the powerful scientific python stack (numpy, scipy, matplotlib) and in parts augmented by functions compiled in C or Fortran, most routines are fast enough to also allow data intensive re-analyses or even real-time applications. From the organizational point of view, wradlib is intended to be community driven. To this end, the source code is made available using a distributed version control system (DVCS) with a publicly hosted repository. Code may be contributed using the fork/pull-request mechanism available to most modern DVCS. Mailing lists were set up to allow dedicated exchange among users and developers in order to fix problems and discuss new developments. Extensive documentation is a key feature of the library, and is available online at http://wradlib.bitbucket.org. It includes an individual function reference as well as examples, tutorials and recipes, showing how those routines can be combined to create complete processing workflows. This should allow new users to achieve results quickly, even without much prior experience with weather radar data.

Pfaff, Thomas; Heistermann, Maik; Jacobi, Stephan

2014-05-01

135

Weather Radar and Hydrology (Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 3XX, 2011).  

E-print Network

Weather Radar and Hydrology (Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 3XX, 2011). Copyright 2011 IAHS Press 1 Operational Radar Refractivity Retrieval for Numerical describes the application of radar refractivity retrieval to the C-band radars of the UK operational weather

Reading, University of

136

Development of Weather Radar Mosaic Products in the U.S. National Weather Service  

NASA Astrophysics Data System (ADS)

The Weather Surveillance Radar 1988 (Doppler) (WSR-88D) network contains 142 units within the conterminous United States, 7 units in Alaska, and 4 units in Hawaii. The units are maintained by several agencies of the federal government, including the National Weather Service, the Federal Aviation Administration, and the Department of Defense. Many users of the data require access to observations from multiple radars simultaneously, and various mechanisms have beendevised to create national- and regional-scale geographic composites. Within the National Weather Service, creation of mosaics at local forecast offices can take up a substantial portion of available computing resources. The Meteorological Development Laboratory has undertaken the development of a system that will centrally produce and disseminate a set of mosaic products covering the conterminous United States, thus reducing the need for local production of the products. The effort has been made possible by the recent completion of communications network upgrades that permit rapid central collection of data from all sites within the WSR-88D network. A review of the radar product suite will be presented. The suite presently includes reflectivity, precipitation ccumulation estimates, vertically-integrated liquid water estimates, 18-dBZ echo top heights, and convective storm cell information such as hail indications and Doppler indications of mesocyclones and tornadoes. The operational goal is the production of mosaics at approximately 2-km spatial resolution for reflectivity and 4-km resolution for other fields, on a 5-minute update cycle. Some products are currently made available in graphical format via the World-Wide Web. Substantial progress has been made in developing an automated procedure to identify nonprecipitation echoes, including birds, insects, ground clutter, and anomalous propagation. Tests comparing the outcome of automated target identification with manual identification will be presented.

Kitzmiller, D. H.; Guan, S.; Mello, C.; Dai, J.

2002-05-01

137

Microphysical variability of tropical and mid-latitude rainfall as revealed by polarimetric radar  

NASA Astrophysics Data System (ADS)

Gorgucci et al. (2006) showed that a parameter space defined by several polarimetric radar variables could be used to characterize the shape of raindrops. This study has been extended using the so-called self-consistency analysis to identify rainfall regimes, specifically warm rain coalescence compared to the melting of large ice particles that have grown by riming. For a given rainfall regime, the behavior of Kdp/Z (where Kdp is the specific differential phase and Z is the linear reflectivity) plotted against Zdr (differential reflectivity) in rain-only regions is useful in identifying precipitation physics. Kdp is proportional to water mass content and mass-weighted oblateness ratio, whereas Zdr is a measure of particle oblateness of the largest drops in a sample volume. Z is proportional to concentration and diameter. Using data from polarimetric radar observations at several places (both tropical and mid-latitude) around the globe we demonstrate microphysical variability in rainfall associated with intraseasonal variability, differences in organization (isolated convection vs. organized), and regional variability. Several of these datasets have resulted from TRMM and GPM field campaigns, including the Mid-Latitude Continental Convective Clouds Experiment (MC3E) and Iowa Flood Studies (IFloodS). Implications for Z-based rain estimation as used by the TRMM and GPM precipitation radars will be discussed. This technique could also be applied to the nation's NEXRAD WSR-88DP data to better understand the microphysical characteristics of rainfall across the U.S.

Rutledge, S. A.; Dolan, B.; Chandrasekar, C. V.; Kennedy, P.; Wolff, D. B.; Petersen, W. A.

2013-12-01

138

Effects of Multiple Scattering for Millimeter-Wavelength Weather Radars  

NASA Technical Reports Server (NTRS)

Effects of multiple scattering on the reflectivity measurement for millimeter-wavelength weather radars are studied, in which backscattering enhancement may play an important role. In the previous works, the backscattering enhancement has been studied for plane wave injection, the reflection of which is received at the infinite distance. In this paper, a finite beam width of a Gaussian antenna pattern along with spherical wave is taken into account. A time-independent second order theory is derived for a single layer of clouds of a uniform density. The ordinary second-order scattering (ladder term) and the second-order backscattering enhancement (cross term) are derived for both the copolarized and cross-polarized waves.

Kobayashi, Satoru; Tanelli, Simone; Im, Eastwood

2004-01-01

139

The MST radar technique: Requirements for operational weather forecasting  

NASA Technical Reports Server (NTRS)

There is a feeling that the accuracy of mesoscale forecasts for spatial scales of less than 1000 km and time scales of less than 12 hours can be improved significantly if resources are applied to the problem in an intensive effort over the next decade. Since the most dangerous and damaging types of weather occur at these scales, there are major advantages to be gained if such a program is successful. The interest in improving short term forecasting is evident. The technology at the present time is sufficiently developed, both in terms of new observing systems and the computing power to handle the observations, to warrant an intensive effort to improve stormscale forecasting. An assessment of the extent to which the so-called MST radar technique fulfills the requirements for an operational mesoscale observing network is reviewed and the extent to which improvements in various types of forecasting could be expected if such a network is put into operation are delineated.

Larsen, M. F.

1983-01-01

140

The scattering simulation of DSDs and the polarimetric radar rainfall algorithms at C-band frequency  

NASA Astrophysics Data System (ADS)

This study explores polarimetric radar rainfall algorithms at C-band frequency using a total of 162,415 1-min raindrop spectra from an extensive disdrometer dataset. Five different raindrop shape models have been tested to simulate polarimetric radar variables-the reflectivity factor (Z), differential reflectivity (Zdr) and specific differential phase (Kdp), through the T-matrix microwave scattering approach. The polarimetric radar rainfall algorithms are developed in the form of R(Z), R(Kdp), R(Z, Zdr) and R(Zdr, Kdp) combinations. Based on the best fitted raindrop spectra models rain rate retrieval information using disdrometer derived rain rate as a reference, the algorithms are further explored in view of stratiform and convective rain regimes. Finally, an “artificial” algorithm is proposed which considers the developed algorithms for stratiform and convective regimes and uses R(Z), R(Kdp) and R(Z, Zdr) in different scenarios. The artificial algorithm is applied to and evaluated by the Thurnham C-band dual polarized radar data in 6 storm cases perceiving the rationalization in terms of rainfall retrieval accuracy as compared to the operational Marshall-Palmer algorithm (Z=200R1.6). A dense network of 73 tipping bucket rain gauges is employed for the evaluation, and the result demonstrates that the artificial algorithm outperforms the Marshall-Palmer algorithm showing R2=0.84 and MAE=0.82 mm as opposed to R2=0.79 and MAE=0.86 mm respectively.

Islam, Tanvir

2014-11-01

141

Simulation of Tornado over Brahmanbaria on 22 March 2013 using Doppler Weather Radar and WRF Model  

NASA Astrophysics Data System (ADS)

A tornado accompanied with thunderstorm, rainfall and hailstorm affected Brahmanbaria of Bangladesh in the afternoon of 22 March 2013. The tornadic storms are studied based on field survey, ground and radar observations. Low level moisture influx by southerly flow from the Bay of Bengal coupled with upper level westerly jet stream causing intense instability and shear in the wind fields triggered a series of storms for the day. The exact time and locations of the storms are investigated by using the Agartala and Cox's Bazar Doppler Weather Radar (DWR). Subsequently, the storms are simulated by using the WRF-ARW model at 1 km horizontal resolution based on 6 hourly analyses and boundary conditions of NCEP-FNL. Among the typical characteristics of the storms, the CAPE, surface wind speed, flow patterns, T-? gram, rainfall, sea level pressure, vorticity and vertical velocity are studied. Results show that while there are differences of 2-3 hours between the observed and simulated time of the storms, the distances between observed and simulated locations of the storms are several tens of kilometers. The maximum CAPE was generally above 2400 J kg-1 in the case. The maximum intensity of surface wind speed simulated by the model was only 38 m sec-1. This seems to be underestimated. The highest vertical velocity (updraft) simulated by the model was 250 m sec-1 around 800-950 hPa. The updraft reached up to 150 hPa. It seems that the funnel vortex reached the ground, and might have passed some places a few meters above the surface. According to the Fujita Pearson scale, this tornado can be classified as F-2 with estimated wind speed of 50-70 ms-1. Keywords: Tornado, DWR, NCEP-FNL, T-? gram, CAPE.

Das, M. K.; Chowdhury, M.; Das, S.

2013-12-01

142

Quantitative estimation of Tropical Rainfall Mapping Mission precipitation radar signals from ground-based polarimetric radar observations  

NASA Astrophysics Data System (ADS)

The Tropical Rainfall Mapping Mission (TRMM) is the first mission dedicated to measuring rainfall from space using radar. The precipitation radar (PR) is one of several instruments aboard the TRMM satellite that is operating in a nearly circular orbit with nominal altitude of 350 km, inclination of 35°, and period of 91.5 min. The PR is a single-frequency Ku-band instrument that is designed to yield information about the vertical storm structure so as to gain insight into the intensity and distribution of rainfall. Attenuation effects on PR measurements, however, can be significant and as high as 10-15 dB. This can seriously impair the accuracy of rain rate retrieval algorithms derived from PR signal returns. Quantitative estimation of PR attenuation is made along the PR beam via ground-based polarimetric observations to validate attenuation correction procedures used by the PR. The reflectivity (Zh) at horizontal polarization and specific differential phase (Kdp) are found along the beam from S-band ground radar measurements, and theoretical modeling is used to determine the expected specific attenuation (k) along the space-Earth path at Ku-band frequency from these measurements. A theoretical k-Kdp relationship is determined for rain when Kdp ? 0.5°/km, and a power law relationship, k = a Zhb, is determined for light rain and other types of hydrometers encountered along the path. After alignment and resolution volume matching is made between ground and PR measurements, the two-way path-integrated attenuation (PIA) is calculated along the PR propagation path by integrating the specific attenuation along the path. The PR reflectivity derived after removing the PIA is also compared against ground radar observations.

Bolen, Steven M.; Chandrasekar, V.

2003-06-01

143

Potential use of weather radar to study movements of wintering waterfowl  

USGS Publications Warehouse

To protect and restore wintering waterfowl habitat, managers require knowledge of routine wintering waterfowl movements and habitat use. During preliminary screening of Doppler weather radar data we observed biological movements consistent with routine foraging flights of wintering waterfowl known to occur near Lacassine National Wildlife Refuge (NWR), Louisiana. During the winters of 2004–2005 and 2005–2006, we conducted field surveys to identify the source of the radar echoes emanating from Lacassine NWR. We compared field data to weather radar reflectivity data. Spatial and temporal patterns consistent with foraging flight movements appeared in weather radar data on all dates of field surveys. Dabbling ducks were the dominant taxa flying within the radar beam during the foraging flight period. Using linear regression, we found a positive log-linear relationship between average radar reflectivity (Z) and number of birds detected over the study area (P r2 = 0.62, n = 40). Ground observations and the statistically significant relationship between radar data and field data confirm that Doppler weather radar recorded the foraging flights of dabbling ducks. Weather radars may be effective tools for wintering waterfowl management because they provide broad-scale views of both diurnal and nocturnal movements. In addition, an extensive data archive enables the study of wintering waterfowl response to habitat loss, agricultural practices, wetland restoration, and other research questions that require multiple years of data.

Randall, Lori A.; Diehl, Robert H.; Wilson, Barry C.; Barrow, Wylie C.; Jeske, Clinton W.

2011-01-01

144

Development of Research Quality Radar-Rainfall Datasets for Hydrologic Studies  

NASA Astrophysics Data System (ADS)

Although there is plethora of radar-rainfall data readily available, there is lack of well-documented research quality data sets over land. Two well-known and extensively studied oceanic radar-rainfall data sets are the GATE and TOGA COARE. Both are well-documented and provide high space and time resolution data. These data sets and the efforts that went into the product development are described in scientific literature. Over land the most popular data sets are the operational products generated by NOAA from the network of WSR-88D radars. Some products combine data from radars and rain gauges but leave out little information for an independent evaluation of the quality of the product. Other long-term data sets, such as the Mississippi River Basin five-year long data sets created under the auspices of the GCIP program are the results of trade-offs between feasibility and accuracy. Data sets developed for TRMM validation are limited to the tropics. Recognizing the need for high-resolution flexible radar data sets for use in hydrologic studies of flood generation mechanism, land-atmosphere-vegetation interactions, and scaling of rainfall processes, we are developing a system that will provide such data sets. The essential characteristics of the system are: (1) ability to effectively remove non-precipitation echo; (2) flexibility in specifying the algorithm that converts the observable (i.e. radar reflectivity) into the variable of interest, i.e. rainfall on the ground according to some specific criteria; and (3) ability to describe the main features of the product uncertainty. Our system, based on the WSR-88D level II reflectivity data will possess these characteristics. It is efficient enough to generate a large (one year or more) data set of rainfall products at the resolution limited only by the raw radar data. It incorporates the quality controlled rain gauge information via a calibration process. The calibration criteria allow trade-off between different error characteristics. We present examples of the products generated using the system from data from Kansas, Oklahoma, and Iowa.

Krajewski, W. F.; Ciach, G. J.; Gupta, V. K.; Furey, P.

2002-12-01

145

Prediction of extreme rainfall event using weather pattern recognition and support vector machine classifier  

NASA Astrophysics Data System (ADS)

A major component of flood alert broadcasting is the short-term prediction of extreme rainfall events, which remains a challenging task, even with the improvements of numerical weather prediction models. Such prediction is a high priority research challenge, specifically in highly urbanized areas like Mumbai, India, which is extremely prone to urban flooding. Here, we attempt to develop an algorithm based on a machine learning technique, support vector machine (SVM), to predict extreme rainfall with a lead time of 6-48 h in Mumbai, using mesoscale (20-200 km) and synoptic scale (200-2,000 km) weather patterns. The underlying hypothesis behind this algorithm is that the weather patterns before (6-48 h) extreme events are significantly different from those of normal weather days. The present algorithm attempts to identify those specific patterns for extreme events and applies SVM-based classifiers for extreme rainfall classification and prediction. Here, we develop the anomaly frequency method (AFM), where the predictors (and their patterns) for SVM are identified with the frequency of high anomaly values of weather variables at different pressure levels, which are present before extreme events, but absent for non-extreme conditions. We observe that weather patterns before the extreme rainfall events during nighttime (1800 to 0600Z) is different from those during daytime (0600 to 1800Z) and, accordingly, we develop a two-phase support vector classifier for extreme prediction. Though there are false alarms associated with this prediction method, the model predicts all the extreme events well in advance. The performance is compared with the state-of-the-art statistical technique fingerprinting approach and is observed to be better in terms of false alarm and prediction.

Nayak, Munir Ahmad; Ghosh, Subimal

2013-11-01

146

A multi-spectral spatial convolution approach of rainfall forecasting using weather satellite imagery  

NASA Astrophysics Data System (ADS)

Flood forecasting has long been a major topic of hydrologic research. Recent events and studies indicate that the success of flood forecasting in Taiwan depends heavily on the accuracy of real-time rainfall forecasting. In this study, we demonstrate a multi-spectral spatial convolution approach for real-time rainfall forecasting using geostationary weather satellite images. The approach incorporates cloud-top temperatures of three infrared channels in a spatial convolution context. It not only characterizes the input output relationship between cloud-top temperature and rainfall at the ground level, but also is more consistent with physical and remote sensing principles than single-pixel matches. Point rainfall measurements at raingauge sites are up-scaled to pixel-average-rainfall by block kriging, then related to multi-spectral cloud-top temperatures derived from Geostationary Meteorological Satellite images by spatial convolution. The kernel function of the multispectral spatial convolution equation is solved by the least squares method. Through a cross-validation procedure, we demonstrate that the proposed approach is capable of achieving high accuracy for 1- to 3-h-lead pixel-average-rainfall forecasting.

Wei, Chiang; Hung, Wei-Chun; Cheng, Ke-Sheng

147

Ground-based weather radar compatibility with digital radio-relay microwave systems  

NASA Astrophysics Data System (ADS)

The potential for ground-based weather radar (meteorological radar) interference to digital microwave systems in the common carrier bands of 3700 to 4200 MHz and 5925 to 6425 MHz is examined. Reported cases of interference to microwave common carrier systems from ground-based weather radar systems have increased due to the trend towards digital modulations. Because of this interference, the National Telecommunications and Information Administration, the Federal Communications Commission and the National Spectrum Managers Association formed an informal working group to investigate and document the potential problems. The existing and planned spectrum uses by ground-based weather radars and digital microwave systems are addressed as well as regulations and policy pertaining to their electromagnetic compatibility. Methods to mitigate the interference in both the radar transmitter and microwave receiver are also provided.

Gawthrop, P. E.; Patrick, G. M.

1990-03-01

148

Linking ENSO and heavy rainfall events over coastal British Columbia through a weather pattern classification  

NASA Astrophysics Data System (ADS)

Classifications of atmospheric weather patterns (WPs) are widely used for the description of the climate of a given region and are employed for many applications, such as weather forecasting, downscaling of global circulation model outputs and reconstruction of past climates. WP classifications were recently used to improve the statistical characterisation of heavy rainfall. In this context, bottom-up approaches, combining spatial distribution of heavy rainfall observations and geopotential height fields have been used to define WP classifications relevant for heavy rainfall statistical analysis. The definition of WPs at the synoptic scale creates an interesting variable which could be used as a link between the global scale of climate signals and the local scale of precipitation station measurements. We introduce here a new WP classification centred on the British Columbia (BC) coastal region (Canada) and based on a bottom-up approach. Five contrasted WPs composed this classification, four rainy WPs and one non-rainy WP, the anticyclonic pattern. The four rainy WPs are mainly observed in the winter months (October to March), which is the period of heavy precipitation events in coastal BC and is thus consistent with the local climatology. The combination of this WP classification with the seasonal description of rainfall is shown to be useful for splitting observed precipitation series into more homogeneous sub-samples (i.e. sub-samples constituted by days having similar atmospheric circulation patterns) and thus identifying, for each station, the synoptic situations that generate the highest hazard in terms of heavy rainfall events. El Niño-Southern Oscillations (ENSO) significantly influence the frequency of occurrence of two coastal BC WPs. Within each WP, ENSO seem to influence only the frequency of rainy events and not the magnitudes of heavy rainfall events. Consequently, heavy rainfall estimations do not show significant evolution of heavy rainfall behaviour between Niño and Niña winters. However, the WP approach captures the variability of the probability of occurrences of synoptic situations generating heavy rainfall depending on ENSO and opening interesting perspectives for the analysis of heavy rainfall distribution in a non-stationary context.

Brigode, P.; Mi?ovi?, Z.; Bernardara, P.; Paquet, E.; Garavaglia, F.; Gailhard, J.; Ribstein, P.

2013-04-01

149

Modeling COSMO-SkyMed measurements of precipitating clouds over the sea using simultaneous weather radar observations  

NASA Astrophysics Data System (ADS)

Several satellite missions employing X-band synthetic aperture radar (SAR) have been activated to provide high-resolution images of normalized radar cross-sections (NRCS) on land and ocean for numerous applications. Rainfall and wind affect the sea surface roughness and consequently the NRCS from the combined effects of corrugation due to impinging raindrops and surface wind. X-band frequencies are sensitive to precipitation: intense convective cells result in irregularly bright and dark patches in SAR images, masking changes in surface NRCS. Several works have modeled SAR images of intense precipitation over land; less adequately investigated is the precipitation effect over the sea surface. These images are analyzed in this study by modeling both the scattering and attenuation of radiation by hydrometeors in the rain cells and the NRCS surface changes using weather radar precipitation estimates as input. The reconstruction of X-band SAR returns in precipitating clouds is obtained by the joint utilization of volume reflectivity and attenuation, the latter estimated by coupling ground-based radar measurements and an electromagnetic model to predict the sea surface NRCS. Radar signatures of rain cells were investigated using X-band SAR images collected from the COSMO-SkyMed constellation of the Italian Space Agency. Two case studies were analyzed. The first occurred over the sea off the coast of Louisiana (USA) in summer 2010 with COSMO-SkyMed (CSK®) ScanSar mode monitoring of the Deepwater Horizon oil spill. Simultaneously, the NEXRAD S-band Doppler radar (KLIX) located in New Orleans was scanning the same portion of ocean. The second case study occurred in Liguria (Italy) on November 4, 2011, during an extraordinary flood event. The same events were observed by the Bric della Croce C-band dual polarization radar located close to Turin (Italy). The polarimetric capability of the ground radars utilized allows discrimination of the composition of the precipitation volume, in particular distinguishing ice from rain. Results shows that for space-borne SAR at X-band, effects due to precipitation on water surfaces can be modeled using coincident ground-based weather radar measurements.

Roberto, N.; Baldini, L.; Facheris, L.; Chandrasekar, V.

2014-07-01

150

Understanding the assimilation of dual-polarimetric radar observations and their impact on convective weather forecasting in mesoscale models  

NASA Astrophysics Data System (ADS)

Dual-polarimetric radars typically transmit/receive both horizontally and vertically polarized radio wave pulses. Owing to the enhanced measurement, dual-pol Doppler variables can provide more information about the liquid and solid cloud and precipitation particles, hence obtain more accurate estimate of rainfall and hydrometeors than non-polarimetric weather radars. The assimilation of dual-pol radar data may be a potential way to improve the performance of short-term forecast of numerical models. At present, not much effort has been given into the dual-pol radar data assimilation research field. With the ongoing upgrade of the current U.S. NEXRAD radar network to include dual-polarimetric capabilities, the dual-pol radar network will cover the whole country within the next couple years. The time is upon us to begin exploring how to best use the polarimetric data to improve forecast of severe storm and forecast initialization. The assimilation of dual-pol data for real cases is a challenging work. In this study, high-resolution (~1 km) WRF model and its 3DVAR data assimilation system are used. The dual-polarimetric radar data used in our studies was collected by the C-band Advanced Radar for Meteorological and Operational Research (ARMOR) radar (located at Huntsville International Airport (34.6804N, 86.7743W)), yet the emphasis now is toward using S-Band data from the upgraded NEXRAD network. Our presentation will highlight our recent work on assimilating the ARMOR radar data for real case convective storms, as well as new work using S-Band observations. Details of the methodology of data assimilation, the influences of different dual-pol variables on model initial condition and on the short-term prediction of precipitation, and the results for the real case storms, will be presented. In addition, before including a new observing system in an assimilation system, (dual-pol observations in this case) it is important to first assess the information content and uncertainty of the observations and forward model. An estimate of the information content in a set of observations requires knowledge of the relationship between measurements and forward observations. If the range of possible values of the measurements and forward observations is represented as a probability distribution, then the information content can be computed from the joint probability density function of the forward observations conditioned on the set of available measurements and on whatever forward model is chosen to relate them. Preliminary results will be shown toward understanding the information content of dual-polarimetric radar observations and their relationship to WRF model physics uncertainty.

Li, X.; Mecikalski, J. R.; Posselt, D. J.

2011-12-01

151

Wind Profiling by Doppler Weather Radar Iwan Holleman (holleman@knmi.nl)  

E-print Network

Wind Profiling by Doppler Weather Radar Iwan Holleman (holleman@knmi.nl) Royal Netherlands wind profiles at a high temporal resolution. Several algorithms and quality ensuring procedures for the extraction of wind profiles from radar volume data have been published. A comparison and verification

Stoffelen, Ad

152

Minimum operational performance standards for airborne weather and ground mapping pulsed radars  

NASA Astrophysics Data System (ADS)

Minimum operational performance standards for airborne weather and ground mapping pulsed radars, including both air carrier and large aircraft-type radar systems, are described. Those requirements and technologies pertinent to general aviation, where limitations on space and/or weight may apply are taken into account.

1980-11-01

153

Quality-based generation of weather radar Cartesian products  

NASA Astrophysics Data System (ADS)

Weather radar data volumes are commonly processed to obtain various 2-D Cartesian products based on the transfer from polar to Cartesian representations through a certain interpolation method. In this research, an algorithm of the spatial interpolation of polar reflectivity data with respect to QI (quality index) data is applied to find the Cartesian reflectivity as PPI (plan position indicator) product and generate a corresponding QI field. On this basis, quality-based versions of standard algorithms for the generation of the following products have been developed: ETOP (echo top), MAX (maximum of reflectivity), and VIL (vertically integrated liquid water). Moreover, as an example of a higher-level product, a CONVECTION (detection of convection) has been defined as a specific combination of the above-listed standard products. A corresponding QI field is determined for each generated product, taking into account the quality of the pixels from which a given product was determined and how large a fraction of the investigated heights was scanned. Examples of such quality-based products are presented in the paper.

O?ródka, K.; Szturc, J.

2014-11-01

154

Effects of Uncertainty in TRMM Precipitation Radar Path Integrated Attenuation on Interannual Variations of Tropical Oceanic Rainfall  

NASA Technical Reports Server (NTRS)

Considerable uncertainty surrounds the issue of whether precipitation over the tropical oceans (30 deg N/S) systematically changes with interannual sea-surface temperature (SST) anomalies that accompany El Nino (warm) and La Nina (cold) events. Time series of rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) over the tropical oceans show marked differences with estimates from two TRMM Microwave Imager (TMI) passive microwave algorithms. We show that path-integrated attenuation derived from the effects of precipitation on the radar return from the ocean surface exhibits interannual variability that agrees closely with the TMI time series. Our analysis of discrepancies between the PR rainfall and attenuation suggests that uncertainty in the assumed drop size distribution and associated attenuation/reflectivity/rainfall relationships inherent in single-frequency radar methods is a serious issue for studies of interannual variability.

Robertson, Franklin R.; Fitzjarrald, Dan E.; Kummerow, Christian D.

2003-01-01

155

A quantitative analysis of the impact of wind turbines on operational Doppler weather radar data  

NASA Astrophysics Data System (ADS)

In many countries wind turbines are rapidly growing in numbers as the demand for energy from renewable sources increases. The continued deployment of wind turbines can, however, be problematic for many radar systems, which are easily disturbed by turbines located in radar line-of-sight. Wind turbines situated in the vicinity of Doppler weather radars can lead to erroneous precipitation estimates as well as to inaccurate wind- and turbulence measurements. This paper presents a quantitative analysis of the impact of a wind farm, located in southeastern Sweden, on measurements from a nearby Doppler weather radar. The analysis is based on six years of operational radar data. In order to evaluate the impact of the wind farm, average values of all three spectral moments (the radar reflectivity factor, absolute radial velocity, and spectrum width) of the nearby Doppler weather radar were calculated, using data before and after the construction of the wind farm. It is shown that all spectral moments, from a large area at and downrange from the wind farm, were impacted by the wind turbines. It was also found that data from radar cells far above the wind farm (near 3 km altitude) were affected by the wind farm. We show that this is partly explained by changes in the atmospheric refractive index, bending the radar beams closer to the ground. In a detailed analysis, using data from a single radar cell, frequency distributions of all spectral moments were used to study the competition between the weather signal and wind turbine clutter. We show that when weather echoes give rise to higher reflectivity values than that of the wind farm, the negative impact of the wind turbines disappears for all spectral moments.

Norin, L.

2014-08-01

156

Debris-flow hazard assessment at regional scale by combining susceptibility mapping and radar rainfall  

NASA Astrophysics Data System (ADS)

This work presents a technique for debris flow (DF) hazard assessment able to be used in the framework of DF early warning systems at regional scale. The developed system is applied at subbasin scale and is based on the concepts of fuzzy logic to combine two ingredients: (i) DF subbasin susceptibility assessment based on geomorphological variables, and (ii) the magnitude of the rainfall situation as depicted from radar rainfall estimates. The output of the developed technique is a three-class hazard level ("low", "moderate" and "high") in each subbasin when a new radar rainfall map is available. The developed technique has been applied in a domain in the Eastern Pyrenees (Spain) from May to October 2010. The estimated hazard level stayed "low" during the entire period in 20% of the subbasins, while, in the most susceptible subbasins, the hazard level was at least moderate for up to10 days. Quantitative evaluation of the estimated hazard level was possible in a subbasin where debris flows were monitored during the analysis period. The technique was able to identify the 3 events observed in the catchment (1 debris flow and 2 hyperconcentrated flow events) and produced no false alarm.

Berenguer, M.; Sempere-Torres, D.; Hürlimann, M.

2014-10-01

157

A sun-tracking method to improve the pointing accuracy of weather radar  

NASA Astrophysics Data System (ADS)

Accurate positioning of data collected by a weather radar is of primary importance for their appropriate georeferencing, which in turn makes it possible to combine those with additional sources of information (topography, land cover maps, meteorological simulations from numerical weather models to list a few). This issue is especially acute for mobile radar systems, for which accurate and stable leveling might be difficult to ensure. The sun is a source of microwave radiation, which can be detected by weather radars and used for accurate positioning of radar data. This paper presents a technique based on the similarity between theodolites and radar systems as well as on the sun echoes to quantify and hence correct the instrumental errors which can affect the pointing accuracy of radar antenna. The proposed method is applied to data collected in the Swiss Alps using a mobile X-band radar system. The obtained instrumental bias values are evaluated by comparing the locations of the ground echoes predicted using these bias estimates with the observed ground echo locations. The very good agreement between the two confirms the accuracy of the proposed method.

Muth, X.; Schneebeli, M.; Berne, A.

2012-03-01

158

A System Concept for the Advanced Post-TRMM Rainfall Profiling Radars  

NASA Technical Reports Server (NTRS)

Atmospheric latent heating field is fundamental to all modes of atmospheric circulation and upper mixed layer circulations of the ocean. The key to understanding the atmospheric heating process is understanding how and where precipitation occurs. The principal atmospheric processes which link precipitation to atmospheric circulation include: (1) convective mass fluxes in the form of updrafts and downdrafts; (2) microphysical. nucleation and growth of hydrometeors; and (3) latent heating through dynamical controls on the gravitation-driven vertical mass flux of precipitation. It is well-known that surface and near-surface rainfall are two of the key forcing functions on a number of geophysical parameters at the surface-air interface. Over ocean, rainfall variation contributes to the redistribution of water salinity, sea surface temperature, fresh water supply, and marine biology and eco-system. Over land, rainfall plays a significant role in rainforest ecology and chemistry, land hydrology and surface runoff. Precipitation has also been closely linked to a number of atmospheric anomalies and natural hazards that occur at various time scales, including hurricanes, cyclones, tropical depressions, flash floods, droughts, and most noticeable of all, the El Ninos. From this point of view, the significance of global atmospheric precipitation has gone far beyond the science arena - it has a far-reaching impact on human's socio-economic well-being and sustenance. These and many other science applications require the knowledge of, in a global basis, the vertical rain structures, including vertical motion, rain intensity, differentiation of the precipitating hydrometeors' phase state, and the classification of mesoscale physical structure of the rain systems. The only direct means to obtain such information is the use of a spaceborne profiling radar. It is important to mention that the Tropical Rainfall Measuring Mission (TRMM) have made a great stride forward towards this ultimate goal. The Precipitation Radar (PR) aboard the TRMM satellite is the first ever spaceborne radar dedicated to three-dimensional, global precipitation measurements over the tropics and the subtropics, as well as the detailed synopsis of a wide range of tropical rain storm systems. In only twelve months since launch, the PR, together with other science instruments abroad the satellite have already provided unprecedented insights into the rainfall systems. It is anticipated the a lot more exciting and important rain observations would be made by TRMM throughout its mission duration. While TRMM has provided invaluable data to the user community, it is only the first step towards advancing our knowledge on rain processes and its contributions to climate variability. It is envisioned that a TRMM follow-on mission is needed in such a way to capitalize on the pioneering information provided by TRMM, and its instrument capability must be extended beyond TRMM in such a way to fully address the key science questions from microphysical to climatic time scale. In fact, a number of new and innovative mission concepts have recently put forth for this purpose. Almost all of these new concepts have suggested the utility of a more advanced, high-resolution, Doppler-enabled, vertical profiling radar that can provide multi-parameter observations of precipitation. In this paper, a system concept for a second- gene ration precipitation radar (PR-2) which addresses the above requirements will be described.

Im, Eastwood; Smith, Eric A.

1998-01-01

159

Rainfall and Snowfall Observations by the Airborne Dual-frequency Precipitation Radar during the Wakasa Bay Experiment  

NASA Technical Reports Server (NTRS)

Radar data obtained through the NASA/JPL Airborne Precipitation Radar APR-2 during the Wakasa Bay Experiment in January/February 2003 were processed to obtain calibrated reflectivity measurements, rainfall/snowfall velocity measurements, classification of the surface type and detection of the boundaries of the melting layer of precipitation. In this paper the processing approach is described together with an overview of the resulting data quality and known issues.

Tanelli, Simone; Im, Eastwood; Durden, Stephen L.; Meagher, Jonathan P.

2004-01-01

160

Network connectivity paradigm for the large data produced by weather radar systems  

NASA Astrophysics Data System (ADS)

The traffic over Internet is constantly increasing; this is due in particular to social networks activities but also to the enormous exchange of data caused especially by the so-called "Internet of Things". With this term we refer to every device that has the capability of exchanging information with other devices on the web. In geoscience (and, in particular, in meteorology and climatology) there is a constantly increasing number of sensors that are used to obtain data from different sources (like weather radars, digital rain gauges, etc.). This information-gathering activity, frequently, must be followed by a complex data analysis phase, especially when we have large data sets that can be very difficult to analyze (very long historical series of large data sets, for example), like the so called big data. These activities are particularly intensive in resource consumption and they lead to new computational models (like cloud computing) and new methods for storing data (like object store, linked open data, NOSQL or NewSQL). The weather radar systems can be seen as one of the sensors mentioned above: it transmit a large amount of raw data over the network (up to 40 megabytes every five minutes), with 24h/24h continuity and in any weather condition. Weather radar are often located in peaks and in wild areas where connectivity is poor. For this reason radar measurements are sometimes processed partially on site and reduced in size to adapt them to the limited bandwidth currently available by data transmission systems. With the aim to preserve the maximum flow of information, an innovative network connectivity paradigm for the large data produced by weather radar system is here presented. The study is focused on the Monte Settepani operational weather radar system, located over a wild peak summit in north-western Italy.

Guenzi, Diego; Bechini, Renzo; Boraso, Rodolfo; Cremonini, Roberto; Fratianni, Simona

2014-05-01

161

RONSARD Radar: Implementation of Dual Polarization on a C-Band Doppler Weather Radar  

Microsoft Academic Search

The French C-band meteorological Doppler radar Recherche sur les Orages et Nuages par un Systeme Associe de Radars Doppler (RONSARD) was recently equipped with dual polarization. This modification required, on the one hand, an additional receiver and, on the other hand, a new design for the antenna geometry in order to decrease strongly the sidelobe level. This new radar configuration

Georges Scialom; Jacques Faroux; Manuel Giraud; Richard Ney; Raquel Evaristo; Yvon Lemaitre; Nicolas Viltard

2009-01-01

162

Coupling Radar Rainfall Estimation and Hydrological Modelling For Flash-flood Hazard Mitigation  

NASA Astrophysics Data System (ADS)

Flood risk mitigation is accomplished through managing either or both the hazard and vulnerability. Flood hazard may be reduced through structural measures which alter the frequency of flood levels in the area. The vulnerability of a community to flood loss can be mitigated through changing or regulating land use and through flood warning and effective emergency response. When dealing with flash-flood hazard, it is gener- ally accepted that the most effective way (and in many instances the only affordable in a sustainable perspective) to mitigate the risk is by reducing the vulnerability of the involved communities, in particular by implementing flood warning systems and community self-help programs. However, both the inherent characteristics of the at- mospheric and hydrologic processes involved in flash-flooding and the changing soci- etal needs provide a tremendous challenge to traditional flood forecasting and warning concepts. In fact, the targets of these systems are traditionally localised like urbanised sectors or hydraulic structures. Given the small spatial scale that characterises flash floods and the development of dispersed urbanisation, transportation, green tourism and water sports, human lives and property are exposed to flash flood risk in a scat- tered manner. This must be taken into consideration in flash flood warning strategies and the investigated region should be considered as a whole and every section of the drainage network as a potential target for hydrological warnings. Radar technology offers the potential to provide information describing rain intensities almost contin- uously in time and space. Recent research results indicate that coupling radar infor- mation to distributed hydrologic modelling can provide hydrologic forecasts at all potentially flooded points of a region. Nevertheless, very few flood warning services use radar data more than on a qualitative basis. After a short review of current under- standing in this area, two issues are examined: advantages and caveats of using radar rainfall estimates in operational flash flood forecasting, methodological problems as- sociated to the use of hydrological models for distributed flash flood forecasting with rainfall input estimated from radar.

Borga, M.; Creutin, J. D.

163

Comparison of Radar Rainfall Retrieval Algorithms in Convective Rain During TOGA COARE  

NASA Technical Reports Server (NTRS)

The authors compare deterministic and stochastic rain-rate retrieval algorithms by applying them to 14-GHz nadir-looking airborne radar reflectivity profiles acquired in tropical convective rain during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment, The deterministic algorithms both use the path-integrated attenuation (PIA), measured by the surface reference technique, as a constraint. One deterministic algorithm corrects the k-R relation, while the second corrects the Z-R relation. The stochastic algorithms are based on applying an extended Kalman filter to the reflectivity profile. One employs radar reflectivity only; the other additionally uses the PIA. The authors find that the stochastic algorithm, which uses the PIA, is the most robust algorithm with regard to incorrect assumptions about the drop size distribution (DSD). The deterministic algorithm that uses the PIA to adjust the Z-R relation is also fairly robust and produces rain rates similar to the stochastic algorithm that uses the PIA, The deterministic algorithm that adjusts only the k-R relation and the stochastic radar-only algorithm are more sensitive to assumptions about the DSD. It is likely that they underestimate convective rainfall, especially if the DSD is erroneously assumed to be appropriate for stratiform rain conditions.

Durden, Stephen L.; Haddad, Z. S.

1998-01-01

164

Ranger© - An Affordable, Advanced, Next-Generation, Dual-Pol, X-Band Weather Radar  

NASA Astrophysics Data System (ADS)

The Enterprise Electronics Corporation (EEC) Ranger© system is a new generation, X-band (3 cm), Adaptive Polarization Doppler Weather Surveillance Radar that fills the gap between high-cost, high-power traditional radar systems and the passive ground station weather sensors. Developed in partnership with the University of Oklahoma Advanced Radar Research Center (ARRC), the system uses relatively low power solid-state transmitters and pulse compression technology to attain nearly the same performance capabilities of much more expensive traditional radar systems. The Ranger© also employs Adaptive Dual Polarization (ADP) techniques to allow Alternating or Simultaneous Dual Polarization capability with total control over the transmission polarization state using dual independent coherent transmitters. Ranger© has been designed using the very latest technology available in the industry and the technical and manufacturing experience gained through over four decades of successful radar system design and production at EEC. The entire Ranger© design concept emphasizes precision, stability, reliability, and value using proven solid state technology combined with the most advanced motion control system ever conceived for weather radar. Key applications include meteorology, hydrology, aviation, offshore oil/gas drilling, wind energy, and outdoor event situational awareness.

Stedronsky, Richard

2014-05-01

165

Operational Wind Retrieval Within the Frame of the French Weather Radar Network  

NASA Astrophysics Data System (ADS)

The recent deployment of an innovative triple-PRT Doppler scheme within the French operational radar network, named ARAMIS, allows collecting reflectivity and radial velocity measurements simultaneously up to a range of 250 km with no ambiguity. This achievement brings new perspectives in terms of exploitation of operational radar measurements such as the long-anticipated capability to perform multiple-Doppler wind retrieval in a fully operational framework. Accordingly, and for the first time ever, a method allowing to consistently retrieve complete wind vector fields (u, v, w) in real-time from operational radar systems is being tested by the French national weather service since early 2007. This study proposes to describe the experimental setup relied upon to operationally retrieve multiple-Doppler winds in the frame of ARAMIS, as well as to investigate the potential of this new product for weather forecast applications. Using high resolution numerical wind forecasts in a variety of weather situations, we also show that these radar-derived wind fields compose unprecedented datasets to evaluate and further improve high-resolution numerical weather prediction systems being currently deployed by many national weather services.

Bousquet, O.; Tabary, P.; Parent-Du-Châtelet, J.; Périer, L.

2008-12-01

166

Effect of simulated rainfall and weathering on release of preservative elements from CCA treated wood.  

PubMed

The release of arsenic from wood pressure-treated with chromated copper arsenate (CCA) can be decreased by application of wood finishes, but little is known about the types of finishes that are best suited for this purpose. This study evaluated the effects of finish water repellent content and ultraviolet (UV) radiation on the release of arsenic, copper, and chromium from CCA-treated wood exposed to simulated rainfall. Deck boards treated with CCA were either left unfinished or dipped in a finish prepared with 1%, 3%, or 5% water repellent. All specimens were exposed to leaching from simulated rainfall, and a subset of specimens was also exposed to UV radiation. The rainfall was collected and analyzed for total elemental arsenic, copper, and chromium. The water repellent significantly decreased the amounts of these elements in the runoff, but for the short duration of this study there was no difference among the three water repellent concentrations. It is possible that water repellent content would have a greater effect over a longer exposure period. Exposure to UV radiation caused a significant increase in leaching from both finished and unfinished specimens. This effect may be a result of increased surface area during weathering as well as loss of fibers caused by UV-induced surface erosion. PMID:14524438

Lebow, Stan; Williams, R Sam; Lebow, Patricia

2003-09-15

167

Adaptive clutter rejection filters for airborne Doppler weather radar applied to the detection of low altitude windshear  

Microsoft Academic Search

An optimum adaptive clutter rejection filter for use with airborne Doppler weather radar is presented. The radar system is being designed to operate at low-altitudes for the detection of windshear in an airport terminal area where ground clutter returns may mask the weather return. The coefficients of the adaptive clutter rejection filter are obtained using a complex form of a

Byron M. Keel

1989-01-01

168

Multi-PRI Signal Processing for the Terminal Doppler Weather Radar. Part II: RangeVelocity Ambiguity Mitigation  

E-print Network

Multi-PRI Signal Processing for the Terminal Doppler Weather Radar. Part II: Range­Velocity developed to combat range­velocity (RV) ambiguity for the Terminal Doppler Weather Radar (TDWR). In Part I and velocity dealiasing using multi-PRI signal transmission and processing are presented. The effectiveness

Cho, John Y. N.

169

On Rainfall Modification by Major Urban Areas. Part 1; Observations from Space-borne Rain Radar on TRMM  

NASA Technical Reports Server (NTRS)

This study represents one of the first published attempts to identify rainfall modification by urban areas using satellite-based rainfall measurements. Data from the first space-based rain-radar, the Tropical Rainfall Measuring Mission's (TRMM) Precipitation Radar, are employed. Analysis of the data enables identification of rainfall patterns around Atlanta, Montgomery, Nashville, San Antonio, Waco, and Dallas during the warm season. Results reveal an average increase of -28% in monthly rainfall rates within 30-60 kilometers downwind of the metropolis with a modest increase of 5.6% over the metropolis. Portions of the downwind area exhibit increases as high as 51%. The percentage chances are relative to an upwind CONTROL area. It was also found that maximum rainfall rates in the downwind impact area can exceed the mean value in the upwind CONTROL area by 48%-116%. The maximum value was generally found at an average distance of 39 km from the edge of the urban center or 64 km from the center of the city. These results are consistent with METROMEX studies of St. Louis almost two decades ago and more recent studies near Atlanta. Future work will investi(yate hypothesized factors causing rainfall modification by urban areas. Additional work is also needed to provide more robust validation of space-based rain estimates near major urban areas. Such research has implications for urban planning, water resource management, and understanding human impact on the environment.

Shepherd, J. Marshall; Pierce, Harold; Starr, David OC. (Technical Monitor)

2001-01-01

170

Weathering-limited rainfall-triggered shallow mass movements in undisturbed steepland tropical rainforest  

NASA Astrophysics Data System (ADS)

Rainfall-triggered landslides in undisturbed tropical rainforests may have been underestimated as contributors to slope development and denudation in the past. Theoretically, ideal conditions for such geomorphic processes, i.e. steep slopes and frequent high magnitude and intensity rainfall events, occur in a number of tropical regions, particularly within Southeast Asia. Therefore, a high frequency of occurrence of shallow slope failures was expected in the undisturbed steeplands of southeast Brunei. Stability conditions of the steep planar slopes were examined using a deterministic modelling approach in order to examine the possibility that most slopes could not fail in response to rainfall because they did not possess a sufficiently thick mantle of residual soil. A simple hillslope hydrology model based on a soil moisture balance approach was used to simulate hillslope responses to measured and simulated rainfall events. The stability of saturated slopes could then be analysed using the infinite slope model, the input shear strength parameters for which were obtained from direct shear tests and then calibrated by back-analysis of a failure which occurred in late 1991. The findings suggest that any slope of 40° and steeper should fail several times every year in response to storm events, but that in reality most of the slopes have failed previously and have not yet regained a critical depth of residual soil. Some approximate values for rates of weathering and slope development suggest that any given slope will not fail at intervals of less than 10,000 years. Therefore, the occurrence of shallow failures will be infrequent but nevertheless significant in terms of regional denudation and ecological diversity.

Dykes, A. P.

2002-07-01

171

Better Weather Prediction and Climate Diagnostics Using Rainfall Measurements from Space  

NASA Technical Reports Server (NTRS)

Progress in understanding of the role of water in global weather and climate is currently limited by our knowledge of the spatial and temporal variability of primary hydrological fields such as precipitation and evaporation. The Tropical Rainfall Measuring Mission (TRMM) has recently demonstrated that use of microwave-based rainfall observations from space in data assimilation can provide better climate data sets and improve short-range weather forecasting. At NASA, we have been exploring non-traditional approaches to assimilating TRMM Microwave Imager (TMI) and Special Sensor Microwavehager (SSM/I) surface rain rate and latent heating profile information in global systems. In this talk we show that assimilating microwave rain rates using a continuous variational assimilation scheme based on moisture tendency corrections improves quantitative precipitation estimates (QPE) and related clouds, radiation energy fluxes, and large-scale circulations in the Goddard Earth Observing System (GEOS) reanalyses. Short-range forecasts initialized with these improved analyses also yield better QPE scores and storm track predictions for Hurricanes Bonnie and Floyd. We present a status report on current efforts to assimilate convective and stratiform latent heating profile information within the general variational framework of model parameter estimation to seek further improvements. Within the next 5 years, there will be a gradual increase in microwave rain products available from operational and research satellites, culminating to a target constellation of 9 satellites to provide global rain measurements every 3 hours with the proposed Global Precipitation Measurement (GPM) mission in 2007/2008. Based on what has been learned from TRMM, there is a high degree of confidence that these observations can play a'major role in improving weather forecasts and producing better global datasets for understanding the Earth's water and energy cycle. The key to success is to adopt an integrated approach to retrieval, validation, modeling, and data assimilation in a coordinated end-to-end observation-application program.

Hou, Arthur; Zhang, Sara; Li, Jui-Lin; Reale, Oreste

2002-01-01

172

Wideband Waveform Design principles for Solid-state Weather Radars  

SciTech Connect

The use of solid-state transmitter is becoming a key part of the strategy to realize a network of low cost electronically steered radars. However, solid-state transmitters have low peak powers and this necessitates the use of pulse compression waveforms. In this paper a frequency diversity wideband waveforms design is proposed to mitigate low sensitivity of solid-state transmitters. In addition, the waveforms mitigate the range eclipsing problem associated with long pulse compression. An analysis of the performance of pulse compression using mismatched compression filters designed to minimize side lobe levels is presented. The impact of range side lobe level on the retrieval of Doppler moments are presented. Realistic simulations are performed based on CSU-CHILL radar data and Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) Integrated Project I (IP1) radar data.

Bharadwaj, Nitin; Chandrasekar, V.

2012-01-01

173

Worldwide Weather Radar Imagery May Allow Substantial Increase in Meteorite Fall Recovery  

NASA Technical Reports Server (NTRS)

Weather radar imagery is a valuable new technique for the rapid recovery of meteorite falls, to include falls which would not otherwise be recovered (e.g. Battle Mountain). Weather radar imagery reveals about one new meteorite fall per year (18 falls since 1998), using weather radars in the United States alone. However, an additional 75 other nations operate weather radar networks according to the UN World Meteorological Organization (WMO). If the imagery of those radars were analyzed, the current rate of meteorite falls could be improved considerably, to as much as 3.6 times the current recovery rate based on comparison of total radar areal coverage. Recently, the addition of weather radar imagery, seismometry and internet-based aggregation of eyewitness reports has improved the speed and accuracy of fresh meteorite fall recovery [e.g. 1,2]. This was demonstrated recently with the radar-enabled recovery of the Sutter's Mill fall [3]. Arguably, the meteorites recovered via these methods are of special scientific value as they are relatively unweathered, fresh falls. To illustrate this, a recent SAO/NASA ADS search using the keyword "meteorite" shows that all 50 of the top search results included at least one named meteorite recovered from a meteorite fall. This is true even though only 1260 named meteorite falls are recorded among the >49,000 individual falls recorded in the Meteoritical Society online database. The US NEXRAD system used thus far to locate meteorite falls covers most of the United States' surface area. Using a WMO map of the world's weather radars, we estimate that the total coverage of the other 75 national weather radar networks equals about 3.6x NEXRAD's coverage area. There are two findings to draw from this calculation: 1) For the past 16 years during which 18 falls are seen in US radar data, there should be an additional 65 meteorite falls recorded in worldwide radar imagery. Also: 2) if all of the world's radar data could be analyzed, the rate of recovery of fresh meteorite falls can increase by as much as 3.6x the current rate. The authors' experience to date indicates that the most effective course of action would be to have local meteorite research groups (outside of the US) form research consortia and develop a working relationship with their nation's weather bureau for access to data. These research consortia could utilize the same, proven methods used for US NEXRAD imagery, internet eyewitness report aggregation, seismometry analysis, etc. to locate meteorite falls. The consortia could then recover and analyze meteorite falls and enrich their own research efforts. It would be beneficial to conduct a global program to coordinate the development of methods and data tools, as well as to coordinate meteorite sample sharing and research. Perhaps an institution such as the Meteoritical Society could lead such an effort.

Fries, Marc; Matson, Robert; Schaefer, Jacob; Fries, Jeffery; Hankey, Mike; Anderson, Lindsay

2014-01-01

174

ECE/METR 6613: Weather Radar Polarimetry (Formerly called: Wave Interactions with Geophysical Media, Prereq. ECE/METR 5673 is being removed)  

E-print Network

1 ECE/METR 6613: Weather Radar Polarimetry (Formerly called: Wave Interactions with Geophysical: R. J. Doviak and D. S. Zrnic: Doppler Radar and Weather Observations, 2006, 1993, 1984 References: A: Polarimetric Doppler Weather Radar: Principle and applications, 2001 Course description This course provides

Zhang, Guifu

175

Clutter Filtering and Spectral Moment Estimation for Doppler Weather Radars Using Staggered Pulse Repetition Time (PRT)  

Microsoft Academic Search

In this paper, a new algorithm for the estimation of spectral parameters from the signal time series, collected using the staggered pulse repetition time (PRT) transmission in a Doppler weather radar, is presented. The algorithm uses the Fourier transform and a magnitude deconvolution procedure to reconstruct the signal spectrum, and then the spectral parameters are estimated from the reconstructed spectrum.

M. Sachidananda; D. S. Zrnic

2000-01-01

176

Remote sensing of precipitation by weather radar system at space station  

Microsoft Academic Search

A space station is considered as the ideal vehicle for a spaceborne weather radar, in virtue of its ability to accomodate an exceptionally large aperture X-band antenna and supply the power levels required for adequate operation. The space station envisioned will orbit at an altitude of 500 km, and can be developed in two distinct stages. The first stage will

K. Okamoto

1983-01-01

177

Wind observations with Doppler weather radar Iwan Holleman  

E-print Network

and the terminal fall velocity of the hydrometeors. When Doppler data are displayed at constant range and elevation different pulse repetition frequencies are used to extend the unambiguous velocity interval of the Doppler atmospheric targets, like rain, snow, dust, and insects. The radar provides the mean radial velocity

Stoffelen, Ad

178

Time-lapse borehole radar for monitoring rainfall infiltration through podosol horizons in a sandy vadose zone  

NASA Astrophysics Data System (ADS)

shallow aquifer on the Gnangara Mound, north of Perth, Western Australia, is recharged by winter rainfall. Water infiltrates through a sandy Podosol where cemented accumulation (B-) horizons are common. They are water retentive and may impede recharge. To observe wetting fronts and the influence of soil horizons on unsaturated flow, we deployed time-lapse borehole radar techniques sensitive to soil moisture variations during an annual recharge cycle. Zero-offset crosswell profiling (ZOP) and vertical radar profiling (VRP) measurements were performed at six sites on a monthly basis before, during, and after annual rainfall in 2011. Water content profiles are derived from ZOP logs acquired in closely spaced wells. Sites with small separation between wells present potential repeatability and accuracy difficulties. Such problems could be lessened by (i) ZOP saturated zone velocity matching of time-lapse curves, and (ii) matching of ZOP and VRP results. The moisture contents for the baseline condition and subsequent observations are computed using the Topp relationship. Time-lapse moisture curves reveal characteristic vadose zone infiltration regimes. Examples are (I) full recharge potential after 200 mm rainfall, (II) delayed wetting and impeded recharge, and (III) no recharge below 7 m depth. Seasonal infiltration trends derived from long-term time-lapse neutron logging at several sites are shown to be comparable with infiltration trends recovered from time-lapse crosswell radar measurements. However, radar measurements sample a larger volume of earth while being safer to deploy than the neutron method which employs a radioactive source. For the regime (III) site, where time-lapse radar indicates no net recharge or zero flux to the water table, a simple water balance provides an evapotranspiration value of 620 mm for the study period. This value compares favorably to previous studies at similar test sites in the region. Our six field examples demonstrate application of time-lapse borehole radar for characterizing rainfall infiltration.

Strobach, Elmar; Harris, B. D.; Dupuis, J. C.; Kepic, A. W.

2014-03-01

179

An Examination of Version5 Rainfall Estimates from the TRMM Microwave Imager, Precipitation Radar, and Rain Gauges on Global, Regional, and Storm Scales  

Microsoft Academic Search

An evaluation of the version-5 precipitation radar (PR; algorithm 2A25) and Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI; algorithm 2A12) rainfall products is performed across the Tropics in two ways: 1) by comparing long-term TRMM rainfall products with Global Precipitation Climatology Centre (GPCC) global rain gauge analyses and 2) by comparing the rainfall estimates from the PR and TMI

Stephen W. Nesbitt; Edward J. Zipser; Christian D. Kummerow

2004-01-01

180

Estimating Watershed Accumulated Precipitation From Radar and Gage Data  

Microsoft Academic Search

Radar-derived precipitation estimates are potentially valuable for studies whereground weather station rainfall data is not available at sufficient spatial density to account for precipitation variation over a study area. Stage IV precipitation analyses are one of the national products produced by the National Centers for Environmental Prediction (NCEP). This product combines data from Doppler weather radar precipitation estimates and surface

M. A. Murphy; C. J. Post

2005-01-01

181

COSMO-SkyMed measurements in precipitation over the sea: analysis of Louisiana summer thunderstorms by simultaneous weather radar observations  

NASA Astrophysics Data System (ADS)

Radar signatures of rain cells are investigated using X-band synthetic aperture radar (X-SAR) images acquired from COSMO-SkyMed constellation over oceans off the coast of Louisiana in summer 2010 provided by ASI archive. COSMO-SkyMed (CSK) monitoring of Deepwater Horizon oil spill provided a big amount of data during the period April-September 2010 and in July-August when several thunderstorms occurred in that area. In X-SAR images, radar signatures of rain cells over the sea usually consist of irregularly shaped bright and dark patches. These signatures originate from 1) the scattering and attenuation of radiation by hydrometers in the rain cells and 2) the modification of the sea roughness induced by the impact of raindrops and by wind gusts associated with rain cell. However, the interpretation of precipitation signatures in X-SAR images is not completely straightforward, especially over sea. Coincident measurements from ground based radars and an electromagnetic (EM) model predicting radar returns from the sea surface corrugated by rainfall are used to support the analysis. A dataset consisting of 4 CSK images has been collected over Gulf of Mexico while a WSR-88D NEXRAD S-band Doppler radar (KLIX) located in New Orleans was scanning the nearby portion of ocean. Terrestrial measurements have been used to reconstruct the component of X-SAR returns due to precipitation by modifying the known technique applied on measurements over land (Fritz et al. 2010, Baldini et al. 2011). Results confirm that the attenuation signature in X-SAR images collected over land, particularly pronounced in the presence of heavy precipitation cells, can be related to the S-band radar reflectivity integrated along the same path. The Normalized Radar Cross Section (NRCS) of land is considered to vary usually up to a few dBs in case of rain but with strong dependency on the specific type and conditions of land cover. While the NRCS of sea surface in clear weather condition can be considered as constant, in case of rain, at X-SAR incidence angles, it exhibits a dependence to precipitation event due the combined effects of corrugation due to the impinging raindrops and to the surface wind. Therefore, when retrieving of X-SAR NRCS in precipitation over the sea, this effect must be accounted for and can be quantified based on the precipitation event using a simple NRCS surface model. In this work, an EM model based on Bahar's Full Wave Model is used for evaluating such NRCS depending on polarization, frequency and incidence angle for different values of wind velocity and the root mean square height of the corrugation induced by rainfall. The reconstruction of X-SAR returns in precipitation is finally obtained by joint utilization of volume reflectivity and attenuation estimated from KLIX and the sea NRCS model.

Roberto, N.; Baldini, L.; Gorgucci, E.; Facheris, L.; Chandrasekar, V.

2012-04-01

182

Under the Weather: Health, Schooling, and Economic Consequences of Early-Life Rainfall. NBER Working Paper No. 14031  

ERIC Educational Resources Information Center

How sensitive is long-run individual well-being to environmental conditions early in life? This paper examines the effect of weather conditions around the time of birth on the health, education, and socioeconomic outcomes of Indonesian adults born between 1953 and 1974. We link historical rainfall for each individual's birth-year and…

Maccini, Sharon L.; Yang, Dean

2008-01-01

183

Statistical modelling of rainfall-induced shallow landsliding using static predictors and numerical weather predictions: preliminary results  

NASA Astrophysics Data System (ADS)

Our study is aimed at estimating the added value provided by Numerical Weather Prediction (NWP) data for the modelling and prediction of rainfall-induced shallow landslides. We implemented a quantitative indirect statistical modelling of such phenomena by using, as input predictors, both geomorphological, geological, climatological information and numerical data obtained by running a limited-area weather model. Two standard statistical techniques are used to combine the predictor variables: a generalized linear model and Breiman's random forests. We tested these models for two rainfall events that occurred in 2011 and 2013 in Tuscany region (central Italy). Modelling results are compared with field data and the forecasting skill is evaluated by mean of sensitivity-specificity receiver operating characteristic (ROC) analysis. In the 2011 rainfall event, the random forests technique performs slightly better than generalized linear model with area under the ROC curve (AUC) values around 0.91 vs. 0.84. In the 2013 rainfall event, both models provide AUC values around 0.7. Using the variable importance output provided by the random forests algorithm, we assess the added value carried by numerical weather forecast. The main results are as follows: (i) for the rainfall event that occurred in 2011 most of the NWP data, and in particular hourly rainfall intensities, are classified as "important" and (ii) for the rainfall event that occurred in 2013 only NWP soil moisture data in the first centimetres below ground is found to be relevant for landslide assessment. In the discussions we argue how these results are connected to the type of precipitation observed in the two events.

Capecchi, V.; Perna, M.; Crisci, A.

2015-01-01

184

Performance of high-resolution X-band weather radar networks - the PATTERN example  

NASA Astrophysics Data System (ADS)

This publication intends to prove that a network of low-cost local area weather radars (LAWR) is a reliable and scientifically valuable complement to nationwide radar networks. A network of four LAWRs has been installed in northern Germany within the framework of the Precipitation and Attenuation Estimates from a High-Resolution Weather Radar Network (PATTERN) project observing precipitation with a temporal resolution of 30 s, a range resolution of 60 m and a sampling resolution of 1° in the azimuthal direction. The network covers an area of 60 km × 80 km. In this paper, algorithms used to obtain undisturbed precipitation fields from raw reflectivity data are described, and their performance is analysed. In order to correct operationally for background noise in reflectivity measurements, noise level estimates from the measured reflectivity field are combined with noise levels from the last 10 time steps. For detection of non-meteorological echoes, two different kinds of clutter algorithms are applied: single-radar algorithms and network-based algorithms. Besides well-established algorithms based on the texture of the logarithmic reflectivity field (TDBZ) or sign changes in the reflectivity gradient (SPIN), the advantage of the unique features of the high temporal and spatial resolution of the network is used for clutter detection. Overall, the network-based clutter algorithm works best with a detection rate of up to 70%, followed by the classic TDBZ filter using the texture of the logarithmic reflectivity field. A comparison of a reflectivity field from the PATTERN network with the product from a C-band radar operated by the German Meteorological Service indicates high spatial accordance of both systems in the geographical position of the rain event as well as reflectivity maxima. Long-term statistics from May to September 2013 prove very good accordance of the X-band radar of the network with C-band radar, but, especially at the border of precipitation events, higher-resolved X-band radar measurements provide more detailed information on precipitation structure because the 1 km range gate of C-band radars is only partially covered with rain. The standard deviation within a range gate of the C-band radar with a range resolution of 1 km is up to 3 dBZ at the borders of rain events. The probability of detection is at least 90%, the false alarm ratio less than 10% for both systems. Therefore, a network of high-resolution low-cost LAWRs can give valuable information on the small-scale structure of rain events in areas of special interest, e.g. urban regions, in addition to the nationwide radar networks.

Lengfeld, K.; Clemens, M.; Münster, H.; Ament, F.

2014-12-01

185

Effects of Uncertainty in TRMM Precipitation Radar Path Integrated Attenuation on Interannual Variations of Tropical Oceanic Rainfall  

NASA Technical Reports Server (NTRS)

Considerable uncertainty surrounds the issue of whether precipitation over the tropical oceans (30 deg N/S) systematically changes with interannual sea-surface temperature (SST) anomalies that accompany El Nino (warm) and La Nina (cold) events. Time series of rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM Precipitation Radar (PR) over the tropical oceans show marked differences with estimates from two TRMM Microwave Imager (TMI) passive microwave algorithms. We show that path-integrated attenuation derived from the effects of precipitation on the radar return from the ocean surface exhibits interannual variability that agrees closely with the TMI time series. Further analysis of the frequency distribution of PR (2A25 product) rain rates suggests that the algorithm incorporates the attenuation measurement in a very conservative fashion so as to optimize the instantaneous rain rates. Such an optimization appears to come at the expense of monitoring interannual climate variability.

Robertson, Franklin R.; Fitzjarrald, Dan E.; Kummerow, Christian D.; Arnold, James E. (Technical Monitor)

2002-01-01

186

A raingage, radar and satellite simulation study of the estimation of convective rainfall by area-time integrals  

NASA Technical Reports Server (NTRS)

Correlations between area-averaged rainrates and the areal fraction of rainrates exceeding a preset threshold, F(T), are examined using data from a network of 22 raingages located within 120 km of the NOAA/Tropical Ocean-Global Atmosphere (TOGA) C-band meteorological radar at Darwin, Australia. The results show that the area averages of convective rainfall are highly correlated with the fraction F(T). To simulate the use of the relationship between area-averaged rainrates and F(T) to obtain space-time averaged rainrates from a satellite sensor, observations from the NOAA/TOGA radar observations are used to estimate F(T) using a reflectivity threshold. The use of area-time integral methods for inferring area-averaged rainrates from satellites is examined, noting the possible use of the methodology for the Tropical Rainfall Measuring Mission.

Short, David A.; Rosenfeld, Daniel; Wolff, David B.; Atlas, David

1989-01-01

187

A High-Resolution 3D Weather Radar, MSG, and Lightning Sensor Observation Composite  

NASA Astrophysics Data System (ADS)

Within the research group 'Object-based Analysis and SEamless prediction' (OASE) of the Hans Ertel Centre for Weather Research programme (HerZ), a data composite containing weather radar, lightning sensor, and Meteosat Second Generation observations is being developed for the use in object-based weather analysis and nowcasting. At present, a 3D merging scheme combines measurements of the Bonn and Jülich dual polarimetric weather radar systems (data provided by the TR32 and TERENO projects) into a 3-dimensional polar-stereographic volume grid, with 500 meters horizontal, and 250 meters vertical resolution. The merging takes into account and compensates for various observational error sources, such as attenuation through hydrometeors, beam blockage through topography and buildings, minimum detectable signal as a function of noise threshold, non-hydrometeor echos like insects, and interference from other radar systems. In addition to this, the effect of convection during the radar 5-minute volume scan pattern is mitigated through calculation of advection vectors from subsequent scans and their use for advection correction when projecting the measurements into space for any desired timestamp. The Meteosat Second Generation rapid scan service provides a scan in 12 spectral visual and infrared wavelengths every 5 minutes over Germany and Europe. These scans, together with the derived microphysical cloud parameters, are projected into the same polar stereographic grid used for the radar data. Lightning counts from the LINET lightning sensor network are also provided for every 2D grid pixel. The combined 3D radar and 2D MSG/LINET data is stored in a fully documented netCDF file for every 5 minute interval, and is made ready for tracking and object based weather analysis. At the moment, the 3D data only covers the Bonn and Jülich area, but the algorithms are planed to be adapted to the newly conceived DWD polarimetric C-Band 5 minute interval volume scan strategy. An extension of the 3D composite to all of Germany is therefore possible and set as a goal.

Diederich, Malte; Senf, Fabian; Wapler, Kathrin; Simmer, Clemens

2013-04-01

188

Using NEXRAD Radar Rainfall to Calibrate a Development Impact Model in a Coastal Watershed  

NASA Astrophysics Data System (ADS)

Low slopes and shallow, impermeable soils are characteristic of the Upper Texas Gulf Coast. These, coupled with large rainfall events, contribute to wide floodplains and ponding. Rapid, high intensity development has further exacerbated flooding in this coastal region. The Clear Creek Watershed is located in southeast Houston and empties into Galveston Bay. During the past decade, the watershed has been impacted by significant historical coastal storms and rainfall events such as Tropical Storm Allison (2001), Hurricane Ike (2008), and the April 2009 Event. In this study, we employ a calibrated, distributed hydrologic model and pre- and LID-development models to analyze how development characteristics have contributed to costly flooding in coastal watersheds. In 2012, Brody et al. used FEMA floodclaims collected over the 11-year period between 1999 and 2009 to examine the pattern of flood loss across the Clear Creek watershed. The results showed that the 100-year floodplain did not adequately represent overall or event-specific loss. Using a spatial cluster analysis, the Turkey Creek sub-area of the Clear Creek watershed was pin-pointed as an area of statistically significant flood loss, an area where there were a considerable number of high-value flood claims. This area is characterized by high-density, poorly constructed development and frequent flooding. In parallel with Brody's study of flood-risk indicators, our study aims to examine the behavior of the flood-wave in the coastal watershed and how it is affected by different development patterns. A distributed hydrologic VfloTM model was built for Turkey Creek using 2008 CCAP land cover data and calibrated using NEXRAD radar rainfall for the Hurricane Ike (2008) and April 2009 events. Once the model was calibrated, both pre- and LID-development models were built using historical land cover data. These models were used to identify how development patterns have influence the flood hydrograph. Early results indicate that the construction of impervious surfaces has greatly increased the flood peak and shortened the time to peak of the flood wave. The study will go further to identify the measures that may be taken to reduce flooding in the Clear Creek Watershed and attempt to extrapolate the best management practices for low impact development in coastal watersheds.

Sebastian, A.; Bedient, P.

2012-12-01

189

Performance of high-resolution X-band weather radar networks - the PATTERN example  

NASA Astrophysics Data System (ADS)

This publication intends to proof that a network of low-cost local area weather radars (LAWR) is a reliable and scientifically valuable complement to nationwide radar networks. A network of four LAWRs has been installed in northern Germany within the framework of the project Precipitation and Attenuation Estimates from a High-Resolution Weather Radar Network (PATTERN) observing precipitation with temporal resolution of 30 s, azimuthal resolution of 1° and spatial resolution of 60 m. The network covers an area of 60 km × 80 km. In this paper algorithms used to obtain undisturbed precipitation fields from raw reflectivity data are described and their performance is analysed. In order to correct for background noise in reflectivity measurements operationally, noise level estimates from the measured reflectivity field is combined with noise levels from the last 10 time steps. For detection of non-meteorological echoes two different kinds of clutter filters are applied: single radar algorithms and network based algorithms that take advantage of the unique features of high temporal and spatial resolution of the network. Overall the network based clutter filter works best with a detection rate of up to 70%, followed by the classic TDBZ filter using the texture of the logarithmic reflectivity field. A comparison of a reflectivity field from the PATTERN network with the product from a C-band radar operated by the German Meteorological Service indicates high spatial accordance of both systems in geographical position of the rain event as well as reflectivity maxima. A longterm study derives good accordance of X-band radar of the network with C-band radar. But especially at the border of precipitation events the standard deviation within a range gate of the C-band radar with range resolution of 1 km is up to 3 dBZ. Therefore, a network of high-resolution low-cost LAWRs can give valuable information on the small scale structure of rain events in areas of special interest, e.g. urban regions, in addition the nationwide radar networks.

Lengfeld, K.; Clemens, M.; Münster, H.; Ament, F.

2014-08-01

190

Ground-based weather radar remote sensing of volcanic ash explosive eruptions  

NASA Astrophysics Data System (ADS)

The explosive eruptions of active volcanoes with a consequent formation of ash clouds represent a severe threat in several regions of the urbanized world. During a Plinian or a sub-Plinian eruption the injection of large amounts of fine and coarse rock fragments and corrosive gases into the troposphere and lower stratosphere is usually followed by a long lasting ashfall which can cause a variety of damages. Volcanic ash clouds are an increasing hazard to aviation safety because of growing air traffic volumes that use more efficient and susceptible jet engines. Real-time and areal monitoring of a volcano eruption, in terms of its intensity and dynamics, is not always possible by conventional visual inspections, especially during worse visibility periods which are quite common during eruption activity. Remote sensing techniques both from ground and from space represent unique tools to be exploited. In this respect, microwave weather radars can gather three-dimensional information of atmospheric scattering volumes up several hundreds of kilometers, in all weather conditions, at a fairly high spatial resolution (less than a kilometer) and with a repetition cycle of few minutes. Ground-based radar systems represent one of the best methods for determining the height and volume of volcanic eruption clouds. Single-polarization Doppler radars can measure horizontally-polarized power echo and Doppler shift from which ash content and radial velocity can be, in principle, extracted. In spite of these potentials, there are still several open issues about microwave weather radar capabilities to detect and quantitatively retrieve ash cloud parameters. A major issue is related to the aggregation of volcanic ash particles within the eruption column of explosive eruptions which has been observed at many volcanoes. It influences the residence time of ash in the atmosphere and the radiative properties of the "umbrella" cloud. Numerical experiments are helpful to explore processes occurring in the eruption column. In this study we use the plume model ATHAM (Active Tracer High Resolution Atmospheric Model) to investigate, in both time and space, processes leading to particle aggregation in the eruption column. In this work a set of numerical simulations of radar reflectivity is performed with the ATHAM model, under the same experimental conditions except for the initial size distribution, i.e. varying the radii of average mass of the two particle dimension modes. A sensitivity analysis is carried out to evaluate the possible impact of aggregate particles on microwave radar reflectivity. It is shown how dimension, composition, temperature and mass concentration are the main characteristics of eruptive cloud particles that contribute to determine different radar reflectivity responses. In order to evaluate Rayleigh scattering approximation accuracy, the ATHAM simulations of radar reflectivity are used to compare in a detailed way the Mie and Rayleigh scattering regimes at S-, C- and X-band. The relationship between radar reflectivity factor and ash concentration has been statistically derived for the various particle classes by applying a new radar reflectivity microphysical model, which was developed starting from results of numerical experiments performed with plume model ATHAM. The ash retrieval physical-statistical algorithm is based on the backscattering microphysical model of volcanic cloud particles, used within a Bayesian classification and optimal regression algorithm. In order to illustrate the potential of this microwave active remote sensing technique, the case study of the eruption of Augustine volcano in Alaska in January 2006 is described. This event was the first time that a significant volcanic eruption was observed within the nominal range of a WSR-88D. The radar data, in conjunction with pilot reports, proved to be crucial in analyzing the height and movement of volcanic ash clouds during and immediately following each eruptive event. This data greatly aided National Weather Service meteorologists in the issuance of

Marzano, F. S.; Marchiotto, S.; Barbieri, S.; Giuliani, G.; Textor, C.; Schneider, D. J.

2009-04-01

191

Use Of Radar-Rainfall Data for the Southwest Coastal Louisiana Feasibility Study: Regional Scale Hydrologic and Salinity Modeling and Management Scenario Analysis for Chenier Plain  

NASA Astrophysics Data System (ADS)

The Chenier Plain, in Southwest Louisiana, extends from Vermilion Bay to Sabine Lake in southeast Texas. It has great economic, industrial, recreational, and ecological value. Over the years, human activities such as dredging ship channels and access canals, building roads, levees, and hydraulic structures have altered the hydrology of the Chenier Plain. These alterations have affected the fragile equilibrium of the marsh ecology. If no action is taken to restore the Chenier Plain, land loss through conversion of marsh to open water would continue. The Southwest Coastal Louisiana Feasibility Study aims at evaluating proposed protection and restoration measures and ultimately submitting a comprehensive plan to protect and preserve the Chenier Plain at the regional scale. The proposed alternatives include marsh creation, terracing, shoreline protection, and freshwater introduction and salinity control structures. A regional scale hydrodynamic and salinity transport model was developed to screen and assess the proposed restoration measures. A critical component of this modeling effort is local rainfall. The strong spatial variability and limited availability of ground-level precipitation measurements limited our ability to capture local rainfall. Thus, a radar-based rainfall product was used as a viable alternative to the rain gauges. These estimates are based on the National Weather Service from the Multi-Sensor Precipitation Estimator (MPE) algorithm. Since the model was used to perform long-term (yearly) simulations, the 4x4 km2 MPE estimates were represented as daily accumulations. The use of the radar-rainfall product data improved the model performance especially on our ability to capture the spatial and temporal variations of salinity. Overall, the model is improving our understanding of the circulation patterns and salinity regimes of the region. The circulation model used here is the MIKE FLOOD software (Danish Hydraulic Institute, DHI 2008) which dynamically integrates a two-dimensional grid (MIKE 21) and a one-dimensional channel flow simulation tool (MIKE 11). The model was successfully calibrated and validated using water level and salinity data collected at monitoring stations in the channels and throughout the marsh areas. The model prediction agreed favorably with the field measurements at the daily and monthly average scale. Uncertainties in the bathymetric data, open water boundary, as well as the operation schedules of water control structures prevented the model from being validated at a higher temporal frequency. Ongoing monitoring efforts are being used to minimize these uncertainties.

Meselhe, E. A.; Michot, B.; Chen, C.; Habib, E. H.

2011-12-01

192

Evaluation of X-band polarimetric radar estimation of rainfall and rain drop size distribution parameters in West Africa  

NASA Astrophysics Data System (ADS)

As part of the African Monsoon Multidisciplinary Analysis (AMMA) field campaign an X-band dual-polarization Doppler radar was deployed in Benin, West-Africa, in 2006 and 2007, together with a reinforced rain gauge network and several optical disdrometers. Based on this data set, a comparative study of several rainfall estimators that use X-band polarimetric radar data is presented. In tropical convective systems as encountered in Benin, microwave attenuation by rain is significant and quantitative precipitation estimation (QPE) at X-band is a challenge. Here, several algorithms based on the combined use of reflectivity, differential reflectivity and differential phase shift are evaluated against rain gauges and disdrometers. Four rainfall estimators were tested on twelve rainy events: the use of attenuation corrected reflectivity only (estimator R(ZH)), the use of the specific phase shift only R(KDP), the combination of specific phase shift and differential reflectivity R(KDP,ZDR) and an estimator that uses three radar parameters R(ZH,ZDR,KDP). The coefficients of the power law relationships between rain rate and radar variables were adjusted either based on disdrometer data and simulation, or on radar-gauges observations. The three polarimetric based algorithms with coefficients predetermined on observations outperform the R(ZH) estimator for rain rates above 10 mm/h which explain most of the rainfall in the studied region. For the highest rain rates (above 30 mm/h) R(KDP) shows even better scores, and given its performances and its simplicity of implementation, is recommended. The radar based retrieval of two parameters of the rain drop size distribution, the normalized intercept parameter NW and the volumetric median diameter Dm was evaluated on four rainy days thanks to disdrometers. The frequency distributions of the two parameters retrieved by the radar are very close to those observed with the disdrometer. NW retrieval based on a combination of ZH-KDP-ZDR works well whatever the a priori assumption made on the drop shapes. Dm retrieval based on ZDR alone performs well, but if satisfactory ZDR measurements are not available, the combination ZH-KDP provides satisfactory results for both Dm and NW if an appropriate a priori assumption on drop shape is made.

Koffi, A. K.; Gosset, M.; Zahiri, E.-P.; Ochou, A. D.; Kacou, M.; Cazenave, F.; Assamoi, P.

2014-06-01

193

The effect of flow and orography on the spatial distribution of the very short-term predictability of rainfall from composite radar images  

NASA Astrophysics Data System (ADS)

The spatial distribution and scale dependence of the very short-term predictability of precipitation by Lagrangian persistence of composite radar images is studied under different flow regimes in connection with the presence of orographic features. Data from the weather radar composite of eastern Victoria, Australia, a 500 × 500 km2 domain at 10 min temporal and 2 × 2 km2 spatial resolutions, covering the period from February 2011 to October 2012, were used for the analyses. The scale dependence of the predictability of precipitation is considered by decomposing the radar rainfall field into an eight-level multiplicative cascade using a fast Fourier transform. The rate of temporal development of precipitation in Lagrangian coordinates is estimated at each level of the cascade under different flow regimes, which are stratified by applying a k-means clustering algorithm on the diagnosed velocity fields. The predictability of precipitation is measured by its lifetime, which is derived by integrating the Lagrangian auto-correlation function. The lifetimes were found to depend on the scale of the feature as a power law, which is known as dynamic scaling, and to vary as a function of flow regime. The lifetimes also exhibit significant spatial variability and are approximately a factor of 2 longer on the upwind compared with the downwind slopes of terrain features. The scaling exponent of the spatial power spectrum also shows interesting geographical differences. These findings provide opportunities to perform spatially inhomogeneous stochastic simulations of space-time precipitation to account for the presence of orography, which may be integrated into design storm simulations and stochastic precipitation nowcasting systems.

Foresti, L.; Seed, A.

2014-11-01

194

Interpolation of daily rainfall networks using simulated radar fields for realistic hydrological modelling of spatial rain field ensembles  

NASA Astrophysics Data System (ADS)

Given a record of daily rainfall over a network of gauges, this paper describes a method of linking the Gauge Wetness Ratio (GWR) on a given day to the joint distribution of the parameters of the anisotropic correlogram defining the spatial statistics of simulated radar-rainfall fields. We generate a large number of Gaussian random fields by sampling from the correlogram parameters conditioned on the GWR and then conditionally merge these fields to the gauge observations transformed into the Gaussian domain. Availability of such a tool allows better spatially distributed hydrological modelling, because good quality ensemble spatial information is required for such work, as it yields uncertainty of the fields so generated. To achieve these ends, correlograms of many Gaussianised daily accumulations of radar images were developed using the Fast Fourier Transform to generate their sample power spectra. Empirical correlograms were fitted using a 2D exponential distribution to yield the 3 key parameters of the correlogram: the range, the anisotropy ratio and the direction of the major axis. It was found that the range follows a Gamma distribution while the anisotropy parameters follow a Loglogistic one; a t5 copula was adequate to capture the bivariate negative dependence structure between the range and ratio. The Radar Wetted Area Ratio (RWAR) drives the parameters of the correlogram, and its link with GWR is modelled by a transition probability matrix. We take each of the generated Gaussian random fields and conditionally merge it with Gaussianised rainfall values at the gauge locations using Ordinary Kriging. The method produces realistic simulated radar images, on a grid chosen to suit the data, which match the gauge observations at their locations. Ensemble simulations of 1000 samples were used to derive the median and the inter-quartile range of the fields; these were found to narrow near the control gauge locations, as expected, emphasising the value of high density gauge networks. Ongoing research is looking towards integration of the presented methodology with a stochastic daily rainfall generator for useful spatial rainfall simulation over catchments with gauged records.

Gyasi-Agyei, Yeboah; Pegram, Geoffrey

2014-11-01

195

Offshore next generation weather radar (NEXRAD) test and evaluation master plan (TEMP)  

NASA Astrophysics Data System (ADS)

This document provides the test philosophy and approach for the Offshore Next Generation Weather Radar (NEXRAD) Test and Evaluation Master Plan (TEMP). The NEXRAD differs from the typical Federal Aviation Administration (FAA) weather radar acquisition in that it is jointly funded by the Department of Defense (DOD), the Department of Commerce (DOC), and the Department of Transportation (DOT). These three agencies chartered the Joint System Program Office (JSPO) to manage the NEXRAD development and subsequent test programs. JSPO has deployed 70 single-channel radar systems across the continental United States (CONUS). The FAA is deploying NEXRAD systems at non-CONUS (offshore) locations such as Alaska, Hawaii, and the Caribbean. The FAA Offshore NEXRAD will have a redundant configuration and a Remote Monitoring Subsystem (EMS). A total of 14 Offshore NEXRAD's will be procured under this acquisition: 3 in the Caribbean, 4 in Hawaii, and 7 in Alaska. Funding constraints will limit the acquisition to seven NEXRAD's in the 1994-1995 timeframe.

Martinez, Radame; Cranston, Robert; Porcello, John

1995-01-01

196

Prediction of a Flash Flood in Complex Terrain. Part II: A Comparison of Flood Discharge Simulations Using Rainfall Input from Radar, a Dynamic Model, and an Automated Algorithmic System.  

NASA Astrophysics Data System (ADS)

Three techniques were employed for the estimation and prediction of precipitation from a thunderstorm that produced a flash flood in the Buffalo Creek watershed located in the mountainous Front Range near Denver, Colorado, on 12 July 1996. The techniques included 1) quantitative precipitation estimation using the National Weather Service's Weather Surveillance Radar-1988 Doppler and the National Center for Atmospheric Research's S-band, dual-polarization radars, 2) quantitative precipitation forecasting utilizing a dynamic model, and 3) quantitative precipitation forecasting using an automated algorithmic system for tracking thunderstorms. Rainfall data provided by these various techniques at short timescales (6 min) and at fine spatial resolutions (150 m to 2 km) served as input to a distributed-parameter hydrologic model for analysis of the flash flood. The quantitative precipitation estimates from the weather radar demonstrated their ability to aid in simulating a watershed's response to precipitation forcing from small-scale, convective weather in complex terrain. That is, with the radar-based quantitative precipitation estimates employed as input, the simulated peak discharge was similar to that estimated. The dynamic model showed the most promise in providing a significant forecast lead time for this flash-flood event. The algorithmic system did not show as much skill in comparison with the dynamic model in providing precipitation forcing to the hydrologic model. The discharge forecasts based on the dynamic-model and algorithmic-system inputs point to the need to improve the ability to forecast convective storms, especially if models such as these eventually are to be used in operational flood forecasting.

Yates, David N.; Warner, Thomas T.; Leavesley, George H.

2000-06-01

197

An automatic identification of clutter and anomalous propagation in polarization-diversity weather radar data using neural networks  

Microsoft Academic Search

Radar polarization measurements have mostly been used to improve rainfall estimation and hydrometeor characterization. The authors extend the use of such measurements to the problem of ground clutter recognition, including the case when this problem is associated with anomalous propagation of the electromagnetic wave. They present a methodology used for recognizing both clutter and meteorological targets. The methodology is based

Reinaldo B. da Silveira; Anthony Roy Holt

2001-01-01

198

The pulse-pair algorithm as a robust estimator of turbulent weather spectral parameters using airborne pulse Doppler radar  

NASA Technical Reports Server (NTRS)

The pulse pair method for spectrum parameter estimation is commonly used in pulse Doppler weather radar signal processing since it is economical to implement and can be shown to be a maximum likelihood estimator. With the use of airborne weather radar for windshear detection, the turbulent weather and strong ground clutter return spectrum differs from that assumed in its derivation, so the performance robustness of the pulse pair technique must be understood. Here, the effect of radar system pulse to pulse phase jitter and signal spectrum skew on the pulse pair algorithm performance is discussed. Phase jitter effect may be significant when the weather return signal to clutter ratio is very low and clutter rejection filtering is attempted. The analysis can be used to develop design specifications for airborne radar system phase stability. It is also shown that the weather return spectrum skew can cause a significant bias in the pulse pair mean windspeed estimates, and that the poly pulse pair algorithm can reduce this bias. It is suggested that use of a spectrum mode estimator may be more appropriate in characterizing the windspeed within a radar range resolution cell for detection of hazardous windspeed gradients.

Baxa, Ernest G., Jr.; Lee, Jonggil

1991-01-01

199

AN UPDATE ON MULTICHANNEL RECEIVER DEVELOPMENT FOR THE REALIZATION MULTI-MISSION CAPABILITIES AT THE NATIONAL WEATHER RADAR TESTBED  

Microsoft Academic Search

This paper describes the status of a new project that will digitize radar signals coming from eight channels on the phased array antenna at the National Weather Radar Testbed (NWRT) in Norman, Oklahoma. At the current time, a single-channel digital receiver is operational to mimic the current WSR-88D capability. The multi-channel digital data will foster a new gener- ation of

M. Yeary; J. Crain; A. Zahrai; T.-Y. Yu; R. Palmer; G. Zhang; Y. Zhang; R. Doviak; P. Chilson; M. Xue; Q. Xu

200

INTRODUCTION TO MULTICHANNEL RECEIVER DEVELOPMENT FOR THE REALIZATION MULTI-MISSION CAPABILITIES AT THE NATIONAL WEATHER RADAR TESTBED  

Microsoft Academic Search

This paper describes the beginning states of a new project that will digitize radar signals coming from eight channels on the phased array antenna at the National Weather Radar Testbed (NWRT) in Norman, Oklahoma. At the current time, a single-channel digital receiver is operational to mimic the current WSR-88D capability. The multi-channel digital data will foster a new gener- ation

M. Yeary; R. Palmer; M. Xue; T.-Y. Yu; G. Zhang; A. Zahrai; J. Crain; Y. Zhang; R. Doviak; Q. Xu; P. Chilson

201

Super-resolution technologies for all-weather sense and avoidance (SAA) radar  

NASA Astrophysics Data System (ADS)

The sense and avoidance (SAA) and due-regard radar systems have strict requirements on size, weight and power (SWaP) and target localization accuracies. Also, the multi-mission capabilities with both weather and hard targets are critical to the survivability of unmanned aerial vehicles (UAV) in the next generation national airspace. The aperture limitations of the aircraft sensor installation, however, have prevented large antennas/arrays to be used. The tradeoffs among frequencies, resolutions and detection range/accuracies have not been fully addressed. Innovative concepts of overcoming the aperture limitation by using a special type of super-resolution technology are introduced. The first technique is based on a combination of thinned antenna array, an extension to the traditional Multiple Signal Classification (MUSIC) technique, and applying a two-dimensional sidelobe mitigation technique. To overcome the degradation of MUSIC-type of approach due to coherent radar signals, a special waveform optimization procedure is used. The techniques for mitigating artifacts due to "thinned" array are also introduced. Simulated results of super-resolution techniques are discussed and evaluated, and the capability of separating multiple targets within aperture-constrained beamwidth is demonstrated. Moreover, the potential capabilities of autonomous weather hazard avoidance are also analyzed.

Zhang, Yan Rockee; Li, Zhengzheng; Wang, Shang; Pan, Yu; Suarez, Hernan

2011-06-01

202

Spatial patterns in thunderstorm rainfall events and their coupling with watershed hydrological response 1907  

Technology Transfer Automated Retrieval System (TEKTRAN)

Weather radar systems provide detailed information on spatial rainfall patterns known to play a significant role in runoff generation processes. In the current study, we present an innovative approach to exploit spatial rainfall information of air mass thunderstorms and link it with a watershed hydr...

203

Characteristics of velocity ambiguity for CINRAD-SA Doppler weather radars  

NASA Astrophysics Data System (ADS)

The velocity ambiguity in Doppler weather radars has inhibited the application of wind field data for long time. One effective solution is software-based velocity dealiasing algorithm. In this paper, in order to better design, optimize and validate velocity dealiasing algorithms for CINRAD-SA, data from operational radars were used to statistically characterize velocity ambiguity. The analyzed characteristic parameters included occurrence rate, and inter-station, inter-type, temporal, and spatial distributions. The results show that 14.9% of cloud-rain files and 0.3% of clear-air files from CINRADSA radars are ambiguous. It is also found that echoes of weak convections have the highest occurrence rate of velocity ambiguity than any other cloud types, and the probability of ambiguity is higher in winter than in summer. A detailed inspection of the occurrence of ambiguity in various cases indicates that ambiguous points usually occur in areas with an elevation angle of 6.0°, an azimuth of 70° or 250°, radial distance of 50-60 km, and height of 5-6 km, and that 99.4% of ambiguous points are in the 1st-folding interval. Suggestions for performing dealiasing at different locations and different time points are provided.

Chu, Zhigang; Yin, Yan; Gu, Songshan

2014-02-01

204

A grid-based distributed flood forecasting model for use with weather radar data: Part 1. Formulation  

NASA Astrophysics Data System (ADS)

A practical methodology for distributed rainfall-runoff modelling using grid square weather radar data is developed for use in real-time flood forecasting. The model, called the Grid Model, is configured so as to share the same grid as used by the weather radar, thereby exploiting the distributed rainfall estimates to the full. Each grid square in the catchment is conceptualised as a storage which receives water as precipitation and generates water by overflow and drainage. This water is routed across the catchment using isochrone pathways. These are derived from a digital terrain model assuming two fixed velocities of travel for land and river pathways which are regarded as model parameters to be optimised. Translation of water between isochrones is achieved using a discrete kinematic routing procedure, parameterised through a single dimensionless wave speed parameter, which advects the water and incorporates diffusion effects through the discrete space-time formulation. The basic model routes overflow and drainage separately through a parallel system of kinematic routing reaches, characterised by different wave speeds but using the same isochrone-based space discretisation; these represent fast and slow pathways to the basin outlet, respectively. A variant allows the slow pathway to have separate isochrones calculated using Darcy velocities controlled by the hydraulic gradient as estimated by the local gradient of the terrain. Runoff production within a grid square is controlled by its absorption capacity which is parameterised through a simple linkage function to the mean gradient in the square, as calculated from digital terrain data. This allows absorption capacity to be specified differently for every grid square in the catchment through the use of only two regional parameters and a DTM measurement of mean gradient for each square. An extension of this basic idea to consider the distribution of gradient within the square leads analytically to a Pareto distribution of absorption capacity, given a power distribution of gradient within the square. The probability-distributed model theory (Moore, 1985) can then be used directly to obtain the integrated runoff production for the square for routing to the catchment outlet. justification for the simple linkage function is in part sought through consideration of variants on the basic model where (i) runoff production is based on a topographic index control on saturation and (ii) absorption capacity is related to the Integrated Air Capacity of the soil, as obtained from soil survey. An impervious area fraction is also introduced based on the use of Landsat classified urban areas. The Grid Model and its variants are assessed in Part 2 (Bell and Moore, 1998), first as simulation models and then as forecasting models, following the development of updating procedures to accommodate recent observations of flow so as to improve forecast performance in a real-time context.

Bell, V. A.; Moore, R. J.

205

Tropical Rainfall Measuring Mission  

NASA Technical Reports Server (NTRS)

Tropical rainfall affects the lives and economics of a majority of the Earth's population. Tropical rain systems, such as hurricanes, typhoons, and monsoons, are crucial to sustaining the livelihoods of those living in the tropics. Excess rainfall can cause floods and great property and crop damage, whereas too little rainfall can cause drought and crop failure. The latent heat release during the process of precipitation is a major source of energy that drives the atmospheric circulation. This latent heat can intensify weather systems, affecting weather thousands of kilometers away, thus making tropical rainfall an important indicator of atmospheric circulation and short-term climate change. Tropical forests and the underlying soils are major sources of many of the atmosphere's trace constituents. Together, the forests and the atmosphere act as a water-energy regulating system. Most of the rainfall is returned to the atmosphere through evaporation and transpiration, and the atmospheric trace constituents take part in the recycling process. Hence, the hydrological cycle provides a direct link between tropical rainfall and the global cycles of carbon, nitrogen, and sulfur, all important trace materials for the Earth's system. Because rainfall is such an important component in the interactions between the ocean, atmosphere, land, and the biosphere, accurate measurements of rainfall are crucial to understanding the workings of the Earth-atmosphere system. The large spatial and temporal variability of rainfall systems, however, poses a major challenge to estimating global rainfall. So far, there has been a lack of rain gauge networks, especially over the oceans, which points to satellite measurement as the only means by which global observation of rainfall can be made. The Tropical Rainfall Measuring Mission (TRMM), jointly sponsored by the National Aeronautics and Space Administration (NASA) of the United States and the National Space Development Agency (NASDA) of Japan, provides visible, infrared, and microwave observations of tropical and subtropical rain systems.The satellite observations are complemented by ground radar and rain gauge measurements to validate satellite rain estimation techniques. Goddard Space Flight Center's involvement includes the observatory, four instruments, integration and testing of the observatory, data processing and distribution, and satellite operations. TRMM has a design lifetime of three years. Data generated from TRMM and archived at the GDAAC are useful not only for hydrologists, atmospheric scientists, and climatologists, but also for the health community studying infectious diseases, the ocean research community, and the agricultural community.

1999-01-01

206

Visualization and Nowcasting for Aviation using online verified ensemble weather radar extrapolation.  

NASA Astrophysics Data System (ADS)

Nowcasting of precipitation events, especially thunderstorm events or winter storms, has high impact on flight safety and efficiency for air traffic management. Future strategic planning by air traffic control will result in circumnavigation of potential hazardous areas, reduction of load around efficiency hot spots by offering alternatives, increase of handling capacity, anticipation of avoidance manoeuvres and increase of awareness before dangerous areas are entered by aircraft. To facilitate this rapid update forecasts of location, intensity, size, movement and development of local storms are necessary. Weather radar data deliver precipitation analysis of high temporal and spatial resolution close to real time by using clever scanning strategies. These data are the basis to generate rapid update forecasts in a time frame up to 2 hours and more for applications in aviation meteorological service provision, such as optimizing safety and economic impact in the context of sub-scale phenomena. On the basis of tracking radar echoes by correlation the movement vectors of successive weather radar images are calculated. For every new successive radar image a set of ensemble precipitation fields is collected by using different parameter sets like pattern match size, different time steps, filter methods and an implementation of history of tracking vectors and plausibility checks. This method considers the uncertainty in rain field displacement and different scales in time and space. By validating manually a set of case studies, the best verification method and skill score is defined and implemented into an online-verification scheme which calculates the optimized forecasts for different time steps and different areas by using different extrapolation ensemble members. To get information about the quality and reliability of the extrapolation process additional information of data quality (e.g. shielding in Alpine areas) is extrapolated and combined with an extrapolation-quality-index. Subsequently the probability and quality information of the forecast ensemble is available and flexible blending to numerical prediction model for each subarea is possible. Simultaneously with automatic processing the ensemble nowcasting product is visualized in a new innovative way which combines the intensity, probability and quality information for different subareas in one forecast image.

Kaltenboeck, Rudolf; Kerschbaum, Markus; Hennermann, Karin; Mayer, Stefan

2013-04-01

207

Hands-On Learning Modules for Interdisciplinary Environments: An Example with a Focus on Weather Radar Applications  

ERIC Educational Resources Information Center

Learning modules provide an effective means of encouraging cognition and active learning. This paper discusses several such modules that have been developed within a course on weather radar applications intended for students from Electrical Engineering and Meteorology. The modules were designed both to promote interdisciplinary exchange between…

Chilson, P. B.; Yeary, M. B.

2012-01-01

208

An optimal design of a cylindrical polarimetric phased array radar for weather sensing  

NASA Astrophysics Data System (ADS)

An optimal design of a cylindrical polarimetric phased array radar (CPPAR) for weather sensing is presented. A recently introduced invasive weed optimization (IWO) technique is employed to obtain the desired radiation pattern of the CPPAR. Instead of optimizing each element excitation in a large array (with expensive calculation costs), the modified Bernstein polynomial distribution, defined by seven parameters, is used to optimize the current distribution for the CPPAR. The simulation results show that the desired sidelobe levels (SLLs) and beam width are achieved in a computationally effective manner. Furthermore, the imaged feed arrangement is used to suppress the cross-polarization level. Both co-polar and cross-polar radiation patterns for broadside and off-broadside directions are presented to show the performance of the optimized CPPAR.

Karimkashi, Shaya; Zhang, Guifu

2012-04-01

209

Regional cloud characteristics over the tropical northwestern Pacific as revealed by Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar and TRMM Microwave Imager  

Microsoft Academic Search

The present study investigates regional cloud characteristics over the tropical northwestern Pacific using Tropical Rainfall Measuring Mission (TRMM) data sets such as rain rate, radar reflectivity, and passive microwave radiometer polarization corrected temperature (PCT). In particular, the tropical northwestern Pacific is divided into two surface rain maxima regions: the South China Sea (SCS) and the Philippine Sea (PS). The TRMM

Myung-Sook Park; Yong-Sang Choi; Chang-Hoi Ho; Chung-Hsiung Sui; Seon Ki Park; Myoung-Hwan Ahn

2007-01-01

210

Assessment of bird response to the Migratory Bird Habitat Initiative using weather-surveillance radar  

USGS Publications Warehouse

In response to the Deepwater Horizon oil spill in spring 2010, the Natural Resources Conservation Service implemented the Migratory Bird Habitat Initiative (MBHI) to provide temporary wetland habitat for migrating and wintering waterfowl, shorebirds, and other birds along the northern Gulf of Mexico via managed flooding of agricultural lands. We used weather-surveillance radar to conduct broad regional assessments of bird response to MBHI activities within the Mississippi Alluvial Valley and the West Gulf Coastal Plain. Across both regions, birds responded positively to MBHI management by exhibiting greater relative bird densities within sites relative to pre-management conditions in prior years and relative to surrounding non-flooded agricultural lands. Bird density at MBHI sites was generally greatest during winter for both regions. Unusually high flooding in the years prior to implementation of the MBHI confounded detection of overall changes in remotely sensed soil wetness across sites. The magnitude of bird response at MBHI sites compared to prior years and to non-flooded agricultural lands was generally related to the surrounding landscape context: proximity to areas of high bird density, amount of forested wetlands, emergent marsh, non-flooded agriculture, or permanent open water. However, these relationships varied in strength and direction between regions and seasons, a finding which we attribute to differences in seasonal bird composition and broad regional differences in landscape configuration and composition. We detected greater increases in relative bird use at sites in closer proximity to areas of high bird density during winter in both regions. Additionally, bird density was greater during winter at sites with more emergent marsh in the surrounding landscape. Thus, bird use of managed wetlands could be maximized by enrolling lands located near areas of known bird concentration and within a mosaic of existing wetlands. Weather-radar observations provide strong evidence that MBHI sites located inland from coastal wetlands impacted by the oil spill provided wetland habitat used by a variety of birds.

Sieges, Mason L.; Smolinsky, Jaclyn A.; Baldwin, Michael J.; Barrow, Wylie C.; Randall, Lori A.; Buler, Jeffrey J.

2014-01-01

211

Using the new dual-polarimetric capability of WSR-88D to eliminate anomalous propagation and wind turbine effects in radar-rainfall  

NASA Astrophysics Data System (ADS)

This study addresses the effect that the interaction between anomalous radar beam propagation (AP) and wind turbines that are located far from the radar has on radar-rainfall estimates. The interference of wind turbines in radar observations may lead to significant errors in rainfall estimates since wind turbines are often clustered to form wind farms. In this study, we propose a novel approach - based on the polarimetric capability recently added to the WSR-88D NEXRAD radars - that identifies and eliminates wind turbine clutter along with common ground clutter AP effects. Our primary objective is to devise a physically meaningful and fully automated dual-polarimetric method that effectively handles clutter features, which are hard to detect using single-channel reflectivity data alone. To address this issue, we explore the feasibility of using polarimetric variables such as differential reflectivity (ZDR), copolar correlation (RHO), and differential phase (PHIDP). Accordingly, we developed three new approaches using polarimetric variables, which are combined with the AP detection algorithm that uses a three-dimensional structure of reflectivity. We evaluate the new algorithms in terms of both eliminating non-meteorological radar returns and preserving returns from actual rain. The proposed algorithm, which uses RHO conditioned on horizontal reflectivity values while also accounting for the variation of ZDR or PHIDP, shows good performance for the presented cases.

Seo, Bong-Chul; Krajewski, Witold F.; Mishra, Kumar Vijay

2015-02-01

212

NEXRAD Single and Dual Polarization Radar-Rainfall Product Comparison for the NASA Iowa Flood Studies (IFloodS)  

NASA Astrophysics Data System (ADS)

During the months of April to June 2013, NASA conducted a field experiment called Iowa Flood Studies (IFloodS) as part of the Ground Validation (GV) program for the Global Precipitation Measurement (GPM) mission in the central and northeastern Iowa in the United States. The purpose of IFloodS is to enhance the understanding of flood-related precipitation processes in events worldwide. While there are multiple rainfall data sets (satellite, radar, and ground reference data products) available as legacy from IFloodS, the authors focus on the comparison of the NEXRAD single and dual polarization precipitation products to evaluate potential benefits of using dual polarization data for flood-related precipitation events. The Hydro-NEXRAD and CSU (Colorado State University)-HIDRO blended precipitation processing algorithms were used to generate single and dual polarization products, respectively. Data from four NEXRAD radars (Des Moines, IA; Davenport, IA; Minneapolis, MN; and La Crosse, WI) were combined to cover the study area. Uncertainties of both products using dense networks of ground reference (e.g., rain gauge and disdrometer) are characterized. Major differences and similarities based on the observed precipitation cases are also discussed.

Seo, B.; Dolan, B.; Krajewski, W. F.; Rutledge, S. A.; Petersen, W. A.

2013-12-01

213

The design and development of signal-processing algorithms for an airborne x-band Doppler weather radar  

NASA Technical Reports Server (NTRS)

Improved measurements of precipitation will aid our understanding of the role of latent heating on global circulations. Spaceborne meteorological sensors such as the planned precipitation radar and microwave radiometers on the Tropical Rainfall Measurement Mission (TRMM) provide for the first time a comprehensive means of making these global measurements. Pre-TRMM activities include development of precipitation algorithms using existing satellite data, computer simulations, and measurements from limited aircraft campaigns. Since the TRMM radar will be the first spaceborne precipitation radar, there is limited experience with such measurements, and only recently have airborne radars become available that can attempt to address the issue of the limitations of a spaceborne radar. There are many questions regarding how much attenuation occurs in various cloud types and the effect of cloud vertical motions on the estimation of precipitation rates. The EDOP program being developed by NASA GSFC will provide data useful for testing both rain-retrieval algorithms and the importance of vertical motions on the rain measurements. The purpose of this report is to describe the design and development of real-time embedded parallel algorithms used by EDOP to extract reflectivity and Doppler products (velocity, spectrum width, and signal-to-noise ratio) as the first step in the aforementioned goals.

Nicholson, Shaun R.

1994-01-01

214

Measuring Winds And Rainfall From Space-the Radar Wind Sounder (saws)  

Microsoft Academic Search

Measurement of winds aloft throughout the world is of great importance because computerized global weather models use these winds as major inputs. The scarcity of such measurements over many parts of the world led to the development of the laser wind sounder (LAWS) for use on Eos. LAWS depends on the Doppler frequency shift of optical-waveleng th backscatter from atmo­

R. K. Moore; W. Xin

1989-01-01

215

Weathering  

NSDL National Science Digital Library

This course handout covers the processes and effects of weathering. The purpose of this handout is to contrast weathering and erosion, contrast and discuss chemical and mechanical weathering, list the products resulting from the chemical weathering of igneous rocks, and list and discuss the factors that influence the type and rate of rock weathering. Many photographs accompany this summary which depict weathered landscapes. Links are provided to the online Physical Geology resources at Georgia Perimeter College.

Pamela Gore

1995-08-29

216

By Air and Land: Estimating Post-Fire Debris-Flow Susceptibility through High-Resolution Radar Reflectivity and Tipping-Bucket Gage Rainfall  

NASA Astrophysics Data System (ADS)

Wildfires often increase the occurrence of post-fire hazardous flash floods and debris flows from steeplands during intense rainfall. Rainfall intensity-duration thresholds have been used to forecast when this hazard increases rapidly; one threshold for Southern California is 15 mm/hr. However, such thresholds are usually developed with point measurements that only capture a small portion of the landscape. In an attempt to limit potential loss of life, the USGS is collaborating with NOAA on a demonstration early-warning system. To address the lack of spatial rainfall coverage, NOAA deployed a small mobile radar truck (SMART-R) to the Day fire in the western Transverse Range during the 2006-07 winter, and to the Canyon and Corral fires in the Santa Monica Mountains near Malibu during the 2007-08 winter. The SMART-R's C-band Doppler radar can be used to estimate rainfall rates over entire burned areas. On topography susceptible to debris flows within these 3 fires, the USGS installed a dense array of ground-based instruments, including 8 tipping- bucket rain gages in the Day fire, and 3 each in the Canyon and Corral fires. After converting hourly time- step grids of SMART-R reflectivity (150 m node spacing) into precipitation estimates, we compared the gage data to its spatially coincident SMART-R cell.Results from the Day fire indicate that SMART-R derived seasonal and event-based rainfall totals were typically greater than gage totals during the 2006-07 winter of record-low rainfall. Both data sets, however, reflected similar spatial patterns of rainfall intensity. In contrast, for the Malibu fires there is no systematic agreement in spatial pattern or rainfall mismatch; the difference between the two data sets. Of the 9 storms recorded during this 2007-08 winter, SMART-R estimates of rainfall totals exceeded the gage totals for only 3, underestimating totals for the remaining 6. The mismatch magnitudes also exceed that of the previous winter recorded at the Day fire, and, for the largest storm of the season, was 129 mm less than a rain gage total.These discrepancies reduce the reliability of a potential SMART-R-advised warning system, assuming truth from ground-based gages. During the 2007-08 winter near Malibu the rain gages recorded that the 15 mm/hr warning threshold was exceeded during only one storm, and only at one gage in the Corral fire. This event transported large amounts of sediment that resulted in road closures, and it produced at least one "firehose" debris flow generated by runoff from steep, exposed bedrock. In contrast, SMART-R derived rainfall intensities exceeded this threshold at all gage locations for 2 of the 3 storms with overestimated rainfall intensities. It underestimated rainfall intensities for the 6 remaining storms; such underestimates could have led to potential false negatives, which are of concern for preserving human life.It is not yet clear which storms are amenable to the use of SMART-R technology for capturing spatial estimates of rainfall intensity, but results from the Day fire showing topographically forced rainfall patterns support validity of the system. Future work needs to address discrepancies arising from comparing spatially continuous atmospheric radar measurements with terrestrial point measurements. One effort to mitigate some interpretation complexities could include the installation of a disdrometer along with the rain gages, to measure rain drop-size distributions to calibrate in near real-time the relation between measured reflectivity and inferred rainfall.

Hanshaw, M. N.; Schmidt, K. M.; Jorgensen, D. P.; Stock, J. D.

2008-12-01

217

Comparison of Two Methods for Estimating the Sampling-Related Uncertainty of Satellite Rainfall Averages Based on a Large Radar Data Set  

NASA Technical Reports Server (NTRS)

The uncertainty of rainfall estimated from averages of discrete samples collected by a satellite is assessed using a multi-year radar data set covering a large portion of the United States. The sampling-related uncertainty of rainfall estimates is evaluated for all combinations of 100 km, 200 km, and 500 km space domains, 1 day, 5 day, and 30 day rainfall accumulations, and regular sampling time intervals of 1 h, 3 h, 6 h, 8 h, and 12 h. These extensive analyses are combined to characterize the sampling uncertainty as a function of space and time domain, sampling frequency, and rainfall characteristics by means of a simple scaling law. Moreover, it is shown that both parametric and non-parametric statistical techniques of estimating the sampling uncertainty produce comparable results. Sampling uncertainty estimates, however, do depend on the choice of technique for obtaining them. They can also vary considerably from case to case, reflecting the great variability of natural rainfall, and should therefore be expressed in probabilistic terms. Rainfall calibration errors are shown to affect comparison of results obtained by studies based on data from different climate regions and/or observation platforms.

Lau, William K. M. (Technical Monitor); Bell, Thomas L.; Steiner, Matthias; Zhang, Yu; Wood, Eric F.

2002-01-01

218

A mobile X-POL weather radar for hydrometeorological applications in the metropolitan area of São Paulo, Brazil  

NASA Astrophysics Data System (ADS)

This paper presents the first mobile X-band dual-polarization Doppler weather radar termed MXPOL operated by the Laboratory of Hydrometeorology (LABHIDRO) of the University of São Paulo, São Paulo, Brazil. It is used in graduate and under graduate courses, real-time monitoring and nowcasting of severe weather in the Metropolitan Area of São Paulo (MASP). It is one of the first of its kind to be used operationally to provide real-time high spatial resolution polarimetric data. MXPOL is an important component of a Hydrometeorological Forecast System (Pereira Filho et al., 2005) for MASP. This manuscript presents some instances of MXPOL polarimetric measurements of weather systems and their respective microphysical, dynamical and boundary layer features that can improve nowcasting.

Pereira Filho, A. J.

2012-11-01

219

A mobile X-POL weather radar for hydrometeorological applications in the metropolitan area of São Paulo, Brazil  

NASA Astrophysics Data System (ADS)

This paper presents the first mobile X-band dual-polarization Doppler weather radar termed MXPOL operated by the Laboratory of Hydrometeorology (LABHIDRO) of the University of São Paulo, São Paulo, Brazil. It is used in graduate and under graduate courses, real time monitoring and nowcasting of severe weather in the Metropolitan Area of São Paulo (MASP). It is one of the first of its kind to be used operationally to provide real time high spatial resolution polarimetric data. MXPOL is an important component of a Hydrometeorological Forecast System (Pereira Filho et al., 2005) for MASP. This manuscript presents some instances of MXPOL polarimetric measurements of weather systems and their respective microphysical, dynamical and boundary layer features that can improve nowcasting.

Pereira Filho, A. J.

2012-05-01

220

Dual polarisation C-band weather radar imagery of the 6 August 2012 Te Maari Eruption, Mount Tongariro, New Zealand  

NASA Astrophysics Data System (ADS)

The 6 August 2012 eruption of Mt. Tongariro from Upper Te Maari Crater in the central North Island of New Zealand was the first volcanic eruption observed by an operational weather radar in New Zealand, and is believed to be one of only a small number of eruptions observed by a dual-polarisation radar worldwide. The eruption was also observed by a GeoNet webcam, and detailed ash deposit studies have permitted analysis of the plume characteristics. A combination of radar and webcam imagery show 5 pulses within the first 13 min of the eruption, and also the subsequent ash transport downwind. Comparison with ash samples show the radar was likely detecting ash particles down to about 0.5 mm diameter. The maximum plume height estimated by the radar is 7.8 ± 1.0 km above mean sea level (amsl), although it is possible this may be a slight under estimation if very small ash particles not detected by the radar rose higher and comprised the very top of the plume. The correlation coefficient and differential reflectivity fields that are additionally measured by the dual polarisation radar provide extra information about the structure and composition of the eruption column and ash cloud. The correlation coefficient easily discriminates between the eruption column and the ash plume, and provides some information about the diversity of ash particle size within both the ash plume and the subsequent detached ash cloud drifting downwind. The differential reflectivity shows that the larger ash particles are falling with a horizontal orientation, and indicates that ice nucleation and aggregation of fine ash particles was probably occurring at high altitudes within 20-25 min of the eruption.

Crouch, John F.; Pardo, Natalia; Miller, Craig A.

2014-10-01

221

The large-scale spatio-temporal variability of precipitation over Sweden observed from the weather radar network  

NASA Astrophysics Data System (ADS)

Using measurements from the national network of 12 weather radar stations for the last decade (2000-2010), we investigate the large-scale spatio-temporal variability of precipitation over Sweden. These statistics provide useful information to evaluate regional climate models as well as for hydrology and energy applications. A strict quality control is applied to filter out noise and artifacts from the radar data. We focus on investigating four distinct aspects namely, the diurnal cycle of precipitation and its seasonality, the dominant time scale (diurnal vs. seasonal) of variability, precipitation response to different wind directions, and the correlation of precipitation events with the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO). When classified based on their intensity, moderate to high intensity events (precipitation > 0.34 mm (3 h)-1) peak distinctly during late afternoon over the majority of radar stations in summer and during late night or early morning in winter. Precipitation variability is highest over the southwestern parts of Sweden. It is shown that the high intensity events (precipitation > 1.7mm (3 h)-1) are positively correlated with NAO and AO (esp. over northern Sweden), while the low intensity events are negatively correlated (esp. over southeastern parts). It is further observed that southeasterly winds often lead to intense precipitation events over central and northern Sweden, while southwesterly winds contribute most to the total accumulated precipitation for all radar stations. Apart from its operational applications, the present study demonstrates the potential of the weather radar data set for studying climatic features of precipitation over Sweden.

Devasthale, A.; Norin, L.

2013-12-01

222

The large-scale spatio-temporal variability of precipitation over Sweden observed from the weather radar network  

NASA Astrophysics Data System (ADS)

Using measurements from the national network of 12 weather radar stations for the 11-year period 2000-2010, we investigate the large-scale spatio-temporal variability of precipitation over Sweden. These statistics provide useful information to evaluate regional climate models as well as for hydrology and energy applications. A strict quality control is applied to filter out noise and artifacts from the radar data. We focus on investigating four distinct aspects: the diurnal cycle of precipitation and its seasonality, the dominant timescale (diurnal versus seasonal) of variability, precipitation response to different wind directions, and the correlation of precipitation events with the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO). When classified based on their intensity, moderate- to high-intensity events (precipitation > 0.34 mm/3 h) peak distinctly during late afternoon over the majority of radar stations in summer and during late night or early morning in winter. Precipitation variability is highest over the southwestern parts of Sweden. It is shown that the high-intensity events (precipitation > 1.7 mm/3 h) are positively correlated with NAO and AO (esp. over northern Sweden), while the low intensity events are negatively correlated (esp. over southeastern parts). It is further observed that southeasterly winds often lead to intense precipitation events over central and northern Sweden, while southwesterly winds contribute most to the total accumulated precipitation for all radar stations. Apart from its operational applications, the present study demonstrates the potential of the weather radar data set for studying climatic features of precipitation over Sweden.

Devasthale, A.; Norin, L.

2014-06-01

223

Simultaneous ocean cross-section and rainfall measurements from space with a nadir-pointing radar  

NASA Technical Reports Server (NTRS)

A method to determine simultaneously the rainfall rate and the normalized backscattering cross section of the surface was evaluated. The method is based on the mirror reflected power, p sub m which corresponds to the portion of the incident power scattered from the surface to the precipitation, intercepted by the precipitation, and again returned to the surface where it is scattered a final time back to the antenna. Two approximations are obtained for P sub m depending on whether the field of view at the surface is either much greater or much less than the height of the reflection layer. Since the dependence of P sub m on the backscattering cross section of the surface differs in the two cases, two algorithms are given by which the path averaged rain rate and normalized cross section are deduced. The detectability of P sub m, the relative strength of other contributions to the return power arriving simultaneous with P sub m, and the validity of the approximations used in deriving P sub m are discussed.

Meneghini, R.; Atlas, D.

1984-01-01

224

On the Tropical Rainfall Measuring Mission (TRMM): Bringing NASA's Earth System Science Program to the Classroom  

NASA Technical Reports Server (NTRS)

The Tropical Rainfall Measuring Mission is the first mission dedicated to measuring tropical and subtropical rainfall using a variety of remote sensing instrumentation, including the first spaceborne rain-measuring radar. Since the energy released when tropical rainfall occurs is a primary "fuel" supply for the weather and climate "engine"; improvements in computer models which predict future weather and climate states may depend on better measurements of global tropical rainfall and its energy. In support of the STANYS conference theme of Education and Space, this presentation focuses on one aspect of NASA's Earth Systems Science Program. We seek to present an overview of the TRMM mission. This overview will discuss the scientific motivation for TRMM, the TRMM instrument package, and recent images from tropical rainfall systems and hurricanes. The presentation also targets educational components of the TRMM mission in the areas of weather, mathematics, technology, and geography that can be used by secondary school/high school educators in the classroom.

Shepherd, J. Marshall

1998-01-01

225

Multi-Watershed Evaluation of WSR-88D (NEXRAD) Radar-Precipitation Products  

Microsoft Academic Search

The National Weather Service (NWS) operates a network of Doppler-radar stations (NEXRAD, WSR- 88D) that produce hourly-rainfall estimates, at approximately 4-km2 resolution, with nominal coverage of 96% of the conterminous US. Utilization of these data by the NWS is primarily for the detection and modeling of extreme-weather events. Radar- precipitation estimates were compared with gauge estimates at six ARS watershed-research

Stuart Hardegree; Steven Van Vactor; Kathleen Healy; Carlos Alonso; James Bonta; David Bosch; Dwight Fisher; Daren Harmel; Jean Steiner; Michael Van Liew

226

Weather  

NSDL National Science Digital Library

What are the different types of weather? In this project you will compare different types of weather by drawing pictures and making it into a flip book. First you will begin by learning about the different types of weather. Read about each topic. Then get together with your partner and draw a picture of each type of weather. 1. Thunder storm Thunder storm Thunder storm Kids 2. Lightning Lightning Lightning picture 3. Tornado Tornadoes Tornado Kids 4. ...

Jennie, Miss

2009-10-22

227

Accessibility and Utilization of WSR-88D Radar Precipitation Data for Natural Resource Modeling Applications  

Microsoft Academic Search

The National Weather Service (NWS) operates approximately 160 WSR-88D radar-precipitation stations as part of a Next Generation Radar (NEXRAD) program that began implementation in 1992. Among other products, these radar sites provide spatial rainfall estimates, at approximately 4 km2 resolution (Stage 1, Level 3 data), with nominal coverage of 96% of the coterminous United States. Effective coverage is much less

S. P. Hardegree

2001-01-01

228

Analysis of airborne Doppler lidar, Doppler radar and tall tower measurements of atmospheric flows in quiescent and stormy weather  

NASA Technical Reports Server (NTRS)

The first experiment to combine airborne Doppler Lidar and ground-based dual Doppler Radar measurements of wind to detail the lower tropospheric flows in quiescent and stormy weather was conducted in central Oklahoma during four days in June-July 1981. Data from these unique remote sensing instruments, coupled with data from conventional in-situ facilities, i.e., 500-m meteorological tower, rawinsonde, and surface based sensors, were analyzed to enhance understanding of wind, waves and turbulence. The purposes of the study were to: (1) compare winds mapped by ground-based dual Doppler radars, airborne Doppler lidar, and anemometers on a tower; (2) compare measured atmospheric boundary layer flow with flows predicted by theoretical models; (3) investigate the kinematic structure of air mass boundaries that precede the development of severe storms; and (4) study the kinematic structure of thunderstorm phenomena (downdrafts, gust fronts, etc.) that produce wind shear and turbulence hazardous to aircraft operations. The report consists of three parts: Part 1, Intercomparison of Wind Data from Airborne Lidar, Ground-Based Radars and Instrumented 444 m Tower; Part 2, The Structure of the Convective Atmospheric Boundary Layer as Revealed by Lidar and Doppler Radars; and Part 3, Doppler Lidar Observations in Thunderstorm Environments.

Bluestein, H. B.; Doviak, R. J.; Eilts, M. D.; Mccaul, E. W.; Rabin, R.; Sundara-Rajan, A.; Zrnic, D. S.

1986-01-01

229

Rain gauge - radar rainfall reanalysis of operational and research data in the Cévennes-Vivarais region, France, estimation error analysis over a wide range of scales.  

NASA Astrophysics Data System (ADS)

In the Cévennes -Vivarais region in France, flash-flood events can occur due to high intensity precipitation events. These events are described in a detailed quantitative precipitation estimates, to be able to better characterize the hydrological response to these rain events in a number of small-scale nested watersheds (<100 km² typically), sampling various landscapes of the Mediterranean region. Radar - rain gauge merging methods described by Delrieu et al (2013) are applied to the 9 events of the autumn of 2012. Rainfall data is merged for both the operational networks in the Cévennes-Vivarais region in France on a 160 x 200 km window, as well as a research network, in the same region on a window of 15x30 km. The radar and rain gauge data of the operational network are collected from three organisms (Météo-France, Service de Prévision des Crues du Grand Delta and EdF/DTG). The research network contains high resolution data are from research rainfall observation systems deployed within the Enhanced Observation Period (autumn 2012-2015) of the HyMeX project (www.hymex.org). This project aims at studying the hydrological cycle in the Mediterranean with emphases on the hydro-meteorological extremes and their evolution in the coming decades. Rain gauge radar merging is performed using a kriging with external drift (KED) technique, and compared to the ordinary kriging (OK) of the rain gauges and the radar products on the same time scale using a cross-validation technique. Also a method is applied to quantify kriging estimation variances for both kriging techniques at the two spatial scales, in order to analyse the error characteristics of the interpolation methods at a scale range of 0.1 - 100 km² and 0.2 - 12 h. The combined information of the reanalysis of the data of the operational network and the research network gives a view on the error structure of rainfall estimations over several orders of magnitudes in spatial scale. This allows understanding of the error structure of these rain events, their relation to availability of data, and gives insight in the added value of detailed rainfall data on the understanding of the rainfall structure on very small, 'missing', scales (smaller than 1km2 and 1 hour time steps).

Wijbrans, Annette; Delrieu, Guy; Nord, Guillaume; Boudevillain, Brice; Berne, Alexis; Grazioli, Jacopo; Confoland, Audrey

2014-05-01

230

Comparison and Validation of Tropical Rainfall Measuring Mission (TRMM) Rainfall Algorithms in Tropical Cyclones.  

E-print Network

?? Tropical Rainfall Measuring Mission (TRMM) rainfall retrieval algorithms are evaluated in tropical cyclones (TCs). Differences between the Precipitation Radar (PR) and TRMM Microwave Imager… (more)

Zagrodnik, Joseph P

2012-01-01

231

Weather radar polarimetry: path integrated differential phase shift optimum polarization and the elliptical EF-basis  

Microsoft Academic Search

Polarimetric pulsed Doppler radar measurements of meteorological targets yield mean backscattering properties of hydrometeors in the considered range cells and provide information on propagation effects along the radar ray of propagation. In this paper, two aspects of choosing an optimum polarimetric measurement basis are examined. First, the polarization dependence of path integrated differential phase shift is studied starting from the

V. Ziegler; E. Lüneburg; A. Schroth

1995-01-01

232

Toward the Assimilation of the Atmospheric Surface Layer Using Numerical Weather Prediction and Radar Clutter Observations  

E-print Network

and Radar Clutter Observations ALI KARIMIAN AND CAGLAR YARDIM Scripps Institution of Oceanography referred to as an evaporation duct (ED). Refractivity from clutter (RFC) is an inversion approach for the estimation of the refractivity profile from radar clutter, and RFC-ED refers to its implementation

Gerstoft, Peter

233

Assessment of Rainfall Estimates Using a Standard Z-R Relationship and the Probability Matching Method Applied to Composite Radar Data in Central Florida  

NASA Technical Reports Server (NTRS)

Precipitation estimates from radar systems are a crucial component of many hydrometeorological applications, from flash flood forecasting to regional water budget studies. For analyses on large spatial scales and long timescales, it is frequently necessary to use composite reflectivities from a network of radar systems. Such composite products are useful for regional or national studies, but introduce a set of difficulties not encountered when using single radars. For instance, each contributing radar has its own calibration and scanning characteristics, but radar identification may not be retained in the compositing procedure. As a result, range effects on signal return cannot be taken into account. This paper assesses the accuracy with which composite radar imagery can be used to estimate precipitation in the convective environment of Florida during the summer of 1991. Results using Z = 30OR(sup 1.4) (WSR-88D default Z-R relationship) are compared with those obtained using the probability matching method (PMM). Rainfall derived from the power law Z-R was found to he highly biased (+90%-l10%) compared to rain gauge measurements for various temporal and spatial integrations. Application of a 36.5-dBZ reflectivity threshold (determined via the PMM) was found to improve the performance of the power law Z-R, reducing the biases substantially to 20%-33%. Correlations between precipitation estimates obtained with either Z-R relationship and mean gauge values are much higher for areal averages than for point locations. Precipitation estimates from the PMM are an improvement over those obtained using the power law in that biases and root-mean-square errors are much lower. The minimum timescale for application of the PMM with the composite radar dataset was found to be several days for area-average precipitation. The minimum spatial scale is harder to quantify, although it is concluded that it is less than 350 sq km. Implications relevant to the WSR-88D system are discussed.

Crosson, William L.; Duchon, Claude E.; Raghavan, Ravikumar; Goodman, Steven J.

1996-01-01

234

Radar data bias correction implementing quantile mapping and investigation of its influence in a hydrological model  

NASA Astrophysics Data System (ADS)

Weather radar is an important source of data for estimating rainfall rate with relatively high temporal and spatial resolution covering large areas. Although weather radar provides fine temporal and spatial resolution data, it is subject to different sources of error. Beside casual problems associated with radar, e.g. clutter and attenuation, weather radar either underestimates or overestimates the rainfall amount. Additionally, time steps with strangely high values result in destroying the structure of time series derived from radar data. In order to estimate areal precipitation for hydrological analyses, radar data could be merged with rain gauge network data. The merging product quality is strongly dependent on radar data quality. The main purpose of this study is to illustrate a method for improving radar data quality and to investigate the influence of radar data quality on merging products by means of cross validation. Quantile mapping on the two sources of data, the radar and rain gauge network, is implemented in this study to improve the radar data quality. After correcting the radar data, considering rain gauge data as the truth, the data is implemented into a hydrological model, HBV-IWW, to investigate the influence of the different input sources regarding model performance. It has been observed that implementing quantile mapping improves radar data quality significantly. On the other hand, using radar data after correction not only improves interpolation performances but also reveals other possible applications like disaggregation of daily rainfall data into finer temporal resolutions. Beside radar data quality, there are other factors influencing the model performance like network density and the applied interpolation technique. The study area is a mesoscale catchment located in Lower Saxony, northern Germany.

Rabiei, Ehsan; Wallner, Markus; Haberlandt, Uwe

2014-05-01

235

Atmosphere-Truth Z-R Rainfall Estimates: A Fresh Approach to an Old Problem  

NASA Astrophysics Data System (ADS)

Common modeling practice for basin calibration uses rainfall fields developed by the statistical use of surface rain gauge observed data or the direct application of NEXRAD National Weather Service WSR-88D Doppler radar Storm Total Rainfall or 1-hr rainfall estimations. Each of these approaches has significant limitations. Rain gages often lack sufficient spatial coverage to measure true storm intensity or the distribution of rainfall in a basin. The NWS WSR-88D Doppler radar algorithms are constantly being improved but still fail to deliver consistent rainfall estimates. Significant problems are caused by an under-estimation of warm coalescence rains and an over-estimation of rainfall in both dry environments and storms with hail contamination. Finally, storm updraft areas are frequently counted as raining portions of the storm producing immediate errors. The statistical techniques often under-estimate rainfall when the heavy rain core of the storm misses the rain gauges or if high winds cause an under-catchment of rainfall. Gauge-adjusted rainfall estimates are also dependant on the core of the storm being observed by a gauge. Statistical approaches often under-estimate rainfall producing insufficient runoff to drive the observed flooding runoffs. The Atmosphere-Truth ZR (ATZR) technique uses an atmosphere-truthed algorithm to produce highly accurate estimates of surface rainfall from Doppler radar data. This approach relies on using a cloud physics approach to determine the atmosphere’s ability to produce 15-min to hourly rain rates. The atmsopheric rainfall is utilizes surface, boundary layer and cloud layer observations of temperature and moisture from conventional National Weather Service observations. The depth of the thunderstorm updraft region that exceeds 0C is used with the precipitable water index and updraft speeds to provide estimates of 15-min to hourly rainfall rates from radar reflectivity areas in the storm greather than 50 dBZ. Rainfall rates are downstepped for reflectivity values from 50dBZ to 25 dBZ. These rain rates are then used to give quantitative meaning to radar reflectivity values on a storm basis. GIS is used to populatre and summate storm rainfall fields for discrete time intervals. This approach frequently produces r-squares for runoff that exceed 0.90. The technique has been used in dozens of calibration studies from coast-to-coast. A large Minnesota watershed experienced a greater than 100-yr rainfall and flooding event in 2005. Flood elevations were calculated using Thiessen polygon, sub-basin average and ATZR rainfall in the SWMM model. The ATZR method provided both refined precipitation volume and temporal distribution than the other conventional approaches.

Henz, J. F.

2010-12-01

236

Developing Dual Polarization Applications For 45th Weather Squadron's (45 WS) New Weather Radar: A Cooperative Project With The National Space Science and Technology Center (NSSTC)  

NASA Technical Reports Server (NTRS)

A new weather radar is being acquired for use in support of America s space program at Cape Canaveral Air Force Station, NASA Kennedy Space Center, and Patrick AFB on the east coast of central Florida. This new radar includes dual polarization capability, which has not been available to 45 WS previously. The 45 WS has teamed with NSSTC with funding from NASA Marshall Spaceflight Flight Center to improve their use of this new dual polarization capability when it is implemented operationally. The project goals include developing a temperature profile adaptive scan strategy, developing training materials, and developing forecast techniques and tools using dual polarization products. The temperature profile adaptive scan strategy will provide the scan angles that provide the optimal compromise between volume scan rate, vertical resolution, phenomena detection, data quality, and reduced cone-of-silence for the 45 WS mission. The mission requirements include outstanding detection of low level boundaries for thunderstorm prediction, excellent vertical resolution in the atmosphere electrification layer between 0 C and -20 C for lightning forecasting and Lightning Launch Commit Criteria evaluation, good detection of anvil clouds for Lightning Launch Commit Criteria evaluation, reduced cone-of-silence, fast volume scans, and many samples per pulse for good data quality. The training materials will emphasize the appropriate applications most important to the 45 WS mission. These include forecasting the onset and cessation of lightning, forecasting convective winds, and hopefully the inference of electrical fields in clouds. The training materials will focus on annotated radar imagery based on products available to the 45 WS. Other examples will include time sequenced radar products without annotation to simulate radar operations. This will reinforce the forecast concepts and also allow testing of the forecasters. The new dual polarization techniques and tools will focus on the appropriate applications for the 45 WS mission. These include forecasting the onset of lightning, the cessation of lightning, convective winds, and hopefully the inference of electrical fields in clouds. This presentation will report on the results achieved so far in the project.

Roeder, W.P.; Peterson, W.A.; Carey, L.D.; Deierling, W.; McNamara, T.M.

2009-01-01

237

Flash flood warning in mountaineous areas using X-band weather radars and the AIGA method in the framework of the RHYTMME project  

NASA Astrophysics Data System (ADS)

The knowledge of precipitations still remains a tricky issue in mountaineous areas: the available rain-gauges are in a limited number and most often located in the valleys, and the radar rainfall estimates have to deal with a lot of problems due to the relief and the difficulty to distinguish the different types of hydrometeors (snow, hail, rain). In this context, the "RHYTMME" project deals with two main issues: - Providing an accurate radar rainfall information in mountainous areas. - Developing a real-time hazards warning system based on this information. To answer to the first issue, a X-band doppler dual polarized radar network is currently implemented in the French South Alps. At the end of the project (2013), three new radars will be installed, completing a pre-existing radar already installed on the Mont Vial top since 2008 (Hydrix® technology developed by the Novimet company, and tested in a previous project). The present communication focuses on the flash flood warning issue. It presents some results obtained by coupling the radar estimates to a simple distributed hydrological model (the AIGA method). Results are compared on damages observed by end-users, which were strongly involved into the project. The RHYTMME project is co-piloted by Meteo-France and the Cemagref and has the financial support of the European Union, the Provence-Alpes-Côte d'Azur Region and the French Ministry in charge of Ecology.

Javelle, Pierre; Defrance, Dimitri; Ecrepont, Stéphane; Fouchier, Catherine; Mériaux, Patrice; Tolsa, Mathieu; Westrelin, Samuel

2013-04-01

238

Large-scale bird migration monitoring using operational weather radar M. de Graafa, H. Leijnsea,*, A. Dokterb,c, J. Shamoun-Baranesc, H. van Gasterenc,d, A. Dekkerd, and W. Boutenc  

E-print Network

Large-scale bird migration monitoring using operational weather radar M. de Graafa, H. Leijnsea Monitoring of bird migration is extremely important for military aviation (see Figure 1), ecology, and disease control. Operational weather radars are promising tools for obtaining information on bird

Haak, Hein

239

Weathering  

NSDL National Science Digital Library

This interactive Flash resource provides information regarding physical and chemical weathering at an introductory physical geology or Earth science level. It includes animations, diagrams, and supplementary information and is suitable for high school or undergraduate students.

Smoothstone; Mifflin, Houghton

240

Methods of Attenuation Correction for Dual-Wavelength and Dual-Polarization Weather Radar Data  

NASA Technical Reports Server (NTRS)

In writing the integral equations for the median mass diameter and number concentration, or comparable parameters of the raindrop size distribution, it is apparent that the forms of the equations for dual-polarization and dual-wavelength radar data are identical when attenuation effects are included. The differential backscattering and extinction coefficients appear in both sets of equations: for the dual-polarization equations, the differences are taken with respect to polarization at a fixed frequency while for the dual-wavelength equations, the differences are taken with respect to frequency at a fixed polarization. An alternative to the integral equation formulation is that based on the k-Z (attenuation coefficient-radar reflectivity factor) parameterization. This-technique was originally developed for attenuating single-wavelength radars, a variation of which has been applied to the TRMM Precipitation Radar data (PR). Extensions of this method have also been applied to dual-polarization data. In fact, it is not difficult to show that nearly identical equations are applicable as well to dualwavelength radar data. In this case, the equations for median mass diameter and number concentration take the form of coupled, but non-integral equations. Differences between this and the integral equation formulation are a consequence of the different ways in which attenuation correction is performed under the two formulations. For both techniques, the equations can be solved either forward from the radar outward or backward from the final range gate toward the radar. Although the forward-going solutions tend to be unstable as the attenuation out to the range of interest becomes large in some sense, an independent estimate of path attenuation is not required. This is analogous to the case of an attenuating single-wavelength radar where the forward solution to the Hitschfeld-Bordan equation becomes unstable as the attenuation increases. To circumvent this problem, the equations can be expressed in the form of a final-value problem so that the recursion begins at the far range gate and proceeds inward towards the radar. Solving the problem in this way traditionally requires estimates of path attenuation to the final gate: in the case of orthogonal linear polarizations, the attenuations at horizontal and vertical polarizations (same frequency) are required while in the dual-wavelength case, attenuations at the two frequencies (same polarization) are required.

Meneghini, R.; Liao, L.

2007-01-01

241

Frequency diversity wideband digital receiver and signal processor for solid-state dual-polarimetric weather radars  

NASA Astrophysics Data System (ADS)

The recent spate in the use of solid-state transmitters for weather radar systems has unexceptionably revolutionized the research in meteorology. The solid-state transmitters allow transmission of low peak powers without losing the radar range resolution by allowing the use of pulse compression waveforms. In this research, a novel frequency-diversity wideband waveform is proposed and realized to extenuate the low sensitivity of solid-state radars and mitigate the blind range problem tied with the longer pulse compression waveforms. The latest developments in the computing landscape have permitted the design of wideband digital receivers which can process this novel waveform on Field Programmable Gate Array (FPGA) chips. In terms of signal processing, wideband systems are generally characterized by the fact that the bandwidth of the signal of interest is comparable to the sampled bandwidth; that is, a band of frequencies must be selected and filtered out from a comparable spectral window in which the signal might occur. The development of such a wideband digital receiver opens a window for exciting research opportunities for improved estimation of precipitation measurements for higher frequency systems such as X, Ku and Ka bands, satellite-borne radars and other solid-state ground-based radars. This research describes various unique challenges associated with the design of a multi-channel wideband receiver. The receiver consists of twelve channels which simultaneously downconvert and filter the digitized intermediate-frequency (IF) signal for radar data processing. The product processing for the multi-channel digital receiver mandates a software and network architecture which provides for generating and archiving a single meteorological product profile culled from multi-pulse profiles at an increased data date. The multi-channel digital receiver also continuously samples the transmit pulse for calibration of radar receiver gain and transmit power. The multi-channel digital receiver has been successfully deployed as a key component in the recently developed National Aeronautical and Space Administration (NASA) Global Precipitation Measurement (GPM) Dual-Frequency Dual-Polarization Doppler Radar (D3R). The D3R is the principal ground validation instrument for the precipitation measurements of the Dual Precipitation Radar (DPR) onboard the GPM Core Observatory satellite scheduled for launch in 2014. The D3R system employs two broadly separated frequencies at Ku- and Ka-bands that together make measurements for precipitation types which need higher sensitivity such as light rain, drizzle and snow. This research describes unique design space to configure the digital receiver for D3R at several processing levels. At length, this research presents analysis and results obtained by employing the multi-carrier waveforms for D3R during the 2012 GPM Cold-Season Precipitation Experiment (GCPEx) campaign in Canada.

Mishra, Kumar Vijay

242

Objective Classification of Precipitating Convective Regimes Using a Weather Radar in Darwin, Australia  

Microsoft Academic Search

A clustering algorithm was applied to Frequency with Altitude Diagrams (FADs) derived from 4 yr of hourly radar data to objectively define four tropical precipitation regimes that occur during the wet season over Darwin Australia. The precipitation regimes defined are distinguished in terms of convective intensity, presence of stratiform precipitation, and precipitation coverage. Regime 1 consists of patchy convection of

Simon Caine; Christian Jakob; Steven Siems; Peter May

2009-01-01

243

Doppler weather radar observations of the 2009 eruption of Redoubt Volcano, Alaska  

USGS Publications Warehouse

The U.S. Geological Survey (USGS) deployed a transportable Doppler C-band radar during the precursory stage of the 2009 eruption of Redoubt Volcano, Alaska that provided valuable information during subsequent explosive events. We describe the capabilities of this new monitoring tool and present data captured during the Redoubt eruption. The MiniMax 250-C (MM-250C) radar detected seventeen of the nineteen largest explosive events between March 23 and April 4, 2009. Sixteen of these events reached the stratosphere (above 10 km) within 2–5 min of explosion onset. High column and proximal cloud reflectivity values (50 to 60 dBZ) were observed from many of these events, and were likely due to the formation of mm-sized accretionary tephra-ice pellets. Reflectivity data suggest that these pellets formed within the first few minutes of explosion onset. Rapid sedimentation of the mm-sized pellets was observed as a decrease in maximum detection cloud height. The volcanic cloud from the April 4 explosive event showed lower reflectivity values, due to finer particle sizes (related to dome collapse and related pyroclastic flows) and lack of significant pellet formation. Eruption durations determined by the radar were within a factor of two compared to seismic and pressure-sensor derived estimates, and were not well correlated. Ash dispersion observed by the radar was primarily in the upper troposphere below 10 km, but satellite observations indicate the presence of volcanogenic clouds in the stratosphere. This study suggests that radar is a valuable complement to traditional seismic and satellite monitoring of explosive eruptions.

Schneider, David J.; Hoblitt, Richard P.

2013-01-01

244

The use of weather radars to estimate hail damage to automobiles: an exploratory study in Switzerland  

NASA Astrophysics Data System (ADS)

As the first of its kind, this study presents damage functions between two damage variables of hail-damaged automobiles and radar-derived hail kinetic energy for a total of 12 severe hailstorms that have occurred over the Swiss Mittelland (1992-1998). Hail kinetic energy is calculated from C-band Doppler radar CAPPIs at low storm level (1.5 km MSL) and is integrated per radar element ( EKINPIX) for entire hail cells. Hail damage claim data were available per Swiss community on a daily basis and transformed (Delaunay triangulation) along with EKINPIX to a regular 3×3 km grid, thereafter allowing cross-correlation between the variables. The results show nonlinear relationships between EKINPIX and both loss ratios and mean damages per hail-damaged car, differing between high hail season storms (15 June-15 August) and storms that occurred during the low season (before and after). A weighted logistic function provides correlation coefficients between EKINPIX and loss ratios of 0.71 (0.79) for high (low) season storms and 0.76 (0.40) for mean damages of high (low) season hailstorms. Maximally possible loss ratios reach 60% (40%) in high (low) season storms with maximum mean damages of CHF 6000 (CHF 3000) and average values around CHF 3100 (CHF 2100). Seasonal differences in hailfall intensities are discussed in terms of atmospheric conditions favoring convective activity and the likelihood of higher numbers of large hailstones (>20 mm in diameter) that induce more severe damage to cars during the high storm season. The results suggest that radar-derived hail kinetic energy could be used by insurance companies in the future to (1) assess hail damage to cars immediately after a storm has passed over a radar observation area and (2) to estimate potential maximal hail losses to car portfolios for parts of central Europe.

Hohl, Roman; Schiesser, Hans-Heinrich; Knepper, Ingeborg

245

Time-dependent Second Order Scattering Theory for Weather Radar with a Finite Beam Width  

NASA Technical Reports Server (NTRS)

Multiple scattering effects from spherical water particles of uniform diameter are studied for a W-band pulsed radar. The Gaussian transverse beam-profile and the rectangular pulse-duration are used for calculation. An second-order analytical solution is derived for a single layer structure, based on a time-dependent radiative transfer theory as described in the authors' companion paper. When the range resolution is fixed, increase in footprint radius leads to increase in the second order reflectivity that is defined as the ratio of the second order return to the first order one. This feature becomes more serious as the range increases. Since the spaceborne millimeter-wavelength radar has a large footprint radius that is competitive to the mean free path, the multiple scattering effect must be taken into account for analysis.

Kobayashi, Satoru; Tanelli, Simone; Im, Eastwood; Ito, Shigeo; Oguchi, Tomohiro

2006-01-01

246

Weather  

NSDL National Science Digital Library

In the project you will learn about thunderstorms and tornadoes and play a weather matching game. What exactly are thunderstorms and tornadoes? Use your T- chart to explain some facts about a thunderstorm and a tornado as we review each. T-Chart Begin by reviewing what a thunderstorm is and how they form. Thunderstorm information What is a thunderstorm? What are thunderstorms most likely to occur? What causes thunder? Next review what a tornado ...

Caitlin, Ms.

2009-10-21

247

Rainfall generator for the Rhine basin: multi-site simulation of daily weather variables by nearest-neighbour resampling  

Microsoft Academic Search

Nearest-neighbour resampling is used here for the joint simulation of daily rainfall and temperature at 36 stations in Germany, Luxemburg, France and Switzerland all situated in the Rhine basin. The daily temperatures are used to determine snow accumulation and melt in winter. A major advantage of a non-parametric resampling technique is that it preserves both the spatial association of daily

Jules J. Beersma; T. Adri Buishand

248

The TRMM Precipitation Radar: Opportunities and Challenges  

NASA Technical Reports Server (NTRS)

Although studies on the feasibility of spaceborne weather radar date back to the 1960's, it was only with the launch of the Tropical Rainfall Measuring Mission (TRMM) Satellite in November 1997 that the first weather radar was placed into low earth orbit. The long delay between the initial concept and implementation was caused not only by the demanding requirements of active sensors such as mass, power, and reliability, but because of scientific and technological challenges. For example, the demand for adequate spatial resolution arises from the need to resolve the horizontal structure of convective storm cells and to avoid surface contamination of the rain return at off-nadir angles. To achieve a horizontal resolution on the order of 4 km from low earth orbit with a modest antenna size of 2 m requires the use of a much higher frequency (Ku-band) than those typically used for ground-based weather radars (S- and C-band). Higher frequencies are subject to higher attenuation. As Hitschfeld and Bordan (1954) showed in their classic paper, attenuation correction with a single-wavelength radar is inherently unstable at high attenuations unless the drop size distribution and the radar constant are known precisely. Since these conditions are seldom met, much work over the last decade has been devoted to formulating and testing alternative methods of attenuation correction. The operational method used in the TRMM radar processing is discussed in section 3 of the paper.

Meneghini, R.; Kozu, T.; Kawanishi, T.; Kuroiwa, H.; Okamoto, K.; Atlas, D.

1999-01-01

249

Estimation of extreme floods of the River Meuse using a stochastic weather generator and a rainfall–runoff model \\/ Estimation des crues extrêmes de la Meuse à l'aide d'un générateur stochastique de variables météorologiques et d'un modèle pluie–débit  

Microsoft Academic Search

A stochastic weather generator has been developed to simulate long daily sequences of areal rainfall and station temperature for the Belgian and French sub-basins of the River Meuse. The weather generator is based on the principle of nearest-neighbour resampling. In this method rainfall and temperature data are sampled simultaneously from multiple historical records with replacement such that the temporal and

Robert Leander; Adri Buishand; Paul Aalders; Marcel De Wit

2005-01-01

250

Second-order multiple-scattering theory associated with backscattering enhancement for a millimeter wavelength weather radar with a finite beam width  

NASA Technical Reports Server (NTRS)

Effects of multiple scattering on reflectivity are studied for millimeter wavelength weather radars. A time-independent vector theory, including up to second-order scattering, is derived for a single layer of hydrometeors of a uniform density and a uniform diameter. In this theory, spherical waves with a Gaussian antenna pattern are used to calculate ladder and cross terms in the analytical scattering theory. The former terms represent the conventional multiple scattering, while the latter terms cause backscattering enhancement in both the copolarized and cross-polarized components. As the optical thickness of the hydrometeor layer increases, the differences from the conventional plane wave theory become more significant, and essentially, the reflectivity of multiple scattering depends on the ratio of mean free path to radar footprint radius. These results must be taken into account when analyzing radar reflectivity for use in remote sensing.

Kobayashi, Satoru; Tanelli, Simone; Im, Eastwood

2005-01-01

251

Spaced-antenna wind estimation using an X-band active phased-array weather radar  

NASA Astrophysics Data System (ADS)

Over the past few decades, several single radar methods have been developed to probe the kinematic structure of storms. All these methods trade angular-resolution to retrieve the wind-field. To date, the spaced-antenna method has been employed for profiling the ionosphere and the precipitation free lower atmosphere. This work focuses on applying the spaced-antenna method on an X-band active phased-array radar for high resolution horizontal wind-field retrieval from precipitation echoes. The ability to segment the array face into multiple displaced apertures allows for flexible spaced-antenna implementations. The methodology employed herein comprises of Monte-Carlo simulations to optimize the spaced-antenna system design and analysis of real data collected with the designed phased-array system. The contribution that underpins this dissertation is the demonstration of qualitative agreement between spaced-antenna and Doppler beam swinging retrievals based on real data. First, simulations of backscattered electric fields at the antenna array elements are validated using theoretical expressions. Based on the simulations, the degrees of freedom in the spaced-antenna system design are optimized for retrieval of mean baseline wind. We show that the designed X-band spaced-antenna system has lower retrieval uncertainty than the existing S-band spaced-antenna implementation on the NWRT. This is because of the flexibility to synthesize small overlapping apertures and the ability to obtain statistically independent samples at a faster rate at X-band. We then demonstrate a technique to make relative phase-center displacement measurements based on simulations and real data from the phased-array spaced-antenna system. This simple method uses statistics of precipitation echoes and apriori beamwidth measurements to make field repeatable phase-center displacement measurements. Finally, we test the hypothesis that wind-field curvature effects are common to both the spaced-antenna and Doppler beam swinging methods. Based on a close-range winter storm data set, we find that the spaced-antenna and fine-resolution Doppler beam swinging retrievals are in qualitative agreement. The correlation between the spaced-antenna and fine-resolution Doppler beam swinging retrievals was 0.57. The lowered correlation coefficient was, in part, due to the high standard deviation of the DBS retrievals. At high wind-speeds, the spaced-antenna retrievals significantly departed from variational retrievals of mean baseline wind.

Venkatesh, Vijay

252

Quasi-global extreme rainfall intensity derived from the Tropical Rainfall Measurement Mission  

NASA Astrophysics Data System (ADS)

The frequency, magnitude and duration of precipitation extremes are closely dependent on climate change and variability. While recent works suggest an ongoing increase of extreme climate events, a comparison between past and actual maxima rainfall intensities across the world is necessary. Previous compilations of the world's greatest rainfall depths are based on rain gauges sparsely located on the global terrestrial surface with significant gaps in remote continental regions and oceans. Unlike rain gauges and weather radars which provide extreme precipitation estimates at the micro- and mesoscale respectively, new remote sensing techniques offer now the possibility of monitoring precipitation over tropical and temperate regions across the world. Also, for the first time, such tools allow to detect rainfall extreme values over oceanic regions. This work provides a comparison between the world's greatest rainfall depths from point measurements in climatological stations during the 20th century (WMO, 1994) and those derived by the Tropical Rainfall Measurement Mission (TRMM) satellite with a 0.25° x 0.25° resolution grid from 1998 until 2013. During this 15 year observational period, global maxima rainfall depths associated to durations ranging between 3 hours and 2 years were estimated. A scaling law and functional form of maxima rainfall over continents and oceans provided for the first time a quasi-global assessment of the temporal and spatial distribution of the most intense rainfall events. In particular, the results show that (1) all the rain gauge-based measurements over the past century exceed the satellite-based values during last 15 years, and (2) the majority of hotspots with maximum rainfall intensity are located in the oceans.

Brena-Naranjo, Agustin; Matamoros-Casanova, Alberto; Pedrozo-Acuña, Adrian

2014-05-01

253

Airborne derivation of microburst alerts from ground-based Terminal Doppler Weather Radar information: A flight evaluation  

NASA Technical Reports Server (NTRS)

An element of the NASA/FAA windshear program is the integration of ground-based microburst information on the flight deck, to support airborne windshear alerting and microburst avoidance. NASA conducted a windshear flight test program in the summer of 1991 during which airborne processing of Terminal Doppler Weather Radar (TDWR) data was used to derive microburst alerts. Microburst information was extracted from TDWR, transmitted to a NASA Boeing 737 in flight via data link, and processed to estimate the windshear hazard level (F-factor) that would be experienced by the aircraft in each microburst. The microburst location and F-factor were used to derive a situation display and alerts. The situation display was successfully used to maneuver the aircraft for microburst penetrations, during which atmospheric 'truth' measurements were made. A total of 19 penetrations were made of TDWR-reported microburst locations, resulting in 18 airborne microburst alerts from the TDWR data and two microburst alerts from the airborne reactive windshear detection system. The primary factors affecting alerting performance were spatial offset of the flight path from the region of strongest shear, differences in TDWR measurement altitude and airplane penetration altitude, and variations in microburst outflow profiles. Predicted and measured F-factors agreed well in penetrations near microburst cores. Although improvements in airborne and ground processing of the TDWR measurements would be required to support an airborne executive-level alerting protocol, the practicality of airborne utilization of TDWR data link data has been demonstrated.

Hinton, David A.

1993-01-01

254

Designing clutter rejection filters with complex coefficients for airborne pulsed Doppler weather radar  

NASA Technical Reports Server (NTRS)

Ground clutter interference is a major problem for airborne pulse Doppler radar operating at low altitudes in a look-down mode. With Doppler zero set at the aircraft ground speed, ground clutter rejection filtering is typically accomplished using a high-pass filter with real valued coefficients and a stopband notch centered at zero Doppler. Clutter spectra from the NASA Wind Shear Flight Experiments of l991-1992 show that the dominant clutter mode can be located away from zero Doppler, particularly at short ranges dominated by sidelobe returns. Use of digital notch filters with complex valued coefficients so that the stopband notch can be located at any Doppler frequency is investigated. Several clutter mode tracking algorithms are considered to estimate the Doppler frequency location of the dominant clutter mode. From the examination of night data, when a dominant clutter mode away from zero Doppler is present, complex filtering is able to significantly increase clutter rejection over use of a notch filter centered at zero Doppler.

Jamora, Dennis A.

1993-01-01

255

Comparison of Spatial and Temporal Rainfall Characteristics in WRF-Simulated Precipitation to Gauge and Radar Observations  

EPA Science Inventory

Weather Research and Forecasting (WRF) meteorological data are used for USEPA multimedia air and water quality modeling applications, within the CMAQ modeling system to estimate wet deposition and to evaluate future climate and land-use scenarios. While it is not expected that hi...

256

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. AP-25, NO. 4, JULY 1977 Analysis of Weather Radar Return  

E-print Network

Radar Return D. v.PAYNE, MEMBER,IEEE 457 Abstr~ct-Amathematicalmodel of detectedclutterfrom an air- : borneweather radar of conventional design is developed.Themodel is the joint probability density of samples of radar return from hydro- meteorsatthe same nominal rangeand scan angle.It is developed fromanalysis

Zhang, Yan

257

Weather Watch  

NSDL National Science Digital Library

The weather watch activity is designed to provide instruction on how to collect weather data from on-line databases. Following completion of this activity the user will be able to look up weather conditions for any city in North America, know what radar maps are used for and how to access them, and know how to access satellite images and make estimated guesses on cloud conditions for their area from them.

Hopson, R.

258

Use and Interpretation of Radar  

NSDL National Science Digital Library

This undergraduate meteorology tutorial from Texas A&M University discusses the basic principles of operation of weather radars, describes how to interpret radar mosaics, and discusses the use of radar in weather forecasting. Students learn the relationship between range and elevation and how to use radar images and mosaics in short-range forecasting.

John Nielsen-Gammon

1996-01-01

259

Engineering Evaluation and Calibration of Iowa X-Band Polarimetric Radars  

NASA Astrophysics Data System (ADS)

The detailed knowledge and extensive monitoring of the precipitation structure at smaller temporal and spatial scales are critical to the scientific understanding of the hydrological cycle and associated processes. The hydrometeorological information at smaller scales is usually not available with the current weather radar systems which operate at lower frequencies such as S- and C-bands. This has necessitated the use of higher frequency (X-band) weather radars to obtain rainfall data at improved accuracy and near-ground coverage at shorter ranges. The University of Iowa has acquired four scanning, mobile, X-band polarimetric (XPOL) Doppler weather radars with the objective of accurate quantitative estimation of the rainfall at a high temporal and spatial resolution. These four XPOL radars will be deployed for short-range multiple-view observations of the same weather event thus reducing uncertainties introduced by the signal attenuation and instrument-wide errors. This network of radars is intended to serve multiple areas of hydrological research including uncertainty modelling, urban hydrology, flood and flash-flood prediction, and soil erosion. Compared to the existing networks of X-band weather radars, several features place the XPOL radar systems in a distinctly attractive position for the scientific community. Firstly, the Iowa XPOL radars are mounted on mobile platforms, and consequently, are deployed at any location of interest. Secondly, these systems are capable of acquiring data at a programmable range sampling which can be as low as 30m. Thirdly, the use of dual-polarization provides additional information about the hydrometeors at smaller scales. The radars can operate in staggered PRT and dual-PRF pulsing modes and can process data using either standard pulse-pair or spectral mode techniques. The Iowa XPOL radar systems are currently being evaluated and calibrated to participate in their first field campaigns in the upcoming NASA IFloodS (Iowa Flood Studies) field experiment during Spring-Summer 2013. This paper will present results obtained through extensive system-level tests conducted on the transmitter-receiver unit and carried out largely in conformity with the NASA Global Precipitation Measurement - Ground Validation (GPM-GV) standards. This includes scrutinizing the temporal stability of the some of the performance parameters. The radar systems will also be calibrated against existing standard weather radar systems during the campaign. The experimental observations of the individual XPOL radar units with respect to the reference ground and weather targets will also be analysed. The paper will also present an inter-XPOL comparison of the findings of these experiments.

Vijay Mishra, Kumar; Kruger, Anton; Krajewski, Witold

2013-04-01

260

The study and real-time implementation of attenuation correction for X-band dual-polarization weather radars  

Microsoft Academic Search

Attenuation of electromagnetic radiation due to rain or other wet hydrometeors along the propagation path has been studied extensively in the radar meteorology community. Recently, use of short range dual-polarization X-band radar systems has gained momentum due to lower system cost compared with the much more expensive S-band systems. Advances in dual-polarization radar research have shown that the specific attenuation

Yuxiang Liu

2008-01-01

261

a Statistical Description of Storm Cells: Analysis of Film Records of the Binghamton, New York WSR-57 PPI Weather Radar  

Microsoft Academic Search

Considerable effort has been expended recently to mathematically model convective rainstorms. Parameter estimation has lagged behind theoretical work. This investigation utilizes digitized radar imagery to estimate the duration and areal extent of convective cells. The parameters were chosen based on a mathematical model proposed by Rodriguez -Iturbe-Eagelson. Three thunderstorms in the area scanned by the Broome County, New York radar

Cynthia Brower Kirby

1991-01-01

262

The Storm-Structure-Severity method for the identification of convective storm characteristics with conventional weather radar  

Microsoft Academic Search

Radar reflectivity information is often displayed in two dimensions, making it difficult to extract the structural characteristics of convective storms. The maximum radar reflectivity and the vertical profile of liquid water distribution in a vertical column of a convective cell is used to determine a structural and intensity classification of the cell. The application of this Storm-Structure-Severity classification is demonstrated

Petrus J. M. Visser

2001-01-01

263

Real-Time Weather Data  

NSDL National Science Digital Library

This website provides real-time and forecast weather maps and data for the United States. The Satellite section contains satellite weather images from the GOES 8 and GOES 10 satellites, the Radar section contains radar weather images from NEXRAD radars, the Surface Data section contains plots of various weather conditions (temperatures, winds, pressure, precipitation), and the Upper Air section plots winds and temperatures across the United States.

264

Use of Dual Polarization Radar in Validation of Satellite Precipitation Measurements: Rationale and Opportunities  

NASA Technical Reports Server (NTRS)

Dual-polarization weather radars have evolved significantly in the last three decades culminating in the operational deployment by the National Weather Service. In addition to operational applications in the weather service, dual-polarization radars have shown significant potential in contributing to the research fields of ground based remote sensing of rainfall microphysics, study of precipitation evolution and hydrometeor classification. Furthermore the dual-polarization radars have also raised the awareness of radar system aspects such as calibration. Microphysical characterization of precipitation and quantitative precipitation estimation are important applications that are critical in the validation of satellite borne precipitation measurements and also serves as a valuable tool in algorithm development. This paper presents the important role played by dual-polarization radar in validating space borne precipitation measurements. Starting from a historical evolution, the various configurations of dual-polarization radar are presented. Examples of raindrop size distribution retrievals and hydrometeor type classification are discussed. The quantitative precipitation estimation is a product of direct relevance to space borne observations. During the TRMM program substantial advancement was made with ground based polarization radars specially collecting unique observations in the tropics which are noted. The scientific accomplishments of relevance to space borne measurements of precipitation are summarized. The potential of dual-polarization radars and opportunities in the era of global precipitation measurement mission is also discussed.

Chandrasekar, V.; Hou, Arthur; Smith, Eric; Bringi, V. N.; Rutledge, S. A.; Gorgucci, E.; Petersen, W. A.; SkofronickJackson, Gail

2008-01-01

265

Radar MeteorologyRadar Meteorology Feb 20, 1941 10 cm (S-band) radar used to track rain showers (Ligda)  

E-print Network

Radar MeteorologyRadar Meteorology Feb 20, 1941 10 cm (S-band) radar used to track rain showers similar observations in the early 1940's (U.S. Air Corps meteorologists receiving "radar" training at MIT in 1943 First operational weather radar, Panama, 1943 Science of radar meteorology born from WWII research

Rutledge, Steven

266

Comparison of short-term rainfall forecasts for model-based flow prediction in urban drainage systems.  

PubMed

Forecast-based flow prediction in drainage systems can be used to implement real-time control of drainage systems. This study compares two different types of rainfall forecast - a radar rainfall extrapolation-based nowcast model and a numerical weather prediction model. The models are applied as input to an urban runoff model predicting the inlet flow to a waste water treatment plant. The modelled flows are auto-calibrated against real-time flow observations in order to certify the best possible forecast. Results show that it is possible to forecast flows with a lead time of 24 h. The best performance of the system is found using the radar nowcast for the short lead times and the weather model for larger lead times. PMID:23863443

Thorndahl, Søren; Poulsen, Troels Sander; Bøvith, Thomas; Borup, Morten; Ahm, Malte; Nielsen, Jesper Ellerbæk; Grum, Morten; Rasmussen, Michael R; Gill, Rasphall; Mikkelsen, Peter Steen

2013-01-01

267

A Mediterranean nocturnal heavy rainfall and tornadic event. Part II: Total lightning analysis  

NASA Astrophysics Data System (ADS)

On the night from 1st to 2nd of November 2008, a multi-cell storm coming from the Mediterranean produced severe weather in the coastal area of Catalonia (NE Spain): ground-level strong damaging wind gusts, a tornado - which caused F2 damage - and heavy rainfall. A general overview of the synoptic framework, damage observed and a radar analysis is given in the first part of the study. This second part is mostly centered on the detailed analysis of the total lightning behavior, its relationship with radar-derived storm parameters, and total lightning correlation with hazardous weather. The purpose is to bring more evidence about the outstanding role of total lightning in severe weather surveillance tasks. The analysis of the storm cells life cycle has showed similar trends between the total lighting flash rates and radar-derived parameters like the area of reflectivity above 30 dBZ at 7-km. Regarding lightning trends, a lightning "jump" pattern - an abrupt increase of the total lightning rate in a short period of time - has been related to severe weather. On the contrary, cloud-to-ground lightning data did not show any pattern related to severe weather. In comparison to other parameters, like the IC:CG ratio, the lightning "jump" pattern seems more robust to forecast in a short-term basis the possible occurrence of severe weather.

Pineda, Nicolau; Bech, Joan; Rigo, Tomeu; Montanyà, Joan

2011-06-01

268

Wacky Weather  

NSDL National Science Digital Library

This 5-lesson unit gives students practice in using calculating, graphing and modeling skills to analyze varoius aspects of weather. Students calculate fractions of a set of rainfall data, graph damage costs of selected hurricanes, and make Venn diagrams to compare droughts and hurricanes. Visuals and student handouts are provided.

Barbara Chichetti

2002-01-01

269

Weather Instruments  

NSDL National Science Digital Library

This Topic in Depth discusses the variety of instruments used to collect climate and weather data. The first two websites provide simple introductions to the many weather instruments. Bethune Academy's Weather Center (1) discusses the functions of psychrometers, anemometers, weather balloons, thermometers, and barometers. The Illinois State Water Survey (2) furnishes many images of various instruments that collect data daily for legal issues, farmers, educators, students, and researchers. The third website (3), created by the Center for Improving Engineering and Science Education (CIESE), provides a classroom activity to educate users on how to build and use weather instruments. By the end of the group project, students should know all about wind vanes, rain gauges, anemometers, and thermometers. Next, the Miami Museum of Science provides a variety of activities to help students learn about the many weather instruments including wind scales and wind chimes (4). Students can learn about the wind, air pressure, moisture, and temperature. At the fifth website, the Tyson Research Center at Washington University describes the devices it uses in its research (5). At the various links, users can find out the center's many projects that utilize meteorological data such as acid rain monitoring. The sixth website, a pdf document created by Dr. John Guyton at the Mississippi State University Extension Service, provides guidance to teachers about the education of weather patterns and instruments (6). Users can find helpful information on pressure systems, humidity, cloud patterns, and much more. Next, the University of Richmond discusses the tools meteorologists use to learn about the weather (7). While providing materials about the basic tools discussed in the other websites, this site also offers information about weather satellites, radar, and computer models. After discovering the many weather instruments, users can learn about weather data output and analysis at the Next Generation Weather Lab website (8). This expansive website provides an abundance of surface data and upper air data as well as satellite and radar images for the United States.

270

Recent Advances In Spaceborne Precipitation Radar Technology  

NASA Astrophysics Data System (ADS)

Information on global, 3-dimensional distribution of clouds and precipitation are important in our understanding of global water cycle, energy budget, long-term climate variability, and short-term weather. One of the most reliable and effective means to acquire such global information is by spaceborne profiling radars. The on-going NASA/JAXA Tropical Rainfall Measuring Mission (TRMM) is the first spaceborne mission that uses a precipitation radar to acquire three-dimensional rainfall intensity field globally. In its sixth years of in-flight operations, the TRMM radar has provided exciting, new data on the 3-D rain structures for a variety of scientific applications. As a continuing effort to provide new and improved spaceborne atmospheric sensing capabilities, NASA has been developing advanced instruments and technologies for future spaceborne precipitation radars, with the over-arching objectives of making such instruments more capable and more cost effective. Two such examples are the Second-Generation Precipitation Radar (PR-2) and the Nexrad-In-Space (NIS). PR-2 is a 14/35-GHz dual-frequency, Doppler rain radar with a deployable 5-meter, wide-swath scanned membrane antenna, a dual-polarized/dual-frequency receiver, and a FPGA-based adaptive-scan control, pulse compression, and Doppler spectral processor. It is intended to provide greatly enhanced rainfall profile retrieval accuracy while using only a fraction of the mass of the current TRMM PR. NIS is designed to be a geostationary radar with the intent of providing hourly monitoring of the life cycle of hurricanes and tropical storms. It uses a 35-m, spherical, light-weight membrane antenna and Doppler processing to acquire 3-dimensional information on the intensity and vertical motion of hurricane rainfall. In this paper, an overview of the instrument design concepts and some of the key technologies developed for these advanced atmospheric radars will be presented. The research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, for the Earth-Sun System Technology Office and the Global Precipitation Measurement Mission, under contract with the National Aeronautics and Space Administration.

Im, E.; Durden, S. L.

2005-12-01

271

Cascading rainfall uncertainty into flood inundation impact models  

NASA Astrophysics Data System (ADS)

Observed and numerical weather prediction (NWP) simulated precipitation products typically show differences in their spatial and temporal distribution. These differences can considerably influence the ability to predict hydrological responses. For flood inundation impact studies, as in forecast situations, an atmospheric-hydrologic-hydraulic model chain is needed to quantify the extent of flood risk. Uncertainties cascaded through the model chain are seldom explored, and more importantly, how potential input uncertainties propagate through this cascade, and how best to approach this, is still poorly understood. This requires a combination of modelling capabilities, the non-linear transformation of rainfall to river flow using rainfall-runoff models, and finally the hydraulic flood wave propagation based on the runoff predictions. Improving the characterisation of uncertainty, and what is important to include, in each component is important for quantifying impacts and understanding flood risk for different return periods. In this paper, we propose to address this issue by i) exploring the effects of errors in rainfall on inundation predictive capacity within an uncertainty framework by testing inundation uncertainty against different comparable meteorological conditions (i.e. using different rainfall products) and ii) testing different techniques to cascade uncertainties (e.g. bootstrapping, PPU envelope) within the GLUE (generalised likelihood uncertainty estimation) framework. Our method cascades rainfall uncertainties into multiple rainfall-runoff model structures using the Framework for Understanding Structural Errors (FUSE). The resultant prediction uncertainties in upstream discharge provide uncertain boundary conditions that are cascaded into a simplified shallow water hydraulic model (LISFLOOD-FP). Rainfall data captured by three different measurement techniques - rain gauges, gridded radar data and numerical weather predictions (NWP) models are evaluated. The study is performed in the Severn catchment over summer 2007, where a series of large rainfall events (over 100mm between the 20th and 21rst of July in certain sub-catchments) caused record floods in the study area. Differences in water level at benchmark stations are compared and the resulting prediction uncertainties are analysed for the different rainfall products. These results quantify how different cascading techniques and rainfall input uncertainty affects the resultant set of behavioural simulations. This allows us to compare the performance of different rainfall products used for real forecasting situations.

Souvignet, Maxime; Freer, Jim E.; de Almeida, Gustavo A. M.; Coxon, Gemma; Neal, Jeffrey C.; Champion, Adrian J.; Cloke, Hannah L.; Bates, Paul D.

2014-05-01

272

a Statistical Description of Storm Cells: Analysis of Film Records of the Binghamton, New York WSR-57 PPI Weather Radar.  

NASA Astrophysics Data System (ADS)

Considerable effort has been expended recently to mathematically model convective rainstorms. Parameter estimation has lagged behind theoretical work. This investigation utilizes digitized radar imagery to estimate the duration and areal extent of convective cells. The parameters were chosen based on a mathematical model proposed by Rodriguez -Iturbe-Eagelson. Three thunderstorms in the area scanned by the Broome County, New York radar were chosen. The film images of the radar scope taken at 5-minute intervals were digitized. Data were extracted from the digitized image concerning the spatial and temporal characteristics of convective cells. The cells were found to have durations of 20 to 30 minutes, with an exponential distribution. Mean cell area was found to be 15 km^2 and best described by a log-normal distribution. Preliminary data descriptions of relative cell precipitation, cell velocity and growth-life-decay cycle were given.

Kirby, Cynthia Brower

273

The Storm-Structure-Severity method for the identification of convective storm characteristics with conventional weather radar  

NASA Astrophysics Data System (ADS)

Radar reflectivity information is often displayed in two dimensions, making it difficult to extract the structural characteristics of convective storms. The maximum radar reflectivity and the vertical profile of liquid water distribution in a vertical column of a convective cell is used to determine a structural and intensity classification of the cell. The application of this Storm-Structure-Severity classification is demonstrated by investigating a tornado event on 15 November 1998 in Harrismith, South Africa, by using volume-scanned reflectivity data from the S-band MRL-5 radar. The regions of convective development, decay and mesocyclone evolution are identified with this classification. The method is able to extract the three-dimensional structural information of convective storms embedded in volume-scanned reflectivity data and present it in a simple display format.

Visser, Petrus J. M.

2001-03-01

274

Rainfall retrieval in urban areas using commercial microwave links from mobile networks: A modelling feasibility study  

NASA Astrophysics Data System (ADS)

Rainfall is usually measured by networks of rain gauges and weather radars. Many cities worldwide are not supplied with these devices; however, they are generally equipped with mobile telecommunication networks. Mobile networks use atmospheric Hyper-Frequency (HF) links whose transmitted signal power is attenuated by rainfall. Measuring that signal attenuation along each link could allow the measurement of path-averaged rainfall [Leijnse et al 2007, Overeem et al 2013, Messer et al 2006, Guili et al 1991, Zinevich et al 2008, Cuccoli et al 2011]. As HF links are concentrated in cities, these networks could constitute a self-sufficient approach to monitoring rainfall in urban areas. We adopt a simulation approach in order to study the feasibility of mapping rainfall fields at the city scale by means of existing HF links. Our domain of study is the central part of the city of Nantes, France, where the density of cellular networks is greatest. As a basis, we use a data set consisting of hundreds of weather radar images recorded by the Météo-France C band weather radar at high spatial (250m x 250m) and temporal (5 minute) resolutions located about 10 km north of the center of Nantes. We convert these images into rainfall maps using the Z-R relation and consider them as reference rainfall fields. The simulation is performed as follows. First, we simulate the measurement of total attenuation along each HF link using a rain-attenuation model based on Mie theory and a known drop size distribution in a continental temperate climate. This procedure is applied for 256 real radio links operating at different frequencies (18, 23, 38 GHz) with lengths ranging from 0.4 to 16 km. This helps us to substitute the attenuation data for the signal power received from microwave links. Error sources affecting measurement accuracy are introduced as a zero-mean Gaussian distributed random variable with variance of 10% of total attenuation. The retrieval of the rainfield is performed by a nonlinear algorithm [Tarantola and Valette 1982] based on the general nonlinear least square criterion. The a priori knowledge used to initialize the algorithm heavily influences the model outcome if the stated problem is underdetermined. In order to evaluate the performance of our model, we carry out a series of rainfall retrieval tests for various rain events (convective and stratiform) with different time intervals. We evaluate retrieval efficiency by comparing observed rain fields with retrieved ones. We perform a sensitivity analysis to define the model's limitations and capabilities by considering essential factors, namely spatial and temporal rainfall structure, the geometry of HF link networks, the choice of a priori information and associated errors.

Zohidov, Bahtiyor; Andrieu, Hervé; Servières, Myriam; Normand, Nicolas

2014-05-01

275

Probabilistic rainfall warning system with an interactive user interface  

NASA Astrophysics Data System (ADS)

A real time 24/7 automatic alert system is in operational use at the Finnish Meteorological Institute (FMI). It consists of gridded forecasts of the exceedance probabilities of rainfall class thresholds in the continuous lead time range of 1 hour to 5 days. Nowcasting up to six hours applies ensemble member extrapolations of weather radar measurements. With 2.8 GHz processors using 8 threads it takes about 20 seconds to generate 51 radar based ensemble members in a grid of 760 x 1226 points. Nowcasting exploits also lightning density and satellite based pseudo rainfall estimates. The latter ones utilize convective rain rate (CRR) estimate from Meteosat Second Generation. The extrapolation technique applies atmospheric motion vectors (AMV) originally developed for upper wind estimation with satellite images. Exceedance probabilities of four rainfall accumulation categories are computed for the future 1 h and 6 h periods and they are updated every 15 minutes. For longer forecasts exceedance probabilities are calculated for future 6 and 24 h periods during the next 4 days. From approximately 1 hour to 2 days Poor man's Ensemble Prediction System (PEPS) is used applying e.g. the high resolution short range Numerical Weather Prediction models HIRLAM and AROME. The longest forecasts apply EPS data from the European Centre for Medium Range Weather Forecasts (ECMWF). The blending of the ensemble sets from the various forecast sources is performed applying mixing of accumulations with equal exceedance probabilities. The blending system contains a real time adaptive estimator of the predictability of radar based extrapolations. The uncompressed output data are written to file for each member, having total size of 10 GB. Ensemble data from other sources (satellite, lightning, NWP) are converted to the same geometry as the radar data and blended as was explained above. A verification system utilizing telemetering rain gauges has been established. Alert dissemination e.g. for citizens and professional end users applies SMS messages and, in near future, smartphone maps. The present interactive user interface facilitates free selection of alert sites and two warning thresholds (any rain, heavy rain) at any location in Finland. The pilot service was tested by 1000-3000 users during summers 2010 and 2012. As an example of dedicated end-user services gridded exceedance scenarios (of probabilities 5 %, 50 % and 90 %) of hourly rainfall accumulations for the next 3 hours have been utilized as an online input data for the influent model at the Greater Helsinki Wastewater Treatment Plant.

Koistinen, Jarmo; Hohti, Harri; Kauhanen, Janne; Kilpinen, Juha; Kurki, Vesa; Lauri, Tuomo; Nurmi, Pertti; Rossi, Pekka; Jokelainen, Miikka; Heinonen, Mari; Fred, Tommi; Moisseev, Dmitri; Mäkelä, Antti

2013-04-01

276

The study and real-time implementation of attenuation correction for X-band dual-polarization weather radars  

NASA Astrophysics Data System (ADS)

Attenuation of electromagnetic radiation due to rain or other wet hydrometeors along the propagation path has been studied extensively in the radar meteorology community. Recently, use of short range dual-polarization X-band radar systems has gained momentum due to lower system cost compared with the much more expensive S-band systems. Advances in dual-polarization radar research have shown that the specific attenuation and differential attenuation between horizontal and vertical polarized waves caused by oblate, highly oriented raindrops can be estimated using the specific differential phase. This advance leads to correction of the measured reflectivity (Zh) and the differential reflectivity (Zdr) due to path attenuation. This thesis addresses via theory, simulations and data analyses the accuracy and optimal estimation of attenuation-correction procedures at X-band frequency. Real-time implementation of the correction algorithm was developed for the first generation of X-band dual-polarized Doppler radar network (Integration Project 1, IP1) operated by the NSF Center for Collaborate Adaptive Sensing of the Atmosphere (CASA). We evaluate the algorithm for correcting the Zh, and the Zdr for rain attenuation using simulations and X-band radar data under ideal and noisy situations. Our algorithm is able to adjust the parameters according to the changes in temperature, drop shapes, and a certain class of drop size distributions (DSD) with very fast convergence. The X-band radar data were obtained from the National Institute of Earth Science and Disaster Prevention (NIED), Japan, and from CASA IP1. The algorithm accurately corrects NIED's data when compared with ground truth calculated from in situ disdrometer-based DSD measurements for a Typhoon event. We have implemented, in real-time, the algorithm in all the CASA IP1 radar nodes. We also evaluate our preliminary method that separately estimates rain and wet ice attenuation using microphysical outputs from a previous supercell simulation using the CSU-RAMS (Regional Atmospheric Modeling System). The retrieved rain and wet ice specific attenuation fields were found to be in close correspondence to the 'true' fields calculated from the simulation. The concept to correct rain and wet ice attenuation separately can be also applied to the CASA IP1 network with additional constraint information possibly provided by the WSR-88D network.

Liu, Yuxiang

277

Climate and Weather  

NSDL National Science Digital Library

This video discusses the differences between climate and weather by defining and presenting examples of each. When presenting examples of weather, the video focuses on severe events and how meteorologists predict and study the weather using measurement, satellites, and radar. The climate focus is primarily on an overview of climate zones.

Geographic, National

278

New software methods in radar ornithology using WSR-88D weather data and potential application to monitoring effects of climate change on bird migration  

USGS Publications Warehouse

Radar ornithology has provided tools for studying the movement of birds, especially related to migration. Researchers have presented qualitative evidence suggesting that birds, or at least migration events, can be identified using large broad scale radars such as the WSR-88D used in the NEXRAD weather surveillance system. This is potentially a boon for ornithologists because such data cover a large portion of the United States, are constantly being produced, are freely available, and have been archived since the early 1990s. A major obstacle to this research, however, has been that identifying birds in NEXRAD data has required a trained technician to manually inspect a graphically rendered radar sweep. A single site completes one volume scan every five to ten minutes, producing over 52,000 volume scans in one year. This is an immense amount of data, and manual classification is infeasible. We have developed a system that identifies biological echoes using machine learning techniques. This approach begins with training data using scans that have been classified by experts, or uses bird data collected in the field. The data are preprocessed to ensure quality and to emphasize relevant features. A classifier is then trained using this data and cross validation is used to measure performance. We compared neural networks, naive Bayes, and k-nearest neighbor classifiers. Empirical evidence is provided showing that this system can achieve classification accuracies in the 80th to 90th percentile. We propose to apply these methods to studying bird migration phenology and how it is affected by climate variability and change over multiple temporal scales.

Mead, Reginald; Paxton, John; Sojda, Richard S.

2010-01-01

279

Ground validation of satellite measurements of precipitation using upgraded dual polarization WSR-88D radar network  

NASA Astrophysics Data System (ADS)

The Global Precipitation Measurement (GPM) core satellite is scheduled for launch in February 2014, just a couple of months after the AGU's 2013 annual fall meeting. The GPM mission is expected to provide accurate and frequent observations of global precipitation which will play an important role in improving weather, climate, and hydrological prediction capabilities. As an indispensable part of GPM mission, ground validation will focus on the demonstration and evaluation of space based precipitation classification and retrieval algorithms. Among various validation tools, dual-polarization radar is a powerful equipment that can be used for accurate surface rainfall measurement. Recently, the Next-Generation Radar (NEXRAD) network has been upgraded with dual-polarization capabilities. The polarization diversity radars have great potential for understanding the precipitation microphysics and cross validation of space based observations. For direct comparison between space- and ground-based radar systems, Bolen and Chandrasekar (2003) proposed a methodology to align the measurement from these two systems. This alignment method has shown a great superiority by comparing the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) reflectivity measurements and ground radar observations. This paper will first present the rationale and opportunities of the usage of dual-polarization radar in validation of GPM precipitation retrieval algorithms. The main focus will be on the dual-polarization based rainfall microphysics retrievals, including the rain drop size distribution (DSD), quantitative precipitation estimation, and hydrometeor classifications. Dual-polarization radar observations from the WSR-88D network will be used extensively, especially when there are satellite overpasses during the post launch ear of GPM, for cross-validating the DSD retrieval algorithms and rainfall relations in different climatological regions. The dual-polarization algorithm for estimating the gamma DSD parameters, namely, Do, and Nw will be described in detail.

Chen, H.; Chandrasekar, C. V.

2013-12-01

280

Convective rain cells: spatio-temporal characteristics, synoptic patterns and a high resolution synoptically conditioned weather generator  

NASA Astrophysics Data System (ADS)

Information on rain cell features was extracted from high-resolution weather radar data for a total of 191,586 radar volume scans from 12 hydrological years. The convective rain cell features (i.e., cell area, rainfall intensity and cell orientation) were obtained using cell segmentation technique and cell tracking algorithm was used to analyze the changes of those features over time. Three synoptic types were defined for the study area (northen Israel), two extratropical winter lows: deep Cyprus low and a shallow low, and a tropical intrusion: Active Red Sea Trough. Empirical distributions were computed to describe the spatiotemporal characteristics of convective rain cells for these synoptic systems. Those empirical distributions were used for the development of the HiReS-WG (high-resolution synoptically conditioned weather generator). This weather generator is a stochastic model that generates high resolution rainfall fields (5 min and 0.25 km2). The WG is composed of four modules: the synoptic generator, the motion vector generator, the convective rain cell generator and the low-intensity rainfall generator. The weather generator was evaluated for annual rain depth, season timing, wet-/dry-period duration, rain-intensity distributions and spatial correlations using 300 years of simulated rainfall data. It was found that the weather generator well-represented the above properties compared to radar and rain-gauge observations from the studied region. The HiReS-WG is a good tool to study catchments' hydrological responses to variations in rainfall, especially small- to medium-size catchments, and it can also be linked to climate models to force the prevailing synoptic conditions.

Peleg, Nadav; Morin, Efrat

2014-05-01

281

Quantitative rainfall metrics for comparing volumetric rainfall retrievals to fine scale models  

NASA Astrophysics Data System (ADS)

Precipitation processes play a significant role in the energy balance of convective systems for example, through latent heating and evaporative cooling. Heavy precipitation "cores" can also be a proxy for vigorous convection and vertical motions. However, comparisons between rainfall rate retrievals from volumetric remote sensors with forecast rain fields from high-resolution numerical weather prediction simulations are complicated by differences in the location and timing of storm morphological features. This presentation will outline a series of metrics for diagnosing the spatial variability and statistical properties of precipitation maps produced both from models and retrievals. We include existing metrics such as Contoured by Frequency Altitude Diagrams (Yuter and Houze 1995) and Statistical Coverage Products (May and Lane 2009) and propose new metrics based on morphology, cell and feature based statistics. Work presented focuses on observations from the ARM Southern Great Plains radar network consisting of three agile X-Band radar systems with a very dense coverage pattern and a C Band system providing site wide coverage. By combining multiple sensors resolutions of 250m2 can be achieved, allowing improved characterization of fine-scale features. Analyses compare data collected during the Midlattitude Continental Convective Clouds Experiment (MC3E) with simulations of observed systems using the NASA Unified Weather Research and Forecasting model. May, P. T., and T. P. Lane, 2009: A method for using weather radar data to test cloud resolving models. Meteorological Applications, 16, 425-425, doi:10.1002/met.150, 10.1002/met.150. Yuter, S. E., and R. A. Houze, 1995: Three-Dimensional Kinematic and Microphysical Evolution of Florida Cumulonimbus. Part II: Frequency Distributions of Vertical Velocity, Reflectivity, and Differential Reflectivity. Mon. Wea. Rev., 123, 1941-1963, doi:10.1175/1520-0493(1995)123<1941:TDKAME>2.0.CO;2.

Collis, Scott; Tao, Wei-Kuo; Giangrande, Scott; Fridlind, Ann; Theisen, Adam; Jensen, Michael

2013-04-01

282

Extratropical cyclones are fundamental to the everyday weather of the midlatitudes. They provide essential rainfall for human activities such as agriculture, but can also cause  

E-print Network

Chapter 7 Conclusion Extratropical cyclones are fundamental to the everyday weather that these cyclones are predicted as accurately and as far in advance as possible by numerical weather prediction (NWP) models. The aim of this thesis is to explore the prediction of extratropical cyclones by NWP using

Froude, Lizzie

283

TRMM Data from the Goddard Earth Sciences (GES) DISC DAAC: Tropical Rainfall Measuring Mission (TRMM)  

NASA Technical Reports Server (NTRS)

Tropical rainfall affects the lives and economies of a majority of the Earth's population. Tropical rain systems, such as hurricanes, typhoons, and monsoons, are crucial to sustaining the livelihoods of those living in the tropics. Excess rainfall can cause floods and great property and crop damage, whereas too little rainfall can cause drought and crop failure. The latent heat release during the process of precipitation is a major source of energy that drives the atmospheric circulation. This latent heat can intensify weather systems, affecting weather thousands of kilometers away, thus making tropical rainfall an important indicator of atmospheric circulation and short-term climate change. The Tropical Rainfall Measuring Mission (TRMM), jointly sponsored by the National Aeronautics and Space Administration (NASA) of the United States and the National Space Development Agency (NASDA) of Japan, provides visible, infrared, and microwave observations of tropical and subtropical rain systems. The satellite observations are complemented by ground radar and rain gauge measurements to validate satellite rain estimation techniques. Goddard Space Flight Center's involvement includes the observatory, four instruments, integration and testing of the observatory, data processing and distribution, and satellite operations. TRMM has a design lifetime of three years. It is currently in its fifth year of operation. Data generated from TRMM and archived at the GES DAAC are useful not only for hydrologists, atmospheric scientists, and climatologists, but also for the health community studying infectious diseases, the ocean research community, and the agricultural community.

2003-01-01

284

Stormfax Weather Services  

NSDL National Science Digital Library

This site offers links to a variety of weather information, including national, international and local weather maps and forecasts, satellite and radar imagery, and severe weather warnings. There are also links to diverse resources such as fire maps, glacier inventories, snow depths, storm surges and tropical storms. There are reports and advisories about El Nino and La Nina. The site also has a glossary of weather terms and conversion charts for temperature, wind speed and atmospheric pressure.

2002-06-10

285

Comparison Between GOES-12 Overshooting-Top Detections, WSR-88D Radar Reflectivity, and Severe Storm Reports  

NASA Technical Reports Server (NTRS)

Studies have found that convective storms with overshooting-top (OT) signatures in weather satellite imagery are often associated with hazardous weather, such as heavy rainfall, tornadoes, damaging winds, and large hail. An objective satellite-based OT detection product has been developed using 11-micrometer infrared window (IRW) channel brightness temperatures (BTs) for the upcoming R series of the Geostationary Operational Environmental Satellite (GOES-R) Advanced Baseline Imager. In this study, this method is applied to GOES-12 IRW data and the OT detections are compared with radar data, severe storm reports, and severe weather warnings over the eastern United States. The goals of this study are to 1) improve forecaster understanding of satellite OT signatures relative to commonly available radar products, 2) assess OT detection product accuracy, and 3) evaluate the utility of an OT detection product for diagnosing hazardous convective storms. The coevolution of radar-derived products and satellite OT signatures indicates that an OT often corresponds with the highest radar echo top and reflectivity maximum aloft. Validation of OT detections relative to composite reflectivity indicates an algorithm false-alarm ratio of 16%, with OTs within the coldest IRW BT range (less than 200 K) being the most accurate. A significant IRW BT minimum typically present with an OT is more often associated with heavy precipitation than a region with a spatially uniform BT. Severe weather was often associated with OT detections during the warm season (April September) and over the southern United States. The severe weather to OT relationship increased by 15% when GOES operated in rapid-scan mode, showing the importance of high temporal resolution for observing and detecting rapidly evolving cloud-top features. Comparison of the earliest OT detection associated with a severe weather report showed that 75% of the cases occur before severe weather and that 42% of collocated severe weather reports had either an OT detected before a severe weather warning or no warning issued at all. The relationships between satellite OT signatures, severe weather, and heavy rainfall shown in this paper suggest that 1) when an OT is detected, the particular storm is likely producing heavy rainfall and/or possibly severe weather; 2) an objective OT detection product can be used to increase situational awareness and forecaster confidence that a given storm is severe; and 3) this product may be particularly useful in regions with insufficient radar coverage.

Dworak, Richard; Bedka, Kristopher; Brunner, Jason; Feltz, Wayne

2012-01-01

286

Observations of the marine environment from spaceborne side-looking real aperture radars  

NASA Technical Reports Server (NTRS)

Real aperture, side looking X-band radars have been operated from the Soviet Cosmos-1500, -1602, -1766 and Ocean satellites since 1984. Wind velocities were inferred from sea surface radar scattering for speeds ranging from approximately 2 m/s to those of hurricane proportions. The wind speeds were within 10-20 percent of the measured in situ values, and the direction of the wind velocity agreed with in situ direction measurements within 20-50 deg. Various atmospheric mesoscale eddies and tropical cyclones were thus located, and their strengths were inferred from sea surface reflectivity measurements. Rain cells were observed over both land and sea with these spaceborne radars. Algorithms to retrieve rainfall rates from spaceborne radar measurements were also developed. Spaceborne radars have been used to monitor various marine hazards. For example, information derived from those radars was used to plan rescue operations of distressed ships trapped in sea ice. Icebergs have also been monitored, and oil spills were mapped. Tsunamis produced by underwater earthquakes were also observed from space by the radars on the Cosmos 1500 series of satellites. The Cosmos-1500 satellite series have provided all weather radar imagery of the earths surface to a user community in real time by means of a 137.4 MHz Automatic Picture Transmission channel. This feature enabled the radar information to be used in direct support of Soviet polar maritime activities.

Kalmykov, A. I.; Velichko, S. A.; Tsymbal, V. N.; Kuleshov, Yu. A.; Weinman, J. A.; Jurkevich, I.

1993-01-01

287

Weather Forecasting  

NSDL National Science Digital Library

Weather Forecasting is a set of computer-based learning modules that teach students about meteorology from the point of view of learning how to forecast the weather. The modules were designed as the primary teaching resource for a seminar course on weather forecasting at the introductory college level (originally METR 151, later ATMO 151) and can also be used in the laboratory component of an introductory atmospheric science course. The modules assume no prior meteorological knowledge. In addition to text and graphics, the modules include interactive questions and answers designed to reinforce student learning. The module topics are: 1. How to Access Weather Data, 2. How to Read Hourly Weather Observations, 3. The National Collegiate Weather Forecasting Contest, 4. Radiation and the Diurnal Heating Cycle, 5. Factors Affecting Temperature: Clouds and Moisture, 6. Factors Affecting Temperature: Wind and Mixing, 7. Air Masses and Fronts, 8. Forces in the Atmosphere, 9. Air Pressure, Temperature, and Height, 10. Winds and Pressure, 11. The Forecasting Process, 12. Sounding Diagrams, 13. Upper Air Maps, 14. Satellite Imagery, 15. Radar Imagery, 16. Numerical Weather Prediction, 17. NWS Forecast Models, 18. Sources of Model Error, 19. Sea Breezes, Land Breezes, and Coastal Fronts, 20. Soundings, Clouds, and Convection, 21. Snow Forecasting.

Nielsen-Gammon, John

1996-09-01

288

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 51, NO. 4, APRIL 2013 2337 Modeling and Prediction of Rainfall Using Radar  

E-print Network

water quantity and quality. A data-mining approach is applied to predict rainfall in a wa- tershed basin, neural network, random forest, classification and regression tree, support vector machine, and k and TB data collected at South Amana (16 km west of Oxford) and Iowa City (25 km east of Oxford

Kusiak, Andrew

289

Urban High-Resolution Precipitation Product: Combining C-Band and Local X-Band Radar Data  

NASA Astrophysics Data System (ADS)

Modelling precipitation induced floods and their impact on flood-prone regions is one of the biggest challenges for hydrometeorological forecasters. The largest source of error in flood forecasting systems is uncertainty in precipitation estimation. In state of the art rainfall-runoff models, precipitation fields from C-band radars are used as input with temporal resolution in the order of 5 minutes and spatial resolution in the order of kilometres. These radars cannot observe the small scale structure of rain events that influences runoff especially in impermeable urban areas. Therefore, precipitation fields with higher spatial and temporal resolution would improve flood forecasting. In recent years radar systems operating in the X-band frequency range have been developed to provide precipitation fields for areas of special interest in higher temporal (1 min or below) and higher spatial resolution (250 m or below) in complementation to nationwide radar networks. However single X-band radars are highly influenced by attenuation. Within the project Precipitation and Attenuation Estimates from a High-Resolution Weather Radar Network (PATTERN) the University of Hamburg and the Max-Planck-Institute for Meteorology operate a single X-band radar covering the city of Hamburg, Germany. The radar provides precipitation fields with temporal resolution of 30 s and range resolution of 60 m. The area is also covered by the C-band radar Fuhlsbüttel operated by the German Weather Service (DWD) that gives precipitation estimates with a temporal resolution of 5 min and a range resolution of 1 km. We will introduce a method to merge the precipitation fields derived from the X-band radar into the precipitation field provided by the C-band radar Fuhlsbüttel. The observations of radar Fuhlsbüttel will also be integrated in the correction of the attenuated measurements of the X-band radar. The merged precipitation field of both radars will be a valid product to improve rainfall-runoff simulations in the city of Hamburg, because it combines the high-resolution of X-band radars with the more accurate rain-rate observations of C-band radars.

Lengfeld, Katharina; Clemens, Marco; Münster, Hans; Ament, Felix

2014-05-01

290

Doppler Radar Technology  

NSDL National Science Digital Library

This resource provides an introduction to the function and uses of the The National Weather Service's (NWS) Weather Surveillance Doppler Radar (WSR-88D). Topics include the components of the system, an overview of the products and overlays the system creates, and some example images with captions explaining what is being shown. There are also links to radar meteorology tutorials and to information on training to use the system and interpret its imagery.

291

Maximum-likelihood spectral estimation and adaptive filtering techniques with application to airborne Doppler weather radar. Thesis Technical Report No. 20  

NASA Technical Reports Server (NTRS)

This dissertation focuses on the signal processing problems associated with the detection of hazardous windshears using airborne Doppler radar when weak weather returns are in the presence of strong clutter returns. In light of the frequent inadequacy of spectral-processing oriented clutter suppression methods, we model a clutter signal as multiple sinusoids plus Gaussian noise, and propose adaptive filtering approaches that better capture the temporal characteristics of the signal process. This idea leads to two research topics in signal processing: (1) signal modeling and parameter estimation, and (2) adaptive filtering in this particular signal environment. A high-resolution, low SNR threshold maximum likelihood (ML) frequency estimation and signal modeling algorithm is devised and proves capable of delineating both the spectral and temporal nature of the clutter return. Furthermore, the Least Mean Square (LMS) -based adaptive filter's performance for the proposed signal model is investigated, and promising simulation results have testified to its potential for clutter rejection leading to more accurate estimation of windspeed thus obtaining a better assessment of the windshear hazard.

Lai, Jonathan Y.

1994-01-01

292

Coupling X-band dual-polarized mini-radars and hydro-meteorological forecast models: the HYDRORAD project  

NASA Astrophysics Data System (ADS)

Hydro-meteorological hazards like convective outbreaks leading to torrential rain and floods are among the most critical environmental issues world-wide. In that context weather radar observations have proven to be very useful in providing information on the spatial distribution of rainfall that can support early warning of floods. However, quantitative precipitation estimation by radar is subjected to many limitations and uncertainties. The use of dual-polarization at high frequency (i.e. X-band) has proven particularly useful for mitigating some of the limitation of operational systems, by exploiting the benefit of easiness to transport and deploy and the high spatial and temporal resolution achievable at small antenna sizes. New developments on X-band dual-polarization technology in recent years have received the interest of scientific and operational communities in these systems. New enterprises are focusing on the advancement of cost-efficient mini-radar network technology, based on high-frequency (mainly X-band) and low-power weather radar systems for weather monitoring and hydro-meteorological forecasting. Within the above context, the main objective of the HYDRORAD project was the development of an innovative integrated decision support tool for weather monitoring and hydro-meteorological applications. The integrated system tool is based on a polarimetric X-band mini-radar network which is the core of the decision support tool, a novel radar products generator and a hydro-meteorological forecast modelling system that ingests mini-radar rainfall products to forecast precipitation and floods. The radar products generator includes algorithms for attenuation correction, hydrometeor classification, a vertical profile reflectivity correction, a new polarimetric rainfall estimators developed for mini-radar observations, and short-term nowcasting of convective cells. The hydro-meteorological modelling system includes the Mesoscale Model 5 (MM5) and the Army Corps of Engineers Hydrologic Engineering Center hydrologic and hydraulic modelling chain. The characteristics of this tool make it ideal to support flood monitoring and forecasting within urban environment and small-scale basins. Preliminary results, carried out during a field campaign in Moldova, showed that the mini-radar based hydro-meteorological forecasting system can constitute a suitable solution for local flood warning and civil flood protection applications.

Picciotti, E.; Marzano, F. S.; Anagnostou, E. N.; Kalogiros, J.; Fessas, Y.; Volpi, A.; Cazac, V.; Pace, R.; Cinque, G.; Bernardini, L.; De Sanctis, K.; Di Fabio, S.; Montopoli, M.; Anagnostou, M. N.; Telleschi, A.; Dimitriou, E.; Stella, J.

2013-05-01

293

Caribbean Radar Cases  

NSDL National Science Digital Library

This module presents radar case studies taken from events in the Caribbean that highlight radar signatures of severe weather. These cases include examples of deep convection, squall lines, bow echoes, tornadoes, and heavy rain resulting in flooding. Each case study includes a discussion of the conceptual models of each type of event as a review before showing the radar signatures and allowing the learner to analyze each one.

COMET

2013-12-31

294

How Do Meteorologists Forecast the Weather?  

NSDL National Science Digital Library

This is a lesson that I developed where students learn how meteorologists predict the weather. Students will use surface weather maps, radar, satellite, and weather models from the National Weather Service to assess the current state of the weather and make a prediction.

David Faysash

2012-07-30

295

Changes in the TRMM Version-5 and Version-6 Precipitation Radar Products Due to Orbit Boost  

NASA Technical Reports Server (NTRS)

The performance of the version-5 and version-6 Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) products before and after the satellite orbit boost is assessed through a series of comparisons with Weather Surveillance Radar (WSR)-88D ground-based radar in Melbourne, Florida. Analysis of the comparisons of radar reflectivity near the storm top from the ground radar and both versions of the PR indicates that the PR bias relative to the WSR radar at Melbourne is on the order of 1dB for both pre- and post-boost periods, indicating that the PR products maintain accurate calibration after the orbit boost. Comparisons with the WSR-88D near-surface reflectivity factors indicate that both versions of the PR products accurately correct for attenuation in stratiform rain. However, in convective rain, both versions exhibit negative biases in the near-surface radar reflectivity with version-6 products having larger negative biases than version-5. Rain rate comparisons between the ground and space radars show similar characteristics

Liao, Liang; Meneghini, Robert

2010-01-01

296

How well can we measure rainfall over large areas?  

NASA Astrophysics Data System (ADS)

Uncertainties in rainfall measurement impose bounds on our capability to predict, and consequently, mitigate floods. Accurate estimation of rainfall over large areas is not a straightforward task, even in densely instrumented regions and when data from multiple observing systems are available. In this study we assess our ability to estimate rainfall over the state of Iowa (approximately 145,000 km2) during the 2013 IFloodS campaign (April - June). We investigate data from multiple sensors, including more than 100 rain gauges from several networks, 5 dual polarization radars, and real time radar rainfall maps based on single polarization radars. We evaluate multiplicative bias, range-dependent errors, and enhancements in rainfall estimation due to dual polarization capabilities. We then apply the fully-distributed, physically-based, and calibration-free IFC rainfall-runoff model to better understand the relationship between rainfall and scale-dependent flood response.

Cunha, L.; Smith, J. A.; Baeck, M. L.; Krajewski, W. F.; Seo, B.

2013-12-01

297

Everything Weather- Archived Data  

NSDL National Science Digital Library

Users can obtain current weather forecasts for their own areas by entering a ZIP code, or they can access a large archive of historic data on severe weather (tornadoes, hail, high winds, hurricanes). Materials presented in the archive include dates, times, and intensities of storms, a photo gallery, maps, radar and other satellite data, storm chaser reports, and links to other weather sites. Raw data can be found in several forms for teachers wishing to have unprocessed data to work with.

2001-01-01

298

Two years of country-wide rainfall maps employing cellular communication networks  

NASA Astrophysics Data System (ADS)

Accurate rainfall observations with high spatial and temporal resolutions are needed for hydrological applications, agriculture, meteorology, and climate monitoring. However, the majority of the land surface of the earth lacks accurate rainfall information and the number of rain gauges is even severely declining in Europe, South-America, and Africa. This calls for alternative sources of rainfall information. Various studies have shown that microwave links from operational cellular telecommunication networks may be employed for rainfall monitoring. Such networks cover 20% of the land surface of the earth and have a high density, especially in urban areas. The basic principle of rainfall monitoring using microwave links is as follows. Rainfall attenuates the electromagnetic signals transmitted from one telephone tower to another. By measuring the received power at one end of a microwave link as a function of time, the path-integrated attenuation due to rainfall can be calculated. Previous studies have shown that average rainfall intensities over the length of a link can be derived from the path-integrated attenuation. This is particularly interesting for those countries where few surface rainfall observations are available. Here we present almost two years of country-wide rainfall maps employing cellular communication networks. A data set from a commercial microwave link network over the Netherlands is analyzed, containing data from an unprecedented number of links (~ 2000) covering the land surface of the Netherlands (35500 square kilometers). This data set almost completely covers the years 2011 and 2012. Fifteen-minute and daily rainfall maps (1 km spatial resolution) are derived from the microwave link data and compared to maps from a gauge-adjusted radar data set. The performance of the rainfall retrieval algorithm will be studied, particularly differences in time and space. Time series of air temperature and snow from automatic weather stations, operated by the Royal Netherlands Meteorological Institute, will be collocated with the link-based rainfall data, to systematically study the performance of the algorithm during the two-year period. Moreover, a case study will be presented to investigate the performance of the algorithm during snow and sleet or to show the influence of dew formation on the antennas on the received signal levels.

Uijlenhoet, Remko; Overeem, Aart; Leijnse, Hidde; Rios Gaona, Manuel Felipe

2014-05-01

299

Rainfall Variability of South East Queensland  

Microsoft Academic Search

The seasonal weather of southeastern Queensland (SEQ) is commonly described by a wet and a dry season. Rainfall in this area has been declining for the past fifty years and climate projections indicate decreasing trends in annual rainfall and increases in temperature. These factors combined with population growth suggest a need for Queensland to re-evaluate its water management. In order

Louise Wilson; Michael Manton; Steven Siems

2010-01-01

300

Location-Based Rainfall Nowcasting Service for Public  

NASA Astrophysics Data System (ADS)

The Hong Kong Observatory has developed the "Short-range Warning of Intense Rainstorms in Localized Systems (SWIRLS)", a radar-based rainfall nowcasting system originally to support forecasters in rainstorm warning and severe weather forecasting such as hail, lightning and strong wind gusts in Hong Kong. The system has since been extended to provide rainfall nowcast service direct for the public in recent years. Following the launch of "Rainfall Nowcast for the Pearl River Delta Region" service provided via a Geographical Information System (GIS) platform in 2008, a location-based rainfall nowcast service served through "MyObservatory", a smartphone app for iOS and Android developed by the Observatory, debuted in September 2012. The new service takes advantage of the capability of smartphones to detect own locations and utilizes the quantitative precipitation forecast (QPF) from SWIRLS to provide location-based rainfall nowcast to the public. The conversion of radar reflectivity data (at 2 or 3 km above ground) to rainfall in SWIRLS is based on the Z-R relationship (Z=aRb) with dynamical calibration of the coefficients a and b determined using real-time rain gauge data. Adopting the "Multi-scale Optical-flow by Variational Analysis (MOVA)" scheme to track the movement of radar echoes and Semi-Lagrangian Advection (SLA) scheme to extrapolate their movement, the system is capable of producing QPF for the next six hours in a grid of 480 x 480 that covers a domain of 256 km x 256 km once every 6 minutes. Referencing the closest point in a resampled 2-km grid over the territory of Hong Kong, a prediction as to whether there will be rainfall exceeding 0.5 mm in every 30 minute intervals for the next two hours at users' own or designated locations are made available to the users in both textual and graphical format. For those users who have opted to receive notifications, a message would pop up on the user's phone whenever rain is predicted in the next two hours in a user-configurable manner. Verification indicates that the service achieves a detection rate of 76% and a false alarm rate of 26% in the first 30 minute forecast. The skill decreases as the forecast range extends, with the detection rate lowered to 40% and false alarm rate increased to 63% for the two hour forecast. A number of factors affect the accuracy of the forecast, notably the anomalous propagation, the sensitivity and vertical coverage of the radar, as well as the growth and decay of the rain echoes. The service has been gaining popularity rapidly since launch, and has already registered over 12,000 users who have opted for notifications. The successful launch of the location-based rainfall nowcast service in Hong Kong and favourable verification results reveal the high practicality of such services.

Woo, Wang-chun

2013-04-01

301

Retrieving rainfall fields through tomographic processing applied to radio base network signals  

NASA Astrophysics Data System (ADS)

As shown in the past years by researchers at the University of Florence, rainfall rate can be estimated in real time by means of tomographic processing applied to power attenuation measurements made simultaneously along microwave links. In this paper, we focus on the possibility to exploit the 'opportunity signals' provided by radio-base station networks for mobile communication systems. We describe a new tomographic algorithm that has been specifically developed for such kind of networks in urban areas, where a high number of microwave connections is typically possible. We describe the performance of the algorithm after having tested it on a 2 hours simulated rainfall event based on a sequence of real weather radar observations and on three kind of link networks, symmetric with lower link density and asymmetric with lower and higher density. We considered 12 GHz for the test carrier frequency of the radio-base network.

Cuccoli, Fabrizio; Facheris, Luca; Gori, Stefano; Baldini, Luca

2011-11-01

302

An Experimental Study of the Rainfall Variability Within TRMM/GPM Precipitation Radar and Microwave Sensor Instantaneous Field of View During MC3E  

NASA Technical Reports Server (NTRS)

Dual tipping bucket gauges were operated at 16 sites in support of ground based precipitation measurements during Mid-latitude Continental Convective Clouds Experiment (MC3E). The experiment is conducted in North Central Oklahoma from April 22 through June 6, 2011. The gauge sites were distributed around Atmospheric Radiation Measurement (ARM) Climate Research facility where the minimum and maximum separation distances ranged from 1 to 12 km. This study investigates the rainfall variability by employing the stretched exponential function. It will focus on the quantitative assessment of the partial beam of the experiment area in both convective and stratiform rain. The parameters of the exponential function will also be determined for various events. This study is unique for two reasons. First is the existing gauge setup and the second is the highly convective nature of the events with rain rates well above 100 mm/h for 20 minutes. We will compare the findings with previous studies.

Tokay, Ali; Petersen, Walter Arthur; Gatlin, Patrick N.; Wingo, Matt; Wolff, David B.; Carey, Lawrence D.

2011-01-01

303

An Experimental Study of the Rainfall Variability Within TRMM/GPM Precipitation Radar and Microwave Sensor Instantaneous Field of View During MC3E  

NASA Technical Reports Server (NTRS)

Dual tipping bucket gauges were operated at 16 sites in support of ground based precipitation measurements during Mid-latitude Continental Convective Clouds Experiment (MC3E). The experiment is conducted in North Central Oklahoma from April 22 through June 6, 2011. The gauge sites were distributed around Atmospheric Radiation Measurement (ARM) Climate Research facility where the minimum and maximum separation distances ranged from 1 to 12 km. This study investigates the rainfall variability by employing the stretched exponential function. It will focus on the quantitative assessment of the partial beam of the experiment area in both convective and stratiform rain. The parameters of the exponential function will also be determined for various events. This study is unique for two reasons. First is the existing gauge setup and the second is the highly convective nature of the events with rain rates well above 100 mm h-1 for 20 minutes. We will compare the findings with previous studies.

Tokay, Ali; Petersen, Arthur; Gatlin, Patrick N.; Wingo, Matt; Wolff, David B.; Carey, Lawrence D.

2011-01-01

304

Ground truth observations for TRMM. [Tropical Rainfall Measuring Mission  

NASA Technical Reports Server (NTRS)

Plans to obtain ground truth data for the validation of the Tropical Rainfall Measuring Mission (TRMM) are examined. The experimental rainfall measuring techniques considered for the program are discussed, including optical and Doppler rain gages, satellite beacon attenuation, underwater hydrophones, profilers, microwave attenuation, multiple frequency/polarization radar, and scanning and airborne Doppler radar. The TRMM validation program is considered, noting observations to compare averaged TRMM rainfall data with similar ground truth data and to compare the rainfall and height distribution data from TRMM with instantaneous ground truth data.

Thiele, Otto W.

1989-01-01

305

Evaluation of the QPF of convective flash flood rainfalls over the Czech territory in 2009  

NASA Astrophysics Data System (ADS)

In this paper, quantitative precipitation forecasts (QPF) are evaluated using several verification techniques and analysis of the results from these techniques. The forecasts were produced by two limited-area numerical weather prediction models: the ALADIN-CZ model operated by the Czech Hydro-Meteorological Institute (CHMI) and the COSMO model operated by the German Weather Service (DWD). Each model was run using two horizontal resolutions over the domain covering the Czech Republic. The ALADIN-CZ model outputs were obtained using resolutions of approximately 9 km and 4.7 km, and the COSMO model outputs were obtained using resolutions of approximately 7 km and 2.8 km. The forecast quality is studied for the flash flood period that occurred in June and July of 2009, when convective rainfalls with durations of 1 to 3 h and a return period of more than 100 years caused devastating floods in many Czech localities. The radar-based rainfalls used to verify the forecasts were produced by the CHMI operational product MERGE, which merges radar-derived rainfalls with the rainfalls that are measured by ground rain gauges. A series of 56 consecutive forecasts of 3-h rainfalls were verified using traditional and spatial verification techniques, and the results from these analyses were compared. The verification was performed using traditional verification scores based on a contingency table, spatial verification by the fractions skill score (FSS) and the SAL (structure-amplitude-location) technique. The FSS represents a fuzzy verification technique and compares the fractional coverage of precipitation grids over a threshold in spatial windows around the observations and forecasts. The SAL is a spatial object-oriented verification technique used to evaluate the structure, amplitude, and location of a precipitation field. The quality of QPF depends strongly on the scale of convective precipitation, and all models provide good forecast quality for extended rainfall systems. The opposite is true for the local and more or less chaotic convection during the final part of the time period. The FSS indicates how the results depend on the threshold and scale of precipitation. The COSMO 2.8 model is able to determine the largest local rainfall values, but models with lower resolution, such as the ALADIN 9 km and COSMO 7 km, provide better results for lower thresholds and larger scales. The use of more verification techniques is suitable for a modeller-oriented evaluation of different aspects of forecast quality.

Zacharov, Petr; Rezacova, Daniela; Brozkova, Radmila

2013-09-01

306

Estimation of Satellite-Rainfall Error Correlation  

NASA Astrophysics Data System (ADS)

With many satellite rainfall products being available for long periods, it is important to assess and validate the algorithms estimating the rainfall rates for these products. Many studies have been done on evaluating the uncertainty of satellite rainfall products over different parts of the world by comparing them to rain-gauge and/or radar rainfall products. In preparation for the field experiment Iowa Flood Studies, or IFloodS, one of the integrated validation activities of the Global Precipitation Measurement mission, we are evaluating three popular satellite-based products for the IFloodS domain of the upper Midwest in the US. One of the relevant questions is the determination of the covariance (correlation) of rainfall errors in space and time for the domain. Three satellite rainfall products have been used in this study, and a radar rainfall product has been used as a ground reference. The three rainfall products are TRMM's TMPA 3B42 V7, CPC's CMORPH and CHRS at UCI's PERSIANN. All the satellite rainfall products used in this study represent 3 hourly, quarter degree, rainfall accumulation. Our ground reference is NCEP Stage IV radar-rainfall, which is available in an hourly, four kilometers, resolution. We discuss the adequacy of the Stage IV product as a ground reference for evaluating the satellite products. We used our rain gauge network in Iowa to evaluate the performance of the Stage IV data on different spatial and temporal scales. While arguably this adequacy is only marginal, we used the radar products to study the spatial and temporal correlation of the satellite product errors. We studied the behavior of the errors, defined as the difference between the satellite and radar product (with matched space time resolution), during the period from the year 2004 through the year 2010. Our results show that the error behavior of the satellite rainfall products is quite similar. Errors are less correlated during warm seasons and the errors of CMORPH and PERSIANN are more correlated than those of TRMM through the study period. We calculated the correlation distance for the different products and it was approximately 75 km. The results also show that the correlation decays considerably with time lag. Our results have implications for the hydrologic studies using satellite data as the error correlation determines basin scales that effectively can filter out the random errors.

ElSaadani, Mohamed; Krajewski, Witold; Seo, Bong Chul; Goska, Radoslaw

2013-04-01

307

Frequency and intensity of precipitation events as seen by the TRMM Precipitation Radar  

NASA Astrophysics Data System (ADS)

We present a very high-resolution (0.05° x 0.05° , about 5km x 5km) monthly climatology and 3-hourly diurnal cycle of precipitation frequency and intensity, as derived from the precipitation radar (PR) aboard TRMM. We show how variations in the frequency of precipitation events dominate over variations in the mean intensity of precipitation to determine local rain rates. In subtropical regions such as the Mediterranean and over the Gulf Stream, climatological rainfall frequency changes very sharply at coastlines and over SST maxima, indicating a strong control of convection by the surface properties, even when rainfall is embedded in large scale weather systems. In some regions of the tropics, diurnally locked local circulations are largely responsible for sharp gradients in the spatial distribution of precipitation frequency and seasonal mean precipitation. Spatial variations in intensity have a large-scale character and sharp gradients appear only in the ice layer, but not at the surface. They indicate a preference for the most intense rainfall to occur in locations and at times when rainfall is relatively infrequent (but not rare). We suggest that regions of frequent rainfall and regions of intense rainfall might influence the stability of the tropical troposphere in different fashions.

Biasutti, M.; Sobel, A. H.; Yuter, S. E.; Burleyson, C. D.

2011-12-01

308

Quality Control and Calibration of the Dual-Polarization Radar at Kwajalein, RMI  

NASA Technical Reports Server (NTRS)

Weather radars, recording information about precipitation around the globe, will soon be significantly upgraded. Most of today s weather radars transmit and receive microwave energy with horizontal orientation only, but upgraded systems have the capability to send and receive both horizontally and vertically oriented waves. These enhanced "dual-polarimetric" (DP) radars peer into precipitation and provide information on the size, shape, phase (liquid / frozen), and concentration of the falling particles (termed hydrometeors). This information is valuable for improved rain rate estimates, and for providing data on the release and absorption of heat in the atmosphere from condensation and evaporation (phase changes). The heating profiles in the atmosphere influence global circulation, and are a vital component in studies of Earth s changing climate. However, to provide the most accurate interpretation of radar data, the radar must be properly calibrated and data must be quality controlled (cleaned) to remove non-precipitation artifacts; both of which are challenging tasks for today s weather radar. The DP capability maximizes performance of these procedures using properties of the observed precipitation. In a notable paper published in 2005, scientists from the Cooperative Institute for Mesoscale Meteorological Studies (CIMMS) at the University of Oklahoma developed a method to calibrate radars using statistically averaged DP measurements within light rain. An additional publication by one of the same scientists at the National Severe Storms Laboratory (NSSL) in Norman, Oklahoma introduced several techniques to perform quality control of radar data using DP measurements. Following their lead, the Topical Rainfall Measuring Mission (TRMM) Satellite Validation Office at NASA s Goddard Space Flight Center has fine-tuned these methods for specific application to the weather radar at Kwajalein Island in the Republic of the Marshall Islands, approximately 2100 miles southwest of Hawaii and 1400 miles east of Guam in the tropical North Pacific Ocean. This tropical oceanic location is important because the majority of rain, and therefore the majority of atmospheric heating, occurs in the tropics where limited ground-based radar data are available.

Marks, David A.; Wolff, David B.; Carey, Lawrence D.; Tokay, Ali

2010-01-01

309

Validation of TRMM Precipitation Radar Through Comparison of its Multi-Year Measurements to Ground-Based Radar  

NASA Technical Reports Server (NTRS)

A procedure to accurately resample spaceborne and ground-based radar data is described, and then applied to the measurements taken from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and the ground-based Weather Surveillance Radar-1988 Doppler (WSR-88D or WSR) for the validation of the PR measurements and estimates. Through comparisons with the well-calibrated, non-attenuated WSR at Melbourne, Florida for the period 1998-2007, the calibration of the Precipitation Radar (PR) aboard the TRMM satellite is checked using measurements near the storm top. Analysis of the results indicates that the PR, after taking into account differences in radar reflectivity factors between the PR and WSR, has a small positive bias of 0.8 dB relative to the WSR, implying a soundness of the PR calibration in view of the uncertainties involved in the comparisons. Comparisons between the PR and WSR reflectivities are also made near the surface for evaluation of the attenuation-correction procedures used in the PR algorithms. It is found that the PR attenuation is accurately corrected in stratiform rain but is underestimated in convective rain, particularly in heavy rain. Tests of the PR estimates of rainfall rate are conducted through comparisons in the overlap area between the TRMM overpass and WSR scan. Analyses of the data are made both on a conditional basis, in which the instantaneous rain rates are compared only at those pixels where both the PR and WSR detect rain, and an unconditional basis, in which the area-averaged rain rates are estimated independently for the PR and WSR. Results of the conditional rain comparisons show that the PR-derived rain is about 9% greater and 19% less than the WSR estimates for stratiform and convective storms, respectively. Overall, the PR tends to underestimate the conditional mean rain rate by 8% for all rain categories, a finding that conforms to the results of the area-averaged rain (unconditional) comparisons.

Liao, Liang; Meneghini, Robert

2010-01-01

310

Optimal combining of ground-based sensors for the purpose of validating satellite-based rainfall estimates  

NASA Technical Reports Server (NTRS)

Two problems related to radar rainfall estimation are described. The first part is a description of a preliminary data analysis for the purpose of statistical estimation of rainfall from multiple (radar and raingage) sensors. Raingage, radar, and joint radar-raingage estimation is described, and some results are given. Statistical parameters of rainfall spatial dependence are calculated and discussed in the context of optimal estimation. Quality control of radar data is also described. The second part describes radar scattering by ellipsoidal raindrops. An analytical solution is derived for the Rayleigh scattering regime. Single and volume scattering are presented. Comparison calculations with the known results for spheres and oblate spheroids are shown.

Krajewski, Witold F.; Rexroth, David T.; Kiriaki, Kiriakie

1991-01-01

311

Climatology of Vertical Air Motion During Rainfall in Niamey, Niger and Black Forest, Germany using an Innovative Cloud Radar Retrieval Technique  

NASA Astrophysics Data System (ADS)

In recent years, the DOE Atmospheric Radiation Measurement (ARM) program has deployed its ARM Mobile Facility (AMF) to collect continuous measurements in several climatologically distinct locations, including a year-long stay in Niamey, Niger and eight months in Germany's Black Forest. The AMF includes a vertically pointing 95 GHz cloud radar, a tool of choice for profiling non-precipitating clouds at high spatial and temporal resolutions, but commonly considered poorly suited to the quantitative study of precipitation, due in large part to attenuation. However, an innovative technique first explored by Lhermitte in the late 1980s, and subsequently by others, sidesteps much of the quantitative uncertainty imposed by attenuation by exploiting non-Rayleigh resonance effects of scattering from raindrops at 95 GHz. Given a modest range of suitable drop sizes, non-Rayleigh resonances appear as distinct peaks and valleys in Doppler spectra, which once identified, can be directly mapped to known drop sizes by Mie theory. Although attenuation in rain at 95 GHz is substantial, key to the technique is that all non-Rayleigh peaks and valleys in a given Doppler spectrum are affected equally, preserving their relative positions and magnitudes (barring feature extinction). Vertical air motion is retrieved very accurately by taking the difference between the measured Doppler velocity of a resonance feature (usually the first valley) and the known terminal velocity of its associated drop size. We have achieved promising retrieval accuracies at spatial and temporal resolutions of 30 meters and 2 seconds. Here we present lessons learned when the retrieval technique is automated and applied to measurements taken in rain over the full durations of the Niamey and Black Forest AMF deployments, comparing vertical air velocity patterns of monsoonal precipitation over the African desert with those of the orographically influenced precipitation in Germany's mountains.

Luke, E. P.; Giangrande, S. E.; Kollias, P.

2008-12-01

312

How Spaceborne Radar Helps Ground Radar in Precipitation Estimation: Real-time Incorporation of TRMM PR into NOAA NMQ System  

NASA Astrophysics Data System (ADS)

The U.S. Next-Generation Radar (NEXRAD) network provides operational precipitation products for the National Weather Service. However, the effective coverage of NEXRAD at low levels is restricted in complex terrain leading to insufficient surveillance of low-level portions of the atmosphere. This problem is especially most severe in the intermountain region of the western US. Quantitative precipitation estimation (QPE) based on radar measurements at high levels above the surface can be over- or underestimated, depending on if the radar beam intercepts or overshoots the melting layer. To mitigate this problem, researchers at the University of Oklahoma (OU) have proposed a VPR Identification and Enhancement (VPR-IE) approach to improve radar-based QPE near the surface. VPR-IE applies the VPR observed by Ku-band Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) to correct the S-band NEXRAD radar reflectivity contaminated by ice-related signals such as the bright band (BB) and dry snow signals. The real-time incorporation of TRMM-PR into the NEXRAD-based National Mosaic and Multi-sensor QPE (NMQ) system faces challenges because of their big difference in temporal resolution. The current study explores how to obtain representative VPRs for the real-time implementation of VPR-IE and investigates the potential error of VPR-IE attributed to the temporal variation of precipitation. The real-time VPR-IE is tested using the archived NMQ data collected in the mountainous West region of the U.S. (southern California, Arizona, and western New Mexico). Analysis results demonstrate the great potential of real-time VPR-IE in improving radar QPE in complex terrain.

Cao, Q.; Hong, Y.; Wen, Y.; Gourley, J. J.; Qi, Y.; Zhang, J.; Kirstetter, P.

2012-12-01

313

Evaluating the potential use of a high-resolution X-band polarimetric radar observations in Urban Hydrology  

NASA Astrophysics Data System (ADS)

The Mediterranean area concentrates the major natural risks related to the water cycle, including heavy precipitation and flash-flooding during the fall season. Every year in central and south Europe we witness several fatal and economical disasters from severe storm rainfall triggering Flash Floods, and its impacts are increasing worldwide, but remain very difficult to manage. The spatial scale of flash flood occurrence is such that its vulnerability is often focused on dispersed urbanization, transportation and tourism infrastructures (De Marchi and Scolobig 2012). Urbanized and industrialized areas shows peculiar hydrodynamic and meteo-oceanographic features and they concentrate the highest rates of flash floods and fatal disasters. The main causes of disturbance being littoral urban development and harbor activities, the building of littoral rail- and highways, and the presence of several polluted discharges. All the above mentioned characteristics limit our ability to issue timely flood warnings. Precipitation estimates based on raingauge networks are usually associated with low coverage density, particularly at high altitudes. On the other hand, operational weather radar networks may provide valuable information of precipitation at these regimes but reliability of their estimates is often limited due to retrieval (e.g. variability in the reflectivity-to-rainfall relationship) and spatial extent constrains (e.g. blockage issues, overshooting effects). As a result, we currently lack accurate precipitation estimates over urban complex terrain areas, which essentially means that we lack accurate knowledge of the triggering factor for a number of hazards like flash floods and debris flows/landslides occurring in those areas. A potential solution to overcome sampling as well as retrieval uncertainty limitations of current observational networks might be the use of network of low-power dual-polarization X-band radars as complement to raingauges and gap-filling to operational, low-frequency (C-band or S-ban) and high-power weather radars. The above hypothesis is examined using data collected during the HyMEX 2012 Special Observation Period (Nov-Feb) the urban and sub-urban complex terrain area in the Central Italy (CI). The area is densely populated and it includes the high-density populated urban and industrial area of Rome. The orography of CI is quite complex, going from sea level to nearly 3000 m in less than 150 km. The CI area involves many rivers, including two major basins: the Aniene-Tiber basin (1000 km long) and the Aterno-Pescara basin (300 km long), respectively on the west and on the east side of the Apennines ridge. Data include observations from i) the National Observatory of Athens' X-band polarimetric weather radar (XPOL), ii) two X-band miniradars (WR25X located in CNR, WR10X located in Rome Sapienza), iii) a dense network of raingauges and disdrometers (i.e. Parsivel type and 2D-video type). In addition, the experimental area is also covered from the nearby the National Research Council (CNR)'s C-band dual-polarization weather radar (Polar55C), which were involved also in the analysis. A number of storm events are selected and compared with the nearby C-band radar to investigate the potential of using high-resolution and microphysically-derived rainfall based on X-band polarimetric radar observations. Events have been discriminated on the basis of rainfall intensity and hydrological response. Results reveal that in contrast with the other two rainfall sources (in situ and C-band radar), X-band radar rainfall estimates offer an improved representation of the local precipitation variability, which turns to have a significant impact in simulating the peak flows associated with these events.

Anagnostou, Marios N.; Kalogiros, John; Marzano, Frank S.; Anagnostou, Emmanouil N.; Baldini, Luca; Nikolopoulos, EfThymios; Montopoli, Mario; Picciotti, Errico

2014-05-01

314

A parameterization of the evaporation of rainfall  

NASA Technical Reports Server (NTRS)

A general theoretical expression for the rainfall rate and the total evaporation rate as a function of the distance below cloud base is developed, and is then specialized to the gamma raindrop size distribution. The theoretical framework is used to analyze the data of Rosenfeld and Mintz (1988) on the radar observations of the rainfall rate as a function of the distance below cloud base, for rain falling from continental convective cells in central South Africa, obtaining a parameterization for the evaporation of rainfall.

Schlesinger, Michael E.; Oh, Jai-Ho; Rosenfeld, Daniel

1988-01-01

315

Radar Technology Applied to Air Traffic Control  

Microsoft Academic Search

Use of primary radars for air traffic control (ATC) is discussed. The location and the parameters of various ATC radars are described. The clutter environment (land clutter, birds, automobiles, and weather) has had a major impact on the configuration of these radars. Signal-processing techniques and antenna techniques utilized to cope with the clutter are described. Future signal-processing techniques for the

WILLIAM W. SHRADER

1973-01-01

316

Analysis of the uncertainty in rainfall forecasts obtained with a probabilistic nowcasting technique  

NASA Astrophysics Data System (ADS)

Nowadays different methodologies have been developed for very short-term precipitation forecasting based on radar observations. When the advection of precipitation explains a significant portion of the temporal evolution of precipitation, the Lagrangian persistence is the most appropriate method. Unfortunately, in convective precipitation episodes it does not occur like this because the growth and decay of precipitation is generally fast and advection provides little information. It is then necessary to introduce probabilistic nowcasting methods that allow to characterize the uncertainty associated with the temporal evolution of precipitation. SBMcast (Berenguer et al., 2011) is an ensemble nowcasting algorithm based on Lagrangian extrapolation of recent radar observations. It generates a set of future rainfall scenarios (ensemble members) compatible with the observations and preserving the spatial and temporal structure of the rainfall field according to the String of Beads model. The parameters used to generate a member of the ensemble model are the time series of a set of variables that model the rainfall field at two levels: at global and at pixel scale. We have analyzed these two components of SBMcast with the aim of identifying the role that each component has in the resulting forecast uncertainty. The final objective of this analysis is understanding the expected impact of the use of additional information to constrain each part of the algorithm. Conventional scores have been used to compare SBMcast with two reference algorithms: deterministic Lagrangian extrapolation, and the probabilistic "Local Lagrangian" technique [the one that demonstrated the best skill, among those analyzed by Germann and Zawadzki (2004)]. The results have been obtained for a set of rainfall episodes in the vicinity of Barcelona, Catalonia (Spain) using the observations of the Catalan Weather Service radar network. References Berenguer, M., D. Sempere-Torres, and G. Pegram, 2011: SBMcast-An ensemble nowcasting technique to assess the uncertainty in rainfall forecasts by Lagrangian extrapolation. Journal of Hydrology, 404, 226-240. Germann, U. and I. Zawadzki, 2004: Scale Dependence of the Predictability of Precipitation from Continental Radar Images. Part II: Probability Forecasts. Journal of Applied Meteorology, 43, 74-89.

Buil, Álex; Berenguer, Marc; Sempere-Torres, Daniel

2014-05-01

317

78 FR 19063 - Airworthiness Approval for Aircraft Forward-Looking Windshear and Turbulence Radar Systems  

Federal Register 2010, 2011, 2012, 2013, 2014

...Forward-Looking Windshear and Turbulence Radar Systems AGENCY: Federal Aviation Administration...forward-looking windshear and turbulence radar systems. The planned advisory circular...Order (TSO)-C63d, Airborne Weather Radar Equipment. The objective is to...

2013-03-28

318

Satellite rainfall estimation over Thailand  

NASA Astrophysics Data System (ADS)

Rainfall plays a fundamental role in the earth's climate system. The measurement of rainfall is essential to our understanding of the hydrological cycle. Satellite observations seem to offer the best possibility for estimating rainfall and provide an excellent complement to continuous monitoring of rain events both spatially and temporally to conventional rain gauge networks or meteorological radars. The development of satellite techniques at better spatial and temporal resolution for accurate rainfall estimation, however, still remains a difficult challenge. The Tropical Rainfall Measuring Mission (TRMM) is the first satellite dedicated to monitoring and understanding tropical rainfall and designed to provide quantitative rainfall information. To improve the data quality, the TRMM algorithms and products are periodically improved and reprocessed. This dissertation is aimed at evaluating TRMM products as well as improving remote sensing techniques for rainfall estimation. For these purposes, the study will be focused specifically on the area of Thailand. Evaluations are conducted by comparing both versions 5 (V5) and 6 (V6) of TRMM and other satellite merged rainfall (3B42) with in situ measurements by rain gauges over Thailand. The V5 is computed from the Adjusted Geosynchronous Precipitation Index (AGPI) and V6 is computed using the TRMM Multi-satellite Precipitation Analysis (TMPA) algorithm. Unlike V5 3B42, V6 3B42 is merged with gauge measurements at the sub-monthly scale. The V5 (satellite only product) shows large biases with respect to the Thailand rain gauges (TG) data. Comparison of daily TG with V6 3B42 rain estimates shows improved performance over V5 in terms of error statistics. However, statistical analyses of rain/no-rain detection show that the critical success index (CSI) is basically unchanged between V5 and V6, indicating no improvement in term of the skill of rainfall detection. In the development of satellite rainfall estimation, an alternative technique, Microwave-calibrated Infrared Split-window Technique (MIST), is introduced by combining the use of microwave and infrared information. The approach is based on the AGPI technique. Additional split-window information from infrared channels is used in the training of the algorithm. The MIST is developed and examined during both rainy and dry months. The MIST provides reasonable performance which is comparable to the V6 3B42, however, the CSI is improved. The technique can be applied to areas where microwave estimates (3B40RT) from TRMM and other microwave sensors and the infrared data from geostationary satellites are available.

Chokngamwong, Roongroj

319

Anatomy of extraordinary rainfall and flash flood in a Dutch lowland catchment  

NASA Astrophysics Data System (ADS)

On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany were struck by a series of rainfall events lasting for more than a day. Over an area of 740 km2 more than 120 mm of rainfall were observed in 24 h. This extreme event resulted in local flooding of city centres, highways and agricultural fields, and considerable financial loss. In this paper we report on the unprecedented flash flood triggered by this exceptionally heavy rainfall event in the 6.5 km2 Hupsel Brook catchment, which has been the experimental watershed employed by Wageningen University since the 1960s. This study aims to improve our understanding of the dynamics of such lowland flash floods. We present a detailed hydrometeorological analysis of this extreme event, focusing on its synoptic meteorological characteristics, its space-time rainfall dynamics as observed with rain gauges, weather radar and a microwave link, as well as the measured soil moisture, groundwater and discharge response of the catchment. At the Hupsel Brook catchment 160 mm of rainfall was observed in 24 h, corresponding to an estimated return period of well over 1000 years. As a result, discharge at the catchment outlet increased from 4.4 × 10-3 to nearly 5 m3 s-1. Within 7 h discharge rose from 5 × 10-2 to 4.5 m3 s-1. The catchment response can be divided into four phases: (1) soil moisture reservoir filling, (2) groundwater response, (3) surface depression filling and surface runoff and (4) backwater feedback. The first 35 mm of rainfall were stored in the soil without a significant increase in discharge. Relatively dry initial conditions (in comparison to those for past discharge extremes) prevented an even faster and more extreme hydrological response.

Brauer, C. C.; Teuling, A. J.; Overeem, A.; van der Velde, Y.; Hazenberg, P.; Warmerdam, P. M. M.; Uijlenhoet, R.

2011-06-01

320

Soil buffer limits flash flood response to extraordinary rainfall in a Dutch lowland catchment  

NASA Astrophysics Data System (ADS)

On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany were struck by a series of very heavy rainfall events lasting for more than a day. Over an area of 740 km2 more than 120 mm of rainfall was observed in 24 h. This extreme event resulted in local flooding of city centres, highways and agricultural fields, and considerable financial loss. In this paper we report on the unprecedented flash flood triggered by this exceptionally heavy rainfall event in the 6.5 km2 Hupsel Brook catchment, which has been the experimental watershed employed by Wageningen University since the 1960s. This study aims to improve our understanding of the dynamics of such lowland flash floods. We present a detailed hydrometeorological analysis of this extreme event, focusing on its synoptic meteorological characteristics, its space-time rainfall dynamics as observed with rain gauges, weather radar and a microwave link, as well as the measured soil moisture, groundwater and discharge response of the catchment. At the Hupsel Brook catchment 159.5 mm of rainfall was observed in 24 h, corresponding to an estimated return period in the order of 6000 years. As a result, discharge at the catchment outlet increased from 4.4 l s-1 to nearly 5 m3 s-1 (i.e. a specific discharge of 0.77 m3 s-1 km-2, or 2.8 mm h-1). Within 7 h discharge rose from 50 to 4.5 m3 s-1. The catchment response can be divided into four phases: (1) soil moisture reservoir filling, (2) groundwater response, (3) surface depression filling and surface runoff and (4) backwater feedback. The first 35 mm of rainfall were stored in the soil without a significant increase in discharge. Relatively dry initial conditions (in comparison to those for past discharge extremes) prevented an even faster and more vigorous hydrological response.

Brauer, C. C.; Teuling, A. J.; Overeem, A.; van der Velde, Y.; Hazenberg, P.; Warmerdam, P. M. M.; Uijlenhoet, R.

2011-01-01

321

The Tropical Rainfall Measuring Mission (TRMM) Sensor Package  

Microsoft Academic Search

This note is intended to serve primarily as a reference guide to users wishing to make use of the Tropical Rainfall Measuring Mission data. It covers each of the three primary rainfall instruments: the passive microwave radiometer, the precipitation radar, and the Visible and Infrared Radiometer System on board the spacecraft. Radiometric characteristics, scanning geometry, calibration procedures, and data products

Christian Kummerow; William Barnes; Toshiaki Kozu; James Shiue; Joanne Simpson

1998-01-01

322

Self-consistency of polarization diversity measurement of rainfall  

Microsoft Academic Search

Polarization diversity measurements of rainfall, namely the reflectivity factor, differential reflectivity, and specific differential propagation phase, vary in a constrained three-dimensional space. Algorithms are derived to quantify this self-consistency of measurements. In particular, estimation of the specific differential propagation phase shift based on reflectivity and differential reflectivity is analyzed in detail. Theoretical simulation as well as radar observations of rainfall

G. Scarchilli; V. Gorgucci; V. Chandrasekar; A. Dobaie

1996-01-01

323

Systems and methods for supplemental weather information presentation on a display  

NASA Technical Reports Server (NTRS)

An embodiment of the supplemental weather display system presents supplemental weather information on a display in a craft. An exemplary embodiment receives the supplemental weather information from a remote source, determines a location of the supplemental weather information relative to the craft, receives weather information from an on-board radar system, and integrates the supplemental weather information with the weather information received from the on-board radar system.

Bunch, Brian (Inventor)

2010-01-01

324

How are Rainfall Rates Measured?  

NSDL National Science Digital Library

In this problem-based learning activity, students learn about weather forecasting and the role of the TRMM (Tropical Rainfall Measuring Mission) satellite in data collection. Assuming the role of climatologists, students assist a reporter in determining the accuracy of weather predictions published in The Old Farmer's Almanac. The lesson requires a street map of the local community, acetate sheets to cover the map, materials needed to build a homemade rain gauge, and sample pages of the almanac. Teacher notes, student worksheet, glossary and an appendix introducing problem-based learning are included. This resource is the first of the 3-part learning module, Investigating the Climate System: Precipitation.

325

A Quality Control Concept for Radar Reflectivity, Polarimetric Parameters, and Doppler Velocity  

Microsoft Academic Search

Over the last few years the use of weather radar data has become a fundamental part of various applications like rain-rate estimation, nowcasting of severe weather events, and assimilation into numerical weather prediction models. The increasing demand for radar data necessitates an automated, flexible, and modular quality control. In this paper a quality control procedure is developed for radar reflectivity

Katja Friedrich; Martin Hagen; Thomas Einfalt

2006-01-01

326

Development of the Solid State X-band Radar and the Phased Array Radar System in Japan  

E-print Network

-band radar for meteorological application using the state of the art solid state amplifier and the phasedDevelopment of the Solid State X-band Radar and the Phased Array Radar System in Japan By DR. TOMOO. This is the first X-band solid-state weather radar in service in Japan, which adopted new technologies including

Droegemeier, Kelvin K.

327

Cockpit weather information needs  

NASA Technical Reports Server (NTRS)

The primary objective is to develop an advanced pilot weather interface for the flight deck and to measure its utilization and effectiveness in pilot reroute decision processes, weather situation awareness, and weather monitoring. Identical graphical weather displays for the dispatcher, air traffic control (ATC), and pilot crew should also enhance the dialogue capabilities for reroute decisions. By utilizing a broadcast data link for surface observations, forecasts, radar summaries, lightning strikes, and weather alerts, onboard weather computing facilities construct graphical displays, historical weather displays, color textual displays, and other tools to assist the pilot crew. Since the weather data is continually being received and stored by the airborne system, the pilot crew has instantaneous access to the latest information. This information is color coded to distinguish degrees of category for surface observations, ceiling and visibilities, and ground radar summaries. Automatic weather monitoring and pilot crew alerting is accomplished by the airborne computing facilities. When a new weather information is received, the displays are instantaneously changed to reflect the new information. Also, when a new surface or special observation for the intended destination is received, the pilot crew is informed so that information can be studied at the pilot's discretion. The pilot crew is also immediately alerted when a severe weather notice, AIRMET or SIGMET, is received. The cockpit weather display shares a multicolor eight inch cathode ray tube and overlaid touch panel with a pilot crew data link interface. Touch sensitive buttons and areas are used for pilot selection of graphical and data link displays. Time critical ATC messages are presented in a small window that overlays other displays so that immediate pilot alerting and action can be taken. Predeparture and reroute clearances are displayed on the graphical weather system so pilot review of weather along the route can be accomplished prior to pilot acceptance of the clearance. An ongoing multiphase test series is planned for testing and modifying the graphical weather system. Preliminary data shows that the nine test subjects considered the graphical presentation to be much better than their current weather information source for situation awareness, flight safety, and reroute decision making.

Scanlon, Charles H.

1992-01-01

328

Radar Images of the Earth: Interferometry  

NSDL National Science Digital Library

This site features links to nineteen NASA radar images using interferometry to enhance details or measure changes in elevation. The image pages contain brief descriptions of the respective processes and settings. They were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

329

Radar Images of the Earth: Volcanoes  

NSDL National Science Digital Library

This site features links to thirty-five NASA radar images of the world's volcanoes, including brief descriptions of the respective processes and settings involved. The images were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

330

Radar Images of the Earth: Cities  

NSDL National Science Digital Library

This site features links to more than fifty NASA radar images of the world's cities, including brief descriptions of the respective processes and settings involved. The images were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

331

Space Radar Images of the Earth: Archaeology  

NSDL National Science Digital Library

This site features links to twelve NASA radar images of the world's famous archaeology sites, including brief descriptions of the respective processes and settings involved. The images were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

332

Radar Images of the Earth: Oceans  

NSDL National Science Digital Library

This site features links to seven NASA radar images of the world's oceans, including brief descriptions of the respective processes and settings. The images were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

333

Estimation of sampling errors and scale parameters using two- and three-dimensional rainfall data analyses  

Microsoft Academic Search

This paper presents the analysis of rainfall data based on radar echoes collected in the vicinity of Darwin, Australia, during special observation periods in 1988. The study was conducted to estimate the scale parameters (such as timescale and length scale) present in the rainfall data, which are important in parameterizing many stochastic rainfall models. Another equally important issue addressed here

Vishwas V. Soman; Juan B. Valdés; Gerald R. North

1996-01-01

334

Evaluation of Satellite Rainfall Products over NASA's Iowa Flood Studies (IFloodS) Domain  

NASA Astrophysics Data System (ADS)

Iowa Flood Studies (IFloodS) is a NASA Global Precipitation Measurement (GPM) Mission to provide better understanding of the strengths and limitations of satellite products in the context of hydrologic applications. IFloodS took place in the central to north eastern part of Iowa in Midwestern United States during the months of April-June, 2013. Quantifying the physical characteristics, space/time variability and assessing satellite rainfall retrieval uncertainties at instantaneous to daily time scales are of the main objectives of IFloodS field experiment beside assessing hydrologic predictive skills as a function of space/time scales and discerning the relative roles of rainfall quantities in flood genesis. Our study consists of two parts; first part is concerned with the evaluation of satellite rainfall products such as TRMM's TMPA 3B42 V7, CPC's CMORPH and CHRS at UCI's PERSIANN, and the quantification of their uncertainties. In the second part of the study we evaluated the performance of some radar rainfall products such as NCEP Stage IV and Q2 as ground references since they are being used for this purpose in many hydro-climatological applications. In the first part of the study, three satellite rainfall products have been used, and a radar rainfall product has been used as a ground reference. All the satellite rainfall products used in this study represent 3 hourly, quarter degree, rainfall accumulation or finer resolutions. Our ground reference is NCEP Stage IV radar-rainfall, which is available in an hourly, four kilometers, resolution. While arguably the adequacy of radar rainfall as a ground reference is only marginal, we used the radar products to study the spatial and temporal correlation of the satellite product errors. We studied the behavior of the errors, defined as the difference between the satellite and radar product (with matched space time resolution), during the period from the year 2004 through the year 2010. Our results show that the error behavior of the satellite rainfall products is quite similar. For the second part of our study we discuss the adequacy of the Stage IV and other radar rainfall products as ground references for evaluating satellite rainfall products. We used our rain gauge network in Iowa to evaluate the performance of radar rainfall data on different spatial and temporal scales. We also produced beam blockage maps and probability of detection (POD) maps for the NEXRAD radars used in radar rainfall to find links, if any, between beam blockage and radar rainfall mosaic techniques, and the inconsistencies in the results of some hydrologic models.

ElSaadani, M. A.; Krajewski, W. F.; Goska, R.

2013-12-01

335

Precipitation observations from high frequency spaceborne polarimetric synthetic aperture radar and ground-based radar: Theory and model validation  

NASA Astrophysics Data System (ADS)

Global weather monitoring is a very useful tool to better understand the Earth's hydrological cycle and provide critical information for emergency and warning systems in severe cases. Developed countries have installed numerous ground-based radars for this purpose, but they obviously are not global in extent. To address this issue, the Tropical Rainfall Measurement Mission (TRMM) was launched in 1997 and has been quite successful. The follow-on Global Precipitation Measurement (GPM) mission will replace TRMM once it is launched. However, a single precipitation radar satellite is still limited, so it would be beneficial if additional existing satellite platforms can be used for meteorological purposes. Within the past few years, several X-band Synthetic Aperture Radar (SAR) satellites have been launched and more are planned. While the primary SAR application is surface monitoring, and they are heralded as "all weather'' systems, strong precipitation induces propagation and backscatter effects in the data. Thus, there exists a potential for weather monitoring using this technology. The process of extracting meteorological parameters from radar measurements is essentially an inversion problem that has been extensively studied for radars designed to estimate these parameters. Before attempting to solve the inverse problem for SAR data, however, the forward problem must be addressed to gain knowledge on exactly how precipitation impacts SAR imagery. This is accomplished by simulating storms in SAR data starting from real measurements of a storm by ground-based polarimetric radar. In addition, real storm observations by current SAR platforms are also quantitatively analyzed by comparison to theoretical results using simultaneous acquisitions by ground radars even in single polarization. For storm simulation, a novel approach is presented here using neural networks to accommodate the oscillations present when the particle scattering requires the Mie solution, i.e., particle diameter is close to the radar wavelength. The process of transforming the real ground measurements to spaceborne SAR is also described, and results are presented in detail. These results are then compared to real observations of storms acquired by the German TerraSAR-X satellite and by one of the Italian COSMO-SkyMed satellites both operating in co-polar mode (i.e., HH and VV). In the TerraSAR-X case, two horizontal polarization ground radars provided simultaneous observations, from which theoretical attenuation is derived assuming all rain hydrometeors. A C-band fully polarimetric ground radar simultaneously observed the storm captured by the COSMO-SkyMed SAR, providing a case to begin validating the simulation model. While previous research has identified the backscatter and attenuation effects of precipitation on X-band SAR imagery, and some have noted an impact on polarimetric observations, the research presented here is the first to quantify it in a holistic sense and demonstrate it using a detailed model of actual storms observed by ground radars. In addition to volumetric effects from precipitation, the land backscatter is altered when water is on or near the surface. This is explored using TRMM, Canada's RADARSAT-1 C-band SAR and Level 3 NEXRAD ground radar data. A weak correlation is determined, and further investigation is warranted. Options for future research are then proposed.

Fritz, Jason P.

336

Analysis of TRMM Precipitation Radar Algorithms and Rain over the Tropics and Southeast Texas  

E-print Network

The Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) 2A23 algorithm classifies rain echo as stratiform or convective while the 2A25 algorithm corrects vertical profiles of radar reflectivity for attenuation and calculates rain...

Funk, Aaron

2013-12-10

337

New approach to radar rainfall measurement  

NASA Technical Reports Server (NTRS)

This paper integrates individual studies of the Area-Time Integrals method and climatic tuning methods. The latter is extended to a new approach which generalizes the technique so that it is no longer restricted to power law relations between effective reflectivity and rain rate.

Atlas, David; Rosenfeld, Daniel; Wolff, David B.

1991-01-01

338

Ground truth for oceanic rainfall  

NASA Technical Reports Server (NTRS)

Communications systems operating at frequencies in excess of 10 GHz are degraded significantly by rainfall. To provide the information needed for design of these millimeter wave systems, rain attentuation models were developed and data bases of propagation related information were accumulated. These data bases were developed based on the signal level measurements of geostationary satellite beacons at selected frequencies. Groundbased radar reflection measurements were able to develop data bases for system design. The rain attenuation models allow accurate correlation between the rain rate and the attenuation.

Dorman, C. E.

1981-01-01

339

A total electron content space weather study of the nighttime Weddell Sea Anomaly of 1996\\/1997 southern summer with TOPEX\\/Poseidon radar altimetry  

Microsoft Academic Search

This paper reports on a total electron content space weather study of the nighttime Weddell Sea Anomaly, overlooked by previously published TOPEX\\/Poseidon climate studies, and of the nighttime ionosphere during the 1996\\/1997 southern summer. To ascertain the morphology of spatial TEC distribution over the oceans in terms of hourly, geomagnetic, longitudinal and summer-winter variations, the TOPEX TEC, magnetic, and published

Ildiko Horvath

2006-01-01

340

Analysis and very short range forecast of cyclone "AILA" with radar data assimilation with rapid intermittent cycle using ARPS 3DVAR and cloud analysis techniques  

NASA Astrophysics Data System (ADS)

In this study, both reflectivity and radial velocity are assimilated into the Weather Research and Forecasting (WRF) model using ARPS 3DVAR technique and cloud analysis procedure for analysis and very short range forecast of cyclone ÁILA. Doppler weather radar (DWR) data from Kolkata radar are assimilated for numerical simulation of landfalling tropical cyclone. Results show that the structure of cyclone AILA has significantly improved when radar data is assimilated. Radar reflectivity data assimilation has strong influence on hydrometeor structures of the initial vortex and precipitation pattern and relatively less influence is observed on the wind fields. Divergence/convergence conditions over cyclone inner-core area in the low-to-middle troposphere (600-900 hPa) are significantly improved when wind data are assimilated. However, less impact is observed on the moisture field. Analysed minimum sea level pressure (SLP) is improved significantly when both reflectivity and wind data assimilated simultaneously (RAD-ZVr experiment), using ARPS 3DVAR technique. In this experiment, the centre of cyclone is relocated very close to the observed position and the system maintains its intensity for longer duration. As compared to other experiments track errors are much reduced and predicted track is very much closer to the best track in RAD-ZVr experiment. Rainfall pattern and amount of rainfall are better captured in this experiment. The study also reveals that cyclone structure, intensification, direction of movement, speed and location of cyclone are significantly improved and different stages of system are best captured when both radar reflectivity and wind data are assimilated using ARPS 3DVAR technique and cloud analysis procedure. Thus optimal impact of radar data is realized in RAD-ZVr experiment. The impact of DWR data reduces after 12 h forecast and it is due to the dominance of the flow from large-scale global forecast system model. Successful coupling of data assimilation package ARPS 3DVAR with WRF model for Indian DWR data is also demonstrated.

Srivastava, Kuldeep; Bhardwaj, Rashmi

2014-04-01

341

The Ponape ST radar  

NASA Astrophysics Data System (ADS)

In May, 1984, a 50-MHz ST radar was installed on the island of Ponape in the western equatorial Pacific (7 deg N, 158 deg E) by the Aeronomy Laboratory of NOAA. The radar consists of a 100 m x 100 m array with a single, vertically directed, beam and is initially transmitting micro sec. (2.25 km) pulses. The radar is operating continuously, with Doppler spectra being recorded at approximately 1 1/2 minute intervals and sent to Boulder for later analysis. One of the principal goals of the radar is to measure vertical motions in the troposphere and lower stratosphere at a location which is within the intertropical convergence zone during part of the year. First results, during generally fair weather conditions, show detectable echoes up to about 21 km with the tropopause at 17-18 km. Once daily balloon soundings are available locally from a NOAA Weather Service Office on the island, it is planned that this radar will be joined in the coming year by two others with oblique as well as vertical beams on two yet-to-be-selected equatorial islands as part of the TOGA (Tropical Oceans Global Atmosphere) program.

Carter, D. A.; Ecklund, W. L.; Balsley, B. B.

1984-12-01

342

Rainfall Variability of South East Queensland  

NASA Astrophysics Data System (ADS)

The seasonal weather of southeastern Queensland (SEQ) is commonly described by a wet and a dry season. Rainfall in this area has been declining for the past fifty years and climate projections indicate decreasing trends in annual rainfall and increases in temperature. These factors combined with population growth suggest a need for Queensland to re-evaluate its water management. In order to understand the rainfall variability of SEQ, it is useful to consider the impact of the different weather patterns or synoptic regimes on the regional rainfall. Previous studies have examined the synoptic patterns associated with extreme wind and rainfall events in SEQ and the correlation between rainfall in northern Queensland and atmospheric variables, but a comprehensive climatology for the SEQ region is missing. Analysis of routine soundings is found to reveal relationships between surface precipitation and atmospheric structure. Cluster analysis was performed on daily radiosonde data for Brisbane Airport spanning the period 01/01/1990-11/11/2009. The clustering was initially performed on seven atmospheric variables: total-totals, 850mb winds, wind shear between 850mb and 500mb, moisture flux and total water calculated from the sounding data. A sensitivity study reveals that the moisture flux parameters followed by total water and total-totals are the key variables in determining the regimes. The clusters were combined with daily rainfall records spanning the period 01/01/1995 - 01/06/2008 to determine the contribution of each regime to monthly rainfall. The seven-cluster case describes three separate southeasterly regimes, three westerly regimes and an easterly regime. The contribution of each regime to annual rainfall was also determined. The regimes for SEQ can be divided into ‘wet' and ‘dry' cases. It is apparent that the rainfall is largely limited to the coastal strip, with maxima near regions with steep terrain. The main rainfall period is from November through to February, with peak falls tending to be in February. The ‘wet' regimes are responsible for the majority of the region's rainfall. Southeasterly wind regimes are commonly associated with trade wind or ‘stream' showers and coastal trade wind cumulus. When there is significant moisture such as for the ‘moist' southeasterly regime these systems can bring significant rainfall to the region. The northwesterly regime can produce deep convection and contributes greatly to the total annual rainfall (21.7%) despite occurring less than 7% of the time. The easterly and westerly regimes also are major contributors to annual rainfall. There are also significant rainfall events during the dry season such as intense sub-tropical cyclones (east-coast lows) that bring sustained strong winds and intense rainfall to the region. In general, however, the winter season is dry and is well described by a southwesterly regime and a ‘dry' southeasterly regime. The dominant synoptic regime, the southeasterly regime, does not contribute significantly to the total rainfall in any month. The relationship between the Southern Oscillation Index (SOI) and rainfall over most of Queensland is strong. The correlation between SEQ monthly rainfall anomalies and the Southern Oscillation Index (SOI) was calculated over the period 1858-2008. A small but significant correlation is found between the SOI and rainfall in southeastern Queensland. The low correlation indicates that the rainfall is controlled by other factors in addition to the El Nino - Southern Oscillation.

Wilson, Louise; Manton, Michael; Siems, Steven

2010-05-01

343

Extreme Rainfall In A City  

NASA Astrophysics Data System (ADS)

Cities contain many structures and activities that are vulnerable to severe weather. Heavy precipitation cause floods which can damage structures, compromise transportation and water supply systems, and slow down economic and social activities. Rain induced flood patterns in cities must be well understood to enable effective placement of flood control and other regulatory measures. The planning goal is not to eliminate all floods but to reduce their frequency and resulting damage. Possible approaches to such planning include probability based extreme event analysis. Precipitation is normally the most variable hydrologic element over a given area. This variability results from the distribution of clouds and in cloud processes in the atmosphere, the storm path, and the distribution of topographical features on the ground along path. Some studies suggest that point rainfall patterns are also affected by urban industrial effects hence some agreement that cities are wetter than the country surrounding them. However, there are still questions regarding the intra- urban distribution of precipitation. The sealed surfaces, urban structures, and the urban heat anomaly increase convection in cities which may enhance the generation of clouds. Increased dust and gaseous aerosols loads are effective condensation and sublimation nuclei which may also enhance the generation of precipitation. Based on these associations, the greatest amount of convection type rainfall should occur at city center. A study of summer rainfall in Calgary showed that frequencies of trace amounts of rainfall and events under 0.2mm are highest downtown than elsewhere. For amounts greater than than 0.2 mm, downtown sites were not favored. The most compelling evidence for urban-industrial precipitation enhancement came from the Metromex project around St. Loius, Missouri where maximum increases of between 5 to 30 per cent in summer rainfall downwind of the city was linked to urbanization and industrialization. The development of small cloud droplets into larger particles requires time. A single thunderstorm cell has a mean development time of about 20 minutes and a life time of around 45 minutes with a mean mind of 10m/s, an air parcel would travel 12 km from the beginning of droplet formation to the first precipitation. That means that the precipitation field is shifted downwind of settlements. It could also explain the the higher frequency of the trace to small amounts observed in Calgary since those events occur under relatively calm weather. Whereas the majority of studies have focused on summer convectional type events, little appears to have been done on the extreme rainfall events on which most structural designs are based. Is there a detectable urban bias in these events? Do urban areas intensify them? What are the implications of point distribution of extreme rainfall events on flood frequency across a city. This paper examines the spatial distribution of the mean annual maximum rainfall event in Calgary, Canada, with a view to determining the relative contribution of geographical setting and urbanisation to point patterns. The data are subsequently maximized to produce maps of probable maximum precipitation for the city. The major results are as follows: (a) position along storm path is the most important variable determining maximum rainfall hazard, (b) higher grounds receive up to seventy percent more maximum rainfall than values based on spatial trend, (c) urban structure and geometry correlate negatively with maximum rainfall intensity, however, (d) zones of maximum flood peaks are found down slope of areas of maximum precipitation increasing flood hazard in the inner city in spite of its lower precipitation. Drainage networks based on point rainfall patterns have proved grossly inadequate for flood mitigation. The new design based on this study recognizes the strong moisture gradients caused by rapid movement of water and other elements down slope. Snow and river flow hazards reflect similar environmental controls.

Nkemdirim, Lawrence

344

J1.10 FAA SURVEILLANCE RADAR DATA AS A COMPLEMENT TO THE WSR-88D NETWORK *  

E-print Network

Surveillance Radars (ASRs), Air Route Surveillance Radars (ARSRs) and Terminal Doppler Weather Radars (TDWRs). Current generation terminal and en route aircraft surveillance radars (ASR-9, ASR-11 and ARSR-4) feature of these "weather channels" will be upgraded to measure Doppler velocity, supporting, for example, wind shear

Droegemeier, Kelvin K.

345

Evaluation of a Spectral-Based Nonlinear Stochastic Nowcasting Model (PhaSt) on Italian radar mosaic  

NASA Astrophysics Data System (ADS)

Evaluation of a Spectral-Based Nonlinear Stochastic Nowcasting Model (PhaSt) on Italian radar mosaic G. Cummings1, N. Rebora2 and F. Silvestro2 1Hydrometeorological Service, Ministry of Agriculture, Georgetown, Guyana 2CIMA research foundation, Savona, Italy The forecasting of precipitation events and flash floods are critical for civil protection. The temporal and spatial resolution of weather radar data as the input for nowcasting models has shown significant promise in improving forecasts in recent years. This work aims to evaluate the performance of a Spectral-Based Nonlinear Stochastic Nowcasting Model (PhaSt) in the Italian radar domain with 76 rainfall events and to assess the hydrological applicability of the forecasts for small to medium size river basins. The results were validated by comparison of the forecasted precipitation fields with the radar observations and by computing simple forecast skill scores. In addition to model evaluation based on seasonal occurrence, the 76 weather events considered were also classified into 2 types: long-lived and spatially distributed (Type I) or brief and localized (Type II). The results showed that PhaSt produced good results for up to 60 minutes for all seasons and event types, and for all the selected model parameter values.

Rhandhir Cummings, Garvin; Rebora, Nicola; Silvestro, Francesco

2014-05-01

346

An Investigation of the Influence of Urban Areas on Rainfall Using the TRMM Satellite and a Cloud-Mesoscale Model  

NASA Technical Reports Server (NTRS)

A recent paper by Shepherd and Pierce (in press at Journal of Applied Meteorology) used rainfall data from the Precipitation Radar on NASA's Tropical Rainfall Measuring Mission's (TRMM) satellite to identify warm season rainfall anomalies downwind of major urban areas. Data (PR) were employed to identify warm season rainfall (1998-2000) patterns around Atlanta, Montgomery, Nashville, San Antonio, Waco, and Dallas. Results reveal an average increase of approx. 28% in monthly rainfall rates within 30-60 kilometers downwind of the metropolis with a modest increase of 5.6% over the metropolis. Portions of the downwind area exhibit increases as high as 51%. The percentage changes are relative to an upwind control area. It was also found that maximum rainfall rates in the downwind impact area exceeded the mean value in the upwind control area by 48%-116%. The maximum value was generally found at an average distance of 39 km from the edge of the urban center or 64 km from the center of the city. Results are consistent with METROMEX studies of St. Louis almost two decades ago and with more recent studies near Atlanta. A convective-mesoscale model with extensive land-surface processes is currently being employed to (a) determine if an urban heat island (UHI) thermal perturbation can induce a dynamic response to affect rainfall processes and (b) quantify the impact of the following three factors on the evolution of rainfall: (1) urban surface roughness, (2) magnitude of the UHI temperature anomaly, and (3) physical size of the UHI temperature anomaly. The sensitivity experiments are achieved by inserting a slab of land with urban properties (e.g. roughness length, albedo, thermal character) within a rural surface environment and varying the appropriate lower boundary condition parameters. The study will discuss the feasibility of utilizing satellite-based rainfall estimates for examining rainfall modification by urban areas on global scales and over longer time periods. The talk also introduces very preliminary results from the modeling component of the study. Such research has implications for weather forecasting, urban planning, water resource management, and understanding human impact on the environment and climate.

Shepherd, J. Marshall; OCStarr, David (Technical Monitor)

2002-01-01

347

TRMM (Tropical Rainfall Measuring Mission): A satellite mission to measure tropical rainfall  

NASA Technical Reports Server (NTRS)

The Tropical Rainfall Measuring Mission (TRMM) is presented. TRMM is a satellite program being studied jointly by the United States and Japan which would carry out the systematic study of tropical rainfall required for major strides in weather and climate research. The scientific justification for TRMM is discussed. The implementation process for the scientific community, NASA management, and the other decision-makers and advisory personnel who are expected to evaluate the priority of the project is outlined.

Simpson, Joanne (editor)

1988-01-01

348

Spatial rainfall data in open source environment  

NASA Astrophysics Data System (ADS)

Since January 2013 The Netherlands have access to innovative high-quality rainfall data that is used for watermanagers. This product is innovative because of the following reasons. (i) The product is developed in a 'golden triangle' construction - corporation between government, business and research. (ii) Second the rainfall products are developed according to the open-source GPL license. The initiative comes from a group of water boards in the Netherlands that joined their forces to fund the development of a new rainfall product. Not only data from Dutch radar stations (as is currently done by the Dutch meteorological organization KNMI) is used but also data from radars in Germany and Belgium. After a radarcomposite is made, it is adjusted according to data from raingauges (ground truth). This results in 9 different rainfall products that give for each moment the best rainfall data. Specific knowledge is necessary to develop these kind of data. Therefore a pool of experts (KNMI, Deltares and 3 universities) participated in the development. The philosophy of the developers (being corporations) is that products like this should be developed in open source. This way knowledge is shared and the whole community is able to make suggestions for improvement. In our opinion this is the only way to make real progress in product development. Furthermore the financial resources of government organizations are optimized. More info (in Dutch): www.nationaleregenradar.nl

Schuurmans, Hanneke; Maarten Verbree, Jan; Leijnse, Hidde; van Heeringen, Klaas-Jan; Uijlenhoet, Remko; Bierkens, Marc; van de Giesen, Nick; Gooijer, Jan; van den Houten, Gert

2013-04-01

349

Rainfall maps from cellular communication networks: Assessing uncertainties  

NASA Astrophysics Data System (ADS)

Several studies show the potential applicability of commercial cellular communication networks in the retrieval of rainfall fields, sometimes even for an entire country. The key principle of rainfall monitoring using microwave links is based on the attenuation, due to rainfall, of the electromagnetic signals transmitted from one telephone tower to another. By measuring the received power at one end of a microwave link, as a function of time, the path-averaged rainfall intensity can be estimated. This study focuses on the quality of country-wide rainfall maps derived from commercial microwave link data compared to a quality-controlled gauge-adjusted radar rainfall data set, considered as ground-truth. Part of the differences can be attributed to the interpolation methodology, as well as to the much higher spatial resolution (?38.000 pixels of 0.9 by 0.9 km2) of the radar data compared to the relatively low density of the microwave link network (?1700 microwave links with an average length of 3.1 km). The magnitude of these factors is assessed by simulating microwave link rainfall depths from the radar rainfall data set. The Ordinary-Kriging (OK) methodology is used to obtain rainfall maps based on the simulated and real microwave link data. This work quantifies what percentage of the errors in link-based rainfall maps can be attributed to the interpolation methodology itself and the limited spatial density of the microwave link network. Moreover, the spatial distribution of the error in rainfall maps is quantified in relation to the spatial density and temporally variable availability of links, which is highly relevant since the microwave link data are non-uniformly distributed in space or time. Finally, the applicability of the OK-methodology is tested over Dutch areas with different spatial densities of commercial microwave links.

Rios Gaona, Manuel Felipe; Overeem, Aart; Leijnse, Hidde; Uijlenhoet, Remko

2014-05-01

350

Predicting the Weather  

NSDL National Science Digital Library

This Topic in Depth explores the science behind predicting the weather. First, the United States Search and Rescue Task Force describe the basic tools and knowledge used to create weather forecasts (1). Students can find concise, clear explanations of weather, fronts and air masses, high and low pressure, precipitation, and water vapor and humidity as well. By performing the activities presented in the second website, fourth grade students can learn about weather instruments and data collection (2). This website, produced by the Government of Saskatchewan, also explores how the weather can impact local communities. Third, Edheads offers a Macromedia Flash Player enhanced interactive module allowing students to predict the weather by examining weather maps (3 ). Through this website, users can become familiar with the concepts of warm and cold fronts, wind direction and speed, air pressure, and humidity. The fourth website, supplied by Annenberg / CPB, discusses weather satellites, Doppler radar, and additional tools forecasters use to predict the weather (4). Students can find a wind chill calculator along with a brief discussion of the history of forecasting and weather lore. Next, NOAA provides graphics for five forecast models: the ETA, the Global Forecast System (GFS), the Wave Watch III (WW3), the Nested Grid model (NGM), and the Rapid Update Cycle (RUC) (5). Outputs are available for North America, North Pacific, Western North Atlantic, and the Polar Ice Drift. Users can find links to detailed descriptions of the inputs and history of each model. Sixth, the British government's Met Office describes numerical modeling and its components (6). Students and educators can learn about the future in forecasting as well as educational opportunities with the Cooperative Program for Meteorology, Education, and Training (COMET).

351

Iterative synthetic aperture radar imaging algorithms   

E-print Network

Synthetic aperture radar is an important tool in a wide range of civilian and military imaging applications. This is primarily due to its ability to image in all weather conditions, during both the day and the night, ...

Kelly, Shaun Innes

2014-06-30

352

Airborne radar radiometer measurements of tropical storms  

NASA Technical Reports Server (NTRS)

The results from an airborne radar radiometer experiment of rainfall measurement in tropical storms are presented. The experiment was conducted in the Western Pacific in September 1990 with the NASA/DC-8 aircraft which was equipped with a nadir-loking dual-frequency rain radar operating at X band and Ka band, and several channels of microwave radiometers. The X-band radar has a capability of dual-polarization reception which enables the measurements of Linear Depolarization Ratio (LDR). The data of the microwave radiometers are compared with the radar data.

Kumagai, H.; Meneghini, R.; Kozu, T.; Okamoto, K.

1992-01-01

353

A multiplier-based method of generating stochastic areal rainfall from point rainfalls  

NASA Astrophysics Data System (ADS)

Catchment modelling for water resources assessment is still mainly based on rain gauge measurements as these are more easily available and cover longer periods than radar and satellite-based measurements. Rain gauges however measure the rain falling on an extremely small proportion of the catchment and the areal rainfall obtained from these point measurements are consequently substantially uncertain. These uncertainties in areal rainfall estimation are generally ignored and the need to assess their impact on catchment modelling and water resources assessment is therefore imperative. A method that stochastically generates daily areal rainfall from point rainfall using multiplicative perturbations as a means of dealing with these uncertainties is developed and tested on the Berg catchment in the Western Cape of South Africa. The differences in areal rainfall obtained by alternately omitting some of the rain gauges are used to obtain a population of plausible multiplicative perturbations. Upper bounds on the applicable perturbations are set to prevent the generation of unrealistically large rainfall and to obtain unbiased stochastic rainfall. The perturbations within the set bounds are then fitted into probability density functions to stochastically generate the perturbations to impose on areal rainfall. By using 100 randomly-initialized calibrations of the AWBM catchment model and Sequent Peak Analysis, the effects of incorporating areal rainfall uncertainties on storage-yield-reliability analysis are assessed. Incorporating rainfall uncertainty is found to reduce the required storage by up to 20%. Rainfall uncertainty also increases flow-duration variability considerably and reduces the median flow-duration values by an average of about 20%.

Ndiritu, J. G.

354

Mechanism of shallow disrupted slide induced by extreme rainfall  

NASA Astrophysics Data System (ADS)

On July 16, 2010, extreme rainfall attacked western Japan and it caused very intense rainfall in Shobara city, Hiroshima prefecture, Japan. This rainfall induced hundreds of shallow disrupted slides and many of those became debris flows. One of this debris flows attacked a house standing in front of the exit of a channel, and claimed a resident’s life. Western Japan had repeatedly similar disasters in the past. Last event took place from July 19 to 26, 2009, when western Japan had a severe rainstorms and caused floods and landslides. Most of the landslides are debris slide - debris flows. Most devastated case took place in Hofu city, Japan. On July 21, extremely intense rainstorm caused numerous debris flows and mud flows in the hillslopes. Some of the debris flows destroyed residential houses and home for elderly people, and finally killed 14 residents. One of the unusual feature of both disaster was that landslides are distributed in very narrow area. In the 2010 Shobara city disaster, all of the landslides were distributed in 5 km x 3 km, and in the 2009 Hofu city disaster, most devastated zone of landslides were 10 km x 5 km. Rain radars of Meteorological Agency of Government of Japan detected the intense rainfall, however, the spatial resolution is usually larger than 5 km and the disaster area is too small to predict landslides nor issue warning. Furthermore, it was found that the growth rate of baby clouds was very quick. The geology of both areas are rhyolite (Shobara) and granite (Hofu), so the areal assessment of landslide hazard should be prepared before those intense rainfall will come. As for the Hofu city case, it was proved that debris flows took place in the high precipitation area and covered by covered by weathered granite sands and silts which is called “masa". This sands has been proved susceptible against landslides under extreme rainfall conditions. However, the transition from slide - debris flow process is not well revealed, except authors past experiment on the similar masa samples in June 1999 Hiroshima debris flow case. Authors have embedded pore pressure control system for the undrained ring shear apparatus. Strongly weathered sandy soils were sampled just on the smooth and flat granitic sliding surface of one of the upstream small-scale landslides. Those contained finer grains and lower permeability rather than the one sampled in the Hiroshima case. Sample was consolidated by smaller stress corresponding to the site condition, and saturated by overnight circulating de-aired water. Normal stress and shear stress corresponding the slope condition was given, then, pore pressure (back pressure) was raised artificially at constant rate. When the effective stress reached the failure line, suddenly measured pore pressure monitored at about 2 mm above the shear plane, quickly increased. This sudden change abruptly accelerate the shear displacement. Stress condition soon reached the steady state and remained there thereafter. The reason of the excess pore pressure generation was the negative dilatancy, following a slight positive dilatancy. Most of the negative dilatancy could be explained by collapse of loose soil skelton as well as grain crushing during deformation and shearing.

Igwe, O.; Fukuoka, H.

2010-12-01

355

Weather Watch  

ERIC Educational Resources Information Center

Suggests a number of ways in which Federal Aviation Agency weather report printouts can be used in teaching the weather section of meteorology. These weather sequence reports can be obtained free of charge at most major airports. (JR)

Bratt, Herschell Marvin

1973-01-01

356

The Effects of Rainfall Inhomogeneity on Climate Variability of Rainfall Estimated from Passive Microwave Sensors  

NASA Technical Reports Server (NTRS)

Passive microwave rainfall estimates that exploit the emission signal of raindrops in the atmosphere are sensitive to the inhomogeneity of rainfall within the satellite field of view (FOV). In particular, the concave nature of the brightness temperature (T(sub b)) versus rainfall relations at frequencies capable of detecting the blackbody emission of raindrops cause retrieval algorithms to systematically underestimate precipitation unless the rainfall is homogeneous within a radiometer FOV, or the inhomogeneity is accounted for explicitly. This problem has a long history in the passive microwave community and has been termed the beam-filling error. While not a true error, correcting for it requires a priori knowledge about the actual distribution of the rainfall within the satellite FOV, or at least a statistical representation of this inhomogeneity. This study first examines the magnitude of this beam-filling correction when slant-path radiative transfer calculations are used to account for the oblique incidence of current radiometers. Because of the horizontal averaging that occurs away from the nadir direction, the beam-filling error is found to be only a fraction of what has been reported previously in the literature based upon plane-parallel calculations. For a FOV representative of the 19-GHz radiometer channel (18 km X 28 km) aboard the Tropical Rainfall Measuring Mission (TRMM), the mean beam-filling correction computed in this study for tropical atmospheres is 1.26 instead of 1.52 computed from plane-parallel techniques. The slant-path solution is also less sensitive to finescale rainfall inhomogeneity and is, thus, able to make use of 4-km radar data from the TRMM Precipitation Radar (PR) in order to map regional and seasonal distributions of observed rainfall inhomogeneity in the Tropics. The data are examined to assess the expected errors introduced into climate rainfall records by unresolved changes in rainfall inhomogeneity. Results show that global mean monthly errors introduced by not explicitly accounting for rainfall inhomogeneity do not exceed 0.5% if the beam-filling error is allowed to be a function of rainfall rate and freezing level and does not exceed 2% if a universal beam-filling correction is applied that depends only upon the freezing level. Monthly regional errors can be significantly larger. Over the Indian Ocean, errors as large as 8% were found if the beam-filling correction is allowed to vary with rainfall rate and freezing level while errors of 15% were found if a universal correction is used.

Kummerow, Christian; Poyner, Philip; Berg, Wesley; Thomas-Stahle, Jody

2007-01-01

357

Rainfall characteristics along mountainous transect  

NASA Astrophysics Data System (ADS)

The HYdrological cycle in Mediterranean EXperiment is an experiment framework that aims at improving our understanding and quantification of processes related to the hydrological cycle in the Mediterranean region at different scales (from the individual event scale to seasonal and inter-annual variability). During the Special Observation Period (SOP-1) conducted from September 5th to November 6th 2012, an important and complementary remote sensing network (operational radars, X band research radars, Micro Rain Radars, disdrometers, and a dense network of rain gauges) has been deployed in the Cévennes-Vivarais region (South of France). This network was specifically designed to investigate the structure and the heterogeneity of precipitations as well as, in particular, the impact of orography on this structure and it has provided us with high resolution data (time and space) along strong topographic gradients (small hills, foothills and mountain). Hence, these data will support our research to precisely describe the precipitation systems and their structures over a complex terrain. In this work, we will describe the characteristics of rainfall along two topographic gradients based on the major events observed during the fall 2012 campaign period. A classification according to the type of precipitation (convective, stratiform and orographic) which can affect the region has been made to investigate orographic impact under different rainfall regimes. We will also examine the influence of the relief on the vertical and horizontal structure of precipitation. In particular, we will illustrate the modification of the drop size distribution toward smaller droplets as we go from the small hills to the mountains.

Zwiebel, Jimmy; Van Baelen, Joël; Anquetin, Sandrine; Pointin, Yves; Boudevillain, Brice

2014-05-01

358

The Effects of Amazon Deforestation on Rainfall  

NASA Technical Reports Server (NTRS)

This study begins with the hypothesis that heavily deforested regions will experience increased surface heating, leading to local circulations that will ultimately enhance the rainfall, or at least, change the pattern of diurnal evolution of rainfall. This would be an important finding because several modeling studies have concluded that widespread deforestation would lead to decreased rainfall. Towards that end rain estimates from a combined GOES infrared/TRMM microwave technique were analyzed with respect to percent forest cover from Landsat data (courtesy of TRFIC at Michigan State University) and GOES visible channel data over a deforested area in Rondonia (southwest Brazil). Five 1" x 1" areas of varying forest cover were examined during the onset of the wet season in Amazonia (Aug-Sept), when the effects of the surface would not be dominated by large-scale synoptic weather patterns. Preliminary results revealed that: maximum rainfall fell in most deforested area; heavily forested areas received the least rainfall; cumulus cloud development initiated at borders; the amplitude of the diurnal cycle of precipitation was a function of th surface cover. Further work will be presented detailing effects of land surface cover on the GOES infrared-measured surface heating, GOES visible observed cumulus development, thunderstorm initiation based on the location of temperature minima in the infrared data, and estimated rainfall and its diurnal cycle from a combined GOES/TRMM technique. Rainfall estimates derived from non-geosynchronous microwave observations (i.e. Goddard Profiling Algorithm, GPROF) will also be examined.

Starr, David OC. (Technical Monitor); Negri, Andrew J.; Adler, Robert F.; Surratt, Jason

2002-01-01

359

The MST Radar Technique  

NASA Technical Reports Server (NTRS)

The past ten year have witnessed the development of a new radar technique to examine the structure and dynamics of the atmosphere between roughly 1 to 100 km on a continuous basis. The technique is known as the MST (for Mesosphere-Stratosphere-Troposphere) technique and is usable in all weather conditions, being unaffected by precipitation or cloud cover. MST radars make use of scattering from small scale structure in the atmospheric refractive index, with scales of the order of one-half the radar wavelength. Pertinent scale sizes for middle atmospheric studies typically range between a fraction of a meter and a few meters. The structure itself arises primarily from atmospheric turbulence. The technique is briefly described along with the meteorological parameters it measures.

Balsley, B. B.

1985-01-01

360

The MST radar technique  

NASA Astrophysics Data System (ADS)

The past ten year have witnessed the development of a new radar technique to examine the structure and dynamics of the atmosphere between roughly 1 to 100 km on a continuous basis. The technique is known as the MST (for Mesosphere-Stratosphere-Troposphere) technique and is usable in all weather conditions, being unaffected by precipitation or cloud cover. MST radars make use of scattering from small scale structure in the atmospheric refractive index, with scales of the order of one-half the radar wavelength. Pertinent scale sizes for middle atmospheric studies typically range between a fraction of a meter and a few meters. The structure itself arises primarily from atmospheric turbulence. The technique is briefly described along with the meteorological parameters it measures.

Balsley, B. B.

1985-07-01

361

WSR-88D doppler radar detection of corn earworm moth migration  

Technology Transfer Automated Retrieval System (TEKTRAN)

Flying insects, birds, and bats contribute to radar reflectivity and radial velocity measured by Doppler weather radars. A study was conducted in the Lower Rio Grande Valley of Texas to determine the capability of Weather Service Radar (version 88D) (WSR-88D) to monitor migratory flights of corn ea...

362

Performance evaluation of the retrieval of a two hours rainfall event through microwave tomography applied to a network of radio-base stations  

NASA Astrophysics Data System (ADS)

Critical precipitation events occurred over the Italian territory have been often characterized by high intensity and very fast development, frequently over small catchment areas. The detection of this kind of phenomena is a major issue that poses remarkable problems that cannot be tackled completely only with 'standard' instrumentation (even when available), such as a weather radars or raingauges. Indeed, the rainfall sampling modalities of these instruments may jeopardize the attempts to provide a sufficiently fast risk alert: - the point-like, time-integrated way of sampling of raingauges can completely/partially miss local rainfall cores of high intensity developing in the neighborhoods. Moreover, raingauges provide cumulated rainfall measurements intrinsically affected by a time delay. - In the case of weather radars, several factors may limit the advantages brought by range resolution and instantaneous sampling: precipitation might be sampled at an excessive height due to the distance of the radar site and/or the orography surrounding the valleys/catchments where the aforementioned kind of events is more likely to form up; distance may limit the resolution in the cross-range direction; beam screening due to orography causes a loss of power that is interpreted in the farther range bins as a reduced precipitation intensity. In this context, a positive role for flagging the criticality of a precipitation event can be played by signal attenuation measurements made along microwave links, as available through the infrastructure of a mobile communications network. Three are the interesting features of such networks: 1) the communications among radio-base stations occur where point-to-point electromagnetic visibility is guaranteed, namely along valleys or between tops/flanks of hills or mountains; 2) the extension of these links (few kilometres) is perfectly compatible with the detection of severe but localized precipitation events; 3) measurements can be made on a practically continuous-time basis. In the past years, we showed that new scenarios for tomographic rainfall monitoring have been disclosed by the availability of widespread networks of radio-base stations for mobile communications (i.e., GSM, GPRS, UMTS). Such networks could be employed as the backbone of a low cost system able to provide 2D estimates of rainfall in real time. Monitoring capabilities increase in more populated sites, as urban areas, where such radio links form up a dense network that can be exploited to get detailed information also about structure and evolution of rainfall phenomena. In 2010, we presented a novel tomographic processing method for rainfall rate estimation, specifically adaptable to the dense and asymmetric topologies of urban networks of radio-base stations. In this paper, we show its application to a simulated time sequence of specific attenuation (K) maps, derived from true weather radar data gathered during a rainfall event specifically selected to evaluate the performance of the tomographic retrieval in critical conditions. The event was in fact very localized and intense and lasted two hours. 12 GHz is assumed for the carrier frequency of the radio-base network. We show the reconstruction performance of the 2D K fields achieved resorting first to a symmetric, regular network and then to a couple of totally asymmetric ones.

Facheris, L.; Cuccoli, F.; Baldini, L.

2012-04-01

363

LPI-radar for helicopter obstacle warning  

Microsoft Academic Search

Employing the frequency range of maximum atmospheric attenuation around 60 GHz, a short range obstacle warning radar for helicopters was developed which can be operated under low probability of intercept conditions. Test flights with this noncoherent solid state radar showed that power cables as well as tall trees can be detected, even under adverse weather conditions. System considerations and test

H. Meinel; H. G. Wippich; B. Rembold; W. F. X. Frank

1984-01-01

364

Performance evaluations of Frequency Diversity Radar system  

Microsoft Academic Search

Frequency diversity radar combines two or more conventional transceivers through a common antenna, in a multiplex arrangement on the same RF transmission channel. It significantly improves radar detection performance and reduces false alarms under adverse weather conditions, here in case of normal distributed background clutter. Evaluations about advantages between different algorithms are discussed.

Valentina Ravenni

2007-01-01

365

The Orbital Checkout Status of the Dual-frequency Precipitation Radar (DPR) on the Global Precipitation Measurement (GPM) core observatory  

NASA Astrophysics Data System (ADS)

The Dual-frequency Precipitation Radar (DPR) on the Global Precipitation Measurement (GPM) core observatory is developed by Japan Aerospace Exploration Agency (JAXA) with National Institute of Information and Communications Technology (NICT). GPM objective is to observe global precipitation more frequently and accurately. GPM contributes to climate and water cycle change studies, flood prediction and numerical weather forecast. GPM consists of the GPM core observatory and constellation satellites carrying microwave radiometers (MWRs) and/or sounders (MWSs). The frequent measurement will be achieved by constellation satellites, and the accurate measurement will be achieved by the DPR with high sensitivity and dual frequency capability. The GPM core observatory is jointly developed by National Aeronautics and Space Administration (NASA) and JAXA. NASA is developing the satellite bus and GPM microwave radiometer (GMI), and JAXA is developing the DPR. The DPR consists of Ku-band (13.6 GHz) radar suitable for heavy rainfall in the tropical region, and Ka-band (35.55 GHz) radar suitable for light rainfall in higher latitude region. Drop size distribution information will be derived which contributes to the improvement of rainfall estimate accuracy. DPR will also play a key role to improve rainfall estimation accuracy of constellation satellites. DPR proto-flight test at JAXA Tsukuba space center has been completed in February 2012. The DPR has handed over to NASA and integrated to the core observatory in May 2012. The system test of the core observatory has completed in November 2013 and DPR test results satisfied its system requirements. The core observatory was shipped to launch site of JAXA Tanegashima space center in Japan. Launch site activities have started on November 2013 and GPM core observatory will be launched in early 2014. DPR orbital check out will be started in March 2014 and it will be completed in April 2014. In this presentation, the orbital check out status of DPR will be reported.

Miura, Takeshi; Kojima, Masahiro; Furukawa, Kinji; Hyakusoku, Yasutoshi; Ishikiri, Takayuki; Kai, Hiroki; Iguchi, Toshio; Hanado, Hiroshi; Nakagawa, Katsuhiro

2014-05-01

366

In-flight icing hazard detection radar  

Microsoft Academic Search

Technology Service Corporation (TSC) is developing a prototype dual-frequency airborne radar system for remotely sensing hazardous in-flight icing conditions. The system, which is based on integrating a Ka-band radar into a commercial X-band weather radar, will be used to demonstrate the feasibility of the differential attenuation technique used to remotely measure cloud liquid water content (LWC). This paper provides an

R. J. Lefevre; Charles A. Shipley; Donald N. Woods; Randy F. van Daden Wetters

2000-01-01

367

Precipitation Observations with NSSL's X-band Polarimetric Radar during the SNOW-V10 Campaign  

NASA Astrophysics Data System (ADS)

In support of SNOW-V10, the National Oceanic Administration/National Severe Storms Laboratory (NOAA/NSSL) mobile dual-polarized X-band (NO-XP) radar was deployed to Birch Bay State Park in Birch Bay, Washington from 3 January 2010 to 17 March 2010. In addition to being made available in real time for Science and NOWcasting of the Olympic Weather for Vancouver 2010 (SNOW-V10) operations, NO-XP data are used here to demonstrate the capabilities of easily deployable, polarimetric X-band radar systems, especially for regions where mountainous terrain results in partial beam blockage. A rainfall estimator based on specific attenuation is shown to mitigate the effects of partial beam blockage and provide potential improvement in rainfall estimation. The ability of polarimetric X-band radar to accurately detect melting layer (ML) height is also shown. A 16 h comparison of radar reflectivity ( Z), differential reflectivity ( Z DR), and correlation coefficient (?hv) measurements from NO-XP with vertically pointing Micro Rain Radar observations indicates that the two instruments provide ML height evolution that exhibit consistent temporal trends. Since even slight changes in the ML height in regions of mountainous terrain might result in a change in precipitation type measured at the surface, this shows that horizontally extensive information on ML height fluctuations, such as provided by the NO-XP, is useful in determining short term changes in expected precipitation type. Finally, range-height indicator (RHI) scans of NO-XP Z, Z DR, and ?hv fields from SNOW-V10 are used to demonstrate the ability of polarimetric radar to diagnose microphysical processes (both above and below the ML) that otherwise remain unseen by conventional radar. Near-surface enhancements in Z DR are attributed to either differential sedimentation or the preferential evaporation of smaller drops. Immediately above the ML, regions of high Z, low Z DR, and high ?hv are believed to be associated with convective turrets containing heavily aggregated or rimed snow that supply water/ice mass that later result in enhanced regions of precipitation near the surface. Higher up, horizontally extensive regions of enhanced Z DR are attributed to rapid dendritic growth and the onset of snow aggregation, a feature that has been widely observed with both S band and C band radars.

Schuur, Terry J.; Ryzhkov, Alexander V.; Forsyth, Douglas E.; Zhang, Pengfei; Reeves, Heather D.

2014-01-01

368

Classification of radar clutter in an air traffic control environment  

Microsoft Academic Search

The results of an experimental study aimed at the classification of radar clutter encountered on ground-based coherent scanning radar systems used for air traffic control are presented. The clutter signals of interest are primarily those due to birds and to clouds and weather systems. A historical perspective on the radar clutter classification problem is given, and related issues are discussed.

SIMON HAYKIN; WOLFGANG STEHWIEN; CONG DENG; PETER WEBER; RICHARD MANN

1991-01-01

369

32nd Conf. Radar Meteorology Albuquerque, NM, 2005  

E-print Network

32nd Conf. Radar Meteorology Albuquerque, NM, 2005 J1J.4 MULTIPLE DOPPLER WIND ANALYSIS AND ASSIMILATION VIA 3DVAR USING SIMULATED OBSERVATIONS OF THE PLANNED CASA NETWORK AND WSR-88D RADARS Jidong Gao, Norman 1. Introduction The advantages of using Doppler weather radar to track and forecast mesoscale

Xue, Ming

370

Doppler Radar Wind Profiles Iwan Holleman (holleman@knmi.nl)  

E-print Network

Doppler Radar Wind Profiles Iwan Holleman (holleman@knmi.nl) Royal Netherlands Meteorological Institute (KNMI), The Netherlands ABSTRACT Doppler weather radars can be employed to determine wind profiles profiles from radar volume data have been published. A comparison and verification of the extracted wind

Stoffelen, Ad

371

Microwave Power Modules (MPMs) Miniature Microwave Amplifiers for Radars  

Microsoft Academic Search

A recent and dramatic shift with military aircraft has been the widespread use of UAVs (unmanned aerial vehicles). Most previous-generation UAVs do not carry radar and, therefore, do not have all-weather visibility. But now, nearly all large UAVs have radars as standard equipment. UAVs require miniature and lightweight radars with low power consumption. Previously, there was little demand for such

Tom Ninnis

372

Comparison of simulated and actual wind shear radar data products  

NASA Technical Reports Server (NTRS)

Prior to the development of the NASA experimental wind shear radar system, extensive computer simulations were conducted to determine the performance of the radar in combined weather and ground clutter environments. The simulation of the radar used analytical microburst models to determine weather returns and synthetic aperture radar (SAR) maps to determine ground clutter returns. These simulations were used to guide the development of hazard detection algorithms and to predict their performance. The structure of the radar simulation is reviewed. Actual flight data results from the Orlando and Denver tests are compared with simulated results. Areas of agreement and disagreement of actual and simulated results are shown.

Britt, Charles L.; Crittenden, Lucille H.

1992-01-01

373

Extreme Rainfall Rates: An Extreme Retrieval Challenge  

NASA Astrophysics Data System (ADS)

One of the greatest challenges in remote sensing, from space, or from surface-based measurements, is making accurate estimates of extremely heavy rainfall rates. These extreme rainfall rates, quite understandably, often are responsible for natural disasters that include flooding and landslides. The particular focus of this talk is to demonstrate that extreme rainfall rates can come from two distinctly different types of storms, and to show that the TRMM Precipitation Radar retrievals may have large errors in these storms. One type of extreme storm occurs more frequently in the United States than in Japan, and is characterized by very high radar reflectivity throughout the depth of the troposphere. The second type of extreme storm is characterized by a "low echo centroid", with relatively weak radar echoes in the upper troposphere, and may be more amenable to accurate rain rate retrievals. The first type of storm presents more difficulties for retrievals because of the much greater total path attenuation. Some examples of both types of storms are shown in both the United States and Japan.

Zipser, E. J.; Liu, C.; Hamada, A.; Takayabu, Y. N.

2013-12-01

374

A spatial Bayesian approach to weather derivatives  

Microsoft Academic Search

Purpose – While the demand for weather-based agricultural insurance in developed regions is limited, there exists significant potential for the use of weather indexes in developing areas. The purpose of this paper is to address the issue of historical data availability in designing actuarially sound weather-based instruments. Design\\/methodology\\/approach – A Bayesian rainfall model utilizing spatial kriging and Markov chain Monte

Nicholas D. Paulson; Chad E. Hart; Dermot J. Hayes

2010-01-01