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1

Climatology of extreme rainfall from rain gauges and weather radar  

E-print Network

Climatology of extreme rainfall from rain gauges and weather radar Aart Overeem #12;Thesis the auspices of the SENSE Research School. #12;Climatology of extreme rainfall from rain gauges and weather:30 PM in the Aula #12;Aart Overeem Climatology of extreme rainfall from rain gauges and weather radar

Stoffelen, Ad

2

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

3

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, M.

2014-10-01

4

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

5

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

6

Research relative to weather radar measurement techniques  

NASA Technical Reports Server (NTRS)

Research relative to weather radar measurement techniques, which involves some investigations related to measurement techniques applicable to meteorological radar systems in Thailand, is reported. A major part of the activity was devoted to instruction and discussion with Thai radar engineers, technicians, and meteorologists concerning the basic principles of radar meteorology and applications to specific problems, including measurement of rainfall and detection of wind shear/microburst hazards. Weather radar calibration techniques were also considered during this project. Most of the activity took place during two visits to Thailand, in December 1990 and February 1992.

Smith, Paul L.

1992-01-01

7

Spaceborne weather radar  

NASA Technical Reports Server (NTRS)

The present work on the development status of spaceborne weather radar systems and services discusses radar instrument complementarities, the current forms of equations for the characterization of such aspects of weather radar performance as surface and mirror-image returns, polarimetry, and Doppler considerations, and such essential factors in spaceborne weather radar design as frequency selection, scanning modes, and the application of SAR to rain detection. Attention is then given to radar signal absorption by the various atmospheric gases, rain drop size distribution and wind velocity determinations, and the characteristics of clouds, as well as the range of available estimation methods for backscattering, single- and dual-wavelength attenuation, and polarimetric and climatological characteristics.

Meneghini, Robert; Kozu, Toshiaki

1990-01-01

8

Censoring Biological Echoes in Weather Radar Images Valliappa Lakshmanan  

E-print Network

to censor all non-precipitating artifacts in weather radar reflectivity data. We demonstrate, to precipitation. By removing ground clutter contamination, rainfall from the radar data using the National Weather to classify radar range gates into precipitation or non-precipitation, and followed the pixel- wise

Lakshmanan, Valliappa

9

New weather radar coming  

NASA Astrophysics Data System (ADS)

What would you call the next generation of radar for severe weather prediction? NEXRAD, of course. A prototype for the new system was recently completed in Norman, Okla., and by the early 1990s up to 195 stations around the United States will be tracking dangerous weather and sending faster, more accurate, and more detailed warnings to the public.NEXRAD is being built for the Departments of Commerce, Transportation, and Defense by the Unisys Corporation under a $450 million contract signed in December 1987. Th e system will be used by the National Weather Service, the Federal Aviation Administration (FAA), and the U.S. Air Force and Navy. The NEXRAD radar tower in Norman is expected to be operational in October.

Maggs, William Ward

10

Probabilistic forecasts based on radar rainfall uncertainty  

NASA Astrophysics Data System (ADS)

The potential advantages resulting from integrating weather radar rainfall estimates in hydro-meteorological forecasting systems is limited by the inherent uncertainty affecting radar rainfall measurements, which is due to various sources of error [1-3]. The improvement of quality control and correction techniques is recognized to play a role for the future improvement of radar-based flow predictions. However, the knowledge of the uncertainty affecting radar rainfall data can also be effectively used to build a hydro-meteorological forecasting system in a probabilistic framework. This work discusses the results of the implementation of a novel probabilistic forecasting system developed to improve ensemble predictions over a small urban area located in the North of England. An ensemble of radar rainfall fields can be determined as the sum of a deterministic component and a perturbation field, the latter being informed by the knowledge of the spatial-temporal characteristics of the radar error assessed with reference to rain-gauges measurements. This approach is similar to the REAL system [4] developed for use in the Southern-Alps. The radar uncertainty estimate can then be propagated with a nowcasting model, used to extrapolate an ensemble of radar rainfall forecasts, which can ultimately drive hydrological ensemble predictions. A radar ensemble generator has been calibrated using radar rainfall data made available from the UK Met Office after applying post-processing and corrections algorithms [5-6]. One hour rainfall accumulations from 235 rain gauges recorded for the year 2007 have provided the reference to determine the radar error. Statistics describing the spatial characteristics of the error (i.e. mean and covariance) have been computed off-line at gauges location, along with the parameters describing the error temporal correlation. A system has then been set up to impose the space-time error properties to stochastic perturbations, generated in real-time at gauges location, and then interpolated back onto the radar domain, in order to obtain probabilistic radar rainfall fields in real time. The deterministic nowcasting model integrated in the STEPS system [7-8] has been used for the purpose of propagating the uncertainty and assessing the benefit of implementing the radar ensemble generator for probabilistic rainfall forecasts and ultimately sewer flow predictions. For this purpose, events representative of different types of precipitation (i.e. stratiform/convective) and significant at the urban catchment scale (i.e. in terms of sewer overflow within the urban drainage system) have been selected. As high spatial/temporal resolution is required to the forecasts for their use in urban areas [9-11], the probabilistic nowcasts have been set up to be produced at 1 km resolution and 5 min intervals. The forecasting chain is completed by a hydrodynamic model of the urban drainage network. The aim of this work is to discuss the implementation of this probabilistic system, which takes into account the radar error to characterize the forecast uncertainty, with consequent potential benefits in the management of urban systems. It will also allow a comparison with previous findings related to the analysis of different approaches to uncertainty estimation and quantification in terms of rainfall [12] and flows at the urban scale [13]. Acknowledgements The authors would like to acknowledge the BADC, the UK Met Office and Dr. Alan Seed from the Australian Bureau of Meteorology for providing the radar data and the nowcasting model. The authors acknowledge the support from the Engineering and Physical Sciences Research Council (EPSRC) via grant EP/I012222/1.

Liguori, S.; Rico-Ramirez, M. A.

2012-04-01

11

Assimilation of Doppler weather radar observations in a mesoscale model for the prediction of rainfall associated with mesoscale convective systems  

Microsoft Academic Search

Obtaining an accurate initial state is recognized as one of the biggest challenges in accurate model prediction of convective\\u000a events. This work is the first attempt in utilizing the India Meteorological Department (IMD) Doppler radar data in a numerical\\u000a model for the prediction of mesoscale convective complexes around Chennai and Kolkata. Three strong convective events both\\u000a over Chennai and Kolkata

S. Abhilash; Someshwar Das; S. R. Kalsi; M. Das Gupta; K. Mohankumar; J. P. George; S. K. Banerjee; S. B. Thampi; D. Pradhan

2007-01-01

12

Correction of Polarimetric Radar Reflectivity Measurements and2 Rainfall Estimates for Apparent Vertical Profile in Stratiform Rain3  

E-print Network

1 1 Correction of Polarimetric Radar Reflectivity Measurements and2 Rainfall Estimates for Apparent and rainfall2 estimates (VPR) in plan-position indicator (PPI) scans of polarimetric weather radars.17 18 19 Keywords ­ Polarimetric weather radar, stratiform rain, vertical profile of reflectivity

Marzano, Frank Silvio

13

Radar Rainfall Measurements from Space  

NASA Astrophysics Data System (ADS)

Existing spaceborne rain-rate retrieval algorithms have unreasonable assumptions, and usually yield unrealistic and/or inaccurate rain-rate estimates. The relative errors in the rain-rate estimates of existing algorithms are typically larger than 50%. Practical constraints, and spatial and temporal variability of rain have made the potential rain -rate estimation from a spaceborne platform very erroneous. The robust rain-rate retrieval (RRR) algorithm accurately extracts rain-rate profiles, using information from active and passive microwave sensors. Simulation results show that the total error in the RRR algorithm is within 20%. The RRR algorithm binds the rain-rate and rain-parameter estimators with guess intervals, utilizes radar properties of rain and concepts from existing rain -rate retrieval algorithms to further refine the rain-rate estimators, employs an adaptive weighted nonlinear least -squares technique, accounts for the presence of melting layers, and robustly produces unique and accurate rain -rate profiles. Measurement of rainfall from space will provide climatological data over regions where rain gauges are sparse, particularly over the oceans and developing countries. The planned Tropical Rainfall Measuring Mission (TRMM) radar will scan from side to side (i.e., the SSS mode). The proposed conical scanning (CS) mode offers many advantages over the side-to-side scanning (SSS) mode. For example, the high surface-clutter interference near vertical in the SSS mode is absent in the CS mode. The CS mode can be attained in three ways. They involve the use of a mechanically scanned parabolic-reflector antenna or fixed array, a single large fixed vertical electronically space -fed antenna, and two small tilted electronically scanned space-fed antenna. The work here studied the feasibility of space-fed array (i.e., lens arrays and reflectarrays), active arrays, parabolic reflectors for the rain radar in the CS mode.

Kieu, Duc Cong

14

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

15

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

16

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...

17

ERAD 2012 -THE SEVENTH EUROPEAN CONFERENCE ON RADAR IN METEOROLOGY AND HYDROLOGY Investigating the influence of rainfall spatial  

E-print Network

errors inherent to the radar rainfall estimates greatly affect rainfall-runoff simulations. As a result reanalysis over France at the hourly time step over a 10-year period combining radar data and rain gauge measurements: weather radar data were corrected and adjusted with both hourly and daily rain gauge data

Paris-Sud XI, Université de

18

ERAD 2012 -THE SEVENTH EUROPEAN CONFERENCE ON RADAR IN METEOROLOGY AND HYDROLOGY Scaling properties of rainfall and their impact on  

E-print Network

properties of rainfall and their impact on rain rate estimation from weather radar S. Verrier1, L. Barthès1 Guyancourt, France, contact : verrier@latmos.ipsl.fr 1. Introduction Radar rainfall estimates are generally of collocated radar and rain gauge data aggregated at different scales (1-5 km, 5-120 min). These authors found

Paris-Sud XI, Université de

19

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

20

Reducing Spaceborne-Doppler-Radar Rainfall-Velocity Error  

NASA Technical Reports Server (NTRS)

A combined frequency-time (CFT) spectral moment estimation technique has been devised for calculating rainfall velocity from measurement data acquired by a nadir-looking spaceborne Doppler weather radar system. Prior spectral moment estimation techniques used for this purpose are based partly on the assumption that the radar resolution volume is uniformly filled with rainfall. The assumption is unrealistic in general but introduces negligible error in application to airborne radar systems. However, for spaceborne systems, the combination of this assumption and inhomogeneities in rainfall [denoted non-uniform beam filling (NUBF)] can result in velocity measurement errors of several meters per second. The present CFT spectral moment estimation technique includes coherent processing of a series of Doppler spectra generated in a standard manner from data over measurement volumes that are partially overlapping in the along-track direction. Performance simulation of this technique using high-resolution data from an airborne rain-mapping radar shows that a spaceborne Ku-band Doppler radar operating at signal-to-noise ratios greater than 10 dB can achieve root-mean-square accuracy between 0.5 and 0.6 m/s in vertical-velocity estimates.

Tanelli, Simone; Im, Eastwood; Durden, Stephen L.

2008-01-01

21

Real-time estimation of rainfall fields using radar rainfall and rain gage data  

Microsoft Academic Search

New attempts at real-time estimation of rainfall fields using rain gage and radar rainfall data are reported. Based on multiplicative decomposition of expectation of rainfall into conditional expectation of rainfall given raining and probability of rainfall, the estimation procedures explicitly account for both within-storm variability of rainfall and variability due to fractional coverage of rainfall. As a result, in addition

D.-J. Seo

1998-01-01

22

An Improved Polarimetric Radar Rainfall Algorithm With Hydrometeor Classification Optimized For Rainfall Estimation  

NASA Astrophysics Data System (ADS)

The efficacy of dual polarimetric radar for quantitative precipitation estimation (QPE) is firmly established. Specifically, rainfall retrievals using combinations of reflectivity (ZH), differential reflectivity (ZDR), and specific differential phase (KDP) have advantages over traditional Z-R methods because more information about the drop size distribution and hydrometeor type are available. In addition, dual-polarization radar measurements are generally less susceptible to error and biases due to the presence of ice in the sampling volume. A number of methods have been developed to estimate rainfall from dual-polarization radar measurements. However, the robustness of these techniques in different precipitation regimes is unknown. Because the National Weather Service (NWS) will soon upgrade the WSR 88-D radar network to dual-polarization capability, it is important to test retrieval algorithms in different meteorological environments in order to better understand the limitations of the different methodologies. An important issue in dual-polarimetric rainfall estimation is determining which method to employ for a given set of polarimetric observables. For example, under what circumstances does differential phase information provide superior rain estimates relative to methods using reflectivity and differential reflectivity? At Colorado State University (CSU), a "blended" algorithm has been developed and used for a number of years to estimate rainfall based on ZH, ZDR, and KDP (Cifelli et al. 2002). The rainfall estimators for each sampling volume are chosen on the basis of fixed thresholds, which maximize the measurement capability of each polarimetric variable and combinations of variables. Tests have shown, however, that the retrieval is sensitive to the calculation of ice fraction in the radar volume via the difference reflectivity (ZDP - Golestani et al. 1989) methodology such that an inappropriate estimator can be selected in situations where radar echo is relatively weak (< 40 dBZ). In this study, a new blended rainfall algorithm is developed using hydrometeor identification (HID) to drive the rainfall estimation algorithm. HID discrimination for rainfall application namely, (1) all rain, (2) mixed precipitation, and (3) all ice, is used to guide the selection of the most appropriate rainfall estimator. Data collected from the CSU-CHILL radar and a network of rain gauges are used to test the performance of the new algorithm in a variety of precipitation situations. The results are compared to similar results using the algorithm from the National Severe Storm Laboratory (NSSL), derived from Oklahoma precipitation events ( Ryzhkov et al. 2005 ). The applicability of the method derived from Oklahoma observations to Colorado precipitation events is also explored.

Cifelli, R.; Wang, Y.; Lim, S.; Kennedy, P.; Chandrasekar, V.; Rutledge, S. A.

2009-05-01

23

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

24

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

25

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

26

Influence of assimilating rainfall derived from WSR-88D radar on the rainstorm forecasts over the southwestern United States  

Microsoft Academic Search

In this study, the impact of rainfall assimilation on the forecasts of convective rainfall over the mountainous areas in the southwestern United States is investigated. The rainfall is derived from the U.S. Weather Surveillance Radar1988 Doppler (WSR-88D) radar network, and the fifth-generation Mesoscale Model (MM5) Four-Dimensional Variational (4DVAR) system is employed in the study. We evaluate the rainfall assimilation skill

Jianjun Xu; Qingnong Xiao; X. Gao; S. Sorooshian

2006-01-01

27

Real-Time Flood Estimation by Using Radar Rainfall data and Distributed Rainfall-Runoff Model  

NASA Astrophysics Data System (ADS)

This study aims to establish a flood prediction model in Dajia River by using a grid-based distributed rainfall-runoff model (GDRRM) combined with the predicted QPESUMS radar rainfalls. Flood disasters caused damage to human and property. A proper flood prediction model can provide warning messages against disasters. Since the radar rainfall technology has been developed for years, it has the ability to represent the precipitation in each location. Coupling the real-time radar rainfall with the distributed rainfall-runoff model, it can be used to provide the probable flow in downstream. The study area, Dajia River basin, is located in central Taiwan. The river flow is mainly controlled by two major reservoirs, Shih-Kang Dam in downstream and Te-Chi Reservoir in upstream. Thus, three components are considered for establishing the flood prediction model. The first one is the application of radar rainfalls. The real-time and predicted (1-3hr ahead) radar rainfall data provided by the Central Weather Bureau, Taiwan were set as the input data. It can represent the actual distributed rainfalls of the basin. The second one is the estimation of reservoir inflow by using a GDRRM. The basin was divided into 1234 regular grids (1km by 1km) to exhibit the heterogeneity in the watershed. The parameters of GDRRM were generated by using DEM, Formosat-2 satellite image and soil map to represent the actual geography and physiography of each grid. With the input of real-time and predicted radar rainfall data, the inflow of Te-Chi Reservoir and Shih-Kang Dam can be calculated by using two GDRRMs respectively. The third one is the operation rules of reservoir used for simulating the outflow of the reservoirs during the flow simulation. Then, the downstream (Shih-Kang Dam) GDRRM coupled with the operation rules was used to calculate the outflow of the Te-Chi Reservoir. Thus, the flood can be predicted in advance during typhoon period. The results revealed that the flood prediction model has good performances in simulating the outflows of seven historical typhoon events. With the proposed flood prediction model, it can be coupled with flow routing and sediment transport models to develop a warning system for bridge damage in downstream of Dajia River.

Yu, P.; Chou, J.; Chiu, Y.; Yang, T.; Kuo, C.

2011-12-01

28

Effects of Radar Beam Shielding on Rainfall Estimation for the Polarimetric C-Band Radar  

E-print Network

-based rainfall estimates to beam shielding for C-band radar data during four typical rain events encounteredEffects of Radar Beam Shielding on Rainfall Estimation for the Polarimetric C-Band Radar KATJA. Introduction Rainfall estimation by radar is subject to smaller er- rors when measurements are made at levels

29

14 CFR 121.357 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Airborne weather radar equipment requirements. 121...Requirements 121.357 Airborne weather radar equipment requirements. ...December 31, 1964, unless approved airborne weather radar equipment has been installed...

2012-01-01

30

14 CFR 125.223 - Airborne weather radar equipment requirements.  

...2014-01-01 2014-01-01 false Airborne weather radar equipment requirements. 125...Requirements 125.223 Airborne weather radar equipment requirements. (a...passenger-carrying operations unless approved airborne weather radar equipment is installed in the...

2014-01-01

31

14 CFR 125.223 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Airborne weather radar equipment requirements. 125...Requirements 125.223 Airborne weather radar equipment requirements. (a...passenger-carrying operations unless approved airborne weather radar equipment is installed in the...

2013-01-01

32

14 CFR 125.223 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Airborne weather radar equipment requirements. 125...Requirements 125.223 Airborne weather radar equipment requirements. (a...passenger-carrying operations unless approved airborne weather radar equipment is installed in the...

2010-01-01

33

14 CFR 135.175 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Airborne weather radar equipment requirements. 135...and Equipment 135.175 Airborne weather radar equipment requirements. ...passenger-carrying operations unless approved airborne weather radar equipment is installed in the...

2011-01-01

34

14 CFR 135.175 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Airborne weather radar equipment requirements. 135...and Equipment 135.175 Airborne weather radar equipment requirements. ...passenger-carrying operations unless approved airborne weather radar equipment is installed in the...

2012-01-01

35

14 CFR 135.175 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Airborne weather radar equipment requirements. 135...and Equipment 135.175 Airborne weather radar equipment requirements. ...passenger-carrying operations unless approved airborne weather radar equipment is installed in the...

2013-01-01

36

14 CFR 121.357 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Airborne weather radar equipment requirements. 121...Requirements 121.357 Airborne weather radar equipment requirements. ...December 31, 1964, unless approved airborne weather radar equipment has been installed...

2013-01-01

37

14 CFR 121.357 - Airborne weather radar equipment requirements.  

...2014-01-01 2014-01-01 false Airborne weather radar equipment requirements. 121...Requirements 121.357 Airborne weather radar equipment requirements. ...December 31, 1964, unless approved airborne weather radar equipment has been installed...

2014-01-01

38

14 CFR 135.175 - Airborne weather radar equipment requirements.  

...2014-01-01 2014-01-01 false Airborne weather radar equipment requirements. 135...and Equipment 135.175 Airborne weather radar equipment requirements. ...passenger-carrying operations unless approved airborne weather radar equipment is installed in the...

2014-01-01

39

14 CFR 135.175 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Airborne weather radar equipment requirements. 135...and Equipment 135.175 Airborne weather radar equipment requirements. ...passenger-carrying operations unless approved airborne weather radar equipment is installed in the...

2010-01-01

40

14 CFR 121.357 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Airborne weather radar equipment requirements. 121...Requirements 121.357 Airborne weather radar equipment requirements. ...December 31, 1964, unless approved airborne weather radar equipment has been installed...

2010-01-01

41

14 CFR 121.357 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Airborne weather radar equipment requirements. 121...Requirements 121.357 Airborne weather radar equipment requirements. ...December 31, 1964, unless approved airborne weather radar equipment has been installed...

2011-01-01

42

14 CFR 125.223 - Airborne weather radar equipment requirements.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Airborne weather radar equipment requirements. 125...Requirements 125.223 Airborne weather radar equipment requirements. (a...passenger-carrying 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 2012-01-01 false Airborne weather radar equipment requirements. 125...Requirements 125.223 Airborne weather radar equipment requirements. (a...passenger-carrying operations unless approved airborne weather radar equipment is installed in the...

2012-01-01

44

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

2014-07-01

45

A GIS methodology for the analysis of weather radar precipitation data  

Microsoft Academic Search

A GIS multi-component module was developed within the ArcView GIS environment for processing and analysing weather radar precipitation data. The module is capable of: (a) reading geo-reference radar data and comparing it with rain-gauge network data, (b) estimating the kinematics of rainfall patterns, such as the storm speed and direction, and (c) accumulating radar-derived rainfall depths. By bringing the spatial

M. A. Gad; I. K. Tsanis

2003-01-01

46

Research relative to weather radar measurement techniques  

NASA Technical Reports Server (NTRS)

This grant provides for some investigations related to weather radar measurement techniques applicable to meteorological radar systems in Thailand. Quality data are needed from those systems to support TRMM and other scientific investigations. Activities carried out during a trip to the radar facilities at Phuket are described.

Smith, Paul L.

1992-01-01

47

A study on WRF radar data assimilation for hydrological rainfall prediction  

NASA Astrophysics Data System (ADS)

Mesoscale numerical weather prediction (NWP) models are gaining more attention in providing high-resolution rainfall forecasts at the catchment scale for real-time flood forecasting. The model accuracy is however negatively affected by the "spin-up" effect and errors in the initial and lateral boundary conditions. Synoptic studies in the meteorological area have shown that the assimilation of operational observations, especially the weather radar data, can improve the reliability of the rainfall forecasts from the NWP models. This study aims at investigating the potential of radar data assimilation in improving the NWP rainfall forecasts that have direct benefits for hydrological applications. The Weather Research and Forecasting (WRF) model is adopted to generate 10 km rainfall forecasts for a 24 h storm event in the Brue catchment (135.2 km2) located in southwest England. Radar reflectivity from the lowest scan elevation of a C-band weather radar is assimilated by using the three-dimensional variational (3D-Var) data-assimilation technique. Considering the unsatisfactory quality of radar data compared to the rain gauge observations, the radar data are assimilated in both the original form and an improved form based on a real-time correction ratio developed according to the rain gauge observations. Traditional meteorological observations including the surface and upper-air measurements of pressure, temperature, humidity and wind speed are also assimilated as a bench mark to better evaluate and test the potential of radar data assimilation. Four modes of data assimilation are thus carried out on different types/combinations of observations: (1) traditional meteorological data; (2) radar reflectivity; (3) corrected radar reflectivity; (4) a combination of the original reflectivity and meteorological data; and (5) a combination of the corrected reflectivity and meteorological data. The WRF rainfall forecasts before and after different modes of data assimilation are evaluated by examining the rainfall temporal variations and total amounts which have direct impacts on rainfall-runoff transformation in hydrological applications. It is found that by solely assimilating radar data, the improvement of rainfall forecasts are not as obvious as assimilating meteorological data; whereas the positive effect of radar data can be seen when combined with the traditional meteorological data, which leads to the best rainfall forecasts among the five modes. To further improve the effect of radar data assimilation, limitations of the radar correction ratio developed in this study are discussed and suggestions are made on more efficient utilisation of radar data in NWP data assimilation.

Liu, J.; Bray, M.; Han, D.

2013-08-01

48

Point process models for weather radar images  

Microsoft Academic Search

A framework for analysing weather radar (DBz) images as spatial point processes is presented. Weather radar images are modelled for the purpose of predicting their evolution in time and thereby providing a basis for short-period precipitation forecasts. An observed image sequence is modelled as a set of individual rain cells that are the outcome of a marked 2+1D spatial point

Morten Larsen; Dina KVL

1994-01-01

49

Application of GIS for processing and establishing the correlation between weather radar reflectivity and precipitation data  

Microsoft Academic Search

Correlation between weather radar reflectivity and precipitation data collected by rain gauges allows empirical formulae to be obtained that can be used to create continuous rainfall surfaces from discrete data. Such surfaces are useful in distributed hydrologic modelling and early warning systems in flood management. Because of the spatial relationship between rain gauge locations and radar coverage area, GIS provides

Y. Gorokhovich; G. Villarini

2005-01-01

50

Vertical Variability of Radar Reflectivity and its Impact on Radar Rainfall Estimation  

NASA Astrophysics Data System (ADS)

Micro Rain Radar 2 (MRR-2) rainfall estimates were compared against rain observations from a tipping bucket rain gauge, and MRR-2 reflectivity measurements were compared to the Next Generation Weather Radar (NEXRAD) Level II reflectivity product. Three different storm events were selected for the comparison: 14-15 January, 2010 (lasted approx. 27 hours); 2-3 February, 2010 (lasted approx.19 hours); and 20 March, 2010 (lasted less than two hours). The MRR results show that the second gate (70 m above antenna) cumulative rainfall at one-minute intervals had the best agreement with the gauge cumulative rainfall observations, with an ? = 0.94. Overall, both the MRR-2 rain rate (RR) and the rain rate derived from the Z-R relationship (Rz) underestimated rainfall at the one-minute and hourly intervals. The MRR-2 RR increased with height while Rz decreased significantly. In comparing reflectivity, the MRR agreed well with NEXRAD Level II reflectivity ( ? = 0.71) for the gate centered at 980 m elevation above ground level. While the comparison between MRR and NEXRAD yielded lower agreement between the two sensors, best correlation between the MRR Rz and NEXRAD Rz was for the gate centered at 875 meters above ground (? = 0.42).

Mazari, N.; Sharif, H. O.; Xie, H.; Zeitler, J. W.

2011-12-01

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

Stochastic Modeling of Daily Rainfall for Pricing Weather Derivatives  

NASA Astrophysics Data System (ADS)

Weather derivatives are getting to be powerful tools for weather risk hedging. A popular method which draws out valid prices of weather derivatives is a stochastic modeling approach. In the method, expected payoffs of weather derivatives based on stochastic weather models are regarded as their valid prices. Although useful stochastic models of temperature have been shown, stochastic models of daily rainfall are still being developed. Therefore, it is considered that pricing of daily rainfall derivatives is difficult. This paper shows a new stochastic daily rainfall model for pricing daily rainfall options. The new model in which a modified geometric distribution model is applied can express stochastic features of daily rainfall. Furthermore, this paper also shows that the combination model of the Markov chain rainy day model and the new model can express stochastic features and risks of daily rainfall option payoffs.

Kubo, Osamu; Kobayashi, Yasuhiro

53

Modeling Radar Rainfall Estimation Uncertainties: Random Error Model  

E-print Network

others, are also sources of discrepancy between radar estimates and rain gauge measurements Jordan et alModeling Radar Rainfall Estimation Uncertainties: Random Error Model A. AghaKouchak1 ; E. Habib2 compared with rain gauge measurements provide higher spatial and temporal resolutions. However, radar data

AghaKouchak, Amir

54

Comparison of radar and raingauge measurements during heavy rainfall.  

PubMed

Five heavy small-scale rainfall events in North Rhine-Westphalia (Germany) were investigated with radar and raingauge data. Special attention was paid to quality check and adjustment of radar data. Attenuation effects could be observed on both, C-Band and on X-Band radar. Adjustment of radar data to raingauge values turned out to be very difficult in the vicinity of heavy local rain cells. For the five affected regions the precipitation was quantified in the form of areal time series and cumulated radar images. As further result of this project, the spatial extent of the precipitation fields was identified and compared with radar and raingauge data. PMID:15790244

Einfalt, T; Jessen, M; Mehlig, B

2005-01-01

55

The error structure of radar rainfall accumulations Sandy Dance and Alan Seed  

E-print Network

In this paper we analyse the relationship between radar and gauge estimations of rainfall in order to figure out it to estimate pure radar rainfall error. Section 10 is the conclusion. 2 Simulating gauge data from radar Gauge rain accumulations from radar, we com- pare radar with gauge rainfall over time. Fig 3(a) uses data

Dance, Sandy

56

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 infrastructure that is used in producing forecasts and issuing hazardous weather warnings. Traditional weather

Mountziaris, T. J.

57

Influences of temporal rainfall radar and spatial rainfall-runoff model resolution on flood prediction  

NASA Astrophysics Data System (ADS)

The rainfall-runoff-model DROGen (Distributed RunOff Generation) was developed to simulate runoff generation processes during floods and flash floods generation with a very high spatial resolution for the whole state of Baden-Wrttemberg in Southwest Germany. The model connects available spatial geo information with detailed process understanding at the plot and hillslope scale and is not calibrated. The model was successfully validated in 8 meso-scale watersheds with different geology, soils, topography and land-use and the results were very satisfying. We believe that the high spatial resolution of 1*1m and a temporal resolution of 1 hour especially improved flow dynamics and the runoff concentration behaviour of the different runoff components. Some spatial information used by DROGen is available in very high resolution of 1*1m (e.g. DEM and degree of sealing of land surface). Other data are much more generalized (e.g. soil information at the scale of 1:200.000) or at a fixed temporal resolution of one hour (e.g. calibrated precipitation radar data of the German weather survey (RADOLAN)). In order to find the adequate temporal and spatial resolution we investigated how the the spatial resolution of the geo data and the temporal resolution of the rainfall radar data effects the model result. Regarding the spatial resolution, we found, that the processes of runoff generation and runoff concentration are sensitive at different spatial scales. A decrease of spatial resolution from 1m to 25m lead to an implausible increase of the generation of saturation overland flow and to an accelerated concentration of subsurface flow, while Hortonian overland flow was almost not affected by the spatial resolution. For the model validation runs we realized that for short convective rain events a one hour resolution of the rainfall data might be not sufficient because of severe underestimation of peak intensities. We developed and tested a new method to estimate the temporal distribution of rain intensity in higher resolution by using only the information of the hourly radar data and an assumed temporal distribution of rainfall at each radar grid cell. The methods preserves the total rainfall amount at each cell and preserves the overall rainfall pattern and movement of precipitation cells. Generally, we could improve the prediction of the model for short convective events in particular for the peak discharge. The higher temporal resolution effects the runoff generation and depends strongly on soil characteristics. On soils with high infiltration capacity the increase of temporal resolution effects the generation of fast overland runoff. This effect decreases with decreasing infiltration capacity of soils. The analysis revealed that a variable temporal resolution is needed to model convective and advective rainfall events with the same model parameterization. A "correct" spatial resolution of the distributed model, however, depends strongly on the dominant runoff generation process in a watershed and is also different for runoff generation and runoff concentration.

Weiler, Markus; Steinbrich, Andreas

2013-04-01

58

Radar rainfall estimation in the context of post-event analysis of flash-flood events  

NASA Astrophysics Data System (ADS)

This communication is about a methodology for radar rainfall estimation in the context of post-event analysis of flash-flood events developed within the HYDRATE project. For such extreme events, some raingauge observations (operational, amateur) are available at the event time scale, while few raingauge time series are generally available at the hydrologic time steps. Radar data is therefore the only way to access to the rainfall space-time organization, but the quality of the radar data may be highly variable as a function of (1) the relative locations of the event and the radar(s) and (2) the radar operating protocol(s) and maintenance. A positive point: heavy rainfall is associated with convection implying better visibility and lesser bright band contamination compared with more current situations. In parallel with the development of a regionalized and adaptive radar data processing system (TRADHy; Delrieu et al. 2009), a pragmatic approach is proposed here to make best use of the available radar and raingauge data for a given flash-flood event by: (1) Identifying and removing residual ground clutter, (2) Applying the "hydrologic visibility" concept (Pellarin et al. 2002) to correct for range-dependent errors (screening and VPR effects for non-attenuating wavelengths, (3) Estimating an effective Z-R relationship through a radar-raingauge optimization approach to remove the mean field bias (Dinku et al. 2002) A sensitivity study, based on the high-quality volume radar datasets collected during two intense rainfall events of the Bollne 2002 experiment (Delrieu et al. 2009), is first proposed. Then the method is implemented for two other historical events occurred in France (Avne 1997 and Aude 1999) with datasets of lesser quality. References: Delrieu, G., B. Boudevillain, J. Nicol, B. Chapon, P.-E. Kirstetter, H. Andrieu, and D. Faure, 2009: Bollne 2002 experiment: radar rainfall estimation in the Cvennes-Vivarais region, France. Journal of Applied Meteorology and Climatology, in press. Dinku, T., E.N. Anagnostou, and M. Borga, 2002: Improving Radar-Based Estimation of Rainfall over Complex Terrain. J. Appl. Meteor., 41, 1163-1178. Pellarin, T., G. Delrieu, G. M. Saulnier, H. Andrieu, B. Vignal, and J. D. Creutin, 2002: Hydrologic visibility of weather radar systems operating in mountainous regions: Case study for the Ardeche Catchment (France). Journal of Hydrometeorology, 3, 539-555.

Delrieu, G.; Bouilloud, L.; Boudevillain, B.; Kirstetter, P.-E.; Borga, M.

2009-09-01

59

Rainfall estimation from TOGA radar observations during LBA field campaign  

Microsoft Academic Search

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

Emmanouil N. Anagnostou; Carlos A. Morales

2002-01-01

60

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

SciTech Connect

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 various properties of the radar-derived rainfall is studied. It is found that use of the proper radar reflectivity-rainfall intensity (Z-R) relationship is the most crucial factor in obtaining correct flood hydrographs. Errors resulting from spatially averaging radar rainfall are acceptable, but the use of discrete point information (i.e. raingage) can lead to serious problems. Reducing the resolution of the 5-min radar signal by temporally averaging over 15 and 30 min does not lead to major errors. Using 3-bit radar data (rather than the usual 8-bit data) to represent intensities results in significant operational savings without serious problems in hydrograph accuracy. 24 refs., 28 figs., 2 tabs.

Pessoa, M.L.; Bras, R.L.; Williams, E.R. (Massachusetts Inst. of Technology, Cambridge (United States))

1993-03-01

61

Statistical evaluation of a radar rainfall system for sewer system management  

NASA Astrophysics Data System (ADS)

Urban areas are faced with mounting demands for managing waste and stormwater for a cleaner environment. Rainfall information is a critical component in efficient management of urban drainage systems. A major water quality impact affecting receiving waterbodies is the discharge of untreated waste and stormwater during precipitation, termed wet weather flow. Elimination or reduction of wet weather flow in metropolitan sewer districts is a major goal of environmental protection agencies and often requires considerable capital improvements. Design of these improvements requires accurate rainfall data in conjunction with monitored wastewater flow data. Characterizing the hydrologic/hydraulic performance of the sewer using distant rain gauges can cause oversizing and wasted expenditures. Advanced technology has improved our ability to measure accurately rainfall over large areas. Weather radar, when combined with rain gauge measurements, provides detailed information concerning rainfall intensities over specific watersheds. Knowing how much rain fell over contributing areas during specific periods aids in characterizing inflow and infiltration to sanitary and combined sewers, calibration of sewer system models, and in operation of predictive real-time control measures. Described herein is the design of a system for managing rainfall information for sewer system management, along with statistical analysis of 60 events from a large metropolitan sewer district. Analysis of the lower quartile rainfall events indicates that the expected average difference is 25.61%. Upper quartile rainfall events have an expected average difference of 17.25%. Rain gauge and radar accumulations are compared and evaluated in relation to specific needs of an urban application. Overall, the events analyzed agree to within 8% based on the median average difference between gauge and radar.

Vieux, B. E.; Vieux, J. E.

2005-09-01

62

Radar analyses of extreme rainfall and flooding in urban drainage basins  

NASA Astrophysics Data System (ADS)

SummaryThe Charlotte, North Carolina metropolitan area has experienced extensive urban and suburban growth during the past 40 years, resulting in increasing flood hazards in the region. Record flooding in the urban core of Charlotte occurred on 23 July 1997 from a storm that produced rainfall accumulations of more than 250 mm during an 18 h period, more than doubling the 24 h rainfall maximum in Charlotte, and causing $60 million in property damage and three fatalities. Analyses of the 23 July 1997 storm and flood are based on rainfall and discharge observations from dense networks of rain gages and stream gages maintained by the U.S. Geological Survey and rainfall estimates from two WSR-88D weather radars, both located approximately 150 km from the urban core of Charlotte. This wealth of observations provides an opportunity to address hydrometeorological questions concerning: (1) the accuracy of radar rainfall estimates for extreme, flood-producing rainfall; (2) the space-time variability of extreme, flood-producing rainfall in urban environments; and (3) the effects of urbanization on extreme flood response in urban environments. It is shown that bias-corrected radar rainfall estimates for the 23 July 1997 storm are quite accurate and provide the capability for resolving the fundamental rainfall forcing associated with regional variation in extreme flood response in urban landscapes. Extreme flood response in urban watersheds is characterized by pronounced nonlinearities in runoff production for rainfall accumulations exceeding 50 mm. Extreme flood response is also characterized by large spatial heterogeneities that are tied to the history of urban development. Case study analyses of four additional flood events in the Charlotte metropolitan area are used to assess the robustness of conclusions derived from analyses of the most extreme event in the region and to examine the transition to "upper tail" properties of extreme flood response.

Villarini, Gabriele; Smith, James A.; Lynn Baeck, Mary; Sturdevant-Rees, Paula; Krajewski, Witold F.

2010-02-01

63

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

64

A new radar technique for satellite rainfall algorithm development  

NASA Technical Reports Server (NTRS)

A potential new radar parameter was investigated for measuring rainfall, namely the summation of the phase shifts at horizontal and vertical polarizations due to propagation through precipitation. The proposed radar technique has several potential advantages over other approaches because it is insensitive to the drop size distribution and to the shapes of the raindrops. Such a parameter could greatly assist the development of satellite rainfall estimation algorithms by providing comparative measurements near the ground. It could also provide hydrologically useful information for such practical applications as urban hydrology. Results of the investigation showed that the parameters can not be measured by radar. However, a closely related radar parameter, propagation differential phase shift, can be readily measured using a polarization diversity radar. It is recommended that propagation differential phase shift be further investigated and developed for radar monitoring of rainfall using a polarization agile radar. It is also recommended that a prototype multiple frequency microwave link be constructed for attenuation measurements not possible by existing radar systems.

Jameson, Arthur R.

1987-01-01

65

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

66

Radar Analyses of Space-Time Variability of Extreme Flood-Producing Rainfall in Urban Drainage Basins  

NASA Astrophysics Data System (ADS)

The Charlotte, North Carolina metropolitan area has experienced extensive urban and suburban growth during the past 40 years, resulting in increasing flood hazards in the region. Record flooding in the urban core of Charlotte occurred on 23 July 1997 from a storm that produced rainfall accumulations of more than 250 mm during an 18 hour period, more than doubling the 24 hour rainfall maximum in Charlotte, and causing 60 million in property damage and three fatalities. Analyses of the 23 July 1997 storm and flood are based on rainfall and discharge observations from dense networks of rain gages and stream gages maintained by the U.S. Geological Survey and rainfall estimates from two WSR-88D weather radars, both located approximately 100 km from the urban core of Charlotte. This wealth of observations provides an opportunity to address hydrometeorological questions concerning: (1) the accuracy of radar rainfall estimates for extreme, flood-producing rainfall; (2) the space-time variability of extreme, flood-producing rainfall in urban environments; and (3) the effects of urbanization on extreme flood response in urban environments. It is shown that bias-corrected radar rainfall estimates for the 23 July 1997 storm are quite accurate and provide the capability for resolving the fundamental rainfall forcing associated with regional variation in extreme flood response. This study shows how the spatial and temporal variability of rainfall combines with the land surface properties to determine extreme flood response in urban drainage basins.

Villarini, G.; Smith, J. A.; Baeck, M. L.; Sturdevant-Rees, P.; Krajewski, W. F.

2009-04-01

67

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.

Comet

2010-12-22

68

Differences in radar derived rainfall amounts due to sampling intervals  

E-print Network

. Furthermore, the total rainfall measured at a point is assumed The citations on the following pages follow the style of the Journal of Climate aod ~alice ~meteoroid to fall uniformly over an area. For hydrological purposes this area is a determining factor...- sity of Chicago Press, Chicago, L, 32a pp. Dovi ak, R. J. , 1983: A survey of radar measurement Techniques. J. Climate ~A l. Meteor. , 22, 832-849. Fornear, J. L. , 1985: Sampling rate effects on radar derived rainfall estimates. M. S. thesis, Texas...

Zdenek, David James

2012-06-07

69

Numerical simulations of radar rainfall error propagation Hatim O. Sharif1  

E-print Network

of rain gauge data. Results indicate that the geometry of the radar beam and coordinate transformations, due to radar-watershed-storm orientation, have an effect on radar rainfall estimation and runoff relationship, there are significant range-dependent and orientation-related radar rainfall estimation errors

Xue, Ming

70

Variabiltiy of summer Florida rainfall and its significance for the estimation of rainfall by gages, radar, and satellite  

Microsoft Academic Search

Simulations based on a month of radar data from the Patrick Air Force Base radar in Florida give the following results for the estimation of daily rainfall amounts over the 124,000 km2 area covered by the radar: (1) 30-min sampling by a perfect satellite sensor will increase the rainfall measurement error by 7% compared with 5-min radar sampling, (2) if

A. Seed; G. L. Austin

1990-01-01

71

Mesoscale Structure of the Heavy Rainfall in Chuzhou in August 2008 by Dual-radar  

NASA Astrophysics Data System (ADS)

Due to the effect of the low-pressure system of Fung-Wong and the cold air, it produced a heavy precipitation in the east region of Anhui province in China, up to 429mm rainfall in Chuzhou and 414mm in Quanjiao from 0800 LST 1 August to 0800 LST 2 August 2008. It is a local, sudden and short time heavy rain. The three dimensional wind fields were retrieved by the volume scan data of the dual-Doppler radar located in Nanjing and Maanshan cities. The evolution of the 3D wind fields and the formation mechanism of the sudden heavy rainfall were investigated. It is a convective cloud precipitation based on the radar echo analyses. The meso-?-scale convective system (M?CS) and the meso-?-scale system located on the M?CS played an important role on this heavy rainfall. The meso-?-scale convective cloud has high precipitation efficiency. The dual-Doppler retrieved wind reveals that the heavy rainfall was caused by the meso-?-scale shear line and the meso-?-scale convergence lines at the low and the medium levels. The shear line spread from west to east. It stayed on the Chuzhou and Quanjiao area for period of time. The shear line triggered and maintained the heavy rainfall. On the other hand, the plentiful water vapour was transported to the rainfall area continuously. These factors greadtly availed to the heavy rainfall. There were strong convergence and vorticity at the low and medium levels of the M?CS. When the shear line at the low and medium levels moved out of the rainfall area, the precipitation began to weak remarkably too. Acknowlegements The work was supported by the National Science Foundation of China (grant 40605014, 40975015) and the foundation of state key laboratory of severe weather(2008LASWZI01).

Haiguang, Zhou

2010-05-01

72

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.

73

Simulation of operational typhoon rainfall nowcasting using radar reflectivity combined with meteorological data  

NASA Astrophysics Data System (ADS)

this study, a practical typhoon effective rainfall nowcasting (TERN) model was developed for use in real-time forecasting. The TERN model was derived from a data-driven adaptive network-based fuzzy inference system (ANFIS). The model inputs include meteorological data and radar reflectivity data. The model simulation process begins with an online typhoon warning issued by the Central Weather Bureau (CWB) of Taiwan. It is then determined whether the typhoon approaches the study area according to the typhoon track predicted by the CWB. When a typhoon hits Taiwan, various data are received from sensor instruments, including the ground precipitation data, typhoon climatological data, and radar reflectivity factor by using Weather Surveillance Radar, 1988, Doppler (WSR-88D) products. The study site was Shihmen Catchment. A maximum of 10 typhoon events from 2000 to 2010 were collected. Regarding the model construction, the input combinations of the ground precipitations and reflectivity factors over the catchment functioned as optimal input variables. To verify the practicability of the ANFIS-based TERN model, Typhoon Krosa, which hit Taiwan in 2007, was simulated. The results demonstrated that the proposed methodology of real-time rainfall forecasts during typhoon warning periods yielded favorable performance levels, reliably predicting results regarding 1 h to 6 h forecasting horizons.

Wei, Chih-Chiang

2014-06-01

74

Statistical modeling of space-time rainfall using radar and rain gage observations  

Microsoft Academic Search

A statistical framework for modeling space-time rainfall using radar and rain gage observations is developed. Three principal tasks are involved in implementing our statistical model. These tasks are referred to as sampling (that is, characterization of the error structure of radar and rain gage measurements of rainfall, modeling), (that is, specification of a stochastic model for space-time rainfall), and parameter

James A. Smith; Witold F. Krajewski

1987-01-01

75

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

E-print Network

precipitation radar Stephen W. Nesbitt1 and Alison M. Anders2 Received 4 March 2009; revised 6 July 2009�2007) rainfall climatology is presented from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar precipitation radar, Geophys. Res. Lett., 36, L15815, doi:10.1029/2009GL038026. 1. Introduction [2] Spatial

Nesbitt, Steve

76

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

E-print Network

@knmi.nl I. INTRODUCTION Weather radars give quantitative precipitation estimates (QPE) over large areas the derivation of a 10- year radar-based precipitation climatology for the Netherlands. Using rain gauges AND RAIN GAUGE DATA A. Radar data Radar reflectivity data were obtained from the two C-band Doppler weather

Stoffelen, Ad

77

The European Weather Radar Network (OPERA): An opportunity for hydrology!  

E-print Network

in the European Weather Radar Network. The third phase of the OPERA program is a joint effort of 28 European session and parallel working group discussions. Two working groups have been established during this phase of OPERA: Working Group 1, chaired by Laurent Delobbe (RMI), is dedicated to "Radar Technology

Stoffelen, Ad

78

Analytical and computer model of a Doppler weather radar system  

Microsoft Academic Search

With advances in Doppler weather radar, severe storm and tornado detection has improved greatly. However, the resolution limitations of deployed radar systems can still limit severe storm detection. In the case of larger tornadoes, characteristic abrupt changes in wind direction can usually be detected between adjacent range-angle bins. However for smaller tornadoes, the rotating cell may be contained within one

Ryan K. Hersey; Mark A. Richards; James H. McClellan

2002-01-01

79

Reconfigurable Data Acquisition System for Weather Radar Applications  

E-print Network

, 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, and perform various processing tasks to cast the raw data into an intelligible and meaningful format

Tessier, Russell

80

International Weather-Radar Networking in Western Europe  

Microsoft Academic Search

During the last few years there has been considerable activity in Western Europe aimed at establishing national radar networks. Concurrent with this work, several bilateral agreements to exchange weather-radar data across national boundaries have been established. Effective international cooperation was stimulated by the European Economic Community (EEC) sponsored COST Project 72 and this has led to the setting up of

C. G. Collier; C. A. Fair; D. H. Newsome

1988-01-01

81

Rainfall: From Fractals to Multifractals, From Weather to Climate  

NASA Astrophysics Data System (ADS)

The Intensity-Duration-Frequency (IDF) curves are a classical example of statistical models relating weather and climate time scales. There are numerous standard IDF models. Whereas these parametric models yield similar values near the centre of the distribution, because they are fitted on low order statistics, the extreme quantiles often differ significantly. Unfortunately, these models are based on hypotheses opposite to the long-range dependencies, non-stationarity and clustering of the extremes displayed by rainfall. Searching for methods that could bridge weather and climate time scales of the IDF curves but incorporating physical principles, there have been numerous applications of scaling theories during the last decade. The majority of available theoretical results concerning the scaling extrapolation of the IDF curves has been obtained either with the help of a ';simple scaling' formalism or the multifractal formalism. While the former oversimplifies a multifractal nature of rainfall, the latter often assumes a strict equivalence between the duration (of a sliding window for moving average) and the scale of data observation (corresponding to disjoint windows). In a general manner, the scaling behavior of IDF curves strongly depends on how the durations are defined. An additional complexity arises from the fact that zero-rainfall generally introduces a scaling break between small and large time scales of the rainfall process. In this presentation we discuss the real scaling nature of the rainfall, the nonlinear transformations associated to scaling and duration changing, including for the climate-relevant return periods that very often exceed the length of available historical records. For this purpose, we use a procedure recently developed for near-wall atmospheric turbulence to define conservative flux proxies from empirical data such that they correspond to well-defined stochastic multiplicative processes in the framework of a nonlinear generalized scale invariance. This extends the scaling range of the empirical data and thus leads to non-ambiguous estimates of the universal multifractal parameters. This procedure has been tested on numerous rainfall data. The results explain why over past decades there have been numerous, unsuccessful attempts of modeling the rainfall process as a product of a stochastic multifractal with a fractal field generating the zero rainfall, whereas the rainfall process does not correspond to a passive scalar or a conservative flux, but to a fractionally integrated flux.

Tchiguirinskaia, I.; Schertzer, D. J.; Fitton, G. F.; Gires, A.

2013-12-01

82

Daily to submonthly weather and climate characteristics of the summer 1998 extreme rainfall over the Yangtze  

E-print Network

Daily to submonthly weather and climate characteristics of the summer 1998 extreme rainfall over floods over the region since the year of 1954. [3] The extreme Meiyu rainfall of summer 1998 has been to submonthly weather and regional climate characteristics associated with the extreme rainfall events over

Zhang, Da-Lin

83

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

84

Quantitative precipitation estimation for an X-band weather radar network  

NASA Astrophysics Data System (ADS)

Currently, the Next Generation (NEXRAD) radar network, a joint effort of the U.S. Department of Commerce (DOC), Defense (DOD), and Transportation (DOT), provides radar data with updates every five-six minutes across the United States. This network consists of about 160 S-band (2.7 to 3.0 GHz) radar sites. At the maximum NEXRAD range of 230 km, the 0.5 degree radar beam is about 5.4 km above ground level (AGL) because of the effect of earth curvature. Consequently, much of the lower atmosphere (1-3 km AGL) cannot be observed by the NEXRAD. To overcome the fundamental coverage limitations of today's weather surveillance radars, and improve the spatial and temporal resolution issues, the National Science Foundation Engineering Center (NSF-ERC) for Collaborative Adaptive Sensing of the Atmosphere (CASA) was founded to revolutionize weather sensing in the lower atmosphere by deploying a dense network of shorter-range, low-power X-band dual-polarization radars. The distributed CASA radars are operating collaboratively to adapt the changing atmospheric conditions. Accomplishments and breakthroughs after five years operation have demonstrated the success of CASA program. Accurate radar quantitative precipitation estimation (QPE) has been pursued since the beginning of weather radar. For certain disaster prevention applications such as flash flood and landslide forecasting, the rain rate must however be measured at a high spatial and temporal resolution. To this end, high-resolution radar QPE is one of the major research activities conducted by the CASA community. A radar specific differential propagation phase (Kdp)-based QPE methodology has been developed in CASA. Unlike the rainfall estimation based on the power terms such as radar reflectivity (Z) and differential reflectivity (Zdr), Kdp-based QPE is less sensitive to the path attenuation, drop size distribution (DSD), and radar calibration errors. The CASA Kdp-based QPE system is also immune to the partial beam blockage and hail contamination. The performance of the CASA QPE system is validated and evaluated by using rain gauges. In CASA's Integrated Project 1 (IP1) test bed in Southwestern Oklahoma, a network of 20 rainfall gauges is used for cross-comparison. 40 rainfall cases, including severe, multicellular thunderstorms, squall lines and widespread stratiform rain, that happened during years 2007 - 2011, are used for validation and evaluation purpose. The performance scores illustrate that the CASA QPE system is a great improvement compared to the current state-of-the-art. In addition, the high-resolution CASA QPE products such as instantaneous rainfall rate map and hourly rainfall amount measurements can serve as a reliable input for various distributed hydrological models. The CASA QPE system can save lived and properties from hazardous flash floods by incorporating hydraulic and hydrologic models for flood monitoring and warning.

Chen, Haonan

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

Mapping Wintering Waterfowl Distributions Using Weather Surveillance Radar  

PubMed Central

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 19981999 and 19992000. 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 19981999. 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. PMID:22911816

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

2012-01-01

87

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 19981999 and 19992000. 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 19981999. 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

88

Real-time rapid refractivity retrieval using the national weather radar testbed phased array radar  

Microsoft Academic Search

A real-time rapid refractivity retrieval platform for the national weather radar testbed phased array radar (NWRT PAR) is currently being developed at the University of Oklahoma, Norman, USA. From our previous efforts in the 2007 KTLX refractivity experiment [1], a software module to produce refractivity products has been developed and will be ported over to the NWRT PAR this year

Boon Leng Cheong; Robert D. Palmer; Christopher Curtis; Tian-You Yu; D. Zrnic; D. Forsyth

2008-01-01

89

The use of composite radar photographs in synoptic weather analysis  

E-print Network

obtained from the photographs on surface weather charts ~ Two methods for combining radar data with surface observations ara suggssteds The author grctsfully acknowledges the helpful ccmmsnts cnd assistance of Qrs. H. G. H. hiads, H. 3. Saucier, end Hr... of the draft, ines; Hrs, 'Hat's Lou Wrisht who plotted some cf the surface data; snd Hr. James Sullivan who performed ths photographic work in preparation of the fisurss. The original radar data and other facilities ware made possi- ble by the air porte...

Smith, G. D.

2012-06-07

90

Comparison between radar and rain gauges data at different distances from radar and correlation existing between the rainfall values in the adjacent pixels  

Microsoft Academic Search

Rainfall intensity data in pixels very far from radar are less correlated than values in pixels near the radar, because at far distances the width of a range-bin is comparable or bigger than the pixel width, so in a pixel there are one or just a few rainfall intensity values. Vice versa, near the radar, there are many radar resolution

S. Sebastianelli; F. Russo; F. Napolitano; L. Baldini

2010-01-01

91

Improved radar data processing algorithms for quantitative rainfall estimation in real time.  

PubMed

This paper describes a new methodology to process C-band radar data for direct use as rainfall input to hydrologic and hydrodynamic models and in real time control of urban drainage systems. In contrast to the adjustment of radar data with the help of rain gauges, the new approach accounts for the microphysical properties of current rainfall. In a first step radar data are corrected for attenuation. This phenomenon has been identified as the main cause for the general underestimation of radar rainfall. Systematic variation of the attenuation coefficients within predefined bounds allows robust reflectivity profiling. Secondly, event specific R-Z relations are applied to the corrected radar reflectivity data in order to generate quantitative reliable radar rainfall estimates. The results of the methodology are validated by a network of 37 rain gauges located in the Emscher and Lippe river basins. Finally, the relevance of the correction methodology for radar rainfall forecasts is demonstrated. It has become clearly obvious, that the new methodology significantly improves the radar rainfall estimation and rainfall forecasts. The algorithms are applicable in real time. PMID:19587415

Krmer, S; Verworn, H R

2009-01-01

92

Estimating subcatchment runoff coefficients using weather radar and a downstream runoff sensor.  

PubMed

This paper presents a method for estimating runoff coefficients of urban drainage subcatchments based on a combination of high resolution weather radar data and flow measurements from a downstream runoff sensor. By utilising the spatial variability of the precipitation it is possible to estimate the runoff coefficients of the separate subcatchments. The method is demonstrated through a case study of an urban drainage catchment (678 ha) located in the city of Aarhus, Denmark. The study has proven that it is possible to use corresponding measurements of the relative rainfall distribution over the catchment and downstream runoff measurements to identify the runoff coefficients at subcatchment level. PMID:24056426

Ahm, Malte; Thorndahl, Sren; Rasmussen, Michael R; Bass, Lene

2013-01-01

93

Investigation of the scale-dependent variability of radar-rainfall and rain gauge error covariance  

Microsoft Academic Search

There is a significant spatial sampling mismatch between radar and rain gauge data. The use of rain gauge data to estimate radar-rainfall error variance requires partitioning of the variance of the radar and rain gauge difference to account for the sampling mismatch. A key assumption in the literature pertaining to the error variance separation method used to partition the variance

Bong-Chul Seo; Witold F. Krajewski

2011-01-01

94

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

E-print Network

the promise of much more accurate rainfall-rate R estimates than are possible from radar reflectivity factor Z in the size distribution. Conven- tional radars are also unable to distinguish hail from heavy rain Radar ROBIN J. HOGAN Department of Meteorology, University of Reading, Reading, United Kingdom

Hogan, Robin

95

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

E-print Network

Precipitation Radar and ICESat/Geoscience Laser Altimeter System Sean P. F. Casey,1 Andrew E. Dessler,1) Precipitation Radar (PR). Fractional areal coverage (FAC) data is calculated at each of the three levels Rainfall Measuring Mission Precipitation Radar and ICESat/Geoscience Laser Altimeter System, J. Geophys

96

Clutter rejection for Doppler weather radars which use staggered pulses  

Microsoft Academic Search

Several methods for canceling ground clutter in Doppler weather radars which operate with staggered pulse repetition times (PRTs) are investigated. A scheme is developed which consists of two filters that operate sequentially, so that the overall filter is time-varying, with periodically changing coefficients. This filter is analyzed theoretically and through simulations for a stagger ratio of 3\\/2, which extends the

Zoran B. Banjanin; Dusan S. Zrnic

1991-01-01

97

Doppler weather radar with predictive wind shear detection capabilities  

NASA Technical Reports Server (NTRS)

The status of Bendix research on Doppler weather radar with predictive wind shear detection capability is given in viewgraph form. Information is given on the RDR-4A, a fully coherent, solid state transmitter having Doppler turbulence capability. Frequency generation data, plans, modifications, system characteristics and certification requirements are covered.

Kuntman, Daryal

1991-01-01

98

Multichannel Receiver Design, Instrumentation, and First Results at the National Weather Radar Testbed  

Microsoft Academic Search

When the National Weather Radar Testbed (NWRT) was installed in 2004, a single-channel digital receiver was implemented so that the radar could mimic typical Weather Surveillance Radar (WSR) version 1988 Doppler (WSR-88D) capability. This, however, left unused eight other channels, built into the antenna. This paper describes the hardware instrumentation of a recently completed project that digitizes the radar signals

Mark Yeary; Gerald Crain; Allen Zahrai; Christopher D. Curtis; John Meier; Redmond Kelley; Igor R. Ivic; Robert D. Palmer; Richard J. Doviak; G. Zhang; Tian-You Yu

2012-01-01

99

Initialization Analysis of IIR Ground Clutter Filter in Doppler Weather Radar  

Microsoft Academic Search

This paper analyzes the initialization of IIR ground clutter filter (GCF) in Doppler weather radar. The transients of IIR GCF degrade the theoretical frequency response and different initialization technique produces different suppression characteristic. The initialization performance is tested both with a simulated weather radar signal and an actual weather radar signal. We explore the relation between clutter suppression ratio (the

Yuchun Gao; Yan Liu; He Jianxin

2007-01-01

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.; Grubii?, V.; Moore, J.; Tsai, P.

2014-07-01

101

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

102

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

E-print Network

for correcting errors in radar estimates of rainfall due to attenuation, which is based on the fact that any in rainfall estimates and in radar calibrations using gauges. The extra noise at low radar elevations provides problem for C-band radars, especially in the very storms where the rain is heaviest and accurate rainfall

Reading, University of

103

Hydroclimatologic Analyses of Extreme Rainfall and Flooding in Atlanta, Georgia Using Long-Term Radar-Rainfall Datasets  

NASA Astrophysics Data System (ADS)

A 10-year radar rainfall dataset is being developed for the Atlanta, Georgia metropolitan area using the Hydro-NEXRAD algorithms. Radar rainfall fields are constructed at 15 minute time resolution and 1 km spatial resolution; observations from a dense network of rain gages are used for multiplicative bias correction. The high-resolution dataset will permit the investigation of urban effects on the initiation and evolution of heavy rainfall events. In addition, the climatology of extreme rainfall-runoff relationships will be examined with the aim of improving the understanding of the water balance and flood response of urban catchments during extreme rainfall events. Analyses relating the temporal and spatial distribution of rainfall to basin scale and land-use/land-cover characteristics will assist in developing urban flood frequency relationships. Events of particular interest are the floods of September 20-21, 2009 and May 3-4, 2010, which caused heavy damage and fatalities in portions of the southeastern US including Atlanta. Similar bias-corrected radar datasets in development for the Baltimore, Charlotte, and Milwaukee metropolitan areas will allow for the comparison of climatology of extreme rainfall and urban flooding in different regions of the United States and under different climate regimes.

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

2010-12-01

104

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

105

Kuduck Dwsr-88c Radar Rainfall Estimation and Z-r Relationship By Poss During 2001 In Korea  

NASA Astrophysics Data System (ADS)

The Z-R relationship is derived by linear regression and is used to convert the radar reflectivity Z into the rainfall rate R. It is expressed in terms of an equation of the form as Z=aR^b. The a and b are constant values which have been determined empirically and carried out studies on the calibration of Z-R relationship by many people in many places. However our operational weather radars have been using such as Z=200R^1.6 which can be applied in the case of stratiform clouds. In considering the seasonal vari- ation and rainfall type, this equation is not adequate for many kinds of rainfall events. This fact gives an uncertain result for rainfall estimation and has damage of proper- ties by the incorrect forecast. A statistical Z-R relationship and correction of rainrate were obtained by the drop size distribution(DSD) with calibration of the radar Z-R relationship in Busan city. Precipitation data were observed and measured by a dis- drometer(POSS), a weather radar and a rain gauge of AWS from March to September 2001. As a result, Z-R relationship obtained by disdrometer(POSS) was Z=415R^1.51, even though they can not be sufficiently coverd at all precipitation, since it was not considered the classification of precipitation type and long terms data. New calculated Z-R relationship which was converted to the correlation reflectivity(Zc) between radar reflectivity(Zr) and POSS reflectivity(Zp) was well applied to the estimation of rain- fall rate and it was very variable according to the precipitation events. Therefore, it is found that Kuduck DWSR-88C weather radar has to be operated at more accurate one calibrated and calculated to the new Z-R relationship. In addition, through long precipitation observations with drop size distribution measurements, Z-R relationship has to be continuously provided at each precipitation type.

Lee, D. I.; Jang, M.; You, C. H.; Kim, K. E.; Suh, A. S.

106

THE WEATHER An unusually persistent and moist weather pattern led to rainfall totals from September 9th -15th  

E-print Network

and rainfall over an even larger area. · Mostoftherainfellin36hours,fromtheafternoonofSeptember 11th until" for selected locations are shown. (Map: Colorado Climate Center, CSU) · Seven-day rainfall totals (9/9 to 9 weather station (since 1893) set new records for 1-day (9.08"), 2-day (11.52") and 7-day (16.9") totals

107

Evaluation of Raindrop Size Distributions to Improve Radar Rainfall Estimation during the Colorado Flood  

NASA Astrophysics Data System (ADS)

During the period of 9-16 September 2013, a large area of greater than 150 mm of rain, with local amounts of up to 450 mm, fell over a large part of the Colorado Front Range foothills and adjacent plains. This extreme rainfall event caused severe flooding of main river channels and some localized flash flooding which resulted in millions of dollars of damage to private and public properties. The rainfall regime associated with this extreme precipitation event was atypical of storms usually observed in this region. As a result, the radar rainfall algorithms tuned for this region significantly underestimated the total amount of rainfall. In order to quantify the underestimation and provide insight for improving the radar rainfall estimates for this unique precipitation regime, a comparison study has been conducted using data from several disdrometers that were operating throughout the event. Disdrometers observed over 5000 minutes of rainfall during the event. Analysis of the raindrop spectra indicated that most of the rainfall was comprised of a large number of small drops (< 2 mm in diameter). The raindrop spectra have been stratified by the precipitation regime. For these different regimes, new radar rainfall estimators are being derived from the raindrop spectra. The new estimators will be applied to the radar data to provide new rainfall estimates. These estimates will be evaluated using independent rain gauge data. The presentation will provide an overview of the Colorado Flood and a summary of results from the precipitation analysis.

Kucera, Paul; Klepp, Christian

2014-05-01

108

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

109

Radar rainfall estimation in the context of post-event analysis of flash-flood events  

NASA Astrophysics Data System (ADS)

SummaryA method to estimate rainfall from radar data for post-event analysis of flash-flood events has been developed within the EC-funded HYDRATE project. It follows a pragmatic approach including careful analysis of the observation conditions for the radar system(s) available for the considered case. Clutter and beam blockage are characterised by dry-weather observations and simulations based on a digital terrain model of the region of interest. The vertical profile of reflectivity (VPR) is either inferred from radar data if volume scanning data are available or simply defined using basic meteorological parameters (idealised VPR). Such information is then used to produce correction factor maps for each elevation angle to correct for range-dependent errors. In a second step, an effective Z-R relationship is optimised to remove the bias over the hit region. Due to limited data availability, the optimisation is carried out with reference to raingauge rain amounts measured at the event time scale. Sensitivity tests performed with two well-documented rain events show that a number of Z = aRb relationships, organised along hyperbolic curves in the (a and b) parameter space, lead to optimum assessment results in terms of the Nash coefficient between the radar and raingauge estimates. A refined analysis of these equifinality patterns shows that the total additive conditional bias can be used to discriminate between the Nash coefficient equifinal solutions. We observe that the optimisation results are sensitive to the VPR description and also that the Z-R optimisation procedure can largely compensate for range-dependent errors, although this shifts the optimal coefficients in the parameter space. The time-scale dependency of the equifinality patterns is significant, however near-optimal Z-R relationships can be obtained at all time scales from the event time step optimisation.

Bouilloud, Ludovic; Delrieu, Guy; Boudevillain, Brice; Kirstetter, Pierre-Emmanuel

2010-11-01

110

Forecasting of storm rainfall by combined use of radar, rain gages and linear models  

Microsoft Academic Search

An integrated approach to real-time prediction of point rainfall is presented. This is based on the assumption that hourly rainfall at a station can be predicted by a Multivariate AutoRegressive Integrated Moving Average (MARIMA) process. The real-time calibration of the multivariate model is performed by combining radar maps and data from rain gages. Accordingly, radar maps provide the basic information

Paolo Burlando; Alberto Montanari; Roberto Ranzi

1996-01-01

111

Specification of predictors necessary for the determination of over or underestimation of radar derived total rainfall  

E-print Network

SPECIFICATION OF PREDICTORS NECESSARY FOR THE DETERMINATION OF OVER OR UNDERESTIMATION OF RADAR DERIVED TOTAL RAINFALL A Thesis by VINCENT PATRICK HOLBROOK Submitted to the Graduate College of Texas A&M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE August 1987 Major Subject: Meteorology SPECIFICATION OF PREDICTORS NECESSARY FOR THE DETERMINATION OF OVER OR UNDERESTIMATION OF RADAR DERIVED TOTAL RAINFALL A Thesis by VINCENT PATRICK HOLBROOK Approved...

Holbrook, Vincent Patrick

2012-06-07

112

Combining radar and rain gauge rainfall estimates using conditional merging  

Microsoft Academic Search

The Hydrologist's traditional tool for measuring rainfall is the rain gauge. Rain gauges are relatively cheap, easy to maintain and provide a direct and suitably accurate estimate of rainfall at a point. What rain gauges fail to capture well is the spatial variability of rainfall with time, an important aspect for the credible modelling of a catchment's response to rainfall.

Scott Sinclair; Geoff Pegram

2005-01-01

113

Siting of Doppler weather radars to shield ground targets  

NASA Astrophysics Data System (ADS)

Weather radars are usually sited so they can survey as large an area as possible. A large surveillance area is achieved by placing the antenna as high as practical but then the radar can be blind to weather targets near the ground because of ground clutter interference. There are applications where it is necessary to have fine resolution of low altitude divergence and wind shear near the ground in regions of weak weather reflectivity. This requirement can be most conveniently satisfied when surveillance is near the radar, but it brings attention to the problem of reducing ground clutter. Although cancelers help to reduce ground target echoes, they cannot eliminate them, and reduction for scanning beams is limited to about 40 dB. Proper siting to take advantage of natural terrain and man-made shields (clutter fences) can further reduce ground clutter. Criteria are developed that relate ground target illumination to antenna characteristics, shield heights, and the distance to the shield. Both geometric optic and diffraction theory are used to estimate the effectiveness of shields.

Doviak, R. J.; Zrnic, D. S.

1985-07-01

114

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

E-print Network

, Verification 1. INTRODUCTION Weather radars are well known for their ability to detect precipitation at a high of the precipitation. The wavelength of weather radars is optimized for detection of precipitation and is typically 5 of the precipitation. Bird migration can lead to (unexpected) major errors. 2. WIND PROFILING A Doppler radar uses

Stoffelen, Ad

115

Determining weather radar antenna pointing using signals detected from the sun at low antenna elevations  

E-print Network

Determining weather radar antenna pointing using signals detected from the sun at low antenna radiation of the sun for checking of the antenna alignment and of the sensitivity of the receiver chain is a well established method in weather radar maintenance, and radar manufacturers offer sun calibration

Stoffelen, Ad

116

"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 antenna scan, a three dimensional view of the surrounding atmosphere is created. Traditional weather

Mountziaris, T. J.

117

Impacts of rainfall weather on urban traffic in beijing: analysis and modeling  

E-print Network

Recently an increasing number of researches have been focused on the influence of rainfall intensity on traffic flow. Conclusions have been reached that inclement weather does have negative impacts on key traffic parameters. However, due to lack of data, limited work has been implemented in China. In this paper, the impacts of rainfall intensity on urban road traffic flow characteristics are quantified, based on the historical traffic data and weather data in Beijing, capital of China. The reductions of road capacity and operating speed are obtained by statistical estimation for different rainfall intensity categories against clear weather. Then the modified speed-density function and speed-flow function are calibrated at different rainfall levels, from which the reductions of free-flow speed can be calculated. Finally, a generalized continuous speed-flow-rainfall model is developed and calibrated. The validation results show a good accuracy, indicating the new model can be used for urban traffic management u...

Jia, Yuhan; Du, Yiman; Qi, Geqi

2014-01-01

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

Processing of Indian Doppler Weather Radar data for mesoscale applications  

NASA Astrophysics Data System (ADS)

This paper demonstrates the usefulness of Indian Doppler Weather Radar (DWR) data for nowcasting applications, and assimilation into a mesoscale Numerical Weather Prediction (NWP) model. Warning Decision Support System Integrated Information (WDSS-II) developed by National Severe Storm Laboratory (NSSL) and Advanced Regional Prediction System (ARPS) developed at the Centre for Analysis and Prediction, University of Oklahoma are used for this purpose. The study reveals that the WDSS-II software is capable of detecting and removing anomalous propagation echoes from the Indian DWR data. The software can be used to track storm cells and mesocyclones through successive scans. Radar reflectivity mosaics are created for a land-falling tropical cycloneKhaimuk of 14 November 2008 over the Bay of Bengal using observations from three DWR stations, namely, Visakhapatnam, Machilipatnam and Chennai. Assimilation of the quality-controlled radar data (DWR, Chennai) of the WDSS-II software in a very high-resolution NWP model (ARPS) has a positive impact for improving mesoscale prediction. This has been demonstrated for a land-falling tropical cyclone Nisha of 27 November 2008 of Tamil Nadu coast. This paper also discusses the optimum scan strategy and networking considerations. This work illustrates an important step of transforming research to operation.

Roy Bhowmik, S. K.; Sen Roy, Soma; Srivastava, Kuldeep; Mukhopadhay, B.; Thampi, S. B.; Reddy, Y. K.; Singh, Hari; Venkateswarlu, S.; Adhikary, Sourav

2011-03-01

120

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

121

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

122

Estimation of areal rainfall using the radar echo area time integral  

NASA Technical Reports Server (NTRS)

The Area Time Integral (ATI) method of Doneaud et al. (1984) is extended to the measurement of cumulative areawide rainfall for periods up to 12 h. The extended ATI method is used to analyze data from the Florida Area Cumulus Experiment II. The relationship between radar estimated rain volume and radar-measured area covered with echoes is examined to test the possibility of obtaining values similar to conventional reflectivity-rainfall estimates of rainfall using only area measurements. The correlation between gage-estimated rain volume and radar estimated area covered with showers is also studied, focusing on the possible estimation of rain volume values using a small number of echo area observations.

Lopez, Raul E.; Blanchard, David O.; Atlas, David; Rosenfeld, Daniel; Thomas, Jack L.

1989-01-01

123

SEVIRI rainfall retrieval and validation using weather radar observations  

Microsoft Academic Search

This paper presents and validates a new algorithm to detect precipitating clouds and estimate rain rates from cloud physical properties retrieved from the Spinning Enhanced Visible and Infrared Imager (SEVIRI). The precipitation properties (PP) algorithm uses information on cloud condensed water path (CWP), particle effective radius, and cloud thermodynamic phase to detect precipitating clouds, while information on CWP and cloud

R. A. Roebeling; I. Holleman

2009-01-01

124

Effects of Nonuniform Beam Filling on Rainfall Retrieval for the TRMM Precipitation Radar  

NASA Technical Reports Server (NTRS)

The Tropical Rainfall Measuring Mission (TRMM) will carry the first spaceborne radar for rainfall observation. Because the TRMM Precipitation Radar (PR) footprint size of 4.3 km is greater than the scale of some convective rainfall events, there is concern that nonuniform filling of the PR antenna beam may bias the retrieved rain-rate profile. The authors investigate this effect theoretically and then observationally using data from the NASA Jet Propulsion Laboratory Airborne Rain Mapping Radar (ARMAR), acquired during Tropical Oceans Global Atmosphere Coupled Ocean Atmosphere Response Experiment in early 1993. The authors' observational approach is to simulate TRMM PR data using the ARMAR data and compare the radar observables and retrieved rain rate from the simulated PR data with those corresponding to the high-resolution radar measurements. The authors find that the path-integrated attenuation and the resulting path-averaged rain rate are underestimated. The reflectivity and rain rate near the top of the rainfall column are overestimated. The near-surface reflectivity can be overestimated or underestimated, with a mean error very close to zero. The near-surface rain rate, however, is usually underestimated, sometimes severely.

Durden, Stephen L.; Haddad, Z. S.; Kitiyakara, A.; Li, F. K.

1998-01-01

125

2-D spatial distribution of rainfall rate through combined use of radar reflectivity and rain gauge data  

Microsoft Academic Search

This paper describes and comments the results obtained applying a data processing method to a joint set of radar and a rain gauge data for estimating the 2-D rainfall field at ground averaged over a given observation time T and over a radar coverage area that includes a rain gauge network. The estimate of the rainfall field is based on

F. Cuccoli; L. Facheris; D. Giuli; M. Casamaggi

2005-01-01

126

Development of precipitation radar onboard the Tropical Rainfall Measuring Mission (TRMM) satellite  

Microsoft Academic Search

The precipitation radar (PR) onboard the Tropical Rainfall Measuring Mission (TRMM) satellite is the first spaceborne radar to measure precipitation from space. The PR, operating at 13.8 GHz, is a 128-element active phased array that allows a fast and sophisticated cross-track scanning over a swath width of 215 km with a cross-range spatial resolution of about 4.3 km. The PR

Toshiaki Kozu; Toneo Kawanishi; Hiroshi Kuroiwa; Masahiro Kojima; Koki Oikawa; Hiroshi Kumagai; K. Okamoto; M. Okumura; H. Nakatsuka; K. Nishikawa

2001-01-01

127

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

128

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

129

Streamflow Forecasting Based on Statistical Applications and Measurements Made with Rain Gage and Weather Radar  

E-print Network

measurements taken with weather radar. In addition, accurate estimates of lag time can be made from radar observations. For a storm which is unevenly distributed over the watershed, it is demonstrated that a better estimation of lag time may be made from radar...

Hudlow, M.D.

130

Advanced Precipitation Radar Antenna to Measure Rainfall From Space  

NASA Technical Reports Server (NTRS)

To support NASA s planned 20-year mission to provide sustained global precipitation measurement (EOS-9 Global Precipitation Measurement (GPM)), a deployable antenna has been explored with an inflatable thin-membrane structure. This design uses a 5.3 5.3-m inflatable parabolic reflector with the electronically scanned, dual-frequency phased array feeds to provide improved rainfall measurements at 2.0-km horizontal resolution over a cross-track scan range of up to 37 , necessary for resolving intense, isolated storm cells and for reducing the beam-filling and spatial sampling errors. The two matched radar beams at the two frequencies (Ku and Ka bands) will allow unambiguous retrieval of the parameters in raindrop size distribution. The antenna is inflatable, using rigidizable booms, deployable chain-link supports with prescribed curvatures, a smooth, thin-membrane reflecting surface, and an offset feed technique to achieve the precision surface tolerance (0.2 mm RMS) for meeting the low-sidelobe requirement. The cylindrical parabolic offset-feed reflector augmented with two linear phased array feeds achieves dual-frequency shared-aperture with wide-angle beam scanning and very low sidelobe level of -30 dB. Very long Ku and Ka band microstrip feed arrays incorporating a combination of parallel and series power divider lines with cosine-over-pedestal distribution also augment the sidelobe level and beam scan. This design reduces antenna mass and launch vehicle stowage volume. The Ku and Ka band feed arrays are needed to achieve the required cross-track beam scanning. To demonstrate the inflatable cylindrical reflector with two linear polarizations (V and H), and two beam directions (0deg and 30deg), each frequency band has four individual microstrip array designs. The Ku-band array has a total of 166x2 elements and the Ka-band has 166x4 elements with both bands having element spacing about 0.65 lambda(sub 0). The cylindrical reflector with offset linear array feeds reduces the complexity from "NxN" transmit/receive (T/R) modules of a conventional planar-phased array to just "N" T/R modules. The antenna uses T/R modules with electronic phase-shifters for beam steering. The offset reflector does not provide poor cross-polarization like a double- curved offset reflector would, and it allows the wide scan angle in one plane required by the mission. Also, the cylindrical reflector with two linear array feeds provides dual-frequency performance with a single, shared aperture. The aperture comprises a reflective surface with a focal length of 1.89 m and is made from aluminized Kapton film. The reflective surface is of uniform thickness in the range of a few thousandths of an inch and is attached to the chain-link support structure via an adjustable suspension system. The film aperture rolls up, together with the chain-link structure, for launch and can be deployed in space by the deployment of the chain-link structure.

Rahmat-Samii, Yahya; Lin, John; Huang, John; Im, Eastwood; Lou, Michael; Lopez, Bernardo; Durden, Stephen

2008-01-01

131

Direct measurement of the combined effects of lichen, rainfall, and temperature onsilicate weathering  

USGS Publications Warehouse

A key uncertainty in models of the global carbonate-silicate cycle and long-term climate is the way that silicates weather under different climatologic conditions, and in the presence or absence of organic activity. Digital imaging of basalts in Hawaii resolves the coupling between temperature, rainfall, and weathering in the presence and absence of lichens. Activation energies for abiotic dissolution of plagioclase (23.1 ?? 2.5 kcal/mol) and olivine (21.3 ?? 2.7 kcal/mol) are similar to those measured in the laboratory, and are roughly double those measured from samples taken underneath lichen. Abiotic weathering rates appear to be proportional to rainfall. Dissolution of plagioclase and olivine underneath lichen is far more sensitive to rainfall.

Brady, P. V.; Dorn, R. I.; Brazel, A. J.; Clark, J.; Moore, R. B.; Glidewell, T.

1999-01-01

132

Clutter rejection for Doppler weather radars which use staggered pulses  

NASA Astrophysics Data System (ADS)

Several methods for canceling ground clutter in Doppler weather radars which operate with staggered pulse repetition times (PRTs) are investigated. A scheme is developed which consists of two filters that operate sequentially, so that the overall filter is time-varying, with periodically changing coefficients. This filter is analyzed theoretically and through simulations for a stagger ratio of 3/2, which extends the unambiguous velocity interval. The amplitude characteristic of the filter over this interval is very good, but the phase characteristic, which is nonlinear in a small part of the interval, requires that a special decision logic be used for velocity estimation. At a signal-to-noise ratio of 10 dB, mean velocity estimates at the output have average errors smaller than 3.5 percent. Thus the scheme could be suitable for operation in environments with ground clutter.

Banjanin, Zoran B.; Zrnic, Dusan S.

1991-07-01

133

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

134

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

E-print Network

Polarization radar offers the promise of much more accurate rainfall rate (R) estimates than possible from and dp. The scheme is tested on S-band radar data from Southern England in cases of rain, spherical hail. Conventional radars are also unable to distinguish hail from heavy rain and are very difficult to correct

Hogan, Robin

135

Fusion of radar and rain gage measurements for an accurate estimation of rainfall  

Microsoft Academic Search

With the increased availability of rainfall measurements from multiple sensors having different spatiotemporal characteristics, issues of sensor fusion and intercomparison of different estimation methods are emerging as critical research questions. Cokriging is perhaps the most widely used method to fuse measurements from two sensors, for example, radar and rain gages. Cokriging offers a minimum variance estimate and can be shown

Christos Matsoukas; Shafiqul Islam; Ravi Kothari

1999-01-01

136

Spaceborne Doppler Radar Measurements of Rainfall: Correction of Errors Induced by Pointing Uncertainties  

NASA Technical Reports Server (NTRS)

In this paper a sea surface radar echo spectral analysis technique to correct for the rainfall velocity error caused by radar-pointing uncertainty is presented. The correction procedure is quite straightforward when the radar is observing a homogeneous rainfall field. When nonuniform beam filling (NUBF) occurs and attenuating frequencies are used, however, additional steps are necessary in order to correctly estimate the antenna-pointing direction. This new technique relies on the application of the combined frequency-time (CFT) algorithm to correct for uneven attenuation effects on the observed sea surface Doppler spectrum. The performance of this correction technique was evaluated by a Monte Carlo simulation of the Doppler precipitation radar backscatter from high-resolution 3D rain fields (either generated by a cloud resolving numerical model or retrieved from airborne radar measurements). The results show that the antenna-pointing-induced error can, indeed, be reduced by the proposed technique in order to achieve 1 m s(exp -1) accuracy on rainfall vertical velocity estimates.

Tanelli, Simone; Im, Eastwood; Kobayashi, Satoru; Mascelloni, Roberto; Facheris, Luca

2005-01-01

137

Sampling-rate effects on radar-derived rainfall estimates  

E-print Network

greater than e1ght. The mean error from th1s point and greater is less than approximately 5X. Evidently this 1s a po1nt at wh1ch the rainfall temporal profile becomes fairly well defined. In- creas1ng the number of samples beyond this number has little... greater than e1ght. The mean error from th1s point and greater is less than approximately 5X. Evidently this 1s a po1nt at wh1ch the rainfall temporal profile becomes fairly well defined. In- creas1ng the number of samples beyond this number has little...

Fornear, Jeffrey Lynn

2012-06-07

138

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 Mto-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 Mto 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

139

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 20042005 and 20052006, 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

140

Hydrological Assessment of Factors Affecting the Accuracy of Weather Radar Measurements of Rain  

Microsoft Academic Search

A simulation-based study of some errors affecting radar measurements of rain and their hydrological consequences is presented. The followed procedure uses radar data to generate a high-density three-dimensional rainfall field that is used as reference. Then, through simulation, this field is 'degraded' in order to reproduce a series of radar errors. Next, different correction procedures are applied to the degraded

Rafael Snchez-Diezma; Daniel Sempere-Torres; Isztar Zawadzki; Jean Dominique Creutin

141

A multi-sensor physically based weather/non-weather radar echo classifier using polarimetric and environmental data in a real-time  

E-print Network

challenge in radar-derived quantitative precipitation estimation (QPE) is the separation of precipitation; Krajewski and Vignal 2001; Germann and Joss 2002) and the conversion of radar reflectivity into rain rate (iA multi-sensor physically based weather/non-weather radar echo classifier using polarimetric

Lakshmanan, Valliappa

142

Benchmarking High-Resolution Global Satellite Rainfall Products to Radar and Rain-Gauge Rainfall Estimates  

Microsoft Academic Search

This paper presents an in-depth investigation of the error properties of two high-resolution global-scale satellite rain retrievals verified against rainfall fields derived from a moderate-resolution rain-gauge network (25-30-km intergage distances) covering a region in the midwestern U.S. (Oklahoma Mesonet). Evaluated satellite retrievals include the NASA Tropical Rainfall Measuring Mission multisatellite precipitation analysis and the National Oceanic and Atmospheric Administration Climate

Emmanouil N. Anagnostou; Viviana Maggioni; Efthymios I. Nikolopoulos; Tadesse Meskele; Faisal Hossain; Anastasios Papadopoulos

2010-01-01

143

Simulation of air- and spaceborne radar rain path attenuation estimation using the mirror image radar return  

Microsoft Academic Search

The mirror image rain echo, received through the double reflection of the radar from the surface, may provide useful information in estimating the rainfall rate form airborne and spaceborne weather radars. As the TRMM spaceborne weather radar has been successfully launched recently, issues regarding the utility of this measurement are pertinent and timely. In this study, having described a mirror

Liang Liao; Robert Meneghini; Toshio Iguchi

1998-01-01

144

Can Compressed Sensing Be Applied To Dual-Polarimetric Weather Radars?  

NASA Astrophysics Data System (ADS)

The recovery of sparsely-sampled signals has long attracted considerable research interest in various fields such as reflection seismology, microscopy, and astronomy. Recently, such recovery techniques have been formalized as a sampling method called compressed sensing (CS) which uses few linear and non-adaptive measurements to reconstruct a signal that is sparse in a known domain. Many radar and remote sensing applications require efficient and rapid data acquisition. CS techniques have, therefore, enormous potential in dramatically changing the way the radar samples and processes data. A number of recent studies have investigated CS for radar applications with emphasis on point target radars, and synthetic aperture radar (SAR) imaging. CS radar holds the promise of compressing-while-sampling, and may yield simpler receiver hardware which uses low-rate ADCs and eliminates pulse compression/matched filter. The need of fewer measurements also implies that a CS radar may need smaller dwell times without significant loss of information. Finally, CS radar data could be used for improving the quality of low-resolution radar observations. In this study, we explore the feasibility of using CS for dual-polarimetric weather radars. In order to recover a signal in CS framework, two conditions must be satisfied: sparsity and incoherence. The sparsity of weather radar measurements can be modeled in several domains such as time, frequency, joint time-frequency domain, or polarimetric measurement domains. The condition of incoherence relates to the measurement process which, in a radar scenario, would imply designing an incoherent transmit waveform or an equivalent scanning strategy with an existing waveform. In this study, we formulate a sparse signal model for precipitation targets as observed by a polarimetric weather radar. The applicability of CS for such a signal model is then examined through simulations of incoherent measurements along with real weather data obtained from Iowa X-band Polarimetric (XPOL) radar units.

Mishra, K.; Kruger, A.; Krajewski, W. F.

2013-12-01

145

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

146

Validation of GOES-R Rainfall Rate Algorithm through TRMM PR and NIMROD radars  

NASA Astrophysics Data System (ADS)

The next generation Geostationary Operational Environmental Satellite (GOES-R) series will offer a continuation of current products and services and enable improved and new capabilities. The Advanced Baseline Imager (ABI) onboard the GOES-R platform has been designed to offer improved spatial and spectral resolution and temporal sampling, all of which should lead to enhanced capabilities for satellite-based rainfall estimation. The Hydrology Algorithm Team in the GOES-R Algorithm Working Group (AWG) has recommended, developed, and demonstrated an algorithm for the operational rainfall rate product, the GOES-R version of Self-Calibrating Multivariate Precipitation Retrieval (SCaMPR) algorithm. SCaMPR is an effort to combine the relative strengths of infrared (IR)-based and microwave (MW)-based estimates of precipitation. The GOES-R version of SCaMPR currently runs over Europe and Africa and surrounding oceans using the METEOSAT Spinning Enhanced Visible Infra-Red Imager (SEVIRI) data as a proxy for the ABI. Because the algorithm produces a field of instantaneous rainfall rates, radar data (both space-based and ground-based) is the only available source of data for validation against spec. Comparisons are made against Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) data and Nimrod radar data over Western Europe obtained from the British Atmospheric Data Centre (BADC), respectively. This presentation will introduce the analysis methodology for estimating the precision and accuracy and provide the quantitative results in terms of the Functional and Performance Specifications.

Li, Y.; Kuligowski, R. J.

2010-12-01

147

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

148

Spatial and temporal rainfall variation observed by vertically pointing radar clusters and disdrometers  

NASA Astrophysics Data System (ADS)

One of the major uncertainties in quantitative precipitation estimation using scanning radar and in-situ instruments is the temporal and spatial ambiguity between these sensors, such as sample volume mismatch, drop-sorting and horizontal drift by fallout. Information of raindrop size distribution (RDSD) is indispensible for identification and quantification of rainfall variations. The vertically pointing micro rain radar (MRR) can measure RDSD profile and rainfall integral parameters including reflectivity Z with high temporal resolution. It thus fits in as a linkage between in-situ measurements and the radar pixel aloft. Here a comparative analysis using clustered MRRs and disdrometers on variation of rainfall integral and physical RDSD parameters in space and time is presented. Concurrent observations from nine MRRs, two disdrometers (optical and impact type) and one high resolution rain gauge were collected during the AQUARadar (Advances in Quantitative Areal Precipitation Estimation by Radar) field campaign for over three months in summer 2006. The instruments were distributed to two field sites with a separation of 5.5 km in a east-weast alignment. Clustered MRRs at each site were separated by an average distance of 300 m.

Yen, W.; Crewell, S.

2009-04-01

149

Analysis of the heavy rainfall from Typhoon Plum using Doppler Radar  

NASA Astrophysics Data System (ADS)

Using reanalysis and observational data and Doppler radar data, the structure and characteristics of the synoptic and mesoscale meteorological background are analyzed for a heavy rainfall over Xiaoshipeng town of Yingkou City in Liaoning province, China. The results show that: (1) several synoptic scale patterns formed the background for the heavy rainfall: the Pacific subtropical high extended to the West; a strong tropical storm named "Plum" moved to the northwest after it had landed; Northwest jet transported a lot of the water vapor to Liaoning; the weak cold air of Baikal Lake moved to south along the ridge before the northwest flow impact to Liaoning. (2) the factors conducive to strong convective precipitation: the existence of a deep wet layer, a narrow CAPE zone and a relative weak vertical wind sheer. (3) there is nonstop generation of new mesoscale convective cells during the heavy rainfall. There exists a maximum wind zone of 24m/s in the lower layer and a strong radar echo with 35dBz above 5km. And the variation of the low level southwest jet is in step with the variation of rainfall amount. The cyclonic convergence of the warm wet air in the mid-low level is a factor triggering and strengthening convection. The nonstop generation of mesoscale convective cells and the water vapor transport from the low level southwest jet are pushing the rainfall radar echo to above 40dBz and lasting for more than 5 hours and are considered the direct cause of this heavy rainfall.

Jin, W.; Qu, Y.

2013-12-01

150

Mesoscale divergence, vorticity, and vertical motion compared to radar and rainfall patterns  

E-print Network

and rainfall patterns recorded simultaneously. The two cases chosen are cold frontal passages; one has a strong squall line (April 26, 1969), and the other has a line of scattered echoes (May 16, 1969). Computed values of divergence, vorticity, and vertical... 0 A, cr 25, 1969 la ft. -, . reed across the network. A squall line had formed witn the front and passed through the network between 1600 and 1700 CST. This squall line gave well-defined radar and rainfall patterns, and is, there- fore& a good...

Withers, Donald Mead

2012-06-07

151

On the Feasibility of Precisely Measuring the Properties of a Precipitating Cloud with a Weather Radar  

E-print Network

In this paper the results of an investigation are presented that are concerned with the feasibility of employing a weather radar to make precise measurements of the properties of a precipitating cloud. A schematic cloud is proposed as a model...

Runnels, R.C.

152

Improving Tornado Warnings with the Federal Aviation Administration's Terminal Doppler Weather Radar  

Microsoft Academic Search

The potential role of the Federal Aviation Administration's Terminal Doppler Weather Radar (TDWR) to supplement the Weather Surveillance Radar-1988 Doppler (WSR-88D) for tornado detection is discussed. Compared to the WSR-88D, the TDWR has a narrower beam, lower scan angles, and faster update rates. The 11 August 1999 Salt Lake City, Utah, tornado is used as an illustration of the utility

Steven V. Vasiloff

2001-01-01

153

Monitoring of weather radar receivers using solar signals detected in operational scan data  

E-print Network

-way gaseous attenu- ation, and f the receiver bandwidth. The mean solar power ¯Pf , power standard deviationMonitoring of weather radar receivers using solar signals detected in operational scan data Iwan during radar mainte- nance. Solar signals can, however, be detected automatically in polar reflectivity

Stoffelen, Ad

154

A Time Series Weather Radar Simulator Based on High-Resolution Atmospheric Models  

E-print Network

simulator capable of generating simulated raw time series data for a weather radar has been designed of producing sample-to-sample time series data that are collected by a radar system of virtually any design was limited to generation of time series data within a single range gate. This work was followed

Xue, Ming

155

Dual-polarization C-band weather radar algorithms for rain rate estimation and hydrometeor classification in an alpine region  

Microsoft Academic Search

Dual polarization is becoming the standard for new weather radar systems. In contrast to conventional weather radars, where the reflectivity is measured in one polarization plane only, a dual polarization radar provides transmission in either horizontal, vertical, or both polarizations while receiving both the horizontal and vertical channels simultaneously. Since hydrometeors are often far from being spherical, the backscatter and

H. Paulitsch; F. Teschl; W. L. Randeu

2009-01-01

156

3262 IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 44, NO. 11, NOVEMBER 2006 Polarimetric Weather Radar Retrieval of Raindrop  

E-print Network

Polarimetric Weather Radar Retrieval of Raindrop Size Distribution by Means of a Regularized Artificial Neural) is a critical factor in estimating rain intensity using advanced dual- polarized weather radars. A new neural-shift values. Index Terms--Artificial neural network, radar polarimetry, raindrop size distribution (RSD

Marzano, Frank Silvio

157

Evidence of Rainfall Signatures on X-Band Synthetic Aperture Radar Imagery Over Land  

Microsoft Academic Search

Five spaceborne X-band synthetic aperture radars (X-SARs) are nowadays operating, and several more will be launched in the coming years. These X-SAR sensors, able to image the Earth's surface at metric resolution, may provide a unique opportunity to measure rainfall over land with spatial resolution of about a few hundred meters due to the moving-target degradation effects. This work is

Frank Silvio Marzano; Saverio Mori; James A. Weinman

2010-01-01

158

BALTEX weather radar-based precipitation products and their accuracies  

Microsoft Academic Search

This paper brie y reviews the measurement of precipitation by radar, discusses fac- tors affecting the accuracy of such measurements, and outlines how such factors may be dealt with to improve the quality of precipitation measurements by radar for the purposes of the Baltic Sea Experiment (BALTEX). Precipitation products from the BALTEX Radar Network (BALTRAD) are then brie y presented,

Jarmo Koistinen; Daniel B. Michelson

159

Synergetic use of millimeter and centimeter wavelength radars for retrievals of cloud and rainfall parameters  

NASA Astrophysics Data System (ADS)

A remote sensing approach for simultaneous retrievals of cloud and rainfall parameters in the vertical column above the US Department of Energy's (DOE) Climate Research Facility at the Tropical Western Pacific (TWP) Darwin site in Australia is described. This approach uses vertically pointing measurements from a DOE Ka-band radar and scanning measurements from a nearby C-band radar pointing toward the TWP Darwin site. Rainfall retrieval constraints are provided by data from a surface impact disdrometer. The approach is applicable to stratiform precipitating cloud systems when a separation between the liquid hydrometeor layer, which contains rainfall and liquid water clouds, and the ice hydrometeor layer is provided by the radar bright band. Absolute C-band reflectivities and Ka-band vertical reflectivity gradients in the liquid layer are used for retrievals of the mean layer rain rate and cloud liquid water path (CLWP). C-band radar reflectivities are also used to estimate ice water path (IWP) in regions above the melting layer. The retrieval uncertainties of CLWP and IWP for typical stratiform precipitation systems are about 500-800 g m-2 (for CLWP) and a factor of 2 (for IWP). The CLWP retrieval uncertainties increase with rain rate, so retrievals for higher rain rates may be impractical. The expected uncertainties of layer mean rain rate retrievals are around 20%, which, in part, is due to constraints available from the disdrometer data. The applicability of the suggested approach is illustrated for two characteristic events observed at the TWP Darwin site during the wet season of 2007. A future deployment of W-band radars at the DOE tropical Climate Research Facilities can improve CLWP estimate accuracies and provide retrievals for a wider range of stratiform precipitating cloud events.

Matrosov, S. Y.

2010-01-01

160

Synergetic use of millimeter- and centimeter-wavelength radars for retrievals of cloud and rainfall parameters  

NASA Astrophysics Data System (ADS)

A remote sensing approach for simultaneous retrievals of cloud and rainfall parameters in the vertical column above the US Department of Energy's (DOE) Climate Research Facility at the Tropical Western Pacific (TWP) Darwin site in Australia is described. This approach uses vertically pointing measurements from a DOE Ka-band radar and scanning measurements from a nearby C-band radar pointing toward the TWP Darwin site. Rainfall retrieval constraints are provided by data from a surface impact disdrometer. The approach is applicable to stratiform precipitating cloud systems when a separation between the liquid hydrometeor layer, which contains rainfall and liquid water clouds, and the ice hydrometeor layer is provided by the radar bright band. Absolute C-band reflectivities and Ka-band vertical reflectivity gradients in the liquid layer are used for retrievals of the mean layer rain rate and cloud liquid water path (CLWP). C-band radar reflectivities are also used to estimate ice water path (IWP) in regions above the melting layer. The retrieval uncertainties of CLWP and IWP for typical stratiform precipitation systems are about 500-800 g m-2 (for CLWP) and a factor of 2 (for IWP). The CLWP retrieval uncertainties increase with rain rate, so retrievals for higher rain rates may be impractical. The expected uncertainties of layer mean rain rate retrievals are around 20%, which, in part, is due to constraints available from the disdrometer data. The applicability of the suggested approach is illustrated for two characteristic events observed at the TWP Darwin site during the wet season of 2007. A future deployment of W-band radars at the DOE tropical Climate Research Facilities can improve CLWP estimation accuracies and provide retrievals for a wider range of stratiform precipitating cloud events.

Matrosov, S. Y.

2010-04-01

161

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

162

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

E-print Network

horizons. Index Terms--Data-mining algorithms, radar reflectivity, rain- fall prediction, tipping bucket) rain gauges are commonly used to estimate the amount of rainfall. A physics- based rainfall studies used radar data to estimate the amount of rainfall [8]­[11]. The high spatiotemporal resolution

Kusiak, Andrew

163

Improved accuracy of radar WPMM estimated rainfall upon application of objective classification criteria  

NASA Technical Reports Server (NTRS)

Application of the window probability matching method to radar and rain gauge data that have been objectively classified into different rain types resulted in distinctly different Z(sub e)-R relationships for the various classifications. These classification parameters, in addition to the range from the radar, are (a) the horizontal radial reflectivity gradients (dB/km); (b) the cloud depth, as scaled by the effective efficiency; (c) the brightband fraction within the radar field window; and (d) the height of the freezing level. Combining physical parameters to identify the type of precipitation and statistical relations most appropriate to the precipitation types results in considerable improvement of both point and areal rainfall measurements. A limiting factor in the assessment of the improved accuracy is the inherent variance between the true rain intensity at the radar measured volume and the rain intensity at the mouth of the rain guage. Therefore, a very dense rain gauge network is required to validate most of the suggested realized improvement. A rather small sample size is required to achieve a stable Z(sub e)-R relationship (standard deviation of 15% of R for a given Z(sub e)) -- about 200 mm of rainfall accumulated in all guages combined for each classification.

Rosenfeld, Daniel; Amitai, Eyal; Wolff, David B.

1995-01-01

164

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

165

The impact of reflectivity correction and conversion methods 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. For most of the country this led to over 15 hours of near-continuous precipitation, which resulted in total event accumulations exceeding 150 mm in the eastern part of the Netherlands. Such accumulations belong to the largest sums ever recorded in this country and gave rise to local flooding. Measuring precipitation by weather radar within such mesoscale convective systems is known to be a challenge, since measurements are affected by multiple sources of error. For the current event the operational weather radar rainfall product only estimated about 30% of the actual amount of precipitation as measured by rain gauges. In the current presentation we will try to identify what gave rise to such large underestimations. In general weather radar measurement errors can be subdivided into two different groups: 1) errors affecting the volumetric reflectivity measurements taken, and 2) errors related to the conversion of reflectivity values in rainfall intensity and attenuation estimates. To correct for the first group of errors, the quality of the weather radar reflectivity data was improved by successively correcting for 1) clutter and anomalous propagation, 2) radar calibration, 3) wet radome attenuation, 4) signal attenuation and 5) the vertical profile of reflectivity. Such consistent corrections are generally not performed by operational meteorological services. Results show a large improvement in the quality of the precipitation data, however still only ~65% of the actual observed accumulations was estimated. To further improve the quality of the precipitation estimates, the second group of errors are corrected for by making use of disdrometer measurements taken in close vicinity of the radar. Based on these data the parameters of a normalized drop size distribution are estimated for the total event as well as for each precipitation type separately (convective, stratiform and undefined). These are then used to obtain coherent parameter sets for the radar reflectivity-rainfall rate (Z-R) and radar reflectivity-attenuation (Z-k) relationship, specifically applicable for this event. By applying a single parameter set to correct for both sources of errors, the quality of the rainfall product improves further, leading to >80% of the observed accumulations. However, by differentiating between precipitation type no better results are obtained as when using the operational relationships. This leads to the question: how representative are local disdrometer observations to correct large scale weather radar measurements? In order to tackle this question a Monte Carlo approach was used to generate >10000 sets of the normalized dropsize distribution parameters and to assess their impact on the estimated precipitation amounts. Results show that a large number of parameter sets result in improved precipitation estimated by the weather radar closely resembling observations. However, these optimal sets vary considerably as compared to those obtained from the local disdrometer measurements.

Hazenberg, Pieter; Leijnse, Hidde; Uijlenhoet, Remko

2014-05-01

166

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.; Hrlimann, M.

2014-10-01

167

High resolution measurements of aerial rainfall with X-band radars in New Zealand  

NASA Astrophysics Data System (ADS)

The Atmospheric Physics Group runs a number of high resolution X-band mobile rain radars. The radars are unusual in that they operate at very high spatial and temporal resolution but short range (100m/20sec/20km) as compared with the C-band radars of the New Zealand Meteorological Service (2km/7min/240km). Portability was a key design criterion for the radars, which can either be towed by a personal four wheel drive vehicle or carted by a container truck. Past deployments include the slopes of an erupting volcano, the path of a tropical storm and overwintering in a mountain range. It is well known that sampling and representativeness problems associated with sparse gauge networks and C-band radars can result in high uncertainty in estimates of aerial rainfall. Some of this error is associated with poor sampling of the spatial and temporal scales which are important to precipitation processes. In the case of long range radar, the beam height increase with range also introduces uncertainty when trying to infer precipitation at the ground, even after reflectivity profile correction methods are applied. This paper describes a recently completed field campaign in a hydro power catchment in the North Island of New Zealand. The radar was deployed in a pasture on a farm overlooking the catchment which is about 15km x 10km in size. The catchment is about 150km from the nearest national C-band radar. A number of rain gauges, including high resolution drop counters, were deployed nearby. X-band and comparative C-band radar observations of particular events including orographically initiated convection, frontal systems and widespread rain types are presented. The convective events are characterised by short length scales and rapid evolution, but even the widespread rain has embedded structure. The observations indicate that the evolution time and spatial scales associated with many of the hydrometeors observed in this work precludes aerial estimates being made with sparse gauge networks. Due to the relatively long range and lower spatial and temporal resolution the C-band images contained less information than X-band scans of the same hydrometeors. On the other hand, per event statistics indicate that the majority of variance in rain gauge measurements can be explained from the co-located X-band radar pixel. Quantitative retrieval of accumulation was possible out to about 15km range after applying range and bias correction.

Sutherland-Stacey, Luke; Shucksmith, Paul; Austin, Geoff

2010-05-01

168

On Utilization of NEXRAD Scan Strategy Information to Infer Discrepancies Associated With Radar and Rain Gauge Surface Volumetric Rainfall Accumulations  

NASA Technical Reports Server (NTRS)

To evaluate the Tropical Rainfall Measuring Mission (TRMM) monthly Ground Validation (GV) rain map, 42 quality controlled tipping bucket rain gauge data (1 minute interpolated rain rates) were utilized. We have compared the gauge data to the surface volumetric rainfall accumulation of NEXRAD reflectivity field, (converting to rain rates using a 0.5 dB resolution smooth Z-R table). The comparison was carried out from data collected at Melbourne, Florida during the month of July 98. GV operational level 3 (L3 monthly) accumulation algorithm was used to obtain surface volumetric accumulations for the radar. The gauge records were accumulated using the 1 minute interpolated rain rates while the radar Volume Scan (VOS) intervals remain less than or equal to 75 minutes. The correlation coefficient for the radar and gauge totals for the monthly time-scale remain at 0.93, however, a large difference was noted between the gauge and radar derived rain accumulation when the radar data interval is either 9 minute, or 10 minute. This difference in radar and gauge accumulation is being explained in terms of the radar scan strategy information. The discrepancy in terms of the Volume Coverage Pattern (VCP) of the NEXRAD is being reported where VCP mode is ascertained using the radar tilt angle information. Hourly radar and gauge accumulations have been computed using the present operational L3 method supplemented with a threshold period of +/- 5 minutes (based on a sensitivity analysis). These radar and gauge accumulations are subsequently improved using a radar hourly scan weighting factor (taking ratio of the radar scan frequency within a time bin to the 7436 total radar scans for the month). This GV procedure is further being improved by introducing a spatial smoothing method to yield reasonable bulk radar to gauge ratio for the hourly and daily scales.

Roy, Biswadev; Datta, Saswati; Jones, W. Linwood; Kasparis, Takis; Einaudi, Franco (Technical Monitor)

2000-01-01

169

Comparison of a deterministic model, a stochastic multifractal model and radar rainfall data  

NASA Astrophysics Data System (ADS)

Two primary approaches to model rainfall are the stochastic approaches, which aim at mimicking the rain phenomenology, and the deterministic approaches. The latter mainly rely on geophysical fluid dynamics equations, in particular the Navier-Stokes equations. Solving these equations require simplifying assumptions such as parameterization and scale truncations. In the present case, we used Meso-NH model, which is a meteorological non-hydrostatic mesoscale model developed by Meteo-France/CNRM and Laboratoire d'Arologie (Toulouse, France). Multiplicative cascade models, which are physically based models involving huge ratios of scales and intensities, allow to bridge the gap between the two previously mentioned methods. In this study, we considered a multifractal space-time cascade model, whose space-time anisotropy is defined with the help of a unique scaling exponent. We worked in the framework of universal multifractals in which the scaling variability and the extremes of the rain are quantified with the help of three parameters. The rainfall outputs of the Meso-NH model and the radar data were analyzed in the framework of the stochastic model. We selected a case study corresponding to a heavy rainfall event in the south of France. Both data sets exhibit a similar qualitative multifractal behavior in accordance with the framework of a unified space-time scaling model. Quantitatively, the estimates of the multifractal parameters suggest that the deterministic model under-represent the natural variability of the rainfall field.

Gires, Auguste; Schertzer, Daniel; Tchiguirinskaia, Ioulia; Lovejoy, Shaun

2010-05-01

170

Estimation of Rainfall Kinetic Energy by Rain Intensity and/or Radar Reflectivity Factor  

NASA Astrophysics Data System (ADS)

This study presents an approach to estimate the rainfall kinetic energy (KE) by rain intensity (R) and radar reflectivity factor (Z) separately, or jointly, on the basis of a one- or two-moment scaled formulation. This formulation considers the raindrop size distribution (DSD) as a combination of bulk rainfall variable(s) (R or/and Z) and an intrinsic distribution g(x), which is in function of the scaled raindrop diameter x. Results from previous studies showed that g(x) remains more or less constant, hence the variability of DSD is mainly explained by the bulk rainfall variable(s). In this study, the Gamma probability density function (pdf) with two parameters is used to model the g(x). Considered the self-consistent relationships between parameters, a robust method is proposed to estimate three climatological g(x), in R-, Z- and RZ-scaled formulation respectively, with a 28-month DSD dataset collected in the Cevennes-Vivarais region, France. Three relationships (KE-R, KE-Z and KE-(R,Z)), which link the observations (R and/or Z) to rainfall kinetic energy (KE), are established based on three climatological g(x). As expected, the combination of R and Z yields a significant improvement of the estimation of KE compared to the single-moment formulations. And Z yields a better performance in KE estimating compared to the KE-R relationship. In terms of the application of these relationships based on real radar reflectivity factors and/or rain gauge measurements, the combination of R and Z yields also the best performance in estimation of KE among the three relationships. Different from the application of the disdrometer data, the performance of the real KE-Z relationship degrades compared to the real KE-R relationship, which is probably due to the sampling error of radar. However, KE estimated by radar possess the advantages in spatialization of kinetic energy over that based on rain gauge stations. This study was supported financially by the HYDRATE project of the European Community (GOCE 037024). The first author would also like to thank the SOERE RBV project which provides the travel grants for participation in AGU meeting.

Yu, N.; Delrieu, G.; Boudevillain, B.; Hazenberg, P.; Uijlenhoet, R.

2011-12-01

171

New algorithm for integration between wireless microwave sensor network and radar for improved rainfall measurement and mapping  

NASA Astrophysics Data System (ADS)

One of the main challenges for meteorological and hydrological modelling is accurate rainfall measurement and mapping across time and space. To date, the most effective methods for large-scale rainfall estimates are radar, satellites, and, more recently, received signal level (RSL) measurements derived from commercial microwave networks (CMNs). While these methods provide improved spatial resolution over traditional rain gauges, they have their limitations as well. For example, wireless CMNs, which are comprised of microwave links (ML), are dependant upon existing infrastructure and the ML' arbitrary distribution in space. Radar, on the other hand, is known in its limitation for accurately estimating rainfall in urban regions, clutter areas and distant locations. In this paper the pros and cons of the radar and ML methods are considered in order to develop a new algorithm for improving rainfall measurement and mapping, which is based on data fusion of the different sources. The integration is based on an optimal weighted average of the two data sets, taking into account location, number of links, rainfall intensity and time step. Our results indicate that, by using the proposed new method, we not only generate more accurate 2-D rainfall reconstructions, compared with actual rain intensities in space, but also the reconstructed maps are extended to the maximum coverage area. By inspecting three significant rain events, we show that our method outperforms CMNs or the radar alone in rain rate estimation, almost uniformly, both for instantaneous spatial measurements, as well as in calculating total accumulated rainfall. These new improved 2-D rainfall maps, as well as the accurate rainfall measurements over large areas at sub-hourly timescales, will allow for improved understanding, initialization, and calibration of hydrological and meteorological models mainly necessary for water resource management and planning.

Liberman, Y.; Samuels, R.; Alpert, P.; Messer, H.

2014-10-01

172

Using MSG-SEVIRI Cloud Physical Properties and Weather Radar Observations for the Detection of Cb/TCu Clouds  

E-print Network

Using MSG-SEVIRI Cloud Physical Properties and Weather Radar Observations for the Detection of Cb (SEVIRI) on board Meteosat Second Generation (MSG) satellites and weather radar reflectivity factors/TCu clouds for the collection of pixels that pass the CCM. In this model, MSG-SEVIRI cloud physical

Schmeits, Maurice

173

The Diurnal Cycle of Precipitation from Continental Radar Mosaics and Numerical Weather Prediction Models. Part II: Intercomparison  

E-print Network

The Diurnal Cycle of Precipitation from Continental Radar Mosaics and Numerical Weather Prediction of their ability to reproduce the average diurnal cycle of precipitation during spring 2008. Moreover, radar in the timing of initiation in the zonal motion of the precipitation systems than observed from radar

Xue, Ming

174

Weather and Forecasting Fine-Scale Orographic Precipitation Variability and Gap-Filling Radar Potential in Little  

E-print Network

Weather and Forecasting Fine-Scale Orographic Precipitation Variability and Gap-Filling Radar Title: Fine-Scale Orographic Precipitation Variability and Gap-Filling Radar Potential in Little and forecasting of precipitation in LCC using a gap-filling radar. Powered by Editorial Manager® and Produ

Steenburgh, Jim

175

Operational Monitoring of Rainfall over the Arno River Basin Using Dual-Polarized Radar and Rain Gauges  

Microsoft Academic Search

Reflectivity (ZH) and differential reflectivity (ZDR) measurements collected by Polar 55C over the Arno River basin in Italy are presented. The applicability of dual-polarization (ZDR)-based rainfall algorithms at C band in an operational setting is studied in conjunction with a network of rain gauges. Conventional pointwise comparison of radar and rain gauge estimates of rainfall, as well as statistical comparison

E. Gorgucci; G. Scarchilli; V. Chandrasekar

1996-01-01

176

New algorithm for integration between wireless microwave sensor network and radar for improved rainfall measurement and mapping  

NASA Astrophysics Data System (ADS)

One of the main challenges for meteorological and hydrological modelling is accurate rainfall measurement and mapping across time and space. To date the most effective methods for large scale rainfall estimates are radar, satellites, and more recently, received signal level (RSL) measurements received from commercial microwave networks (CMN). While these methods provide improved spatial resolution over traditional rain gauges, these have their limitations as well. For example, the wireless CMN, which are comprised of microwave links (ML), are dependant upon existing infrastructure, and the ML arbitrary distribution in space. Radar, on the other hand, is known in its limitation in accurately estimating rainfall in urban regions, clutter areas and distant locations. In this paper the pros and cons of the radar and ML methods are considered in order to develop a new algorithm for improving rain fall measurement and mapping, which is based on data fusion of the different sources. The integration is based on an optimal weighted average of the two data sets, taking into account location, number of links, rainfall intensity and time step. Our results indicate that by using the proposed new method we not only generate a more accurate 2-D rainfall reconstructions, compared with actual rain intensities in space, but also the reconstructed maps are extended to the maximum coverage area. By inspecting three significant rain events, we show an improvement of rain rate estimation over CMN or radar alone, almost uniformly, both for instantaneous spatial measurements, as well as in calculating total accumulated rainfall. These new improved 2-D rainfall maps, and the accurate rainfall measurements over large areas at sub-hourly time scales, will allow for improved understanding, initialization and calibration of hydrological and meteorological models necessary, mainly, for water resource management and planning.

Liberman, Y.; Samuels, R.; Alpert, P.; Messer, H.

2014-05-01

177

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

178

A Gaussian field for aggregation and disaggregation of radar rainfall data  

NASA Astrophysics Data System (ADS)

The generation of reliable precipitation products that explicitly account for spatial and temporal structures of precipitation events is challenging, since it requires a combination of data with a variety of error structures and temporal resolutions. In-situ measurements are relatively accurate quantities, but available only at sparse and irregularly distributed locations. Remote measurements cover complete areas but suffer from spatially and temporally inhomogeneous systematic errors and non-linear relations between the measured value reflectivity and the precipitation rate. Our aim is to provide a statistical model based on a latent Gaussian random field that suitably models radar precipitation rates and enables us to aggregate and disaggregate them in space and time. We first transform radar rainfall rates such that they follow a truncated Gaussian distribution using a power transformation proposed by D. Allcroft and C. Glasbey (2003). The advantage of using a truncated Gaussian random field is that occurrence and intensity of rainfall are modeled using a single process. To parameterize the latent Gaussian random field we estimate the empirical correlation as function of lag distance in space using the maximum likelihood method and fit a parametric correlation function to the estimates. This yields a spatial Gaussian random field. The transformation only allocates censored values to dry locations, i.e. the locations below some threshold. In order to obtain a Gaussian random field that covers the whole domain, we need to simulate the unobserved values below the threshold conditional on the observed values. The parametrically defined Gaussian random field now allows us to aggregate and disaggregate the radar measurements to different scales and compare them to measurements from ground based instruments.

Krebsbach, Katharina; Friederichs, Petra

2014-05-01

179

Approximate Bayesian Inference for Reconstructing Velocities of Migrating Birds from Weather Radar  

E-print Network

understanding of many phe- nomena, including bird migration. An accurate algorithm to estimate the velocities information is im- portant for understanding the biology of bird migration. In addition, there is growingApproximate Bayesian Inference for Reconstructing Velocities of Migrating Birds from Weather Radar

180

Estimation of Specific Differential Phase and Differential Backscatter Phase From Polarimetric Weather Radar Measurements of Rain  

Microsoft Academic Search

The estimation of the specific differential phase par- ticularly in the presence of the differential backscatter phase and nonuniform propagation paths is a long-standing goal in weather radar polarimetry. Furthermore, a reliable estimator of the differential backscatter phase for precipitation measure- ments has not been proposed yet, although it contains valuable information about the presence of non-Rayleigh scattering and the

Tobias Otto; Herman W. J. Russchenberg

2011-01-01

181

Radar rain field evaluation and possible use of its high temporal and spatial resolution for hydrological purposes  

Microsoft Academic Search

The purpose of this paper is to show how accurate radar-estimated rainfall, with good temporal and spatial resolution, can be used for hydrological purposes. A recent methodological advance in rainfall measurement using conventional weather radars has made it possible to account for much of the variation between the precipitation radar echo intensity and rain intensity. A method known as the

J. Morin; D. Rosenfeld; E. Amitai

1995-01-01

182

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

183

The Federal Aviation Administration/Massachusetts Institute of Technology (FAA/MIT) Lincoln Laboratory Doppler weather radar program  

NASA Technical Reports Server (NTRS)

The program focuses on providing real-time information on hazardous aviation weather to end users such as air traffic control and pilots. Existing systems will soon be replaced by a Next Generation Weather Radar (NEXRAD), which will be concerned with detecting such hazards as heavy rain and hail, turbulence, low-altitude wind shear, and mesocyclones and tornadoes. Other systems in process are the Central Weather Processor (CWP), and the terminal Doppler weather radar (TDWR). Weather measurements near Memphis are central to ongoing work, especially in the area of microbursts and wind shear.

Evans, James E.

1988-01-01

184

Terminal Doppler Weather Radar (TDWR) system characteristics and design constraints  

NASA Astrophysics Data System (ADS)

TDWR features two scan strategies: hazardous weather mode and monitor mode; the system has redundant transmitters, receiver/exciters, and signal processing channels. The data processing system features data base formation/conditioning, clutter residue editing, point target removal, signal-to-noise thresholding, velocity dealiasing, and a pulse-repetition frequency selection/deobscuration algorithm.

Wieler, J. G.; Shrader, W. W.

185

Terminal Doppler Weather Radar (TDWR) system characteristics and design constraints  

Microsoft Academic Search

TDWR features two scan strategies: hazardous weather mode and monitor mode; the system has redundant transmitters, receiver\\/exciters, and signal processing channels. The data processing system features data base formation\\/conditioning, clutter residue editing, point target removal, signal-to-noise thresholding, velocity dealiasing, and a pulse-repetition frequency selection\\/deobscuration algorithm.

J. G. Wieler; W. W. Shrader

1991-01-01

186

An Examination of Version 5 Rainfall Estimates from the TRMM Microwave Imager, Precipitation Radar, and Rain Gauges on Global, Regional, and Storm Scales  

E-print Network

An Examination of Version 5 Rainfall Estimates from the TRMM Microwave Imager, Precipitation Radar, and more intense radar profiles and 85 GHz ice scattering signatures, and larger rain areas, while microwave and spaceborne radar sensors. However, sources of error in these estimates often stem from

Rutledge, Steven

187

Q.J.R. Meteorol. SOC.(1998), 124,pp. 2417-2434 Radar estimates of rainfall rates at the ground in bright band and non-bright  

E-print Network

the whole region scanned by radar leads to only marginal improvement in rain estimates. Instead, this workQ.J.R. Meteorol. SOC.(1998), 124,pp. 2417-2434 Radar estimates of rainfall rates at the ground with height is less marked. If accurate estimates of surface precipitation are to be made, based upon radar

Reading, University of

188

A Brief Review of History, Principles, and Progress of Merging Radar-Rainfall and Rain Gauge Data (Invited)  

Microsoft Academic Search

The need for combining (merging) estimates of radar-rainfall and rain gauge data was realized over 30 years ago. The need returns and is generalized to combine estimates from multiple data sources. The author reviews early concepts and offers a systematic approach to the problem. The approach requires specification of statistical models of uncertainties associated with individual sensor estimates. While the

W. F. Krajewski

2010-01-01

189

Rainfall-Rate Estimation Using Gaussian Mixture Parameter Estimator: Training and Validation  

E-print Network

develops a Gaussian mixture rainfall-rate estimator (GMRE) for polarimetric radar-based rainfall estimation for weather radar­based parameter estimations. The advantages of GMRE are 1) it is a minimum variance unbiased estimator; 2) it is a general estimator applicable to different rain regimes in different

190

A spatial daily rainfall model for interpolation of raingauge networks using artificial radar fields, for realistic hydrological modelling  

NASA Astrophysics Data System (ADS)

The inherent patchiness and intermittency of daily rainfall make interpolation of sparse point measurements over a catchment very challenging. Usual methods of interpolation of daily rainfall vary from simple numerical averaging through the use of Thiessen polygons to advanced statistical methods such as Kriging. This presentation treats the interpolation problem by conditioning plausible replicas of radar-rainfields on to the point observations and examines the effectiveness of the process by cross-validation. The issues addressed include: * we use Kriging but we first Gaussianise the point rainfall data with special treatment of the zeros to eliminate skewness * Kriging gives us estimates of error in the Gaussian domain to show how good/bad are the interpolations and also offers the standard deviation at each pixel in the field * we choose the form of the [co]variogram to be used in Kriging so as to mimic nature, by using spatial observations given us by radar * the spatial structure of radar rainfall images is peculiar to the accumulation time: instantaneous radar images do not have appreciable spatial anisotropy * by contrast, morphed hourly and daily accumulations of radar images exhibit strong spatial anisotropy * we determine the characteristics of the daily accumulations of radar rainfall and find the spatial correlogram characteristics [orientation, range and ratio of minor to major axes] in the chosen region are strongly related to the radar wetted area ratio: RWAR * to proceed, we simulate correlograms for the chosen day based on the RWAR which is related to the gauge wetness ratio * simulate Gaussian radar fields based on the RWAR with the same variance as the Kriged interpolations of the point values and conditionally merge them with the gauge values, be they observations or simulations * to evaluate the worth of the process, we perform cross-validation of spatial field estimates against gauge values in 'leave-one-out' exercises * the methodology is designed to give a measure of the hydrological response's sensitivity to the uncertainty of spatial interpolation of gauge network rainfall [observed or simulated] by simulating many conditioned spatial replicates, each of which is plausible

Pegram, Geoff; Gyasi-Agyei, Yeboah

2014-05-01

191

Improvements in weather radar rain rate estimates using a method for identifying the vertical profile of reflectivity from volume radar scans  

Microsoft Academic Search

A method for identifying the Vertical Profile of Reflectivity (VPR) when volume weather radar scans are available is presented. The first step in the identification o f the VPR consists in averaging the vertical pro- files of reflectivity observed near the radar. Then the Near Me an Apparent Vertical Profile of Reflectivity (NMAVPR) so obtained is applied in order to

Mara Franco; Rafael Snchez-Diezma; Daniel Sempere-Torres

2006-01-01

192

Improvements in weather radar rain rate estimates using a methodology to identify the vertical profile of reflectivity from volume radar scans  

Microsoft Academic Search

A methodology to identify the Vertical Profile of Reflectivity (VPR) when volume weather radar scans are available is presented. The first step in the identification of the VPR consists of averaging the vertical profiles of reflectivity observed near the radar. Then the so Near-Mean Apparent Vertical Profile of Reflectivity (NMAVPR) obtained is applied to estimate the original VPR on each

Mara Franco; Rafael Snchez-Diezma

193

The Polarimetric Radar Estimation of Rainfall over the Amazon during TRMM-LBA  

NASA Astrophysics Data System (ADS)

The Tropical Rainfall Measuring Mission (TRMM) is a NASA satellite project initiated to address a gap in our ability to accurately observe detailed rainfall patterns over the tropical continents and oceans. To support TRMM, several field campaigns were conducted. The TRMM-LBA (Large-scale Biosphere Atmosphere) experiment was conducted over the southwestern region of the Amazon (state of Rondonia, Brazil) in order to provide detailed information on the precipitation characteristics in the interior of a tropical continent. Information from TRMM-LBA will be used for validation of TRMM satellite products and for initialization and validation of cloud-resolving models and passive microwave retrieval algorithms. During the TRMM-LBA field campaign, a variety of instrumentation was deployed during the wet season (January - February 1999) to measure rainfall including several rain gauge networks, disdrometers, and the S-band polarimetric (NCAR S-POL) research radar. The focus of this study will be on the estimation, validation, and uncertainty of rain rate estimates derived from the NCAR S-POL radar. The S-POL data were carefully corrected for the presence of clear-air echo, ground clutter, anomalous propagation, partial beam blocking, precipitation attenuation, and calibration biases by applying polarimetric radar methods. Using an optimal polarimetric radar technique, maps of rain rate have been calculated from observations of S-POL horizontal reflectivity (Zh), differential reflectivity (Zdr), and specific differential phase (Kdp) every ten minutes from 10 January to 28 February 1999. From these rain rate estimates, daily and 30-day rain accumulation maps have been compiled. When validated against the rain gauge totals, preliminary S-POL estimates of monthly rainfall, which utilized the equilibrium raindrop shape model of Beard and Chuang (1987), have a negative bias error in the range of -5% to -11% and a standard error of 14% to 20%. We will compare these results with the methodology of Gorgucci et al. (2000, 2001), which attempts to account for the variability in the raindrop shape-size relation. Some practical issues involved in the implementation of this method will be discussed. Finally, we will present preliminary attempts to estimate the uncertainty of the rain rates at each grid point following Bringi and Chandrasekar (2001, Ch. 8). As in BC2001, the uncertainty will be expressed as the standard deviation of R divided by R (? (R)/R). The uncertainty will be based on 1) the polarimetric algorithm and measurements utilized in the optimal rain rate approach at each point, 2) an estimate of error associated with measurement error as a function of rain rate, and 3) an estimate of the error associated with the utilized algorithm as a function of rain rate. Since there is inherent ambiguity in estimating uncertainty in this manner, we will also experiment with converting ? (R)/R into a qualitative uncertainty index (UI) ranging from 1 to 5, where 1 is very certain and 5 is very uncertain.

Carey, L. D.; Cifelli, R.; Petersen, W. A.; Rutledge, S. A.

2002-05-01

194

Radar Detected Rainfall Intensity As An Input For Shallow Landslides Slope Stability Model  

NASA Astrophysics Data System (ADS)

The term "shallow landslides" is widely used in literature to describe a slope movement of limited size that mainly develops in soils up to a maximum of a few meters. Shallow landslides are usually triggered by heavy rainfall because, as the water starts to infiltrate in the soil, the pore-water pressure increases so that the shear strength of the soil is reduced leading to slope failure. For this work we have developed a distributed hydrological-geotechnical model for the forecasting of the temporal and spatial distribution of shallow landslide to be used as a warning system for civil protection purpose. The main goal of this work is the use of radar detected rainfall intensity as the input for the hydrological simulation of the infiltration. Using the rainfall pattern detected by the radar is in fact possible to dynamically control the redistribution of groundwater pressure associated with transient infiltration of rain so as to infer the slope stability of the studied area. The model deals with both saturated and unsaturated conditions. Two pilot sites have been chosen to develop and test this model: the Armea basin (Liguria, Italy) and the Ischia Island (Campania, Italy). In recent years several severe rainstorms have occurred in both these areas. In at least two cases these have triggered numerous shallow landslides that have caused victims and damaged roads, buildings and agricultural activities. In its current stage the basic basin-scale model applied for predicting the probable location of shallow landslides involves several stand-alone components. A module for estimating the groundwater pressure head distribution according to radar detected rainfall intensity, a soil depth prediction scheme and a limit-equilibrium infinite slope stability algorithm which produces a factor of safety (FS). The additional ancillary data required have been collected during the field work. The single components are seamlessly integrated into a system that automatically publishes constantly updated FS values to a WebGIS in near-real- time so that local administrators responsible for public safety can access and download the data from the internet. This system has been running for a few months and is now being validated. Several types of problems hinder a correct validation of the system. One major obstacle was overcome when major storms triggered several tens of soil slips in December 2006 for the Armea basin and in April 2006 for Ischia. This events provided both the necessary rainfall data for the soil saturation component, which until then for previous occurred landslides was lacking, and a new landslide inventory for comparison with the FS produced by the slope stability model for the same event. The inventory was derived from a newly acquired VHR satellite image. Another important aspect of the research being performed regards the assessment of the relative importance of the different parameters involved in the limit-equilibrium infinite slope stability model. This statistical sensitivity analysis has the aim of determining which errors in the input variables slope gradient, soil depth, soil saturation, cohesion and angle of internal friction produce the largest errors in the output FS values. Preliminary results indicate the importance of topographic attributes and of soil depth.

Leoni, L.; Rossi, G.; Catani, F.; Righini, G.; Rudari, R.

2008-12-01

195

Rainfall threshold definition using an entropy decision approach and radar data  

NASA Astrophysics Data System (ADS)

Flash flood events are floods characterised by a very rapid response of basins to storms, often resulting in loss of life and property damage. Due to the specific space-time scale of this type of flood, the lead time available for triggering civil protection measures is typically short. Rainfall threshold values specify the amount of precipitation for a given duration that generates a critical discharge in a given river cross section. If the threshold values are exceeded, it can produce a critical situation in river sites exposed to alluvial risk. It is therefore possible to directly compare the observed or forecasted precipitation with critical reference values, without running online real-time forecasting systems. The focus of this study is the Mignone River basin, located in Central Italy. The critical rainfall threshold values are evaluated by minimising a utility function based on the informative entropy concept and by using a simulation approach based on radar data. The study concludes with a system performance analysis, in terms of correctly issued warnings, false alarms and missed alarms.

Montesarchio, V.; Ridolfi, E.; Russo, F.; Napolitano, F.

2011-07-01

196

Imaging eruption columns from the 2009 eruption of Redoubt Volcano, Alaska using Doppler weather radar  

NASA Astrophysics Data System (ADS)

The U.S. Geological Survey deployed a dedicated volcano-monitoring Doppler weather radar system during the 2009 eruption of Redoubt Volcano, Alaska, enabling the collection of an unprecedented radar data set of seventeen explosive events. Radar reflectivity and radial Doppler velocity measurements were made of the column every 70-90 seconds at a vertical resolution of about 2 km. This temporal frequency is 3-6 times higher than what can be achieved by the national system of weather radars (i.e. NEXRAD), and allows for more robust comparisons with traditional geophysical monitoring data from seismic, pressure sensor, web camera and satellite images. The MiniMax-250C radar detected the eruption columns from explosive events with maximum altitudes of 9-19 km above sea level. We describe the preliminary results on imaging these eruption columns. Most of the explosive events were characterized by high radar reflectivity values of 50-60 dBZ in the central core of the eruption column and proximal cloud, which we interpret to be related to the rapid growth of tephra-ice aggregates. Time-series of radial Doppler velocity images documented the transition from turbulent mixing in the column to more uniform expansion of the proximal cloud. Vertical velocities of the eruption column top were estimated from observation of cloud rise in the reflectivity images and ranged from about 25-60 m/s. The duration of the eruptive events ranged from minutes to tens of minutes. Radar-derived duration estimates did not correlate well with seismic and pressure sensor derived durations. The observed maximum column heights were generally higher (perhaps 20% or more) than would be predicted for the mass eruption rate estimated from the mapped deposits.

Schneider, D. J.; Mastin, L. G.

2011-12-01

197

Use of radar to estimate precipitation in a semi-arid area  

E-print Network

raingauge and radar data. This study concerns 11 daily rainfall events observed in the Paris region by a 10-cm weather radar for 98 stations spread over 20, 000 kmz. This method improved the results of radar data slightly and is better than... raingauge and radar data. This study concerns 11 daily rainfall events observed in the Paris region by a 10-cm weather radar for 98 stations spread over 20, 000 kmz. This method improved the results of radar data slightly and is better than...

Al-Khalaf, Abdulrahman Khalaf

2012-06-07

198

Identification of Aviation Weather Hazards Based on the Integration of Radar and Lightning Data.  

NASA Astrophysics Data System (ADS)

The National Weather Service Eastern Region is carrying out a national risk-reduction exercise at the Baltimore-Washington Forecast Office in Sterling, Virginia. The primary objective of this project is to integrate information from remote sensor technologies to produce comprehensive state-of-the-atmosphere reports that promote aviation safety. Techniques have been developed and tested to identify aviation-oriented hazardous weather based on data from conventional radars, a national lightning detection network, and collateral observations from new Automated Surface Observing System (ASOS) sites that are being deployed throughout the nation. From July through September 1993, an experimental observational product to identify convective activity within 30 n mi of six airports from southern Virginia to Delaware was transmitted three times each hour to personnel at Weather Service Offices and Center Weather Service Units and to the meteorologists and flight dispatchers of five major air carriers. This user-oriented evaluation and the associated statistical analysis has provided important feedback to assess the utility of the product as a supplement to ASOS. Integration of information from several products generated by the new Doppler radar at Sterling with lightning network data is being pursued for the second phase of the project. The National Weather Service will determine the viability of this approach to generate products to routinely supplement the information provided by ASOS on either a national or a local basis.

Stern, Andrew D.; Brady, Raymond H., III; Moore, Patrick D.; Carter, Gary M.

1994-12-01

199

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

200

A coupled stochastic spacetime intermittent random cascade model for rainfall downscaling  

E-print Network

is applied to downscale summer daily rainfall for the central United States from a scale of 256 km to a scaleA coupled stochastic spacetime intermittent random cascade model for rainfall downscaling Boosik; published 21 October 2010. [1] Analysis of Next Generation Weather Radar rainfall data indicates

Ramírez, Jorge A.

201

A study of the applicability of weather radar in streamflow forecasting  

E-print Network

Title Page Location of rain gages . . . . . . . . . . . . . 4 Example of isoecho analysis. R values are in mm/hr. . . . . . . . . . . . . . . . . . . 16. Some possible water-surface profiles during passage of a flood wave ~ . . . . . . , . . . 20... complex index of refraction wave length density of water vertical basm width horisontal beam width CHAPTER I INTRODUCTION Need for the Study Since the inception of weather radar, it has become evident that if properly used it can have great value...

Curry, Robert Gene

2012-06-07

202

A Microphysics-Based Simulator for Advanced Airborne Weather Radar Development  

Microsoft Academic Search

Incorporating dual-polarized operation and micro- physics-based processing is becoming a challenge to future sci- entific and commercial airborne weather radars. This paper introduces a Monte Carlo simulation-based approach to address the theoretical basis and uncertainties of hydrometeor scattering along with sensor platform properties. Detailed characterizations of mixed-phase aviation hydrometeor hazards (rain, snow, hail, and mixtures) and the impact of melting

Zhengzheng Li; Yan Zhang; Guifu Zhang; Keith A. Brewster

2011-01-01

203

Performance comparison of pulse-pair and wavelets methods for the pulse Doppler weather radar spectrum  

E-print Network

In the civilian aviation field, the radar detection of hazardous weather phenomena (winds) is very important. This detection will allow the avoidance of these phenomena and consequently will enhance the safety of flights. In this work, we have used the wavelets method to estimate the mean velocity of winds. The results showed that the application of this method is promising compared with the classical estimators (pulse-pair, Fourier).

Lagha, Mohand; Bergheul, Said; Rezoug, Tahar; Bettayeb, Maamar

2012-01-01

204

Flight investigation of helicopter IFR approaches to oil rigs using airborne weather and mapping radar  

NASA Technical Reports Server (NTRS)

Airborne weather and mapping radar is a near-term, economical method of providing 'self-contained' navigation information for approaches to offshore oil rigs and its use has been rapidly expanding in recent years. A joint NASA/FAA flight test investigation of helicopter IFR approaches to offshore oil rigs in the Gulf of Mexico was initiated in June 1978 and conducted under contract to Air Logistics. Approximately 120 approaches were flown in a Bell 212 helicopter by 15 operational pilots during the months of August and September 1978. The purpose of the tests was to collect data to (1) support development of advanced radar flight director concepts by NASA and (2) aid the establishment of Terminal Instrument Procedures (TERPS) criteria by the FAA. The flight test objectives were to develop airborne radar approach procedures, measure tracking errors, determine accpetable weather minimums, and determine pilot acceptability. Data obtained will contribute significantly to improved helicopter airborne radar approach capability and to the support of exploration, development, and utilization of the Nation's offshore oil supplies.

Bull, J. S.; Hegarty, D. M.; Phillips, J. D.; Sturgeon, W. R.; Hunting, A. W.; Pate, D. P.

1979-01-01

205

The scavenging of air pollutants by precipitation, and its estimation with the aid of weather radar  

NASA Astrophysics Data System (ADS)

Precipitation cleanses the air by capturing airborne pollutants and depositing them onto the ground. The efficiency of this process may be expressed by the fractional depletion rate of pollutant concentrations in the air, designated as the scavenging coefficient. It depends on the size distribution of the raindrops and snow crystals and is thereby related to quantities estimated by weather radar, namely, the radar reflectivity factor and the precipitation rate. On the other hand, there are no universal relationships between the scavenging coefficient and these two quantities; the relationships vary depending on the properties of the precipitation and pollutants. In the present thesis, a few estimates for them were derived theoretically and empirically, using in the latter case observations made in Finland either after the Chernobyl nuclear accident or during a wintertime case study near a coal-fired power plant. The greatest advantage in the use of weather radar in assessing precipitation scavenging arises from the fact that radar estimates the spatial distributions of precipitation in real time with a good spatial and temporal resolution. Radar software usually used to create displays of the precipitation rate can easily be modified to show distributions of the scavenging coefficient. Such images can provide valuable information about the areas where a substantial portion of the pollutants is deposited onto the ground or, alternatively, remains airborne. Based on the movement of the precipitation areas, it is also possible to make short-term forecasts of those areas most likely to be exposed to wet deposition. A network of radars may hence form an important part of a real-time monitoring and warning system that can be immediately effective in the event of an accidental releases of hazardous materials into the air.

Jylha, Kirsti Tellervo

2000-09-01

206

A SATELLITE ALGORITHM TO RETRIEVE RAINFALL RATE FOR THE CARIBBEAN Nazario D. Ramirez, 2  

E-print Network

no elements in common. Rain/no rain pixels are identified by using radar rain rate over the study area for estimating rainfall rate. Weather radar data are used to calibrate the model. Empirical analysis of radar and a nonlinear transformation then applied to convert the estimated reflectivity to a rain rate. The radiative

Gilbes, Fernando

207

Amplitude Statistics of Weather Clutter Observed by L-band Radar  

NASA Astrophysics Data System (ADS)

We observed weather clutter from rain clouds using an L-band long-range air-route surveillance radar (ARSR) having a frequency 1.3 GHz, a beamwidth 1.2, and a pulsewidth 3.0 ?s. To determine the weather clutter amplitude, we introduce the Akaike Information Criterion (AIC), which is more rigorous fit of the distribution to the data than the least squares method. It is discovered that the weather clutter amplitudes obey almost the Rayleigh distribution for entire data and the Weibull, log-Weibull, and K-distributions with the shape parameters of 1.73 to 2.43, 10.60, and 5.13 to 50.93, respectively, for data within the beam width of an antenna.

Sayama, Shuji; Ishii, Seishiro; Sekine, Matsuo

208

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

209

MicroRadarNet: a Network of Weather Micro Radars for the Identification of Local High-Resolution Precipitation Patterns  

NASA Astrophysics Data System (ADS)

MicroRadarNet (MRN) is a network of high-resolution, low-cost, low-power consumption micro radars for continuous, unattended meteorological monitoring. The MRN project started in the framework of the European INTERREG IIIB Alpine Space Programme (within the FORALPS project) since 2004 and was developed and operated by the Remote Sensing Group at the Politecnico di Torino from its early design stages. MRN is currently under its final pre-release testing and validation stage, cooperating with professional weather operators (e.g. civil protection offices) to run extensive on-field tests. The key aspects of MRN are a short range strategy (about thirty kilometers) and the implementation of an effective sensor network approach. Raw spatial and temporal data is processed on-board in real-time, yielding a consistent evaluation of the information from the sensor and compressing the data to be transmitted. Network servers receive and merge the data sets coming from each unit yielding a synthetic, high resolution plot of meteorological events (updated every minute). This networked approach implies in turn a sensible reduction of the overall operational costs, including management and maintenance aspects, if compared to the traditional long range C-band approach. An ever-growing database of meteorological events is being collected, thus providing a real-data test bench to refine assessment and data enhancement algorithms. Assessment techniques have been adopted for the estimation of precipitation, based on systematic rain gauges comparisons. Efforts were also devoted to the design and implementation of specific decluttering algorithms. New techniques to mitigate the effect of co-channel interference sources are also under testing. It is shown how these enhancement algorithms further improve the assessment process raising the overall data quality. A consistent amount of case studies clearly shows that MicroRadarNet has enough potentialities to act as a fast-reacting weather monitoring tool. The proposed strategy, based on a network of short range radars, shall effectively perform high resolution monitoring while lowering the overall operational costs. This could prevent, by design, the volumetric resolution loss at higher ranges, as well as the need for atmospheric corrections and the shielding shortcomings which typically occur in orographically complex areas.

Turso, Stefano; Zambotto, Marco; Notarpietro, Riccardo; Orione, Fiammetta; Gabella, Marco; Perona, Giovanni

2010-05-01

210

Structure of precipitating systems over Taiwans complex terrain during Typhoon Morakot (2009) as revealed by weather radar and rain gauge observations  

NASA Astrophysics Data System (ADS)

This study documents from an observational perspective the structure of precipitation systems over the complex topography of Taiwan as Typhoon Morakot (2009) impinged on the island on 8 August 2009. An advanced multiple-Doppler radar synthesis technique particularly designed for dealing with non-flat surfaces is applied to analyze the three-dimensional wind fields over the ocean and terrain. In the northern and southern portion of the analysis domain where the mountain slope is relatively gentle and steep, respectively, the radar reflectivity measurements indicate that the precipitation systems exhibit very distinct features, namely, horizontal translation in the north and abrupt intensification in the south. While still far from the southern mountainous region, a north-south oscillation of an east-west-oriented band of strong radar reflectivity (>40 dBZ) with a horizontal span of 20 km is observed. Along the mountain slopes, the band of strong radar reflectivity has a much wider north-south extent. Both the radar and rain gauge observations show that the major precipitation is primarily confined to the windward side of the mountains. An analysis of the saturated Brunt-Visl frequency reveals that the upstream atmosphere is statically unstable, which implies that the lifting of the incoming convective cells by the topography will easily trigger precipitation. Thus, most of the moisture will be consumed before the air reaches the leeward side of the mountains. The long duration and the wide range of heavy precipitation in the mountainous regions resulted in a record-breaking average (over the gauges) rainfall amount of 2000 mm over 4 days. The prevailing winds approaching the mountains are from the west. The cross-barrier wind speed has a maximum (?40 m s-1) above the mountain crest that can be reasonably explained by a simplified shallow water model. The capability of applying the weather radar to provide a reliable quantitative estimate of the rainfall over a large area with high temporal and spatial resolution is demonstrated using dual-polarimetric radar data. The potential applications of the knowledge of the wind and precipitation characteristics in hydrology and other fields are addressed in this manuscript.

Liou, Yu-Chieng; Wang, Tai-Chi Chen; Tsai, Yi-Chun; Tang, Yu-Shuang; Lin, Pay-Liam; Lee, Yung-An

2013-12-01

211

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

212

Transformation of point rainfall to areal rainfall by estimating areal reduction factors, using radar data, for Texas  

E-print Network

Information about extreme precipitation is of great interest for a variety of purposes, which include dam design and its operation, public safety, engineering projects concerned with river management and drainage as well as rainfall-runoff relations... 18. Region 7 ? Big Bend Country. ........................................................................ 87 Figure 19. Arrangement of 5x5 Blocks............................................................................. 92 Figure 20. Arrangement...

Gill, Tarun Deep

2005-08-29

213

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

214

Coupling a vertically looking K-band radar and a C-band weather radar to obtain a complete profile of reflectivity  

NASA Astrophysics Data System (ADS)

In a project funded under the German Climate Research Programme (DEKLIM), data from novel ground-based sensors are combined with data of the German weather radar network in order to retrieve quantitative precipitation data over land and sea. Usually, rain gauge measurements have to be interpolated for areal precipitation. Alternatively, areal radar reflectivity measurements taken somewhere aloft are often forcefully adjusted to rain gauge data at the ground not considering the low areal representativity of the latter. In this project, ambiguities of the relation between radar reflectivity and surface precipitation rates shall be mitigated on a physical basis using auxiliary profile measurements. A low-power vertically pointing K-Band Doppler micro rain radar (MRR) provides profiles of Doppler spectra from precipitation in the lower 3000 meters of the atmosphere. Thus, information about the modification of precipitation on its way to the ground is gained, e.g. the vertical reflectivity profile (VRP) including the melting zone. Disdrometers and ombrometers are used to convert MRR data into rain rates at the bottom of this column. At its top, the VRP has to be matched to the areal measurement of the weather radar. To ensure continuity at this point, a comparison has been conducted between the Rostock weather radar at the German Baltic coast and the MRR at Zingst 50 kms northeast. The MRR Doppler spectra are converted to drop-size-distributions from which the reflectivity factor Z can be derived. For an eight-weeks-period, this is directly compared to weather radar measurements at C-band. The best correlation achieved using dBZ time series was 0.912.

Wagner, A.; Seltmann, J.; Diederich, M.; Peters, G.

2003-04-01

215

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

E-print Network

is in solid form through complex processes. Thus, accurate knowledge of precipitation levels is a fundamental precipitation forecasts, and to verify the performance of precipitation forecast models. These gridded rainfall of rainfall information in terms of an underlying unobservable spatial temporal process with the true rainfall

Reich, Brian J.

216

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

217

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

218

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

Microsoft Academic Search

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

A. P. Dykes

2002-01-01

219

Spatial correlations of monthly rainfall: Applications in climatology and weather modification experiments  

Microsoft Academic Search

Spatial correlations based on monthly rainfall totals from northwest Georgia for the period 1949--77 are studied. This work, a part of the Meteorological Effects of Thermal Energy Releases (METER) Program, determines natural variability rainfall trends and assists the field studies of potential precipitation effects of the Bowen Electric Generating Plant near Cartersville, Georgia. The spatial correlations, based on the overall

A. A. N. Patrinos; N. C. J. Chen; R. L. Miller

1979-01-01

220

Analysis of daily rainfall of the Sahelian weather-station Lingure (Senegal) - Trends and its impacts on the local population  

NASA Astrophysics Data System (ADS)

In the 20th century, the West African Sahel has been a hot-spot of climatic changes. After severe drought-events in the 1970s and 1980s which were followed by a significant drop in annual precipitation, rainfall seems to increase again during the past years. Most studies are based on monthly or yearly datasets. However, many processes and events which are important for the local population depending on rainfall are not related to monthly or annual precipitation but are related to intra-annual, often daily scales. During this study, interviews with farmers and herders were conducted in the Senegalese Sahel. The results show, that wet months with unsuitably distributed precipitation can cause more harm than bringing benefits - depending on the phenological stage of the plants. Agricultural crops for example need rainfall breaks. On the other hand, natural herbaceous vegetation tolerates longer wet periods. So, a wet season can still hide dry spells that alter crops and vegetation development. Based on the results of these interviews, this study developed two indexes, one for local farmers and one for herders separately, showing if the year was favorable for them or not. The indexes integrate the length of rainy seasons, intensity and frequency of rainfall events, breaks between events and also the previous year. This way, each year is assigned to one of 5 classes. Using daily rainfall data of the Lingure weather-station (from the Senegal Meteorological Service, ANACIM), trends of the indexes from 1945 to 2002 are detected and compared to results of the interviews. Statistically relating the indexes to yearly and monthly data demonstrates, how much information can be gathered by those datasets. Furthermore, changes in intensity and frequency are related with yearly and monthly sums showing relations between daily data and annual sums. For example, a high correlation (r=0.73) between the amount of rain days (> 1 mm) and the annual rainfall is observed in Lingure.

Strommer, Gabriel; Brandt, Martin; Diongue-Niang, Aida; Samimi, Cyrus

2013-04-01

221

Application of X- and S-band radars for rain rate estimation over an urban area  

Microsoft Academic Search

The potential of ground-based radar systems operating at X-band for rainfall estimation over urban areas is investigated. To this end, rainfall measurements from the X-band weather surveillance radar SOLIDAR are compared against those from the colocated S-band research radar DARR and a line configuration of 4 tipping bucket rain gages located at ranges between 5 and 10 km from the

R. Uijlenhoet; J. N. M. Stricker; H. W. J. Russchenberg

1997-01-01

222

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

223

Pseudowhitening of weather Radar signals to improve spectral moment and polarimetric variable estimates at low signal-to-noise ratios  

Microsoft Academic Search

Pseudowhitening of oversampled signals in range is proposed as a method to improve the performance of spectral moment and polarimetric variable estimators on weather surveillance radars. In an attempt to overcome the noise sensitivity of the whitening transformation, a solution based on the minimum mean-square-error criterion is considered first; however, this transformation is less practical than whitening because it requires

Sebastin M. Torres; Christopher D. Curtis; J. R. Cruz

2004-01-01

224

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

225

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

226

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., Jr.; Randall, Lori A.; Buler, Jeffrey J.

2014-01-01

227

Assimilation of Doppler Radar Observations with a Regional 3DVAR System: Impact of Doppler Velocities on Forecasts of a Heavy Rainfall Case  

Microsoft Academic Search

In this paper, the impact of Doppler radar radial velocity on the prediction of a heavy rainfall event is examined. The three-dimensional variational data assimilation (3DVAR) system for use with the fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5) is further developed to enable the assimilation of radial velocity observations. Doppler velocities from the Korean Jindo radar are assimilated into MM5

Qingnong Xiao; Ying-Hwa Kuo; Juanzhen Sun; Wen-Chau Lee; Eunha Lim; Yong-Run Guo; Dale M. Barker

2005-01-01

228

Rainfall observations by an airbourne dual-fequency precipitation radar during CAMEX-4  

NASA Technical Reports Server (NTRS)

The 2d Generation Precipitation Radar is a new design for a dual-frequency (13.4 and 35.6 GHz) spaceborne precipitation radar. An airborne PR-2 simulator has been developed to demonstrate key technologies. This airborne system was flown on the NASA DC-8 aircraft during the 4th Convection and Moisture Experiment in 2001. Data were acquired in Tropical Storms Chantal and Gabrielle, Hurricane Humberto, and in several more localized convective systems. The authors discuss the design of thePR-2 airborne radar and show observations from CAMEX-4. Overall, the observations validated the design of PR-2 and provide an extensive data set for scientific analysis.

Im, E.; Durden, S. L.; Sadowy, G.; Li, L.

2002-01-01

229

The potential for hail and intense rainfall enhancement over urban areas: improving urban extreme weather risk assessment  

NASA Astrophysics Data System (ADS)

Urban communities and their infrastructure are particularly vulnerable to the impacts of organized thunderstorm systems. Current models of urban extreme weather risk do not fully represent the complexity of the hydrometeorological processes involved, particularly in relation to intense convective precipitation and severe weather. Hail is a severe thunderstorm hazard that can be extremely damaging to property (especially automobiles, buildings and agriculture) over and in proximity to urban environments. This study identifies some of the mechanisms that future generations of catastrophe models should consider incorporating in their representation of hydrometeorlogical hazards in urban areas. In addition, such information could help to inform planning policy and improve urban resilience to extreme events. Evidence is provided that urban environments, through the existence of high-rise buildings and densely build-up areas, but also through air-pollution (aerosols) can potentially lead to an enhancement of both flooding and hail. Conclusions are drawn from two separate studies over the heavily urbanized corridor of the northeastern United States but could be expanded to apply to other urban areas. Observational and modelling (Weather Research and Forecasting - WRF) analyses of an extreme thunderstorm over the Baltimore, Maryland metropolitan area on 7 July 2004 provided evidence that the urban canopy redistributed heavy rainfall and convergence centres in the vicinity of the urban environment. Modelling analyses suggest that convective rainfall around the urban core was increased by about 30% due to the heterogeneities of land surface processes associated with the city of Baltimore. Chesapeake Bay also played an important role in rainfall distribution by acting as a divergence zone for northerly winds. Cloud-to-ground lightning analyses show that the city of Baltimore and the Chesapeake Bay combined played a role in the distribution of lightning in the periphery of the urban core. Detailed modelling analyses (WRF-Chem) of a series of convective storms over the New York City metropolitan area, suggest that under certain meteorological conditions, increased concentrations of aerosols can lead to better organization of convection, higher vertical velocities and significantly increased convective rainfall accumulations. Higher vertical velocities were more widespread and reached deeper atmospheric levels when meteorological conditions were favourable, under increased aerosol concentrations. Areas that are downstream of sources of aerosols (i.e. New York City) are more prone to experience convective enhancement.

Ntelekos, A. A.; Smith, J. A.; Krajewski, W. F.; Foote, M.

2009-04-01

230

Weather  

NSDL National Science Digital Library

This is a first grade weather unit. SEASONS Fall Winter Build a Snowman Spring Summer What things determine and effect the weather? Cloud Precipitation Sunshine Temperature Visibility Wind Direction Wind Force WEATHER VIDEOS Tornado Hurricane Hail Lightning FUN AND GAMES Dress the Bear for the Weather The Great Weather Race Game Weather coloring books for kids ...

Stearns, Ms.

2008-10-25

231

Weather  

NSDL National Science Digital Library

This lesson is written for fourth grade students. Students will explore weather and the effects it has on their lives. What is weather? video of what is weather Let's take a walk through the weather. Put on your hats and coats! Clouds Cloud Types Clouds - Dan's Wild Weather Page What to Wear? What to Wear? What to Drink? Weather Patterns and Climatic Regions ...

Bullough, Ms.

2010-06-24

232

Study on multifractal modeling of rainfall  

NASA Astrophysics Data System (ADS)

The identification of the spatial structure of rainfall is widely recognized as a key issue in the hydrological applications. An approach to this problem is based on the empirical detection of some regularities in hydrological observations, such as the scale-invariance properties of rainfall (e.g. [1]). Scaling properties can provide simple relationships to link the statistical distribution of the rainfall process at different spatial and temporal scales, in the ranges of which the power-law assumption can be verified [2]. However, it is very difficult if not impossible to be able to properly capture the high spatial variability of rainfall fields with traditional rain gauge networks, while modern weather radars are, potentially, an instrument capable of meeting this need because of the fine spatial resolution of radar data. This work focuses on the analysis of the scaling properties of rainfall in space by using data from a high density rain gauge network and from a weather radar both covering the urban area of Rome. The aim of the study is the identification of spatial scaling regimes, their ranges of validity, and the evaluation of the corresponding scaling properties. REFERENCES [1] Lovejoy, S. and Schertzer, D. Generalized scale invariance in the atmosphere and fractal models of rain. Water Resour. Res., 21(8), 1233-1250, 1985. [2] Marani, M. Non-power-law-scale properties of rainfall in space and time, Water Resour. Res., 41, W08413, doi:10.1029/2004WR003822, 2005.

Volpi, Elena; Lombardo, Federico; Russo, Fabio; Napolitano, Francesco; Baldini, Luca

2010-05-01

233

Space-Time Characteristics of Rainfall Diurnal Variations  

NASA Technical Reports Server (NTRS)

The space-time features of rainfall diurnal variation of precipitation are systematically investigated by using the Tropical Rainfall Measuring Mission (TRMM) precipitation products retrieved from TRMM microwave imager (TMI), precipitation radar (PR) and TMI/PR combined algorithms. Results demonstrate that diurnal variability of precipitation is obvious over tropical regions. The dominant feature of rainfall diurnal cycle over, ocean is that there is consistent rainfall peak in early morning, while there is a consistent rainfall peak in mid-late afternoon over land. The seasonal variation on intensity of rainfall diurnal cycle is clearly evidenced. Horizontal distributions of rainfall diurnal variations indicate that there is a clearly early-morning peak with a secondary peak in the middle-late afternoon in ocean rainfall at latitudes dominated by large-scale convergence and deep convection. There is also an analogous early-morning peak in land rainfall along with a stronger afternoon peak forced by surface heating. Amplitude analysis shows that the patterns and its evolution of rainfall diurnal cycle are very close to rainfall distribution pattern and its evolution. These results indicate that rainfall diurnal variations are strongly associated with large-scale convective systems and climate weather systems. Phase studies clearly present the regional and seasonal features of rainfall diurnal activities. Further studies on convective and stratiform rainfall show different characteristics of diurnal cycles. Their spatial and temporal variations of convective and stratiform rainfall indicate that mechanisms for rainfall diurnal variations vary with time and space.

Yang, Song; Kummerow, Chris; Olson, Bill; Smith, Eric A.; Einaudi, Franco (Technical Monitor)

2001-01-01

234

Weather  

NSDL National Science Digital Library

Have you ever wondered how the weather man, or meteorolgist, on TV knows what to say about tomorrow\\'s weather? It\\'s because they have certain tools that they use that help them predict what the weather will be. Throughout this school year you are going to be making tools and predicting weather just like a meterorologist! Task You are going to be weather forcasters! You are going to record and track weather patterns throughout the year. You will also use weather tools to make predictions about the weather like real weather forecasters! The Process 1. First we need to learn a little bit about weather so ...

Williams, Ms.

2005-10-25

235

Preliminary evaluation of polarimetric parameters from a new dual-polarization C-band weather radar in an alpine region  

NASA Astrophysics Data System (ADS)

The first operational weather radar with dual polarization capabilities was recently installed in Austria. The use of polarimetric radar variables rises several expectations: an increased accuracy of the rain rate estimation compared to standard Z-R relationships, a reliable use of attenuation correction methods, and finally hydrometeor classification. In this study the polarimetric variables of precipitation events are investigated and the operational quality of the parameters is discussed. For the new weather radar also several polarimetric rain rate estimators, which are based on the horizontal polarization radar reflectivity, ZH, the differential reflectivity, ZDR, and the specific differential propagation phase shift, KDP, have been tested. The rain rate estimators are further combined with an attenuation correction scheme. A comparison between radar and rain gauge indicates that ZDR based rain rate algorithms show an improvement over the traditional Z-R estimate. KDP based estimates do not provide reliable results, mainly due to the fact, that the observed KDP parameters are quite noisy. Furthermore the observed rain rates are moderate, where KDP is less significant than in heavy rain.

Paulitsch, H.; Teschl, F.; Randeu, W. L.

2010-05-01

236

Lithological and textural controls on radar and diurnal thermal signatures of weathered volcanic deposits, Lunar Crater region, Nevada  

NASA Technical Reports Server (NTRS)

Radar backscatter intensity as measured by calibrated synthetic aperture radar (SAR) systems is primarily controlled by three factors: local incidence angle, wavelength-scale roughness, and dielectric permittivity of surface materials. Radar observations may be of limited use for geological investigations of surface composition, unless the relationships between lithology and the above characteristics can be adequately understood. In arid terrains, such as the Southwest U.S., weathering signatures (e.g. soil development, fracturing, debris grain size and shape, and hill slope characteristics) are controlled to some extent by lithologic characteristics of the parent bedrock. These textural features of outcrops and their associated debris will affect radar backscatter to varying degrees, and the multiple-wavelength capability of the JPL Airborne SAR (AIRSAR) system allows sampling of textures at three distinct scales. Diurnal temperature excursions of geologic surfaces are controlled primarily by the thermal inertia of surface materials, which is a measure of the resistance of a material to a change in temperature. Other influences include albedo, surface slopes affecting insolation, local meteorological conditions and surface emissivity at the relevant thermal wavelengths. To first order, thermal inertia variations on arid terrain surfaces result from grain size distribution and porosity differences, at scales ranging from micrometers to tens of meters. Diurnal thermal emission observations, such as those made by the JPL Thermal Infrared Multispectral Scanner (TIMS) airborne instrument, are thus influenced by geometric surface characteristics at scales comparable to those controlling radar backscatter. A preliminary report on a project involving a combination of field, laboratory and remote sensing observations of weathered felsic-to basaltic volcanic rock units exposed in the southern part of the Lunar Crater Volcanic Field, in the Pancake Range of central Nevada is presented. Focus is on the relationship of radar backscatter cross sections at multiple wavelengths, apparent diurnal temperature excursions identified in multi-temporal TIMS images, surface geometries related to weathering style, and parent bedrock lithology.

Plaut, Jeffrey J.; Rivard, Benoit

1992-01-01

237

Lithological and textural controls on radar and diurnal thermal signatures of weathered volcanic deposits, Lunar Crater region, Nevada  

NASA Astrophysics Data System (ADS)

Radar backscatter intensity as measured by calibrated synthetic aperture radar (SAR) systems is primarily controlled by three factors: local incidence angle, wavelength-scale roughness, and dielectric permittivity of surface materials. Radar observations may be of limited use for geological investigations of surface composition, unless the relationships between lithology and the above characteristics can be adequately understood. In arid terrains, such as the Southwest U.S., weathering signatures (e.g. soil development, fracturing, debris grain size and shape, and hill slope characteristics) are controlled to some extent by lithologic characteristics of the parent bedrock. These textural features of outcrops and their associated debris will affect radar backscatter to varying degrees, and the multiple-wavelength capability of the JPL Airborne SAR (AIRSAR) system allows sampling of textures at three distinct scales. Diurnal temperature excursions of geologic surfaces are controlled primarily by the thermal inertia of surface materials, which is a measure of the resistance of a material to a change in temperature. Other influences include albedo, surface slopes affecting insolation, local meteorological conditions and surface emissivity at the relevant thermal wavelengths. To first order, thermal inertia variations on arid terrain surfaces result from grain size distribution and porosity differences, at scales ranging from micrometers to tens of meters. Diurnal thermal emission observations, such as those made by the JPL Thermal Infrared Multispectral Scanner (TIMS) airborne instrument, are thus influenced by geometric surface characteristics at scales comparable to those controlling radar backscatter. A preliminary report on a project involving a combination of field, laboratory and remote sensing observations of weathered felsic-to basaltic volcanic rock units exposed in the southern part of the Lunar Crater Volcanic Field, in the Pancake Range of central Nevada is presented. Focus is on the relationship of radar backscatter cross sections at multiple wavelengths, apparent diurnal temperature excursions identified in multi-temporal TIMS images, surface geometries related to weathering style, and parent bedrock lithology.

Plaut, Jeffrey J.; Rivard, Benoit

1992-06-01

238

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

239

Improvements of Satellite-derived High Impact Weather Rainfall over Global Oceans and Implications for NWP models  

NASA Astrophysics Data System (ADS)

High impact weather precipitation fields of cyclone case studies over global ocean precipitation centers are presented using the technology of the HOAPS-II (Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite data) data base. All case studies are compared to the Global Precipitation Climatology Project (GPCP) data set and to ECMWF numerical weather prediction output. A detailed in situ rainfall validation is presented using voluntary observing ships (VOS). Results show that only the HOAPS data base recognizes the development of frequently occurring mesoscale cyclones and gales over the North Atlantic and North Pacific ocean as observed by VOS data. In case of landfall these events cause high socio-economic impact to the society. GPCP and the ECMWF model are frequently missing these mesoscale storms. For example, the gale Lothar known as the `Christmas Storm', could have been nowcasted using the HOAPS data base. HOAPS probably allows to give high impact weather warning in the near future on a near real time basis.

Klepp, C.; Bakan, S.; Gral, H.

2003-04-01

240

Application of wind-profiling radar data to the analysis of dust weather in the Taklimakan Desert.  

PubMed

The Urumqi Institute of Desert Meteorology of the China Meteorological Administration carried out an atmospheric scientific experiment to detect dust weather using a wind-profiling radar in the hinterland of the Taklimakan Desert in April 2010. Based on the wind-profiling data obtained from this experiment, this paper seeks to (a) analyze the characteristics of the horizontal wind field and vertical velocity of a breaking dust weather in a desert hinterland; (b) calculate and give the radar echo intensity and vertical distribution of a dust storm, blowing sand, and floating dust weather; and (c) discuss the atmosphere dust counts/concentration derived from the wind-profiling radar data. Studies show that: (a) A wind-profiling radar is an upper-air atmospheric remote sensing system that effectively detects and monitors dust. It captures the beginning and ending of a dust weather process as well as monitors the sand and dust being transported in the air in terms of height, thickness, and vertical intensity. (b) The echo intensity of a blowing sand and dust storm weather episode in Taklimakan is about -1~10 dBZ while that of floating dust -1~-15 dBZ, indicating that the dust echo intensity is significantly weaker than that of precipitation but stronger than that of clear air. (c) The vertical shear of horizontal wind and the maintenance of low-level east wind are usually dynamic factors causing a dust weather process in Taklimakan. The moment that the low-level horizontal wind field finds a shear over time, it often coincides with the onset of a sand blowing and dust storm weather process. (d) When a blowing sand or dust storm weather event occurs, the atmospheric vertical velocity tends to be of upward motion. This vertical upward movement of the atmosphere supported with a fast horizontal wind and a dry underlying surface carries dust particles from the ground up to the air to form blown sand or a dust storm. PMID:23099859

Wang, Minzhong; Wei, Wenshou; Ruan, Zheng; He, Qing; Ge, Runsheng

2013-06-01

241

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.

Gore, Pamela

1995-08-29

242

A New Dual-Polarization Radar Rainfall Algorithm: Application in Colorado Precipitation Events  

E-print Network

-polarization radar for quantitative precipitation estimation (QPE) has been demon- strated in a number of previous, dual-polarization-based rain-rate estimators can better account for the presence of ice in the sampling- formation provide superior rain estimates relative to methods using reflectivity and differential

Rutledge, Steven

243

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

244

Flash flood prediction using an uncalibrated hydrological model and radar rainfall data in a Mediterranean watershed under changing hydrological conditions  

NASA Astrophysics Data System (ADS)

SummaryFlash floods cause some of the most severe natural disasters in Europe but Mediterranean areas are especially vulnerable. They can cause devastating damage to property, infrastructures and loss of human life. The complexity of flash flood generation processes and their dependency on different factors related to watershed properties and rainfall characteristics make flash flood prediction a difficult task. In this study, as part of the EU-FLASH project, we used an uncalibrated hydrological model to simulate flow events in a 27 km2 Mediterranean watershed in Israel to analyze and better understand the various factors influencing flows. The model is based on the well-known SCS curve number method for rainfall-runoff calculations and on the kinematic wave method for flow routing. Existing data available from maps, GIS and field studies were used to define model parameters, and no further calibration was conducted to obtain a better fit between computed and observed flow data. The model rainfall input was obtained from the high temporal and spatial resolution radar data adjusted to rain gauges. Twenty flow events that occurred within the study area over a 15 year period were analyzed. The model shows a generally good capability in predicting flash flood peak discharge in terms of their general level, classified as low, medium or high (all high level events were correctly predicted). It was found that the model mainly well predicts flash floods generated by intense, short-lived convective storm events while model performances for low and moderate flows generated by more widespread winter storms were quite poor. The degree of urban development was found to have a large impact on runoff amount and peak discharge, with higher sensitivity of moderate and low flow events relative to high flows. Flash flood generation was also found to be very sensitive to the temporal distribution of rain intensity within a specific storm event.

Rozalis, Shahar; Morin, Efrat; Yair, Yoav; Price, Colin

2010-11-01

245

Weather modification from cooling towers: A test based on the distributional properties of rainfall  

Microsoft Academic Search

A statistical technique for the treatment of data from weather modification experiments is presented. This work, a part of the Meteorological Effects of Thermal Energy Release (METER) Program, is aimed at determining the potential precipitation modification effects of the Bowen Electric Generating Plant near Cartersville, Georgia. For that purpose a network of 49 recording raingages and four recording windsets situated

A. A. N. Patrinos; K. O. Bowman

1980-01-01

246

Maximum-likelihood spectral estimation and adaptive filtering techniques with application to airborne Doppler weather radar  

NASA Astrophysics Data System (ADS)

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.

1994-11-01

247

Maximum-Likelihood Spectral Estimation and Adaptive Filtering Techniques with Application to Airborne Doppler Weather Radar.  

NASA Astrophysics Data System (ADS)

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 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 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, Yingcho

248

Spaceborne meteorological radar studies  

NASA Technical Reports Server (NTRS)

Various radar designs and methods are studied for the estimation of rainfall parameters from space. An immediate goal is to support the development of the spaceborne radar that has been proposed for the Tropical Rain Measuring Mission (TRMM). The effort is divided into two activities: a cooperative airborne rain measuring experiment with the Radio Research Laboratory of Japan (RRL), and the modelling of spaceborne weather radars. An airborne rain measuring experiment was conducted at Wallops Flight Facility in 1985 to 1986 using the dual-wavelength radar/radiometer developed by RRL. The data are presently being used to test a number of methods that are relevant to spaceborne weather radars. An example is shown of path-averaged rain rates as estimated from three methods: the standard reflectivity rain rate method (Z-R), a dual-wavelength method, and a surface reference method. The results from the experiment shows for the first time the feasibility of using attenuation methods from space. The purposes of the modelling are twofold: to understand in a quantitative manner the relationships between a particular radar design and its capability for estimating precipitation parameters and to help devise and test new methods. The models are being used to study the impact of various TRMM radar designs on the accuracy of rain rate estimation as well as to test the performance of range-profiling algorithms, the mirror-image method, and some recently devised graphical methods for the estimation of the drop size distribution.

Meneghini, R.

1988-01-01

249

Input uncertainty in catchment models: an evaluation of the suitability of multiplicative rainfall error models using high resolution raingauge and radar data  

NASA Astrophysics Data System (ADS)

This paper presents an investigation of rainfall error models used in rainfall-runoff model calibration and prediction. A growing number of studies now specify an error model for rainfall input, usually simple in form due to computational constraints during parameter estimation. Such rainfall error models have not typically been validated against experimental evidence. If the data uncertainty hypotheses and assumptions are unsupported, the interactions between input and structural model error may significantly contaminate the inference and lead to unreliable parameter estimates and model predictions. It is therefore important that the data error models should be developed using data analysis that is independent from the hydrological model calibration, to bring genuine independent information into the inference. In this study we use data from the 50 km2 Mahurangi catchment in Northland, New Zealand, where there is detailed space-time information on rainfall from both a dense tipping bucket raingauge network (13 stations) and X-band radar rainfall estimates. This high resolution data is used to provide insights on the suitability of the common multiplicative rainfall error model for use at varying spatial and temporal scales of hydrological models. We first present an analysis of the spatial variability and uncertainty in rainfall when considered solely as a binary (wet/dry) process. This type of analysis is a crucial check on the assumptions underlying multiplicative rainfall error models, since the latter cannot account for rain events with only partial catchment cover that are hence not recorded by a rain gauge. Secondly, we examine the consistency of rainfall quantities over the catchment; based both on complete rainfall records and also for individual storm events when correct estimation of rainfall is most crucial. This allows us to estimate the statistical distributions of rainfall multipliers and test if these could form the basis of an adequate rainfall error model and put multipliers into the context of events. Results highlight some important results for understanding rainfall uncertainty and deriving data-based probabilistic error models for use in hydrological calibration. In the Mahurangi catchment, multiplicative error appears to be a suitable formulation for correcting mean catchment rainfall values during high-rainfall periods (e.g. intensities over 1 mm/hour); or for longer timesteps at any rainfall intensity (timestep 1 day or greater). We suggest that the effect of timestep on multiplier suitability is regulated by catchment size: specifically the time required for typical raincells to cross the catchment could be used as a first estimate of critical timestep. The standard distribution used for rainfall multipliers, the lognormal, provided a relatively close fit to the empirical multiplier distributions. However the empirical distributions have greater excess kurtosis and positive skew than the lognormal. Since heavy rainfall events display multiplier distributions differing most significantly from the lognormal, a skewed and heavier-tailed distribution to be used for times of high rainfall would more faithfully reproduce the observed error characteristics. Lastly, the high resolution of the data available demonstrated the time/space complexity of rainfall behaviour that cannot be corrected by a simple multiplicative error on measured rainfall. A hydrological model that aims to capture the full effects of rainfall variability would need an additional mechanism, such as a distribution function approach to rainfall input; or a blurred threshold for processes such as infiltration excess.

Jackson, Bethanna; McMillan, Hilary; Clark, Martyn; Kavetski, Dmitri; Woods, Ross

2010-05-01

250

Short period forecasting of catchment-scale precipitation. Part II: a water-balance storm model for short-term rainfall and flood forecasting  

Microsoft Academic Search

A simple two-dimensional rainfall model, based on advection and conservation of mass in a vertical cloud column, is investigated for use in short-term rainfall and flood forecasting at the catchment scale under UK conditions. The model is capable of assimilating weather radar, satellite infra-red and surface weather observations, together with forecasts from a mesoscale numerical weather prediction model, to obtain

V. A. Bell; R. J. Moore

2000-01-01

251

Weather.  

ERIC Educational Resources Information Center

This theme issue of "The Goldfinch" focuses on weather in Iowa and weather lore. The bulletin contains historical articles, fiction, activities, and maps. The table of contents lists: (1) "Wild Rosie's Map"; (2) "History Mystery"; (3) "Iowa's Weather History"; (4) "Weather Wonders"; (6) "Seasonal Jobs"; (7) "Fiction: Winter Courage"; (8) "Stayin'

Ruth, Amy, Ed.

1996-01-01

252

ERADERAD 20062006Proceedings ofProceedings of Detecting weather radar clutter  

E-print Network

of precipitation for every pixel in a Meteosat-8 scene. Via pixel-level image fusion of the radar data and the Precipitating Clouds product, supervised classification of the radar echoes into clutter and precipitation. However, misclassification of radar echoes is observed both during no-clutter precipitation events

253

Precipitation estimation and forecasting using radar and rain gage measurements with artificial neural networks  

Microsoft Academic Search

Quantitative precipitation estimation and forecasting continue to be critical components of the weather research programs. The objective of this dissertation is twofold: First, to propose a method that fuses rainfall measurements from rain gages and radar. Second, to design a technique that produces real-time rainfall forecasts for the next hour. Cokriging is perhaps the most widely used method to fuse

Christos Matsoukas

2000-01-01

254

Intelligent weather agent for aircraft severe weather avoidance  

E-print Network

avoidance capability has increased. In this thesis, an intelligent weather agent is developed for general aviation aircraft. Using a radar image from an onboard weather radar, the intelligent weather agent determines the safest path around severe weather...

Bokadia, Sangeeta

2012-06-07

255

A mobile X-POL weather radar for hydrometeorological applications in the metropolitan area of So 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 So Paulo, So Paulo, Brazil. It is used in graduate and under graduate courses, real time monitoring and nowcasting of severe weather in the Metropolitan Area of So 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

256

A mobile X-POL weather radar for hydrometeorological applications in the metropolitan area of So 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 So Paulo, So Paulo, Brazil. It is used in graduate and under graduate courses, real-time monitoring and nowcasting of severe weather in the Metropolitan Area of So 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

257

Rain-Mapping Radar  

NASA Technical Reports Server (NTRS)

Orbiting radar system measures rates of rainfall from 0.5 to 60 mm/h. Radar waves scattered and absorbed by rainfall to extents depending on wavelength, polarization, rate of rainfall, and distribution of sizes and shapes of raindrops. Backscattered radar signal as function of length of path through rain used to infer detailed information about rain. Accumulated radar return signals processed into global maps of monthly average rainfall for use in climatological studies.

Im, K. E.; Li, F. K.; Wilson, W. J.; Rosing, D.

1988-01-01

258

Q. J. R. Meteorol. Soc. (2003), 129, pp. 477493 doi: 10.1256/qj.02.23 Relations between radar re ectivity, liquid-water content, and rainfall rate  

E-print Network

of climate change.Scanning weather radars yield maps of radar re ectivity (Z) which can be used to estimate the surface. Biases in the estimate of the near-surface re ectivity of rain can result from the followingQ. J. R. Meteorol. Soc. (2003), 129, pp. 477­493 doi: 10.1256/qj.02.23 Relations between radar re

Yuter, Sandra

259

Weather  

NSDL National Science Digital Library

Introduction: How much do you know about weather? What kinds of weather do we have surrounding us? What is the weather like today? You may know a lot about weather already, you may not. Either way, you will learn more now as we take a look into what causes our weather and the methods we use to record and predict it. We will all become meteorologists, which are scientists who study the atmosphere and can predict weather. Put on your raincoats, and lets started! Task: You are the resident meteorologist at a local news station. It is your job to record and predict the weather each day, and then present it that night on the evening news. Not only should you be able to show the weather that we will be experiencing right ...

Hendricks, Ms.

2007-12-06

260

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

261

An approach to combine radar and gauge based rainfall data under consideration of their qualities in low mountain ranges of Saxony  

NASA Astrophysics Data System (ADS)

An approach to combine gauge and radar data and additional quality information is presented. The development was focused on the improvement of the diagnostic for temporal (one hour) and spatial (11 km2) highly resolved precipitation data. The method is embedded in an online tool and was applied to the target area Saxony, Germany. The aim of the tool is to provide accurate spatial rainfall estimates. The results can be used for rainfall run-off modelling, e.g. in a flood management system. Quality information allows a better assessment of the input data and the resulting precipitation field. They are stored in corresponding fields and represent the static and dynamic uncertainties of radar and gauge data. Objective combination of various precipitation and quality fields is realised using a cost function. The findings of cross validation reveal that the proposed combination method merged the benefits and disadvantages of interpolated gauge and radar data and leads to mean estimates. The sampling point validation implies that the presented method slightly overestimated the areal rain as well as the high rain intensities in case of convective and advective events, while the results of pure interpolation method performed better. In general, the use of presented cost function avoids false rainfall amount in areas of low input data quality and improves the reliability in areas of high data quality. It is obvious that the combined product includes the small-scale variability of radar, which is seen as the important benefit of the presented combination approach. Local improvements of the final rain field are possible due to consideration of gauges that were not used for radar calibration, e.g. in topographic distinct regions.

Jatho, N.; Pluntke, T.; Kurbjuhn, C.; Bernhofer, C.

2010-03-01

262

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

263

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

264

6/18/14, 9:45 AMWeather app teaches kids to read radar with the goal of saving l Page 1 of 2http://www.okcfox.com/story/25743818/weather-app-teaches-kids-to-read-radar-with-the-goal-of-saving-lives  

E-print Network

6/18/14, 9:45 AMWeather app teaches kids to read radar with the goal of saving l Page 1 of 2http://www.okcfox.com/story/25743818/weather-app-teaches-kids-to-read-radar-with-the-goal-of-saving-lives Weather app teaches kids CDT By: Rebecca Schleicher, Primetime Reporter - bio | email Kids can save lives when severe weather

McGovern, Amy

265

An analysis of the data collection modes of a digital weather radar system with respect to significant severe weather features  

E-print Network

, ubstituting Eq (6) into Eq (5) we get log Z = 2 log r + log P + 9. 0 e3 r log Z = 2 log r + log P + 10. 1 e10 r (7 a) (7b) The digital value of P is converted to its dBm equivalent (always r negative) through the use of calibration data for each... shades of grey is called video contouring. These threshold levels can be set digitally in 0. 5 dB steps. A radar return that falls within level 1 is displayed as grey (half bright- ness), level 2 is displayed as white (full brightne s), and level 3 i...

Neyland, Michael Arthur

2012-06-07

266

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

267

Simulations of mirror image returns of air\\/space-borne radars in rain and their applications in estimating path attenuation  

Microsoft Academic Search

The mirror image (MI) rain echo, received through the double reflection of the radar pulse from the surface, may provide useful information in estimating the rainfall rate from airborne and spaceborne weather radars. However, because of the complicated scattering mechanisms involving the surface and rain and the relatively small amount of measured data, studies of the MI effect have been

Liang Liao; Robert Meneghini; Toshio Iguchi

1999-01-01

268

Observations of Kelvin-Helmholtz instability at a cloud base with the middle and upper atmosphere (MU) and weather radars  

NASA Astrophysics Data System (ADS)

Using the very high frequency (46.5 MHz) middle and upper atmosphere radar (MUR), Ka band (35 GHz) and X band (9.8 GHz) weather radars, a Kelvin-Helmholtz (KH) instability occurring at a cloud base and its impact on modulating cloud bottom altitudes are described by a case study on 8 October 2008 at the Shigaraki MU Observatory, Japan (34.85N, 136.10E). KH braids were monitored by the MUR along the slope of a cloud base gradually rising with time around an altitude of 5.0 km. The KH braids had a horizontal wavelength of about 3.6 km and maximum crest-to-trough amplitude of about 1.6 km. Nearly monochromatic and out of phase vertical air motion oscillations exceeding 3 m s-1 with a period of 3 min 20 s were measured by the MUR above and below the cloud base. The axes of the billows were at right angles of the wind and wind shear both oriented east-north-east at their altitude. The isotropy of the radar echoes and the large variance of Doppler velocity in the KH billows (including the braids) indicate the presence of strong turbulence at the Bragg (3.2 m) scale. After the passage of the cloud system, the KH waves rapidly damped and the vertical scale of the KH braids progressively decreased down to about 100 m before their disappearance. The radar observations suggest that the interface between clear air and cloud was conducive to the presence of the dynamical shear instability by reducing static stability (and then the Richardson number) near the cloud base. Downward cloudy protuberances detected by the Ka band radar had vertical and horizontal scales of about 0.6-1.1 and 3.2 km, respectively, and were clearly associated with the downward air motions. Observed oscillations of the reflectivity-weighted Doppler velocity measured by the X band radar indicate that falling ice particles underwent the vertical wind motions generated by the KH instability to form the protuberances. The protuberances at the cloud base might be either KH billow clouds or perhaps some sort of mamma. Reflectivity-weighted particle fall velocity computed from Doppler velocities measured by the X band radar and the MUR showed an average value of 1.3 ms-1 within the cloud and in the protuberance environment.

Luce, Hubert; Mega, Tomoaki; Yamamoto, Masayuki K.; Yamamoto, Mamoru; Hashiguchi, Hiroyuki; Fukao, Shoichiro; Nishi, Noriyuki; Tajiri, Takuya; Nakazato, Masahisa

2010-10-01

269

MicroRadarNet: a Network of Integrated High-Resolution Weather Micro Radars to Service Tracking and Forecasting of Local Precipitation Patterns  

NASA Astrophysics Data System (ADS)

MicroRadarNet (MRN) is a network of high-resolution, low-cost, low-power consumption micro radars for continuous, unattended meteorological monitoring. The MRN project started in the framework of the European INTERREG IIIB Alpine Space Programme (within the FORALPS project) since 2004 and was developed and operated by the Remote Sensing Group at the Politecnico di Torino from its early design stages. MRN is currently under its release and operational validation phase, cooperating with professional weather operators (e.g. civil protection offices) to run extensive on-field tests. The key aspects of MRN are a short range strategy (about thirty kilometers) and the implementation of an effective sensor network approach. Raw spatial and temporal data is processed on-board in real-time, yielding a consistent evaluation of the information from the sensor and compressing the data to be transmitted. Network servers receive and merge the data sets coming from each unit yielding a synthetic, high-resolution plot of meteorological events (updated every minute). This networked approach implies in turn a sensible reduction of the overall operational costs, including management and maintenance aspects, if compared to the traditional long range C-band approach. An ever-growing database of meteorological events is being collected, thus providing a real-data test bench to refine assessment and data enhancement algorithms. Assessment techniques have been adopted for the estimation of precipitation, based on systematic rain gauges comparisons. Efforts were also devoted to the design and implementation of specific decluttering algorithms. New techniques to mitigate the effect of co-channel interference sources are also under testing. It is shown how these enhancement algorithms further improve the assessment process raising the overall data quality. Furthermore, new data analysis modules for the identification of precipitation patterns are being evaluating, including tracking routines for the short term prediction of meteorological cells motion and morphing. We strongly expect that these enhancements will be of some interest to the final users, contributing to the relevance of the provided weather information. Finally, particular attention has been devoted to set up efficient data availability and presentation mechanisms in other to ease weather services access for a broad range of purposes. Up-to-date Web techniques have been implemented accordingly. A consistent amount of case studies clearly shows that MicroRadarNet has enough potentialities to act as a fast-reacting weather monitoring tool. The proposed strategy, based on a network of short range radars, shall effectively collect high-resolution quality datasets while lowering the overall operational costs. This could prevent, by design, the volumetric resolution loss at higher ranges, as well as the need for atmospheric corrections and the shielding shortcomings which typically occur in orographically complex areas.

Turso, S.; Terzo, O.; Gabella, M.; Perona, G.

2010-09-01

270

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

NASA Technical Reports Server (NTRS)

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 square root normalized recursive least squares lattice estimation algorithm which models the clutter return data as an autoregressive process. The normalized lattice structure implementation of the adaptive modeling process for determining the filter coefficients assures that the resulting coefficients will yield a stable filter and offers possible fixed point implementation. A 10th order FIR clutter rejection filter indexed by geographical location is designed through autoregressive modeling of simulated clutter data. Filtered data, containing simulated dry microburst and clutter return, are analyzed using pulse-pair estimation techniques. To measure the ability of the clutter rejection filters to remove the clutter, results are compared to pulse-pair estimates of windspeed within a simulated dry microburst without clutter. In the filter evaluation process, post-filtered pulse-pair width estimates and power levels are also used to measure the effectiveness of the filters. The results support the use of an adaptive clutter rejection filter for reducing the clutter induced bias in pulse-pair estimates of windspeed.

Keel, Byron M.

1989-01-01

271

High resolution fire danger modeling : integration of quantitative precipitation amount estimates derived from weather radars as an input of FWI  

NASA Astrophysics Data System (ADS)

Fire meteo indices provide efficient guidance tools for the prevention, early warning and surveillance of forest fires. The indices are based on meteorological input data. The underlying approach is to exploit meteorological information as fully as possible to model the soil water content, biomass condition and fire danger. Fire meteorological danger is estimated by Mto-France at national level through the use of Fire Weather Index. The fire index services developed within the PREVIEW project (2005-2008) offer for the first time very high resolution mapping of forest fire risk. The high resolution FWI has been implemented in France complementary to the existing EFFIS operated by the Joint Research Center. A new method (ANTILOPE method) of combining precipitation data originating from different sources like rain gauges and weather radar measurements has been applied in the new service. Some of the advantages of this new service are: Improved detection of local features of fire risk More accurate analysis of meteorological input data used in forest fire index models providing added value for forest fire risk forecasts Use of radar precipitation data "as is utilizing the higher resolution, i.e. avoiding averaging operations The improved accuracy and spatial resolution of the indices provide a powerful early warning tool for national and regional civil protection and fire fighting authorities to alert and initiate forest fire fighting actions and measures.

Cloppet, E.; Regimbeau, M.

2009-09-01

272

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

NASA Astrophysics Data System (ADS)

In the Cvennes -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 km 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 Cvennes-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 (Mto-France, Service de Prvision 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 km 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

273

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

274

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

275

A seamless flash-flood early warning tool based on IDF-curves and coupling of weather-radar with numerical weather predictions  

NASA Astrophysics Data System (ADS)

A flash-flood is a flood that develops rapidly after a heavy precipitation event. Flash-flood forecasting is an important field of research because flash floods cause a lot of fatalities and damage. A flash-flood early warning tool is developed based on precipitation statistics. Our target areas are small ungauged areas of southern-Switzerland. A total of 759 sub-cathcments was considered. In a first intensity-duration-frequency (IDF) curves for each catchment have been calculated basin on: A) Gridded precipitation products for the period 1961 to 2012 and B) gridded reforecast of the COSMO-LEPS NWP for the period 1971-2000. These different IDF-curves at the catchment level in combination with precipitation forecasts are the basis for the flash-flood early warning tool. The forecast models used are COSMO-2 (deterministic, updated every three hours and with a lead time of 24 hours) and COSMO-LEPS (probabilistic, 16 member and with a lead time of five days). In operational mode COSMO-2 is nudged to real-time data of a weather-radar precipitation obtained by blending the radar qpe with information from a national network of precipitation data. This product is called COMBIPRECIP. The flash-flood early warning tool has been evaluated against observed events. These events are either discharge peaks in gauged sub-areas or reports of damages caused by flash-flood events. The hypothesis that it is possible to detect hydrological events with the flash-flood early warning tool can be partly confirmed. The highest skill is obtained if the return-period of weather radar QPE is assessed at hourly time scale. With this it was possible to confirm most of the damage events occurred in 2010 and 2011. The prototype tool is affected by several false alarms. This is because initial conditions of the soils are not considered. Further steps will be therefore focussed on the addition of real-time hydrological information as obtained from the application of high resolution distributed models.

Liechti, Kaethi; Knechtl, Valentin; Andres, Norina; Sideris, Ioannis; Zappa, Massimiliano

2014-05-01

276

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

277

Runoff simulation using radar and rain gauge data  

Microsoft Academic Search

The conceptual rainfall-runoff model TOPMODEL is used to simulate runoffs of the Meishan and Nianyushan catchments during\\u000a the summers of 1998 and 1999 in the GAME\\/HUBEX (GEWEX Asia Monsoon Experiment\\/HUAIHE River Basin Experiment) project. The\\u000a rainfall distributions are estimated by weather radar and rain gauge networks according to different methods. Observed and\\u000a simulated runoffs are compared and analyzed for both

Liu Xiaoyang; Mao Jietai; Zhu Yuanjing; Li Jiren

2003-01-01

278

Characterizing response of total suspended solids and total phosphorus loading to weather and watershed characteristics for rainfall and snowmelt events in agricultural watersheds  

USGS Publications Warehouse

Understanding the response of total suspended solids (TSS) and total phosphorus (TP) to influential weather and watershed variables is critical in the development of sediment and nutrient reduction plans. In this study, rainfall and snowmelt event loadings of TSS and TP were analyzed for eight agricultural watersheds in Wisconsin, with areas ranging from 14 to 110 km2 and having four to twelve years of data available. The data showed that a small number of rainfall and snowmelt runoff events accounted for the majority of total event loading. The largest 10% of the loading events for each watershed accounted for 7397% of the total TSS load and 6488% of the total TP load. More than half of the total annual TSS load was transported during a single event for each watershed at least one of the monitored years. Rainfall and snowmelt events were both influential contributors of TSS and TP loading. TSS loading contributions were greater from rainfall events at five watersheds, from snowmelt events at two watersheds, and nearly equal at one watershed. The TP loading contributions were greater from rainfall events at three watersheds, from snowmelt events at two watersheds and nearly equal at three watersheds. Stepwise multivariate regression models for TSS and TP event loadings were developed separately for rainfall and snowmelt runoff events for each individual watershed and for all watersheds combined by using a suite of precipitation, melt, temperature, seasonality, and watershed characteristics as predictors. All individual models and the combined model for rainfall events resulted in two common predictors as most influential for TSS and TP. These included rainfall depth and the antecedent baseflow. Using these two predictors alone resulted in an R2 greater than 0.7 in all but three individual models and 0.61 or greater for all individual models. The combined model yielded an R2 of 0.66 for TSS and 0.59 for TP. Neither the individual nor the combined models were substantially improved by using additional predictors. Snowmelt event models were statistically significant for individual and combined watershed models, but the model fits were not all as good as those for rainfall events (R2 between 0.19 and 0.87). Predictor selection varied from watershed to watershed, and the common variables that were selected were not always selected in the same order. Influential variables were commonly direct measures of moisture in the watershed such as snowmelt, rainfall + snowmelt, and antecedent baseflow, or measures of potential snowmelt volume in the watershed such as air temperature.

Danz, Mari E.;Corsi, Steven;Brooks, Wesley R.; Bannerman, Roger T.

2013-01-01

279

Multi-Watershed Evaluation of WSR-88D (NEXRAD) Radar-Precipitation Products for Hydrologic and Natural Resources Modeling Applications  

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 are primarily for the detection and modeling of extreme-weather events. Radar-precipitation estimates were compared with gauge estimates at 6 ARS watershed-research locations in

S. P. Hardegree; S. S. van Vactor; K. R. Healy; C. V. Alonso; J. V. Bonta; D. D. Bosch; D. S. Fisher; D. C. Goodrich; R. D. Harmel; J. L. Steiner; M. W. van Liew

2003-01-01

280

Forward Greedy ANN input selection in a stacked framework with Adaboost.RT - A streamflow forecasting case study exploiting radar rainfall estimates  

NASA Astrophysics Data System (ADS)

In input selection (or feature selection), modellers are interested in identifying k of the d dimensions that provide the most information. In hydrology, this problem is particularly relevant when dealing with temporally and spatially distributed data such as radar rainfall estimates or meteorological ensemble forecasts. The most common approaches for input determination of artifitial neural networks (ANN) in water resources are cross-correlation, heuristics, embedding window analysis (chaos theory), and sensitivity analyses. We resorted here to Forward Greedy Selection (FGS), a sensitivity analysis, for identifying the inputs that maximize the performance of ANN forecasting. It consists of a pool of ANNs with different structures, initial weights, and training data subsets. The stacked ANN model was setup through the joint use of stop training and a special type of boosting for regression known as AdaBoost.RT. Several ANN are then used in series, each one exploiting, with incremental probability, data with relative estimation error higher than a pre-set threshold value. The global estimate is then obtained from the aggregation of the estimates of the models (here the median value). Two schemes are compared here, which differ in their input type. The first scheme looks at lagged radar rainfall estimates averaged over entire catchment (the average scenario), while the second scheme deals with the spatial variation fields of the radar rainfall estimates (the distributed scenario). Results lead to three major findings. First, stacked ANN response outperforms the best single ANN (in the same way as many others reports). Second, a positive gain in the test subset of around 20%, when compared to the average scenario, is observed in the distributed scenario. However, the most important result from the selecting process is the final structure of the inputs, for the distributed scenario clearly outlines the areas with the greatest impact on forecasting in terms of the estimated radar precipitation and the forecast horizon. Thus, this research facilitates interpretability of the results under a downward approach, in which the zones of influence of rainfall at different forecasting horizons help understanding the pattern of the hydrologic response at the event scale. Third, the input selection is slightly different between experiments due to the active principle of diversity, defined as hydrological model complementarities addressing different aspects of the forecast. Finally the following guidelines favoured efficient stacked ANNs: i) design different combiners, ii) base the stack preprocess on probabilistic score representations oriented toward the bias of the ensemble (e.g. the ignorance score), and iii) evaluate more powerful multi-criterion selection algorithms such as multiobjective evolutionary algorithms (MOEA).

Brochero, D.; Anctil, F.; Gagn, C.

2012-04-01

281

Identification of Aviation Weather Hazards Based on the Integration of Radar and Lightning Data  

Microsoft Academic Search

The National Weather Service Eastern Region is carrying out a national risk-reduction exercise at the Baltimore-Washington Forecast Office in Sterling, Virginia. The primary objective of this project is to integrate information from remote sensor technologies to produce comprehensive state-of-the-atmosphere reports that promote aviation safety. Techniques have been developed and tested to identify aviation-oriented hazardous weather based on data from conventional

Andrew D. Stern; Raymond H. Brady III; Patrick D. Moore; Gary M. Carter

1994-01-01

282

A Reduction in Rainfall Associated with Smoke from SugarCane Fires--An Inadvertent Weather Modification?  

Microsoft Academic Search

An examination of 60 years of rainfall during three months of the cane-harvesting season has shown a reduction of rainfall at inland stations coinciding with increasing cane production; no such reduction occurred at a `control' station upwind of smoke from the cane fires. The reduction is consistent with the hypothesis that through their activity as condensation nuclei the smoke particles

J. Warner

1968-01-01

283

A method for Doppler Weather Radar raw data compression based on wavelet transform modulus maxima denoising  

Microsoft Academic Search

A lossy data compression algorithm based on wavelet transform modulus maxima denoising (WTMM-D) has been proposed. Firstly, analysis for radar raw data is presented to identify data characteristics and correlation. Then, we transform the data format and compare the experimental results using different lossless compression algorithms to compress the transformed raw data. Finally, a method based on WTMM-D is presented,

Xiao Lil; Xuehong Cao; Chen Li; Yue Zhang

2010-01-01

284

The Use of a Vertically Pointing Pulsed Doppler Radar in Cloud Physics and Weather Modification Studies  

Microsoft Academic Search

It is shown that Doppler radar measurements of the changes with height of the average fallspeeds of solid precipitation particles can be used together with radiosonde data to distinguish between growth of ice particles by riming and growth by deposition from the vapor phase. Under some conditions this information can be deduced from real-time observations, but generally spectral broadening by

Richard R. Weiss; Peter V. Hobbs

1975-01-01

285

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 atmospheres 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

286

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

NASA Astrophysics Data System (ADS)

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.

2013-06-01

287

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 25 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

288

The FlySafe project: How weather radars can improve the en-route bird strike warning system. Hans van Gasteren1,2  

E-print Network

1 The FlySafe project: How weather radars can improve the en-route bird strike warning system. Hans Graaf3 and Willem Bouten1 In civil aviation the majority of bird strikes occur below 1000 ft, thus civil bird strikes predominantly occur on and around aerodromes. In military aviation, however, the problem

Graaf, Martin de

289

Comparative analyses for the prediction of streamflow from small watershed by use of digitized radar data  

E-print Network

compared to rainfall values estimated from 0-deg and tilt, digital-radar data for April 26 and 27, 1972. . 83 xi LIST OF TABLES (CONTINfJED) Table Page Comparison of observed surface runoff and that computed by using the NWS API program with ARS... from 0-deg radar data between 2000-2100 CST, May 31, 1971 79 xiv LIST OF FIGURES (CONTINUED) Figure Page 25. Isohytal map (in inches) for rainfall estimated from tilt, digital-radar between 2000-2100 CST, May 31, 1971 80 26. Surface weather map...

Braatz, Dean Thomas

2012-06-07

290

Using X-band Weather Radar Measurements to Monitor the Integrity of Digital Elevation Models for Synthetic Vision Systems  

NASA Technical Reports Server (NTRS)

Synthetic Vision Systems (SVS) provide pilots with displays of stored geo-spatial data representing terrain, obstacles, and cultural features. As comprehensive validation is impractical, these databases typically have no quantifiable level of integrity. Further, updates to the databases may not be provided as changes occur. These issues limit the certification level and constrain the operational context of SVS for civil aviation. Previous work demonstrated the feasibility of using a realtime monitor to bound the integrity of Digital Elevation Models (DEMs) by using radar altimeter measurements during flight. This paper describes an extension of this concept to include X-band Weather Radar (WxR) measurements. This enables the monitor to detect additional classes of DEM errors and to reduce the exposure time associated with integrity threats. Feature extraction techniques are used along with a statistical assessment of similarity measures between the sensed and stored features that are detected. Recent flight-testing in the area around the Juneau, Alaska Airport (JNU) has resulted in a comprehensive set of sensor data that is being used to assess the feasibility of the proposed monitor technology. Initial results of this assessment are presented.

Young, Steve; UijtdeHaag, Maarten; Sayre, Jonathon

2003-01-01

291

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

292

High resolution rainfall data for urban hydrology, flood modelling and prediction  

NASA Astrophysics Data System (ADS)

Hydrological analysis of urban catchments requires high resolution rainfall and catchment information because of the small size of these catchments, their fast runoff processes and related short response times. Over the last three decades, analysis of the performance of urban drainage systems has been done mainly through hydrodynamic model simulations. Rainfall input into these models has often been restricted to a single or a few rain gauge(s) in or near the catchment, rendering rainfall input into one of the main sources of uncertainty in model calculations. In recent years, rainfall data from weather radars that provide space-time estimates of rainfall is becoming increasingly available. Still, the scale of available radar rainfall information, with pixels of 1 to 2.5 km2, does no not meet the relevant scales of urban hydrology (e.g. Berne et al. 2004; Emmanuel et al., 2011). In addition, studies comparing rainfall data from radar and rain gauges show a deviation of 10 to even 50%, with larger differences for increasing temporal and spatial resolutions (e.g. Overeem and Holleman, 2010). A new type of high resolution (X-band) weather radars promises to provide more accurate rainfall estimates at the spatial and temporal scales that are required for urban hydrological analysis (Willems et al., 2012). Recently, the RAINGAIN project was started to analyse the applicability of this new type of radars in the context of urban hydrological modelling. In this project, rainfall data from C-band and X-band radars and a network of rain gauges will be analysed in four highly urbanised catchments: Leuven (Belgium), two boroughs of London (UK), two catchments in Paris (France) and two polder catchments in Rotterdam (the Netherlands). High resolution rainfall data will be used as input into high resolution urban hydrological and hydrodynamic models to simulate and predict urban flood flooding using hybrid 1D-2D approaches (Simes et al., 2010). Details of the radar equipments, characteristics of the four urban catchments and hydrological and hydrodynamic simulation models will be provided; results of the project stage and of a specialist workshop on radar rainfall estimation will be reported.

ten Veldhuis, J. A. E.; Maksimovic, C.; Schertzer, D.; Willems, P.

2012-04-01

293

Tropical Rainfall Measuring Mission (TRMM) project. III - Japan-U.S. collaborative rain observation experiment using an airborne rain radar  

NASA Technical Reports Server (NTRS)

A collaborative rain-observation experiment using an airborne rain radar was conducted between Communications Research Laboratory (CRL) and Goddard Space Flight Center (GSFC)/NASA. CRL provided an airborne rain-radar/radiometer system and GSFC/NASA provided a NASA P3-A aircraft. Airborne or spaceborne rain-radar echoes have large sea or land-surface echoes. These surface echoes yield rain-estimation algorithms using rain attenuation. The experiment demonstrated the potential of the rain-estimation techniques using rain attenuation.

Meneghini, Robert; Atlas, David; Nakamura, Kenji; Kozu, Toshiaki

1990-01-01

294

Weather Forecasting  

NSDL National Science Digital Library

This website, supplied by Annenberg / CPB, discusses weather satellites, Doppler radar, and additional tools forecasters use to predict the weather. Students can find a wind chill calculator along with a brief discussion of the history of forecasting and weather lore. Once you have a firm grasp on the science of weather forecasting, be sure to check out the other sections of this site, which include: "ice and snow," "our changing climate," "the water cycle," and "powerful storms."

2008-03-27

295

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

296

Estimating Rainfall One Pixel at a Time: A Scientific Activity with Brazilian Students  

NASA Astrophysics Data System (ADS)

Studies of rainfall and precipitation using radars started almost at the same time as radars were developed for military applications in Second World War. Since then, the science behind radars used to monitor weather has evolved constantly. Radar images showing clouds, different types of precipitation, motion and evolution of weather systems are commonplace nowadays and are present in all forms of mass communication. Unfortunately, the layperson and even science students have limited knowledge of how weather radars work, how radar images are produced and what they do really mean. In order to increase the awareness about the use of radars in meteorology and interpretation of images, we started a program to teach science students on how to analyze radar images and to obtain simple estimates of rainfall using radar images alone. The data for the study was collected by a non-polarimetric Doppler radar operating on the C-Band The procedure is simple, radar images are selected, areas of interest (rain cells) are marked and then the color pixels in images are separated and counted according to their color and precipitation index. In this way, the evolution of the rain cell is followed and the amount of precipitation is calculated. As an additional activity, in a reverse analysis process, values of reflectivity are obtained from the estimates of precipitation and the size distribution of rain cloud droplets are calculated using parametric equations. This study was both rewarding and enriching for the students because they could participate in the actual process of collecting and analyzing the data, and the lessons learned and experience gained with this hands-on activity will certainly constitute a valuable asset.

Alves, M. A.; Martin, I. M.; Lyra, C. S.

2009-12-01

297

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

298

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

299

Q. J. R. Meteorol. Soc. (2002), 128, pp. 20452058 Spurious power-law relations among rainfall and radar parameters  

E-print Network

of rainfall studies over the last several decades, we then sample from a collection of rain events in which, the authors examined statistical physics of rain from the point of view of the modern theory of random to the case of the simplest rain model, namely uncorrelated raindrops having a prescribed drop size

Kostinski, Alex

300

Path-Integrated Attenuation from Airborne X-Band Radar and Passive Radiometer Measurements: Implication for Rainfall Measurements  

NASA Technical Reports Server (NTRS)

This study compares path-integrated attenuation (PIA), in precipitation over the ocean, derived from a single-frequency X-band radar, using the surface reference technique (SRT), with that deduced from a radiometer also operating at X band. The data were collected during TRMM field campaigns. The PIA derived from radar using the SRT does not involve any assumptions regarding the precipitation but it assumes that the cross-section of the surface is stable, that is, it is not significantly altered by factors such as surface roughness. The PIA deduced from the radiometer, however, involves assumptions regarding the temperature and emissivity of the surface and absorption and scattering by the intervening precipitation, which in turn depend upon the size, concentration and composition of the precipitation particles. The comparison of the PIA from the two instruments serves not only as a check between the radar and the radiometer but also may yield insights into the structure of the intervening precipitation. Such study can provide valuable information for TRMM in which both radar and radiometers are used for rain measurements. The radiometer PIA was first deduced from the brightness temperature using a simple one-layer radiative transfer model assuming no scattering, an isothermal atmosphere. The initial results show a general agreement between the PIAs deduced from the two instruments. Largo disagreement was found at high values of PIAs that may have been caused saturation of the X-band brightness temperature or by uncertainties in wind roughening of the sea surface that affects the SRT. Further results including the effects of scattering and a non-isothermal atmosphere will be shown at the conference.

Tian, Lin; Heymsfield, Gerry; Weinman, Jim; Starr, David OC. (Technical Monitor)

2002-01-01

301

Physically based simulator for measurements of precipitation with polarimetric and space-borne radars  

NASA Astrophysics Data System (ADS)

A radar is a powerful tool for measurement of the 3-D structure of precipitation. Recently, polarimetric radar is widely used because it can measure the size of raindrops to some degree and therefore can measures more accurate rainfall rate than the conventional weather radar. A space-borne radar is also widely used in precipitation studies. The Tropical Rainfall Measuring Mission (TRMM) satellite has been continuously monitoring precipitation on a global scale since the launch in November, 1977. Following the TRMM, the Global Precipitation Mission (GPM) is scheduled to launch in 2013. The polarimetric parameters observed with the polarimetric radar depend on various precipitation properties in a complex way. Multiple scattering contributions cannot be neglected for a radar operated at higher frequency of 35 GHz higher onboard the GPM. To develop a robust algorithm for more accurate measurements of precipitation from those radars, we should evaluate how micro-physical properties of precipitation link to the received signals. We have developed a generalized radar simulator for polarimetric and space-borne radar (GPASS). This is a physically-based simulator in which the scattering properties of cloud and raindrops are calculated by using radio wave scattering theory. Thus we can make detailed study how the radar signals vary with micro-physical properties of precipitation by using the simulator. We will present the simulator in detail and the limit of the Rayleigh approximation for polarimetric radar.

Kobayashi, Takahisa; Masuda, Kazuhiko; Yamauchi, Hiroshi; Adachi, Ahoro

2011-11-01

302

Real-time flood forecasting with high-resolution NWP rainfall and dual data assimilation  

NASA Astrophysics Data System (ADS)

Mesoscale Numerical Weather Prediction (NWP) models are nowadays gaining more and more attention in providing high-resolution rainfall forecasts for real-time flood forecasting. In this study, the newest generation NWP model, Weather Research & Forecasting (WRF) model, is integrated with the rainfall-runoff model in real-time to generate accurate flow forecasts at the catchment scale. The rainfall-runoff model is chosen as the Probability Distribution Model (PDM), which has widely been used for flood forecasting. Dual data assimilation is carried out for real-time updating of the flood forecasting system. The 3-Dimensional Variational (3DVar) data assimilation scheme is incorporated with WRF to assimilate meteorological observations and weather radar reflectivity data in order to improve the WRF rainfall forecasts; meanwhile real-time flow observations are assimilated by the Auto-Regressive Moving Average (ARMA) model to update the forecasted flow transformed by PDM. The Brue catchment located in Southwest England with a drainage area of 135.2 km2 is chosen to be the study area. A dense rain gauge network was set up during a project named HYREX (Hydrological radar experiment), which contains 49 rain gauges and a C-band weather radar, providing with sufficient hydrological and radar data for WRF model verification and data assimilation. Besides the radar reflectivity data, two types of NCAR archived data (SYNOP and SOUND, http://dss.ucar.edu) are also assimilated by 3DVar, which provide real-time surface and upper-level observations of pressure, temperature, humidity and wind from fixed and mobile stations. Four 24 hour storm events are selected from the HYREX project with different characteristics regarding storm formation and rainfall-runoff responses. Real-time flood forecasting is then carried out by the constructed forecasting system for the four storm events with a forecast lead time of 12 hours. The forecasting accuracy of the whole system is found to be largely improved by incorporating the WRF forecasted rainfall when the forecast lead time is beyond the catchment concentration time. The assimilation of real-time meteorological and radar data also show great advantage in improving the performance of the flood forecasting system. Key words: real-time flood forecasting; Weather Research & Forecasting (WRF) model; high-resolution rainfall forecasts; dual data assimilation.

Liu, Jia; Bray, Michaela; Han, Dawei

2014-05-01

303

Monitoring of the plume from the basaltic phreatomagmatic 2004 Grmsvtn eruptionapplication of weather radar and comparison with plume models  

NASA Astrophysics Data System (ADS)

The Grmsvtn eruption in November 2004 belongs to a class of small- to medium-sized phreatomagmatic eruptions which are common in Iceland. The eruption lasted 6 days, but the main phase, producing most of the 0.02 km3 of magma erupted, was visible for 33 h on the C-band weather radar of the Icelandic Meteorological Office located in Keflavk, 260 km to the west of the volcano. The plume rose to 8-12 km high over sea level during 33 h. The long distance between radar and source severely reduces the accuracy of the plume height determinations, causing 3.5-km steps in recorded heights. Moreover, an apparent height overestimate of ~1.5 km in the uncorrected radar records occurs, possibly caused by wave ducting or super-refraction in the atmosphere. The stepping and the height overestimate can be partly overcome by averaging the plume heights and by applying a height adjustment based on direct aircraft measurements. Adjusted weather radar data on plume height are used to estimate the total mass erupted using empirical plume models mostly based on magmatic eruptions and to compare it with detailed in situ measurements of the mass of erupted tephra. The errors arising because of the large radar plume distance limit the applicability of the data for detailed comparisons. However, the results indicate that the models overestimate the mass erupted by a factor of three to four. This supports theoretical models indicating that high steam content of phreatomagmatic (wet) plumes enhances their height compared to dry plumes.

Oddsson, Bjrn; Gudmundsson, Magns T.; Larsen, Gurn; Karlsdttir, Sigrn

2012-08-01

304

Rainfall estimation in the context of post-event flash flood analysis  

NASA Astrophysics Data System (ADS)

Due to their spatial coverage and space-time resolution, operational weather radar networks offer unprecedented opportunities for the observation of flash flood generating storms. However, the radar rainfall estimation quality highly depends on the relative locations of the event and the radar(s). A mountainous environment obviously adds to the complexity of the radar quantitative precipitation estimation (QPE). A pragmatic methodology is proposed to take the best benefit of the existing rainfall observations (radar and raingauge data) for given flash-flood cases: 1) A precise documentation of the radar characteristics (location, parameters, operating protocol, data archives and processing) needs first to be established. The radar(s) detection domain(s) can then be characterized using the "hydrologic visibility" concepts (Pellarin et al. J Hydrometeor 3(5) 539-555 2002). 2) Rather dense raingauge observations (operational, amateur) are usually available at the event time scale while few raingauge time series exist at the hydrologic time steps. Such raingauge datasets need to be critically analysed; a geostatistical approach is proposed for this task. 3) A number of identifications can be implemented prior to the radar data re-processing: a) Special care needs to be paid to (residual) ground clutter which has a dramatic impact of radar QPE. Dry-weather maps and rainfall accumulation maps may help in this task. b) Various sources of power losses such as screening, wet radome, attenuation in rain need to be identified and quantified. It will be shown that mountain returns can be used to quantify attenuation effects at C-band. c) Radar volume data is required to characterize the vertical profile of reflectivity (VPR), eventually conditioned on rain type (convective, widespread). When such data is not available, knowledge of the 0C isotherm and the scanning protocol may help detecting bright-band contaminations that critically affect radar QPE. d) With conventional radar technology, the radar calibration accuracy and the relevance of the Z-R relationship can only be assessed with external data (raingauges here). Ways for characterizing the equifinality structure and optimal parameters will be presented. Such a procedure will be illustrated and assessed with the radar and raingauge datasets collected during the Aude 1999, Gard 2002 and Slovenia 2007 rain events of interest in the HYDRATE project.

Bouilloud, L.; Delrieu, G.; Boudevillain, B.

2009-04-01

305

Rainfall estimation in the context of post-event flash flood analysis  

NASA Astrophysics Data System (ADS)

Due to their spatial coverage and space-time resolution, operational weather radar networks offer unprecedented opportunities for the observation of flash flood generating storms. However, the radar rainfall estimation quality highly depends on the relative locations of the event and the radar(s). A mountainous environment obviously adds to the complexity of the radar quantitative precipitation estimation (QPE). A pragmatic methodology was developed within the EC-funded HYDRATE project to take the best benefit of the existing rainfall observations (radar and raingauge data) for given flash-flood cases: 1) A precise documentation of the radar characteristics (location, parameters, operating protocol, data archives and processing) needs first to be established. The radar(s) detection domain(s) can then be characterized using the "hydrologic visibility" concepts (Pellarin et al. J Hydrometeor 3(5) 539-555 2002). 2) Rather dense raingauge observations (operational, amateur) are usually available at the event time scale while few raingauge time series exist at the hydrologic time steps. Such raingauge datasets need to be critically analysed; a geostatistical approach is proposed for this task. 3) A number of identifications can be implemented prior to the radar data re-processing: a) Special care needs to be paid to (residual) ground clutter which has a dramatic impact of radar QPE. Dry-weather maps and rainfall accumulation maps may help in this task. b) Various sources of power losses such as screening, wet radome, attenuation in rain need to be identified and quantified. It will be shown that mountain returns can be used to quantify attenuation effects at C-band. c) Radar volume data is required to characterize the vertical profile of reflectivity (VPR), eventually conditioned on rain type (convective, widespread). When such data is not available, knowledge of the 0C isotherm and the scanning protocol may help detecting bright-band contaminations that critically affect radar QPE. d) With conventional radar technology, the radar calibration accuracy and the relevance of the Z-R relationship can only be assessed with external data (raingauges here). Ways for characterizing the equifinality structure and optimal parameters will be presented. Such a procedure will be illustrated and assessed with the radar and raingauge datasets collected for various rain events of interest in the HYDRATE project.

Delrieu, Guy; Boudevillain, Brice; Bouilloud, Ludovic

2010-05-01

306

Countrywide rainfall maps from a commercial cellular telecommunication network  

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. Many countries do not have continuously operating weather radars, and have no or few rain gauges. A new development is rainfall estimation from microwave links of commercial cellular telecommunication networks. Such networks cover large parts of the land surface of the earth and have a high density, especially in urban areas. The estimation of rainfall using commercial microwave links could therefore become a valuable source of information. The data produced by microwave links is essentially a by-product of the communication between mobile telephones. 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. A dataset from a commercial microwave link network over the Netherlands is analyzed, containing data from an unprecedented number of links (1500) covering the land surface of the Netherlands (35500 km2). This dataset consists of 24 days with substantial rainfall in June - September 2011. A rainfall retrieval algorithm is presented to derive rainfall intensities from the microwave link data, which have a temporal resolution of 15 min. Rainfall maps (1 km spatial resolution) are generated from these rainfall intensities using Kriging. This algorithm is suited for real-time application, and is calibrated on a subset (12 days) of the dataset. The other 12 days in the dataset are used to validate the algorithm. Both calibration and validation are done using gauge-adjusted radar data. Validation results reveal that relatively accurate country-wide rainfall maps can be obtained from microwave link data. Since cellular telephone networks are used worldwide, data from such networks could also be used to obtain rainfall maps over larger areas and in areas where no other sources of rainfall data are available.

Overeem, A.; Leijnse, H.; Uijlenhoet, R.

2012-12-01

307

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-Acua, Adrian

2014-05-01

308

Diagnostic analysis of a heavy rainfall event over Beijing on July 21-22, 2012  

NASA Astrophysics Data System (ADS)

The eastward moving low vortex over the North China plain induced the heaviest rainfall in 61 years over Beijing on July 21-22, 2012. This record-breaking heavy rainfall is characterized by its great rainfall amount and intensity, wide range, and high impact, causing dozens of deaths and extensive damage. In this paper, using a set of measurements and the NCEP 11 reanalysis data, the synoptic and mesoscale conditions of the heavy rainfall are firstly diagnosed. The measurements include the intensive surface observations, the observations of the operational sounding station and microwave radiometer, as well as the products of Doppler radar and satellite. Preliminary analysis shows that the eastward moving cold front encounters the warm moist southwest flow around Subtropical High, providing a favorable circulation condition for strong convective weather in this East Asian monsoon region. Meanwhile, the conditions of sustained water vapor, strong vertical ascent of air and unstable stratification are suitable for the formation of a heavy rainfall over Beijing. The mesoscale convective systems (MCSs) which produced the most severe rainfall in Fang Shan area are then analyzed, and the radar and satellite data with mesoscale model forecasts are used to further examine the features of the MCSs evolution. Moreover, the effects of topography and urban heat island which may contribute to the heavy rainfall are also discussed.; Heavy rainfall in Beijing on July 21, 2012 ; The distribution of precipitation (mm) over Beijing during 0200UTC to 2200UTC, July 21

Jiang, X.; Yuan, H.

2012-12-01

309

On problems occurring at close vicinity usage of WiFi and radars, especially ATC and weather  

Microsoft Academic Search

The goal of my paper is to analyze mutual effects of radars and wireless systems on each other. In practice it occurred in many cases that these systems interfered with each other in their normal mode of operation. I studied the problem on radars working in the L band (1- 2 GHz) and in the C band (4-8 GHz). In

T. Micskei; R. Seller

2009-01-01

310

Simultaneous Observations and Analysis of Severe Storms Using Polarimetric X-Band SAR and Ground-Based Weather Radar  

Microsoft Academic Search

Recent advances in synthetic aperture radar (SAR) technology have revived meteorological applications with this type of radar. SARs are designed for surface imaging, but now that several X-band multipolarization SAR satellites are in orbit, the attenuation and backscatter caused by precipitation can be better studied. The results presented here demonstrate some of the possibilities by analyzing observations from dual-polarization (HH,

Jason P. Fritz; V. Chandrasekar

2010-01-01

311

IEICE TRANS. COMMUN., VOL. E79B, NO. 6 JUNE 1996 PAPER Special Issue on Weather Radar Technology  

E-print Network

means to improve the con- ventional -adjustment method require careful treatment so that they do not introduce new sources of errors. key words: TRMM precipitation radar, MU radar, ground truth, rain re- trieval algorithm, numerical simulation 1. Introduction The largest advantage of space-borne measurements

Sato, Toru

312

A patented approach to radiated testing of installed airborne Doppler radar with weather\\/windshear detection capability  

Microsoft Academic Search

Low altitude windshear phenomena has been causally linked to numerous civil transport aircraft incidents with fatalities and injuries exceeding 800, covering a period of more than 25 years. The recent crash of a USAir DC-9 at Charlotte, N.C. on July 2, 1994 has caused an increased focus on windshear and microburst activity. Three sensor systems were investigated; radar, laser radar

John F. Michaels

1995-01-01

313

Linking the Annual Variation of Snow Radar-derived Accumulation in West Antarctica to Long-term Automatic Weather Station Measurements  

NASA Astrophysics Data System (ADS)

Understanding the snow accumulation rate on polar ice sheets is important in assessing mass balance and ice sheet contribution to sea level rise. Measuring annual accumulation on a regional scale and extending back in time several decades has been accomplished using the Center for Remote Sensing of Ice Sheets (CReSIS) Snow Radar on the NASA DC-8 that is part of NASA's Ice-Bridge project. The Snow Radar detects and maps near-surface internal layers in polar firn, operating from 2- 6 GHz and providing a depth resolution of ~4 cm. During November 2011, Snow Radar data were obtained for large areas of West Antarctica, including a flight segment that passed within ~70 km of Byrd Station (80S, 119W). Byrd Station has a very long automatic weather station (AWS) record, extending from present to 1980, with 3 relatively brief gaps in the record. The AWS data for Byrd Station were obtained from the Antarctic Meteorological Research Center (AMRC) at the University of Wisconsin. The L1B Snow Radar data products, available from the National Snow and Ice Data Center (NSIDC), were analyzed using layer picking software to obtain the depth of reflectors in the firn that are detected by the radar. These reflectors correspond to annual markers in the firn, and allow annual accumulation to be determined. Using the distance between the reflectors and available density profiles from ice cores, water equivalent accumulation for each annual layer back to 1980 is obtained. We are analyzing spatial variations of accumulation along flight lines, as well as variations in the time series of annual accumulation. We are also analyzing links between annual accumulation and surface weather observations from the Byrd Station AWS. Our analyses of surface weather observations have focused on annual temperature, atmospheric pressure and wind extremes (e.g. 5th and 95th percentiles) and links to annual snow accumulation. We are also examining satellite-derived sea ice extent records for the Bellingshausen and Amundsen seas sector (60W-120W) over the same 31-year time period and comparing results to annual snow accumulation. Results from this work will be presented at the meeting.

Feng, B.; Braaten, D. A.; Gogineni, P.; Paden, J. D.; Leuschen, C.; Purdon, K.

2013-12-01

314

Cloud and Precipitation Radar  

NASA Astrophysics Data System (ADS)

Precipitation or weather radar is an essential tool for research, diagnosis, and nowcasting of precipitation events like fronts or thunderstorms. Only with weather radar is it possible to gain insights into the three-dimensional structure of thunderstorms and to investigate processes like hail formation or tornado genesis. A number of different radar products are available to analyze the structure, dynamics and microphysics of precipitation systems. Cloud radars use short wavelengths to enable detection of small ice particles or cloud droplets. Their applications differ from weather radar as they are mostly orientated vertically, where different retrieval techniques can be applied.

Hagen, Martin; Hller, Hartmut; Schmidt, Kersten

315

Spatial Scaling of Radar Precipitation Over Complex Terrain  

NASA Astrophysics Data System (ADS)

Spatial downscaling of precipitation is necessary for many purposes. For example, distributed hydrological models need rainfall input with grid-scales of about 1km, but operational numerical weather prediction models deliver rainfall with grid-scales of 10 km and more. Estimation of parameters characterizing scale invariance of the precip- itation field is an inevitable step for the implemention of a scaling-based downscaling scheme (multiplicative random cascade models). Austrian radar data have been examined by wavelet-based multiresolution decompo- sition and a universal multifractal cascade for several rainfall events in the years 1992 to 1999 over complex orography. We present estimates of common scaling parameters like intermittency, smoothness, and spikiness of the precipitation field. We show the dependence of the scaling pa- rameters on the averaging period (0.5, 1, or 3 hours) of the precipitation fields, on the investigated weather type (convectively induced precipitation or stratiform rain), on the evolution of the event, and on underlying orography. Interpretation of radar data over complex orography is challenging and is briefly discussed. Finally, we demon- strate the good performance of an anistropic micro-canonical multiplicative random cascade in precipitation downscaling by application to upscaled radar data and quan- titative comparison of the downscaled product with the original radar data.

Spatzierer, M.; Ahrens, B.

316

Simulating spaceborne X-band polarimetric SAR observations of precipitation using ground-based S-band weather radar data  

NASA Astrophysics Data System (ADS)

Recent advances in X-band Synthetic Aperture Radar (XSAR) technology have revived meteorological applications with this type of radar. At this wavelength, attenuation and backscatter caused precipitation can be detected, and has been observed in current and past XSAR systems. Based on real fully polarimetric S-band ground radar observations of storms, a model is constructed to simulate spaceborne XSAR observations. Simulation results are compared to storm observations from several repeat pass dual polarization TerraSAR-X acquisitions over Florida. Development of these simulations provides a mechanism to explore the capabilites of precipitation surveillance from from XSAR as well as progress towards mitigation of storm effects for traditional SAR applications.

Fritz, Jason; Chandresekar, V.

2010-04-01

317

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  

Microsoft Academic Search

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

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

2000-01-01

318

Particle aggregation in volcanic clouds from the 2009 eruption of Redoubt Volcano, Alaska: Observations of Doppler weather radar, satellite images and tephra-fall deposits  

NASA Astrophysics Data System (ADS)

The combined use of weather radar and thermal infrared satellite images provides complementary evidence that can be used to observe and interpret tephra-fall processes. Radar is ideal for characterizing coarse-grained tephra in the eruption column and proximal cloud, while thermal infrared satellite data are better able to characterize the fine-grained distal volcanic cloud. We present observations of radar, satellite images, and character of the tephra-fall deposits from the 2009 eruption of Redoubt Volcano, Alaska. Accretionary tephra-ice pellets (up to 9 mm in diameter) comprised of fine-grained ash (less than 63 micron diameter) were abundant in the many of the proximal tephra-fall deposits. The eruption column and proximal cloud from seventeen explosive events were observed using the MiniMax-250C (MM-250C) volcano-monitoring Doppler weather radar located 80 km from the vent. Radar reflectivity and radial Doppler velocity measurements were made of the column, every 70-90 seconds at a vertical resolution of about 2 km. Radar reflectivity is highly dependent upon particle size and to a lesser extent, concentration. At 80 km distance, the minimum detectable particle diameter for the MM-250C was about 0.2 mm for a mass concentration of 100 g/m3. Thus, the radar was able to observe the aggregate pellets, and not the fine-grained ash. Most of the explosive events were characterized by high radar reflectivity values of 50-60 dBZ in the central core of the eruption column and proximal cloud, which we interpret to be related to the rapid growth of accretionary tephra-ice pellets. Tephra-fall deposits extended for distances of several hundred kilometers and mapped to a minimum mass density of 10 g/m2. However, the MM-250C radar data were only able to observe the dispersed cloud for tens of kilometers from the source, which was well within the 1000 g/m2 isomass contour. Fine-grained ash was prematurely removed from the eruption cloud in proximal locations due to aggregate formation. The relative lack of fine-grained ash may account for the poor thermal infrared brightness temperature signals observed in satellite images for many of the distal volcanic clouds from the 2009 eruption, and possibly from the 1989-90 eruption as well. Time-series of radial Doppler velocity images documented the transition from turbulent mixing in the column to larger scale entrainment within the proximal cloud. Large scale entrainment begins to develop within minutes of eruption onset. Most of the eruption clouds from the explosive events reached the stratosphere, but the large scale entrainment appears to be better developed in the tropospheric portion of the cloud.

Schneider, D. J.; Wallace, K. L.; Mastin, L. G.

2012-12-01

319

Dissolved rainfall inputs and streamwater outputs in an undisturbed watershed on highly weathered soils in the Brazilian cerrado  

NASA Astrophysics Data System (ADS)

The cerrados of Brazil cover 2 million km2. Despite the extent of these seasonally dry ecosystems, little watershed research has been focused in this region, particularly relative to the watersheds of the Amazon Basin. The cerrado shares pedogenic characteristics with the Amazon Basin in draining portions of the Brazilian shield and in possessing Oxisols over much of the landscape. The objective of this research was to quantify the stream water geochemical relationships of an undisturbed 1200 ha cerrado watershed for comparison to river geochemistry in the Amazon. Furthermore, this undisturbed watershed was used to evaluate stream discharge versus dissolved ion concentration relationships. This research was conducted in the Crrego Roncador watershed of the Reserva Ecolgica do Roncador (RECOR) of the Instituto Brasileiro Geografia e Estatstica (IBGE) near Brasilia, Brazil. Bulk precipitation and stream water chemistry were analysed between May 1998 and May 2000. The upland soils of this watershed are nutrient poor possessing total stocks of exchangeable elements in the upper 1 m of 81 +/- 13, 77 +/- 4, 25 +/- 3, and 1 +/- 1 kg ha-1 of K, Ca, Mg, and P, respectively. Bulk precipitation inputs of dissolved nutrients for this watershed are low and consistent with previous estimates. The nutrient-poor soils of this watershed, however, increase the relative importance of precipitation for nutrient replenishment to vegetation during episodes of ecosystem disturbance. Stream water dissolved loads were extremely dilute with conductivities ranging from 4 to 10 ?S cm-1 during periods of high- and low-flow, respectively. Despite the low concentrations in this stream, geochemical relationships were similar to other Amazonian streams draining shield geologies. Discharge-concentration relationships for Ca and Mg in these highly weathered soils developed from igneous rocks of the Brazilian shield demonstrated a significant negative relationship indicating a continued predominance of groundwater baseflow contributions these cationic elements.

Markewitz, Daniel; Resende, Julio C. F.; Parron, Lucilia; Bustamante, Mercedes; Klink, Carlos A.; Figueiredo, Ricardo De O.; Davidson, Eric A.

2006-08-01

320

Correction of Sampling Errors in Ocean Surface Cross-Sectional Estimates from Nadir-Looking Weather Radar  

NASA Technical Reports Server (NTRS)

The return from the ocean surface has a number of uses for airborne meteorological radar. The normalized surface cross section has been used for radar system calibration, estimation of surface winds, and in algorithms for estimating the path-integrated attenuation in rain. However, meteorological radars are normally optimized for observation of distributed targets that fill the resolution volume, and so a point target such as the surface can be poorly sampled, particularly at near-nadir look angles. Sampling the nadir surface return at an insufficient rate results in a negative bias of the estimated cross section. This error is found to be as large as 4 dB using observations from a high-altitude airborne radar. An algorithm for mitigating the error is developed that is based upon the shape of the surface echo and uses the returned signal at the three range gates nearest the peak surface echo.

Caylor, I. Jeff; Meneghini, R.; Miller, L. S.; Heymsfield, G. M.

1997-01-01

321

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

322

Comparison of TOPMODEL streamflow simulations using NEXRAD-based and measured rainfall data, McTier Creek watershed, South Carolina  

USGS Publications Warehouse

Rainfall is an important forcing function in most watershed models. As part of a previous investigation to assess interactions among hydrologic, geochemical, and ecological processes that affect fish-tissue mercury concentrations in the Edisto River Basin, the topography-based hydrological model (TOPMODEL) was applied in the McTier Creek watershed in Aiken County, South Carolina. Measured rainfall data from six National Weather Service (NWS) Cooperative (COOP) stations surrounding the McTier Creek watershed were used to calibrate the McTier Creek TOPMODEL. Since the 1990s, the next generation weather radar (NEXRAD) has provided rainfall estimates at a finer spatial and temporal resolution than the NWS COOP network. For this investigation, NEXRAD-based rainfall data were generated at the NWS COOP stations and compared with measured rainfall data for the period June 13, 2007, to September 30, 2009. Likewise, these NEXRAD-based rainfall data were used with TOPMODEL to simulate streamflow in the McTier Creek watershed and then compared with the simulations made using measured rainfall data. NEXRAD-based rainfall data for non-zero rainfall days were lower than measured rainfall data at all six NWS COOP locations. The total number of concurrent days for which both measured and NEXRAD-based data were available at the COOP stations ranged from 501 to 833, the number of non-zero days ranged from 139 to 209, and the total difference in rainfall ranged from -1.3 to -21.6 inches. With the calibrated TOPMODEL, simulations using NEXRAD-based rainfall data and those using measured rainfall data produce similar results with respect to matching the timing and shape of the hydrographs. Comparison of the bias, which is the mean of the residuals between observed and simulated streamflow, however, reveals that simulations using NEXRAD-based rainfall tended to underpredict streamflow overall. Given that the total NEXRAD-based rainfall data for the simulation period is lower than the total measured rainfall at the NWS COOP locations, this bias would be expected. Therefore, to better assess the use of NEXRAD-based rainfall estimates as compared to NWS COOP rainfall data on the hydrologic simulations, TOPMODEL was recalibrated and updated simulations were made using the NEXRAD-based rainfall data. Comparisons of observed and simulated streamflow show that the TOPMODEL results using measured rainfall data and NEXRAD-based rainfall are comparable. Nonetheless, TOPMODEL simulations using NEXRAD-based rainfall still tended to underpredict total streamflow volume, although the magnitude of differences were similar to the simulations using measured rainfall. The McTier Creek watershed was subdivided into 12 subwatersheds and NEXRAD-based rainfall data were generated for each subwatershed. Simulations of streamflow were generated for each subwatershed using NEXRAD-based rainfall and compared with subwatershed simulations using measured rainfall data, which unlike the NEXRAD-based rainfall were the same data for all subwatersheds (derived from a weighted average of the six NWS COOP stations surrounding the basin). For the two simulations, subwatershed streamflow were summed and compared to streamflow simulations at two U.S. Geological Survey streamgages. The percentage differences at the gage near Monetta, South Carolina, were the same for simulations using measured rainfall data and NEXRAD-based rainfall. At the gage near New Holland, South Carolina, the percentage differences using the NEXRAD-based rainfall were twice as much as those using the measured rainfall. Single-mass curve comparisons showed an increase in the total volume of rainfall from north to south. Similar comparisons of the measured rainfall at the NWS COOP stations showed similar percentage differences, but the NEXRAD-based rainfall variations occurred over a much smaller distance than the measured rainfall. Nonetheless, it was concluded that in some cases, using NEXRAD-based rainfall data in TOPMODEL streamflow simulations may provide an effective alternative to using measured rainfa

Feaster, Toby D.; Westcott, Nancy E.; Hudson, Robert J.M.; Conrads, Paul A.; Bradley, Paul M.

2012-01-01

323

The Weather Radar Toolkit, National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center's support of interoperability and the Global Earth Observation System of Systems (GEOSS)  

NASA Astrophysics Data System (ADS)

In February 2005, 61 countries around the World agreed on a 10 year plan to work towards building open systems for sharing geospatial data and services across different platforms worldwide. This system is known as the Global Earth Observation System of Systems (GEOSS). The objective of GEOSS focuses on easy access to environmental data and interoperability across different systems allowing participating countries to measure the "pulse" of the planet in an effort to advance society. In support of GEOSS goals, NOAA's National Climatic Data Center (NCDC) has developed radar visualization and data exporter tools in an open systems environment. The NCDC Weather Radar Toolkit (WRT) loads Weather Surveillance Radar 1988 Doppler (WSR-88D) volume scan (S-band) data, known as Level-II, and derived products, known as Level-III, into an Open Geospatial Consortium (OGC) compliant environment. The application is written entirely in Java and will run on any Java- supported platform including Windows, Macintosh and Linux/Unix. The application is launched via Java Web Start and runs on the client machine while accessing these data locally or remotely from the NCDC archive, NOAA FTP server or any URL or THREDDS Data Server. The WRT allows the data to be manipulated to create custom mosaics, composites and precipitation estimates. The WRT Viewer provides tools for custom data overlays, Web Map Service backgrounds, animations and basic filtering. The export of images and movies is provided in multiple formats. The WRT Data Exporter allows for data export in both vector polygon (Shapefile, Well-Known Text) and raster (GeoTIFF, ESRI Grid, VTK, NetCDF, GrADS) formats. By decoding the various Radar formats into the NetCDF Common Data Model, the exported NetCDF data becomes interoperable with existing software packages including THREDDS Data Server and the Integrated Data Viewer (IDV). The NCDC recently partnered with NOAA's National Severe Storms Lab (NSSL) to decode Sigmet C-band Doppler radar data providing the NCDC Viewer/Data Exporter the functionality to read C-Band. This also supports a bilateral agreement between the United States and Canada for data sharing and to support interoperability with the US WSR-88D and Environment Canada radar networks. In addition, the NCDC partnered with the University of Oklahoma to develop decoders to read a test bed of distributed X- band radars that are funded through the Collaborative Adaptive Sensing of the Atmosphere (CASA) project. The NCDC is also archiving the National Mosaic and Next Generation QPE (Q2) products from NSSL, which provide products such as three-dimensional reflectivity, composite reflectivity and precipitation estimates at a 1 km resolution. These three sources of Radar data are also supported in the WRT.

Ansari, S.; Del Greco, S.

2006-12-01

324

Spaceborne Doppler Precipitation Radar: System Configurations and Performance Analysis  

NASA Technical Reports Server (NTRS)

Knowledge of the global distribution of the vertical velocity of precipitation is important in in the study of energy transportation in the atmosphere, the climate and weather. Such knowledge can only be directly acquired with the use of spaceborne Doppler precipitation radars. Although the high relative speed of the radar with respect to the rainfall particles introduces significant broadening in the Doppler spectrum, recent studies have shown that the average vertical velocity can be measured to acceptable accuracy levels by appropriate selection of radar parameters. Furthermore, methods to correct for specific errors arising from NUBF effects and pointing uncertainties have recently been developed. In this paper we will present the results of the trade studies on the performances of a spaceborne Doppler radar with different system parameters configurations.

Tanelli, Simone; Im, Eastwood

2004-01-01

325

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.

326

NASA Satellite Reveals Heavy Rainfall Patterns in California  

NSDL National Science Digital Library

The collision of a flow of moisture from Hawaii known as a "Pineapple Express" and a persistent low pressure system are wreaking havoc on California weather. This movie shows rain accumulation in San Diego from Jan. 6 through Jan. 11 based on data from the Tropical Rainfall Measuring Mission (TRMM)-based Multisatellite Precipitation Analysis. The accumulation is shown in colors ranging from green (less than 50 mm of rain) through red (200 mm or more). The TRMM satellite, using the worlds only spaceborne rain radar and other microwave instruments, measures rainfall over the ocean. In this case instruments were able to reveal rainfall structure resulting from storms "riding" the actual Pineapple Express extending toward Hawaii, which is beyond the range of conventional land-based National Weather Service radars. In early 1995, a Pineapple Express hit California, contributing to a season of winter storms that killed 27 people and did $3 billion in damages and costs. A Pineapple Express in mid-October 2003 wreaked havoc from south of Seattle to north of Vancouver Island. Flooding forced more than 3,000 people from their homes.

Perkins, Lori; Shirah, Greg; Halverson, Jeff

2005-01-12

327

Generation of Spatially Consistent Rainfall Data  

E-print Network

Spatial-temporal modelling using radar data II: modelling of event sequences 32 3.1 Rain Event Arrivals of spatial rainfall for flood estimation . . . . . . . . . . . . . 8 1.2 Background to rainfall model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2 Spatial-temporal modelling using radar data I: modelling of event interiors 12 2.1 Model

Guillas, Serge

328

Rainfall Modification by Urban Areas: New Perspectives from TRMM  

NASA Technical Reports Server (NTRS)

Data from the Tropical Rainfall Measuring Mission's (TRMM) Precipitation Radar (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 -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. Future work is extending the investigation to Phoenix, Arizona, an arid U.S. city, and several international cities like Mexico City, Johannesburg, and Brasilia. The study establishes the possibility of utilizing satellite-based rainfall estimates for examining rainfall modification by urban areas on global scales and over longer time periods. Such research has implications for weather forecasting, urban planning, water resource management, and understanding human impact on the environment and climate.

Shepherd, J. Marshall; Pierce, Harold F.; Negri, Andrew

2002-01-01

329

Climatology of daily rainfall semivariance in The Netherlands  

NASA Astrophysics Data System (ADS)

Rain gauges can offer high quality rainfall measurements at their location. Networks of rain gauges can offer better insight into the space-time variability of rainfall, but they tend to be too widely spaced for accurate estimates between points. While remote sensing systems, such as radars and networks of microwave links, can offer good insight in the spatial variability of rainfall they tend to have more problems in identifying the correct rain amounts at the ground. A way to estimate the variability of rainfall between gauge points is to interpolate between them using fitted variograms. If a dense rain gauge network is lacking it is difficult to estimate accurate variograms. In this paper a 30-year dataset of daily rain accumulations gathered at 29 automatic weather stations operated by KNMI and a one-year dataset of 10 gauges in a network with a radius of 5 km around CESAR (Cabauw Experimental Site for Atmospheric Research) are employed to estimate variograms. Fitted variogram parameters are shown to vary according to season, closely following simple cosine functions allowing for applications in catchment hydrology and rainfall field generation. Semivariances at short ranges during winter and spring tend to be underestimated, but summer and autumn are well predicted. This climatological semivariance can be employed to estimate the accuracy of the rainfall input to a hydrological model even with only few gauges in a given catchment area.

van de Beek, C. Z.; Leijnse, H.; Torfs, P. J. J. F.; Uijlenhoet, R.

2010-03-01

330

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 migration as a by-product meteorological measurements. Here we use a bird profile extraction algorithm

Haak, Hein

331

Probing the Architecture of the Weathering Zone in a Tropical System in the Rio Icacos Watershed (Puerto Rico) With Drilling and Ground Penetrating Radar (GPR)  

NASA Astrophysics Data System (ADS)

Weathering processes in rapidly eroding systems such as humid tropical environments are complex and not well understood. The interface between weathered material (regolith) and non-weathered material (bedrock) is particularly important in these systems as it influences water infiltration and groundwater flow paths and movement. Furthermore, the spatial distribution of this interface is highly heterogeneous and difficult to image with conventional techniques such as direct coring and drilling. In this work we present results from a preliminary geophysical study in the Luquillo Critical Zone Observatory (LCZO) located in the rain forest in the Luquillo Mountains of northeastern Puerto Rico. The Luquillo Mountains are composed of volcaniclastic rocks which have been uplifted and metamorphosed by the Tertiary Rio Blanco quartz diorite intrusion. The Rio Blanco quartz diorite weathers spheroidally, creating corestones of relatively unweathered material that are surrounded by weathered rinds. A number of boreholes were drilled near the top of the Rio Icacos watershed, where the corestones are thought to be in the primary stages of formation, to constrain the regolith/bedrock interface and to provide an understanding of the depth to which corestones form. The depth of the water table was also a target goal in the project. Drilling reveals that corestones are forming in place, separated by fractures, even to depths of 10s of meters below ground surface. One borehole was drilled to a depth of about 25 meters and intersected up to 7 bedrock blocks (inferred to be incipient corestones) and the water table was measured at about 15 meters. Ground Penetrating Radar surveys were conducted in the same location to determine if GPR images variable thicknesses of saprolite overlying corestones. GPR common offset measurements and common midpoint surveys with 50, 100, and 200 MHz antenna frequencies were combined with borehole drillings in order to constrain geophysical results. We will compare drilling observations to GPR data to understand: 1) the lateral extent of the regolith-bedrock interface; 2) distribution of rindlets or spheroidal fracturing around corestones; and 3) presence and extent of corestones. This work has implications for understanding the rate of weathering advance and changes in permeability across rapidly eroding watersheds.

Orlando, J.; Comas, X.; Mount, G. J.; Brantley, S. L.

2012-12-01

332

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

333

A comparison of NEXRAD WSR-88D radar estimates of rain accumulation with gauge measurements for high- and low-reflectivity horizontal gradient precipitation events.  

SciTech Connect

Radar-estimated rainfall amounts from the NEXRAD Weather Surveillance Radar precipitation accumulation algorithm were compared with measurements from numerous rain gauges (1639 radar versus gauge comparisons). Storm total rain accumulations from 43 rain events from 10 radar sites were analyzed. These rain events were stratified into two precipitation types: (1) high-reflectivity horizontal gradient storms and (2) low-reflectivity horizontal gradient events. Overall, the radar slightly overestimated rainfall accumulations for high-reflectivity gradient cases and significantly underestimated accumulations for low-reflectivity gradient cases. Varying degrees of range effects were observed for these two types of precipitation. For high-reflectivity gradient cases, the radar underestimated rainfall at the nearest ranges, overestimated at the middle ranges, and had fairly close agreements at the farthest ranges. A much stronger range bias was evident for low-reflectivity gradient cases. The radar underestimated rainfall by at least a factor of 2 in the nearest and farthest ranges, and to a somewhat lesser extent at midranges.

Klazura, G. E.; Thomale, J. M.; Kelly, D. S.; Jendrowski, P.; Environmental Research; Univ. of Oklahoma; National Weather Service

1999-11-01

334

Federal Aviation Administration weather program to improve aviation safety  

NASA Technical Reports Server (NTRS)

The implementation of the National Airspace System (NAS) will improve safety services to aviation. These services include collision avoidance, improved landing systems and better weather data acquisition and dissemination. The program to improve the quality of weather information includes the following: Radar Remote Weather Display System; Flight Service Automation System; Automatic Weather Observation System; Center Weather Processor, and Next Generation Weather Radar Development.

Wedan, R. W.

1983-01-01

335

A study of how aerosols affect low-level clouds over the Nordic Countries using MODIS, ground-based, ECMWF and weather radar data.  

NASA Astrophysics Data System (ADS)

Several types of data have been combined to investigate how aerosol particles and meteorological parameters affect microphysical, radiative and precipitation properties of low-level clouds over Sweden and Finland. The cloud data was obtained from the MODIS (Moderate Resolution Imaging Spectrometer) instrument on board the Terra and Aqua satellites. The satellite scenes were screened manually for low-level clouds in limited areas around two background aerosol measurement stations. One of the stations, Vavihill, is located in Southern Sweden (56.01 N 13.9 E) and 9 years of number size distribution data from a DMPS (Differential Mobility Particle Sizer) instrument placed there was used in this study. Hyytil, the other station, is situated in central Finland (61.51 N 24.17 E) and 10 years of DMPS from this station data were analysed. Furthermore, modelled meteorological parameters from the European Centre for Medium-Range Forecasts (ECMWF) as well as ground-based precipitation measurements from the SMHI (Swedish Meteorological and Hydrological Institute) and from FMI (Finish Meteorological Institute) have been used in the study. Also, to be able to estimate precipitation rates in the clouds, weather radar data obtained in the BALTEX (Baltic Sea Experiment) project were utilized. The study includes 229 cases from the Vavihill region and 313 cases from the Hyytil area. The results from both regions show that aerosol concentrations measured at the ground-based stations have significant negative correlations with the effective radius (re) of the low-level clouds. The correlation is stronger when the re at 3.7?m is used rather than that at 2.1?m and the highest correlations are obtained when aerosol number concentrations of particles with sizes above 180 nm are used. The correlations between cloud optical thickness (COT) and aerosol number concentrations are on the other hand are positive but lower than for the re. Also, the COT correlate better with particles at larger size than the re and the strongest correlation occur at aerosol number concentrations of particles above 500 nm. However, the relative humidity at 1000 hPa is the variable that has the strongest correlation with COT. Neither the ground-based precipitation data nor the weather radar data show any significant correlations with the aerosol number concentrations at both stations. Nevertheless, there is a significant but low positive correlation between the re and the strength of the radar reflectivity factor. Hence, the first indirect aerosol effect can be detected in this dataset but not the second indirect aerosol effect.

Sporre, M. K.; Swietlicki, E.; Glantz, P.; Kulmala, M.

2012-04-01

336

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 Mto-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, Herv; Servires, Myriam; Normand, Nicolas

2014-05-01

337

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

338

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; Mkel, Antti

2013-04-01

339

Enviropedia: Introduction to Weather  

NSDL National Science Digital Library

This resource provides an overview of weather, the day-to-day changes in temperature, air pressure, moisture, wind, cloudiness, rainfall and sunshine. Links embedded in the text provide access to descriptions of cloud types and to information on weather hazards such as fog, hurricanes, thunderstorms, and tornadoes. Other topics include meteorology, weather measurements, and weather mapping. Materials are also provided on the water cycle and its elements, such as evaporation, uplift and cooling of air, dew point, condensation, and precipitation.

2007-12-12

340

The Status of the Tropical Rainfall Measuring Mission (TRMM) after 2 Years in Orbit  

NASA Technical Reports Server (NTRS)

The Tropical Rainfall Measuring Mission (TRMM) satellite was launched on November 27, 1997, and data from all the instruments first became available approximately 30 days after launch. Since then, much progress has been made in the calibration of the sensors, the improvement of the rainfall algorithms, in related modeling applications and in new datasets tailored specifically for these applications. This paper reports the latest results regarding the calibration of the TRMM Microwave Imager, (TMI), Precipitation Radar (PR) and Visible and Infrared Sensor (VIRS). For the TMI, a new product is in place that corrects for a still unknown source of radiation leaking in to the TMI receiver. The PR calibration has been adjusted upward slightly (by 0.6 dBZ) to better match ground reference targets, while the VIRS calibration remains largely unchanged. In addition to the instrument calibration, great strides have been made with the rainfall algorithms as well, with the new rainfall products agreeing with each other to within less than 20% over monthly zonally averaged statistics. The TRMM Science Data and Information System (TSDIS) has responded equally well by making a number of new products, including real-time and fine resolution gridded rainfall fields available to the modeling community. The TRMM Ground Validation (GV) program is also responding with improved radar calibration techniques and rainfall algorithms to provide more accurate GV products which will be further enhanced with the new multiparameter 10 cm radar being developed for TRMM validation and precipitation studies. Progress in these various areas has, in turn, led to exciting new developments in the modeling area where Data Assimilation, and Weather Forecast models are showing dramatic improvements after the assimilation of observed rainfall fields.

Kummerow, C.; Simpson, J.; Thiele, O.; Barnes, W.; Chang, A. T. C.; Stocker, E.; Adler, R. F.; Hou, A.; Kakar, R.; Wentz, F.

1999-01-01

341

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

342

Unisys Weather  

NSDL National Science Digital Library

The Unisys weather website offers a host of weather analyses and forecasts. In the Analyses link, visitors can find satellite images as well as surface, upper air, and radar images. Visitors can learn the intricacies of Unisys's many forecast models such as the Nested Grid Model (NGM), Aviation Model, and the Rapid Update Cycle (RUC) Model. Users can find archived hurricane data for the Atlantic, the Eastern Pacific, and the Western Pacific. The site also furnishes archived surface maps, infrared satellite images, upper air charts, and sea surface temperature (SST) plots.

343

Radar-Based Depth Area Reduction Factors for Colorado  

NASA Astrophysics Data System (ADS)

More than 340,000 fifteen-minute storm cells, nearly 45,000 one-hour cells, and over 20,000 three-hour cells found in 21 months of gage adjusted radar-rainfall estimates (GARR) over El Paso County, CO, were identified and evaluated using TITAN (Thunderstorm Identification, Tracking, Analysis and Nowcasting) software. TITAN's storm cell identification capability enabled the analysis of the geometric properties of storms, time step by time step. The gage-adjusted radar-rainfall data set was derived for months containing runoff producing events observed in the Fountain Creek Watershed within El Paso County from 1994-2008. Storm centered Depth Area Reduction Factors (DARFs) were computed and compared to DARFs published by the U.S. National Weather Service (NWS) in Technical Paper 29, which are widely used in stormwater infrastructure design. Radar-based storm centered DARFs decay much more sharply than the NWS standard curves. The results suggest lower watershed average rainfall inputs from radar-based storm centered DARFs than from standard NWS DARFs for a given watershed area. The results also suggest that DARFs are variable by return period and, perhaps, by location. Both findings could have significant impacts on design storm standards. Lower design volumes for a given return period translate to lower capacity requirements and lower cost infrastructure. Conversely, the higher volume requirements implied for the NWS DARFs translate to higher capacity requirements, higher costs, but lower risk of failure. Ultimately, a decision about which approach is to use depends on the risk tolerance of the decision maker. However, the growing volume of historical radar rainfall estimates coupled with the type of analysis described herein, supports a better understanding of risk and more informed decision-making by local officials.

Curtis, D. C.; Humphrey, J. H.; Bare, D.

2011-12-01

344

A method to combine spaceborne radar and radiometric observations of precipitation.  

E-print Network

??This dissertation describes the development and application of a combined radar-radiometer rainfall retrieval algorithm for the Tropical Rainfall Measuring Mission (TRMM) satellite. A retrieval framework (more)

Munchak, Stephen Joseph

2010-01-01

345

On the sensitivity of urban hydrodynamic modelling to rainfall spatial and temporal resolution  

NASA Astrophysics Data System (ADS)

Cities are increasingly vulnerable to floods generated by intense rainfall, because of their high degree of imperviousness, implementation of infrastructures, and changes in precipitation patterns due to climate change. Accurate information of convective storm characteristics at high spatial and temporal resolution is a crucial input for urban hydrological models to be able to simulate fast runoff processes and enhance flood prediction. In this paper, a detailed study of the sensitivity of urban hydrological response to high resolution radar rainfall was conducted. Rainfall rates derived from X-band dual polarimetric weather radar for four rainstorms were used as input into a detailed hydrodynamic sewer model for an urban catchment in Rotterdam, the Netherlands. Dimensionless parameters were derived to compare results between different storm conditions and to describe the effect of rainfall spatial resolution in relation to storm and hydrodynamic model properties: rainfall sampling number (rainfall resolution vs. storm size), catchment sampling number (rainfall resolution vs. catchment size), runoff and sewer sampling number (rainfall resolution vs. runoff and sewer model resolution respectively). Results show catchment smearing effect for rainfall resolution approaching half the catchment size, i.e. for catchments sampling numbers greater than 0.5 averaged rainfall volumes decrease about 20%. Moreover, deviations in maximum water depths, form 10 to 30% depending on the storm, occur for rainfall resolution close to storm size, describing storm smearing effect due to rainfall coarsening. Model results also show the sensitivity of modelled runoff peaks and maximum water depths to the resolution of the runoff areas and sewer density respectively. Sensitivity to temporal resolution of rainfall input seems low compared to spatial resolution, for the storms analysed in this study. Findings are in agreement with previous studies on natural catchments, thus the sampling numbers seem to be promising as an approach to describe sensitivity of hydrological response to rainfall variability for intra-urban catchments and local convective storms. More storms and different urban catchments of varying characteristics need to be analysed in order to validate these findings.

Bruni, G.; Reinoso, R.; van de Giesen, N. C.; Clemens, F. H. L. R.; ten Veldhuis, J. A. E.

2014-06-01

346

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

Microsoft Academic Search

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

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

2008-01-01

347

Quantitative precipitation climatology over the Himalayas by using Precipitation Radar on Tropical Rainfall Measuring Mission (TRMM) and a dense network of rain-gauges  

NASA Astrophysics Data System (ADS)

Quantified grid observation data at a reasonable resolution are indispensable for environmental monitoring as well as for predicting future change of mountain environment. However quantified datasets have not been available for the Himalayan region. Hence we evaluate climatological precipitation data around the Himalayas by using Precipitation Radar (PR) data acquired by the Tropical Rainfall Measuring Mission (TRMM) over 10 years of observation. To validate and adjust these patterns, we used a dense network of rain gauges collected by the Asian PrecipitationHighly Resolved Observational Data Integration Towards Evaluation of Water Resources (APHRODITE Water Resources) project (http://www.chikyu.ac.jp/precip/). We used more than 2600 stations which have more than 10-year monthly precipitation over the Himalayan region (75E-105E, 20-36N) including country data of Nepal, Bangladesh, Bhutan, Pakistan, India, Myanmar, and China. The region we studied is so topographically complicated that horizontal patterns are not uniform. Therefore, every path data of PR2A25 (near-surface rain) was averaged in a 0.05-degree grid and a 10-year monthly average was computed (hereafter we call PR). On the other hand, for rain-gauge, we first computed cell averages if each 0.05-degree grid cell has 10 years observation or more. Here we refer to the 0.05-degree rain-gauge climatology data as RG data. On the basis of comparisons between the RG and PR composite values, we defined the parameters of the regressions to correct the monthly climatology value based on the rain gauge observations. Compared with the RG, the PR systematically underestimated precipitation by 28-38% in summer (July-September). Significant correlation between TRMM/PR and rain-gauge data was found for all months, but the correlation is relatively low in winter. The relationship is investigated for different elevation zones, and the PR was found to underestimate RG data in most zones, except for certain zones in February (250-1000m), March (0-1000m), and April (0-1500m). We depicted the adjusted precipitation climatology based on the TRMM/PR composites. The monthly composite patterns of the TRMM/PR for the 10 years show that the southern foothills of the Himalayas always have a clear rain band, with clear dry areas north of the Himalayas. The double rain bands along the Himalayas are clearly shown, and a rain band with a high maximum appeared in the area of Bhutan (around 27N, 90) in summer monsoon season. Little precipitation is observed on the Himalayas or Tibet at elevations higher than 4800 m. In the summer monsoon season, precipitation over the Tibetan Plateau increases, especially in the east. In the winter season (November-March) in particular, more precipitation is seen west of the Himalayas (north India) and very dry areas are observed to the north. Improvement of the APHRODITE's daily grid precipitation analysis by using this climatology will be shown.

Yatagai, A.

2010-09-01

348

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

349

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

350

Interactive Weather Information Network  

NSDL National Science Digital Library

Offered by the National Oceanic and Atmospheric Administration (NOAA), the Interactive Weather Information Network (IWIN) is a collection of interactive weather maps and satellite images that is updated every five seconds. Visitors can see cloud cover animation loops, NEXRAD Radar images of precipitation, a map of all current weather fronts, and an interactive national map to see information about any particular state. Other information on the site includes a listing of any active weather warnings, a link for world weather data, and more, making this a must-see site for all those users interested in the most current weather happenings anywhere.

2002-01-01

351

Statistical characterization of spatial patterns of rainfall cells in extratropical cyclones  

NASA Astrophysics Data System (ADS)

The assumption of a particular type of distribution of rainfall cells in space is needed for the formulation of several space-time rainfall models. In this study, weather radar-derived rain rate maps are employed to evaluate different types of spatial organization of rainfall cells in storms through the use of distance functions and second-moment measures. In particular the spatial point patterns of the local maxima of rainfall intensity are compared to a completely spatially random (CSR) point process by applying an objective distance measure. For all the analyzed radar maps the CSR assumption is rejected, indicating that at the resolution of the observation considered, rainfall cells are clustered. Therefore a theoretical framework for evaluating and fitting alternative models to the CSR is needed. This paper shows how the "reduced second-moment measure" of the point pattern can be employed to estimate the parameters of a Neyman-Scott model and to evaluate the degree of adequacy to the experimental data. Some limitations of this theoretical framework, and also its effectiveness, in comparison to the use of scaling functions, are discussed.

Bacchi, Baldassare; Ranzi, Roberto; Borga, Marco

1996-11-01

352

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

353

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

354

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

355

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

356

Towards Near Real-time Convective Rainfall Observations over Kenya  

NASA Astrophysics Data System (ADS)

The existing meteorological infrastructure in Kenya is poorly suited for the countrywide real-time monitoring of precipitation. Rainfall radar is not available, and the existing network of rain gauges is sparse and challenging to maintain. This severely restricts Kenya's capacity to warn for, and respond to, weather related emergencies. Furthermore, the lack of accurate rainfall observations severely limits Kenya's climate change adaptation capabilities. Over the past decade, the mobile telephone network in Kenya has expanded rapidly. This network makes extensive use of terrestrial microwave (MW) links, received signal level (RSL) data from which can be used for the calculation of rainfall intensities. We present a novel method for the near-real time observation of convective rainfall over Kenya, based on the combined use of MW RSL data and Meteosat Second Generation (MSG) satellite data. In this study, the variable density rainfall information derived from several MW links is scaled up using MSG data to provide full rainfall information coverage for the region surrounding the links. Combining MSG data and MW link derived rainfall data for several adjacent MW links makes it possible to make the distinction between wet and dry pixels. This allows the disaggregation of the MW link derived rainfall intensities. With the distinction between wet and dry pixels made, and the MW derived rainfall intensities disaggregated, these data can then be used to develop instantaneous empirical relationships linking rainfall intensities to cloud physical properties. These relationships are then used to calculate rainfall intensities for the MSG scene. Since both the MSG and the MW data are available at the same temporal resolution, unique empirical coefficients can be determined for each interval. This approach ensures that changes in convective conditions from one interval to the next are taken into account. Initial results from a pilot study, which took place from November 2012 until January 2013, are presented. The work has been carried out in close cooperation with mobile telephone operator Safaricom, using RSL data from 15 microwave links in rain prone areas in Western Kenya (out of a total of 3000 MW links operated by Safaricom in Kenya). The data supplied by Safaricom consist of the mean, minimum and maximum RSL for each MW link over a 15 minute interval. For this pilot study, use has been made of the MSG Cloud Top Temperature data product from the Royal Dutch Meteorological Institute's MSG Cloud Physical Properties database (http://msgcpp.knmi.nl/).

Hoedjes, Joost; Said, Mohammed; Becht, Robert; Kifugo, Shem; Kooiman, Andr; Limo, Agnes; Maathuis, Ben; Moore, Ian; Mumo, Mark; Nduhiu Mathenge, Joseph; Su, Bob; Wright, Iain

2013-04-01

357

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

358

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 Fuhlsbttel 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 Fuhlsbttel. The observations of radar Fuhlsbttel 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; Mnster, Hans; Ament, Felix

2014-05-01

359

Climatology of daily rainfall semi-variance in The Netherlands  

NASA Astrophysics Data System (ADS)

Rain gauges can offer high quality rainfall measurements at their locations. Networks of rain gauges can offer better insight into the space-time variability of rainfall, but they tend to be too widely spaced for accurate estimates between points. While remote sensing systems, such as radars and networks of microwave links, can offer good insight in the spatial variability of rainfall they tend to have more problems in identifying the correct rain amounts at the ground. A way to estimate the variability of rainfall between gauge points is to interpolate between them using fitted variograms. If a dense rain gauge network is lacking it is difficult to estimate variograms accurately. In this paper a 30-year dataset of daily rain accumulations gathered at 29 automatic weather stations operated by KNMI (Royal Netherlands Meteorological Institute) and a one-year dataset of 10 gauges in a network with a radius of 5 km around CESAR (Cabauw Experimental Site for Atmospheric Research) are employed to estimate variograms. Fitted variogram parameters are shown to vary according to season, following simple cosine functions. Semi-variances at short ranges during winter and spring tend to be underestimated, but semi-variances during summer and autumn are well predicted.

van de Beek, C. Z.; Leijnse, H.; Torfs, P. J. J. F.; Uijlenhoet, R.

2011-01-01

360

Damage Survey, Radar, and Environment Analyses on the First-Ever Documented Tornado in Beijing during the Heavy Rainfall Event of 21 July 2012  

E-print Network

Damage Survey, Radar, and Environment Analyses on the First-Ever Documented Tornado in Beijing the most detailed information in all of the published tornado damage surveys so far in China, this work showed significant evidence that the wind damage was caused by a mesocyclonic tornado rated as a category

Meng, Zhiyong

361

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

362

Remotely-Sensed Rainfall for the Wettest Season in Oklahoma on Record  

NASA Astrophysics Data System (ADS)

In the summer of 2007 Oklahoma experienced the wettest June on record, Oklahoma City had 20 consecutive days of reported rainfall (also a record), and damaging flash floods occurred on 15 days. This study analyzes the spatial patterns, temporal variability, and magnitudes of remotely-sensed rainfall from TRMM satellite, PERSIANN-CCS, and the operational rainfall product in the US National Weather Service (NWS) that relies on radar data with adjustments from rain gauges and human quality control. Conclusions drawn from this part of the study will help guide future steps toward integrated, multisensor precipitation estimation as applied to a season of extreme rainfall. The second part of the study applies the rainfall estimates under evaluation to an extreme flash flood case over the heavily instrumented Ft. Cobb basin in Oklahoma. Discharge is simulated and compared to observed streamflow on three subbasins using the NWS's distributed hydrologic model. Results will help determine if satellite-based rainfall estimates can be used, given proper downscaling, as inputs to hydrologic prediction models for extreme, small-scale hydrometeorological events.

Flamig, Z.; Gourley, J.; Hong, Y.; Li, L.

2009-05-01

363

CESAR Rainfall Experiment 2002 (C-Rex'02) - Experimental Setup and First Results  

NASA Astrophysics Data System (ADS)

The Cabauw Experimental Site for Atmospheric Research (CESAR) is a consortium of major universities and research institutes in The Netherlands involved in research regarding ground-based remote sensing of the atmosphere and of the land surface. The Cabauw site, with its 213 m tower for meteorological observations, has been the centre of experimental research of the atmospheric research group at the KNMI since the early 1970s. In the framework of CESAR, an important collection of ground-based remote sensing devices has been added to the original configuration of in situ instruments. Between early September and the end of December 2002, the Precipitation Research Group within the CESAR consortium has coordinated the CESAR Rainfall Experiment 2002 (C-Rex'02). The objective of the experiment was to characterize the space-time variability of rainfall across a range of scales with a view to the quantitative use of ground-based and space-borne rainfall remote sensors (e.g. (E)GPM). Instruments available during C-Rex'02 included a 3 GHz doppler-polarimetric atmospheric research radar, a 35 GHz cloud radar, a 1 GHz wind profiler, a 5 GHz operational weather radar, a 24 GHz micro doppler rain profiler, a Joss-Waldvogel disdrometer, two optical spectro-pluviometers, a 2-D video disdrometer, and a network of rain gauges. With this extensive configuration of instruments, CESAR seems ideally suited to serve as a ground validation site for the upcoming Global Precipitation Mission (GPM), and its European component EGPM.

Uijlenhoet, R.; Heijnen, S.; Holleman, I.; Hovius, W.; Klein Baltink, H.; Russchenberg, H.; Stricker, H.; Warmer, J.; van der Zwan, F.

2003-04-01

364

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

E-print Network

. INTRODUCTION Weather radars are well known for their ability to detect precipitation at a high spatial and temporal resolution. Precipitation data deduced from reflectivity measurements by weather radars. The wavelength of weather radars is optimized for detection of precipitation and is typically 5 or 10 cm

Stoffelen, Ad

365

Analysis of rain cell size distribution from meteorological radar data for rain attenuation studies  

Microsoft Academic Search

The ability of radar to scan a wide area around the radar site and not just a particular path made it a very attractive for many types of investigations. Radar can be used to measure the rainfall rate indirectly. This is achieved by knowing the radar reflectivity and then converting them into rainfall rate. The S-band frequency of the meteorological

NorHisham Haji Khamis; Jafri Din; T. A. Rahman

2005-01-01

366

Validating NEXRAD MPE and Stage III precipitation products for uniform rainfall on the Upper Guadalupe  

E-print Network

truth to evaluate radar rainfall estimation. This study proposes a new parameter probability of rain-area representativeness error of gauge rainfall is a major concern in assessment of radar rainfall estimation, this study form 7 September 2007; accepted 18 September 2007 KEYWORDS NEXRAD; Stage III; MPE; Rain gauge

Texas at San Antonio, University of

367

Needed weather information where it belongs; in the cockpit  

NASA Technical Reports Server (NTRS)

The availability of inflight weather data to the cockpit is discussed. The need for real-time information systems to warn of hazardous weather conditions is emphasized. It is suggested that the Weather Service severe weather radar network be collocated with the FAA radar to provide information for real-time decision making.

Gatlin, H. G.

1979-01-01

368

National Weather Service: Watch, Warning, Advisory Display  

MedlinePLUS

... Fire Wx Outlooks RSS Feeds E-Mail Alerts Weather Information Storm Reports Exp. Storm Reports NWS Hazards ... National RADAR Product Archive Norman, OK WX NOAA Weather Radio Research Non-op. Products Forecast Tools Svr. ...

369

APPLICATION OF WEATHER RADAR TO FALLOUT PREDICTION. Quarterly Technical Report No. 8 Covering Period December 1, 1960 through February 29, 1960  

Microsoft Academic Search

Much of the emphasis in instrumentation has been directed toward the ; problem of accuracy of radar calibrations and the reliability of standard targets ; for calibration purposes. Both mylar radar mesh balloon covers and small ; aluminum spheres, six inches in diameter, have been tested and deemed ; unsatisfactory because the signal fluctuates widely. The peak values from these

1960-01-01

370

Precipitation estimation and forecasting using radar and rain gage measurements with artificial neural networks  

NASA Astrophysics Data System (ADS)

Quantitative precipitation estimation and forecasting continue to be critical components of the weather research programs. The objective of this dissertation is twofold: First, to propose a method that fuses rainfall measurements from rain gages and radar. Second, to design a technique that produces real-time rainfall forecasts for the next hour. Cokriging is perhaps the most widely used method to fuse measurements from two sensors, for example, radar and rain gages. Here an alternative fusion methodology, based on recent developments in Artificial Neural Networks (ANNs) is presented. ANNs are nonlinear estimators and thus have a distinct advantage over traditional statistical methods. Intercomparison of rainfall estimation, using cokriging and ANN methods, suggests that ANNs provide a more attractive and robust fusion from radar and rain gages for several storms from Oklahoma. It is shown that simply nowcasting the fused estimates gives better forecasts than the traditional nowcasting with radar data. Moreover, the rainfall field at the next hour is predicted with a methodology that is based on radial-basis ANNs. The advantage of this method is that it provides a framework for the automated segmentation of the rainfall field in rainfall clusters that have their own advection vectors. Each cluster is shifted individually for the prediction step. Thus, the method accounts for nonhomogeneous advection conditions. The results show that this method has the capability to generate improved predictions compared to nowcasting. It appears that its full strength will be realized if a data set with a temporal resolution finer than hourly is used. In summary, an integrated ANN approach has been produced that estimates rainfall from two sensors and produces a forecast. In the appendix I also include a study on the nature of long-range rainfall and streamflow correlations, using a method called Detrended Fluctuation Analysis. The findings show the existence of power-law correlations in both variables. Moreover, it is shown that what controls the correlation structure is not the actual rainfall values, but the pattern of alternating wet and dry spells. The employed method also highlights the dampening effect of the soil in the transformation of rainfall to streamflow.

Matsoukas, Christos

2000-11-01

371

Radar applications  

NASA Astrophysics Data System (ADS)

Papers are presented on air-traffic control radar, surveillance radar, missile guidance radar, and high-performance tactical three-dimensional radar. Also considered are the airborne early warning radar, the Foxhunter airborne intercept radar, and environmental remote sensing. Other topics include spaceborne SARs, the Pioneer Orbiter radar, and a bistatic pulse-Doppler intruder-detection radar.

Skolnik, Merrill I.

372

Radar applications  

Microsoft Academic Search

Papers are presented on air-traffic control radar, surveillance radar, missile guidance radar, and high-performance tactical three-dimensional radar. Also considered are the airborne early warning radar, the Foxhunter airborne intercept radar, and environmental remote sensing. Other topics include spaceborne SARs, the Pioneer Orbiter radar, and a bistatic pulse-Doppler intruder-detection radar.

Merrill I. Skolnik

1988-01-01

373

LDAR observations of a developing thunderstorm correlated with field mill, ground strike location, and weather radar data including the first report of the design and capabilities of a new, time-of-arrival Ground-strike Location System (GSLS)  

NASA Technical Reports Server (NTRS)

An experiment designed to observe and measure a thunderstorm prior to, during, and after its development over the Kennedy Space Center was successful. Correlated measurements of airborne field strength, ground-based field strength, LDAR lightning discharge location in the clouds, weather radar percipitation echoes, plus ground strike location with the new KSC Ground Strike Location System (GSLS) were gathered, and reported. This test marks the first operational use of the GSLS System, and this report contains the first report of its design and capabilities.

Poehler, H. A.

1978-01-01

374

Plymouth State Weather Center  

NSDL National Science Digital Library

The Plymouth State Weather Center provides a variety of weather information, including a tropical weather menu with current and archived data on tropical depressions, storms, or hurricanes in the Atlantic or Eastern Pacific Oceans. An interactive Weather Product Generator allows students to make their own surface data maps and meteograms (24-hour summaries of weather at a specific location), and view satellite imagery. There are also interactive weather maps for the U.S., Canada, and Alaska that display the latest observations, and text servers which provide current written observations for New England and North America. A set of past and current weather data products provides information on minimum and maximum temperatures, wind chill, and heat index. In addition, there are collections of satellite loops/movies, radar/lightning images, loops, and movies, and a set of tutorials on clouds, the sun and its effects on the environment, and balanced atmospheric flows.

375

Dynamical linkage of tropical and subtropical weather systems to the intraseasonal oscillations of the Indian summer monsoon rainfall. Part II: Simulations in the ENSEMBLES project  

NASA Astrophysics Data System (ADS)

We assess the ability of individual models (single-model ensembles) and the multi-model ensemble (MME) in the European Union-funded ENSEMBLES project to simulate the intraseasonal oscillations (ISOs; specifically in 10-20-day and 30-50-day frequency bands) of the Indian summer monsoon rainfall (ISMR) over the Western Ghats (WG) and the Bay of Bengal (BoB), respectively. This assessment is made on the basis of the dynamical linkages identified from the analysis of observations in a companion study to this work. In general, all models show reasonable skill in simulating the active and break cycles of the 30-50-day ISOs over the Indian summer monsoon region. This skill is closely associated with the proper reproduction of both the northward propagation of the intertropical convergence zone (ITCZ) and the variations of monsoon circulation in this band. However, the models do not manage to correctly simulate the eastward propagation of the 30-50-day ISOs in the western/central tropical Pacific and the eastward extension of the ITCZ in a northwest to southeast tilt. This limitation is closely associated with a limited capacity of models to accurately reproduce the magnitudes of intraseasonal anomalies of both the ITCZ in the Asian tropical summer monsoon regions and trade winds in the tropical Pacific. Poor reproduction of the activity of the western Pacific subtropical high on intraseasonal time scales also amplify this limitation. Conversely, the models make good reproduction of the WG 10-20-day ISOs. This success is closely related to good performance of the models in the representation of the northward propagation of the ITCZ, which is partially promoted by local air-sea interactions in the Indian Ocean in this higher-frequency band. Although the feature of westward propagation is generally represented in the simulated BoB 10-20-day ISOs, the air-sea interactions in the Indian Ocean are spuriously active in the models. This leads to active WG rainfall, which is not present in the observed BoB 10-20-day ISOs. Further analysis indicates that the intraseasonal variability of the ISMR is generally underrepresented in the simulations. Skill of the MME in seasonal ISMR forecasting is strongly dependent on individual model performance. Therefore, in order to improve the model skill with respect to seasonal ISMR forecasting, we suggest it is necessary to better represent the robust dynamical links between the ISOs and the relevant circulation variations, as well as the proportion of intraseasonal variability in the individual models.

Ma, Shujie; Rod, Xavier; Song, Yongjia; Cash, Benjamin A.

2012-09-01

376

Exploring and Validating CASA Radars' Potential in Water Resources  

E-print Network

at UMass, will be compared with precipitation data from other rain gauges and radars in the area to show MA and weaknesses by comparing its data to that from other radars and rain gauges data within its range. Figure 6 validate the MA1 radar. The data should also be compared against NWS radar based rainfall estimation

Mountziaris, T. J.

377

The development of an hourly gridded rainfall product for hydrological applications in England and Wales  

NASA Astrophysics Data System (ADS)

This research presents a newly developed observed sub-daily gridded precipitation product for England and Wales. Importantly our analysis specifically allows a quantification of rainfall errors from grid to the catchment scale, useful for hydrological model simulation and the evaluation of prediction uncertainties. Our methodology involves the disaggregation of the current one kilometre daily gridded precipitation records available for the United Kingdom[1]. The hourly product is created using information from: 1) 2000 tipping-bucket rain gauges; and 2) the United Kingdom Met-Office weather radar network. These two independent datasets provide rainfall estimates at temporal resolutions much smaller than the current daily gridded rainfall product; thus allowing the disaggregation of the daily rainfall records to an hourly timestep. Our analysis is conducted for the period 2004 to 2008, limited by the current availability of the datasets. We analyse the uncertainty components affecting the accuracy of this product. Specifically we explore how these uncertainties vary spatially, temporally and with climatic regimes. Preliminary results indicate scope for improvement of hydrological model performance by the utilisation of this new hourly gridded rainfall product. Such product will improve our ability to diagnose and identify structural errors in hydrological modelling by including the quantification of input errors. References [1] Keller V, Young AR, Morris D, Davies H (2006) Continuous Estimation of River Flows. Technical Report: Estimation of Precipitation Inputs. in Agency E (ed.). Environmental Agency.

Liguori, Sara; O'Loughlin, Fiachra; Souvignet, Maxime; Coxon, Gemma; Freer, Jim; Woods, Ross

2014-05-01

378

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

379

Multi-resolution rainfall modelling in Alpine watersheds  

NASA Astrophysics Data System (ADS)

Distributed hydrological modelling in Alpine watersheds needs high-resolution (~1~km in space, 1~h in time) rainfall input. Typical grid-spacings of operational limited area weather prediction models are 10~km. Therefore, further downscaling of the precipitation fields is necessary. Here, we propose an example of a parsimonious anisotropic micro-canonical multiplicative random cascade model for stochastic downscaling. Its scaling characteristics will be discussed and scaling parameters will be estimated by multi-resolution analysis of radar data. In forecast mode the deterministic limited area prediction fields have to be augmented into higher-resolution scales by stochastic downscaling in a consistent way. This will be discussed and deterministic/stochastic precipitation fields with different effective resolution (1 to 40~km) are applied in hydrological modelling experiments in an Alpine watershed (total area: 2627~km^2). The impact of precipitation resolution on hydrological modelling will be shown.

Ahrens, B.

2003-04-01

380

Oceanic rainfall off the Pacific Northwest Coast  

NASA Astrophysics Data System (ADS)

Rainfall within 55 km of the northwest coast of the United States was measured from a buoy and estimated from weather reports at lightships. Results show that precipitation at sea was only about one half to one third of that found at coastal land stations. Rainfall typically occurs both at sea and on shore on the same days but for fewer hours at sea. The relative amount at sea seems to vary with the type of atmospheric system producing the rainfall.

Elliott, William P.; Reed, R. K.

1973-02-01

381

Space-time simulation of intermittent rainfall with prescribed advection field: Adaptation of the turning band method  

NASA Astrophysics Data System (ADS)

Space-time rainfall simulation is useful to study questions like, for instance, the propagation of rainfall-measurement uncertainty in hydrological modeling. This study adapts a classical Gaussian field simulation technique, the turning-band method, in order to produce sequences of rainfall fields satisfying three key features of actual precipitation systems: (i) the skewed point distribution and the space-time structure of nonzero rainfall (NZR); (ii) the average probability and the space-time structure of intermittency; and (iii) a prescribed advection field. The acronym of our simulator is SAMPO, for simulation of advected mesoscale precipitations and their occurrence. SAMPO assembles various theoretical developments available from the literature. The concept of backtrajectories introduces a priori any type of advection field in the heart of the turning band method (TBM). TBM outputs transformation into rainfall fields with a desired structure is controlled using Chebyshev-Hermite polynomial expansion. The intermittency taken as a binary process statistically independent of the NZR process allows the use of a common algorithm for both processes. The 3-D simulation with a space-time anisotropy captures important details of the precipitation kinematics summarized by the Taylor velocity of both NZR and intermittency. A case study based on high-resolution weather radar data serves as an example of model inference. Illustrative simulations revisit some classical questions about rainfall variography like the influence of advection or intermittency. They also show the combined role of Taylor's and advection velocities.

Leblois, Etienne; Creutin, Jean-Dominique

2013-06-01

382

Catastrophic rainfall from an upslope thunderstorm in the central Appalachians: The Rapidan Storm of June 27, 1995  

NASA Astrophysics Data System (ADS)

A storm system near the Blue Ridge Mountains of Virginia produced peak rainfall accumulations exceeding 600 mm in a 6-hour period during the morning and early afternoon of June 27, 1995. The peak flood discharge of 3,000 m3 s-1 on the Rapidan River at a drainage area of 295 km2 places this event on the envelope curve of flood discharge for the United States east of the Mississippi River. Observations of radar reflectivity factor and Doppler velocity made by the Sterling, Virginia, WSR-88D (Weather Surveillance Radar-1988 Doppler) are used for analyses of the storm. The temporal and spatial variability of rainfall are examined on a 1-km grid scale and 6-min timescale. Like many heavy rainfall events, storm motion played a key role in the production of heavy rainfall for the Rapidan storm. Storm motion and storm evolution for the Rapidan storm were closely linked to topographic features at the scale of the ridges which extend southward from the Blue Ridge and delineate the Rapidan basin. Key elements of the storm environment included strong boundary layer winds directed upslope toward the Blue Ridge, weak upper level winds, high precipitable water values, and a near-saturated atmospheric column up to 6 km. An important element of storm structure was the low-reflectivity centroid of the storm. This feature of the storm was related both to the exceptional rainfall rates of the storm and to the underestimation of storm total rainfall by the operational WS-88D precipitation products. Components of the atmospheric and land surface water budgets are derived. The cumulative discharge from the Rapidan River was 0.87108 m3 (296 mm over the 295-km2 catchment). The storm total precipitation for the Rapidan basin was 1.01108 m3 (344 mm over the catchment). The precipitation efficiency of the storm, that is, the ratio of storm total rainfall to atmospheric water vapor inflow, was approximately 90%.

Smith, James A.; Baeck, Mary Lynn; Steiner, Matthias; Miller, Andrew J.

1996-10-01

383

Absolute Calibration of Radar Reflectivity Using Redundancy of the Polarization Observations and Implied Constraints on Drop Shapes  

E-print Network

form 9 October 2008) ABSTRACT A major limitation of improved radar-based rainfall estimation of radar-based rain rates is limited by the calibration of radar reflectivity ZH, which must be measured within 1 dB for rainfall estimates to have an accuracy of 15%. Several approaches to radar calibra- tion

Reading, University of

384

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

385

A Copula Based Space-Time Rainfall Simulation Model  

NASA Astrophysics Data System (ADS)

Stochastically generated rainfall data are used as input to hydrological and meteorological models to assess model uncertainties and climate variability in water resources systems. Currently, there are very well defined methods to generate time series of rainfall data for a single point. However, hydrological and meteorological modeling over large scales requires high resolution rainfall data to capture temporal and spatial variability of rainfall that is proven to affect the quality of hydrological predictions (Osborn and Reynolds, 1963; Osborn and Keppel, 1966; Rodda, 1967; Dawdy and Bergman, 1969, Seliga et al., 1992; Corradini and Singh, 1985; Obled et al., 1994; Troutman, 1983; Hamlin, 1983; Faures et al., 1995; Shah et al., 1996, Goodrich et al., 1995). In this paper a copula base space-time rainfall simulation model is introduced for simulation of two-dimensional rainfall field based on observed radar data. In contrast with most rainfall simulation techniques, which describe the spatial dependence structure of rainfall fields with a covariance function or a variogram, we introduce spatial dependence without the influence of the marginal distribution using copula. Radar data of the state of Baden-Wrttemberg in Germany with temporal resolution of 5min and spatial resolution of 1 km2 are used in this study. Gaussian copula and a number of non-Gaussian copulas are used to describe the dependency structure of radar rainfall data. For each radar image, realizations of radar rainfall patters are simulated. The simulation technique used in this work preserves the spatial dependence structure as well and temporal variability of simulated fields similar to the observed radar data. Each simulated realization is then used as input to a hydrological model resulting in an ensemble of predicted runoff hydrographs. The main conclusions are: (a) copula techniques can be used to describe the spatial dependence structure or rainfall fields instead of a simple covariance function; (b) rainfall is not Gaussian and using Gaussian based simulation techniques lead to unrealistic simulated fields.

Aghakouchak, A.; Brdossy, A.; Habib, E.

2008-05-01

386