The Experts below are selected from a list of 11802 Experts worldwide ranked by ideXlab platform
Felix Ament - One of the best experts on this subject based on the ideXlab platform.
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performance of high resolution x band weather radar networks the pattern example
Atmospheric Measurement Techniques, 2014Co-Authors: Katharina Lengfeld, Marco Clemens, Hans Munster, Felix AmentAbstract:Abstract. This publication intends to prove that a network of low-cost local area weather radars (LAWR) is a reliable and scientifically valuable complement to nationwide radar networks. A network of four LAWRs has been installed in northern Germany within the framework of the Precipitation and Attenuation Estimates from a High-Resolution Weather Radar Network (PATTERN) project observing precipitation with a temporal resolution of 30 s, a range resolution of 60 m and a sampling resolution of 1° in the azimuthal direction. The network covers an area of 60 km × 80 km. In this paper, algorithms used to obtain undisturbed precipitation Fields from raw Reflectivity data are described, and their performance is analysed. In order to correct operationally for background noise in Reflectivity measurements, noise level estimates from the measured Reflectivity Field are combined with noise levels from the last 10 time steps. For detection of non-meteorological echoes, two different kinds of clutter algorithms are applied: single-radar algorithms and network-based algorithms. Besides well-established algorithms based on the texture of the logarithmic Reflectivity Field (TDBZ) or sign changes in the Reflectivity gradient (SPIN), the advantage of the unique features of the high temporal and spatial resolution of the network is used for clutter detection. Overall, the network-based clutter algorithm works best with a detection rate of up to 70%, followed by the classic TDBZ filter using the texture of the logarithmic Reflectivity Field. A comparison of a Reflectivity Field from the PATTERN network with the product from a C-band radar operated by the German Meteorological Service indicates high spatial accordance of both systems in the geographical position of the rain event as well as Reflectivity maxima. Long-term statistics from May to September 2013 prove very good accordance of the X-band radar of the network with C-band radar, but, especially at the border of precipitation events, higher-resolved X-band radar measurements provide more detailed information on precipitation structure because the 1 km range gate of C-band radars is only partially covered with rain. The standard deviation within a range gate of the C-band radar with a range resolution of 1 km is up to 3 dBZ at the borders of rain events. The probability of detection is at least 90%, the false alarm ratio less than 10% for both systems. Therefore, a network of high-resolution low-cost LAWRs can give valuable information on the small-scale structure of rain events in areas of special interest, e.g. urban regions, in addition to the nationwide radar networks.
Kenneth W Howard - One of the best experts on this subject based on the ideXlab platform.
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radar based quantitative precipitation estimation for the cool season in complex terrain case studies from the noaa hydrometeorology testbed
Journal of Hydrometeorology, 2012Co-Authors: Jian Zhang, David E Kingsmill, Kenneth W HowardAbstract:AbstractThis study explores error sources of the National Weather Service operational radar-based quantitative precipitation estimation (QPE) during the cool season over the complex terrain of the western United States. A new, operationally geared radar QPE was developed and tested using data from the National Oceanic and Atmospheric Administration Hydrometeorology Testbed executed during the 2005/06 cool season in Northern California. The new radar QPE scheme includes multiple steps for removing nonprecipitation echoes, constructing a seamless hybrid scan Reflectivity Field, applying vertical profile of Reflectivity (VPR) corrections to the Reflectivity, and converting the Reflectivity into precipitation rates using adaptive Z–R relationships. Specific issues in radar rainfall accumulations were addressed, which include wind farm contaminations, blockage artifacts, and discontinuities due to radar overshooting. The new radar QPE was tested in a 6-month period of the 2005/06 cool season and showed signifi...
Matthew R Clark - One of the best experts on this subject based on the ideXlab platform.
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doppler radar observations of mesovortices within a cool season tornadic squall line over the uk
Atmospheric Research, 2011Co-Authors: Matthew R ClarkAbstract:Abstract On 7 December 2006 a tornado of T5 (F2) intensity struck northwest London injuring six people and damaging over 200 houses. In this paper, the squall line responsible for the tornado is analysed using Reflectivity and radial wind data obtained from Met Office Doppler radars. The environment of the squall line is also analysed using available observations. The squall line developed in a weakly unstable polar maritime airmass to the rear of an active cold front and south of a deep depression moving eastwards over northern Scotland. The tornado was associated with a strong vortex of approximately 2–4 km diameter which formed along the leading edge of a bowing segment embedded within the squall line. The tornado occurred close to the time of maximum vortex strength, which followed a short period of rapid vortex intensification. This vortex was one of the strongest, and the longest-lived, of a number of mesovortices traceable in the Doppler radial velocity Field for periods of up to 75 min. Mature vortices were often associated with characteristic ‘broken-S’ signatures in the Reflectivity Field, with inflow notches to their north and localised line-bowing to the south. Velocity couplets were also observed in the radial velocity Field, especially when vortices were located within 50 km range of the radar. The presence of cyclonic and anti-cyclonic vortex pairs early in the evolution of at least one cyclonic vortex, straddling a small bulging section in the leading edge of the line, suggests that localised tilting of the ambient horizontal vorticity was the most likely vortex-genesis mechanism. The analysis reveals that individual vortices developed and evolved rapidly, suggesting that in similar cases, the issuance of tornado warnings based on the detection of individual vortices may result in limited success. However, a tendency for stronger and longer-lived vortices to form along and north of the bowing line segment was observed. In similar cases this could prove useful for identification of sections within a given squall line most prone to stronger mesovortex development, with their attendant risk of localised damaging winds.
Jian Zhang - One of the best experts on this subject based on the ideXlab platform.
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radar based quantitative precipitation estimation for the cool season in complex terrain case studies from the noaa hydrometeorology testbed
Journal of Hydrometeorology, 2012Co-Authors: Jian Zhang, David E Kingsmill, Kenneth W HowardAbstract:AbstractThis study explores error sources of the National Weather Service operational radar-based quantitative precipitation estimation (QPE) during the cool season over the complex terrain of the western United States. A new, operationally geared radar QPE was developed and tested using data from the National Oceanic and Atmospheric Administration Hydrometeorology Testbed executed during the 2005/06 cool season in Northern California. The new radar QPE scheme includes multiple steps for removing nonprecipitation echoes, constructing a seamless hybrid scan Reflectivity Field, applying vertical profile of Reflectivity (VPR) corrections to the Reflectivity, and converting the Reflectivity into precipitation rates using adaptive Z–R relationships. Specific issues in radar rainfall accumulations were addressed, which include wind farm contaminations, blockage artifacts, and discontinuities due to radar overshooting. The new radar QPE was tested in a 6-month period of the 2005/06 cool season and showed signifi...
Katharina Lengfeld - One of the best experts on this subject based on the ideXlab platform.
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performance of high resolution x band weather radar networks the pattern example
Atmospheric Measurement Techniques, 2014Co-Authors: Katharina Lengfeld, Marco Clemens, Hans Munster, Felix AmentAbstract:Abstract. This publication intends to prove that a network of low-cost local area weather radars (LAWR) is a reliable and scientifically valuable complement to nationwide radar networks. A network of four LAWRs has been installed in northern Germany within the framework of the Precipitation and Attenuation Estimates from a High-Resolution Weather Radar Network (PATTERN) project observing precipitation with a temporal resolution of 30 s, a range resolution of 60 m and a sampling resolution of 1° in the azimuthal direction. The network covers an area of 60 km × 80 km. In this paper, algorithms used to obtain undisturbed precipitation Fields from raw Reflectivity data are described, and their performance is analysed. In order to correct operationally for background noise in Reflectivity measurements, noise level estimates from the measured Reflectivity Field are combined with noise levels from the last 10 time steps. For detection of non-meteorological echoes, two different kinds of clutter algorithms are applied: single-radar algorithms and network-based algorithms. Besides well-established algorithms based on the texture of the logarithmic Reflectivity Field (TDBZ) or sign changes in the Reflectivity gradient (SPIN), the advantage of the unique features of the high temporal and spatial resolution of the network is used for clutter detection. Overall, the network-based clutter algorithm works best with a detection rate of up to 70%, followed by the classic TDBZ filter using the texture of the logarithmic Reflectivity Field. A comparison of a Reflectivity Field from the PATTERN network with the product from a C-band radar operated by the German Meteorological Service indicates high spatial accordance of both systems in the geographical position of the rain event as well as Reflectivity maxima. Long-term statistics from May to September 2013 prove very good accordance of the X-band radar of the network with C-band radar, but, especially at the border of precipitation events, higher-resolved X-band radar measurements provide more detailed information on precipitation structure because the 1 km range gate of C-band radars is only partially covered with rain. The standard deviation within a range gate of the C-band radar with a range resolution of 1 km is up to 3 dBZ at the borders of rain events. The probability of detection is at least 90%, the false alarm ratio less than 10% for both systems. Therefore, a network of high-resolution low-cost LAWRs can give valuable information on the small-scale structure of rain events in areas of special interest, e.g. urban regions, in addition to the nationwide radar networks.