IEE Colloquium on Radio Communications at Microwave and Millimetre Wave Frequencies, 1996
New microwave or millimetre communication systems are designed to use dual-polarisation channels ... more New microwave or millimetre communication systems are designed to use dual-polarisation channels in order to increase the communication capacity without increasing the bandwidth. Even at 38 GHz, which is increasingly being brought into use, since its allocation for the interconnections of PCN base stations, the potential use of both horizontal and vertical polarisations has attracted much attention. A study of rain-induced depolarisation at 38 GHz is presented, including the effects of various rainfall rates, raindrop shape models, and water temperatures. The intervening medium between the two terminals is assumed to have constant rainfall rate and the cross-polar effects are evaluated for various link separations and for various rain intensities. Additionally, data obtained from the Chilbolton radar are used and the depolarisation effects due to typical precipitation events are assessed. (7 pages)
Comprehensive analysis of an unusual graupel-shower event recorded by an S-band polarimetric rada... more Comprehensive analysis of an unusual graupel-shower event recorded by an S-band polarimetric radar and two optical-imaging surface instruments is presented. The primary radar characteristic was negative differential reflectivity Zdr values along a vertical column. During the afternoon hours of 16 February 2015, a sequence of three showers that were composed primarily of small (8–15-mm diameter) graupel affected the ground instrumentation site that was established for the Multi-Angle Snowflake Camera and Radar (MASCRAD) experiment in the high plains of Colorado. While these showers passed the instrumentation site, the CSU–CHILL radar conducted high-time-resolution (~2.5-min cycle time) range–height indicator (RHI) scans from a range of 13 km. The RHI data show that the negative Zdr values extended vertically through much of the reflectivity cores, implying that the reflectivity-weighted mean axis ratios of the graupel particles in this event remained somewhat prolate throughout their...
Examines one aspect of the CCIR model, namely the difference in transmission loss between forward... more Examines one aspect of the CCIR model, namely the difference in transmission loss between forward and back scatter statistics. This difference is predicted by the model at low time percentages because of the difference in path attenuation inside the raincell. For the back scatter case, the transmission loss includes contributions from the scatter off the near-edge of the rain cell, which suffers very little attenuation within the cell itself. This contribution increases in importance for higher rain rates. The corresponding contribution for the forward scatter, however, will always include this component of attenuation, the magnitude of which generally increases with rain rate, and it is this factor which causes the predicted forward scatter transmission loss to be significantly higher than the back scatter transmission loss for high rain rates. The predicted asymmetry is examined by simulating hydrometeor scatter events using the data obtained from the 3 GHz dual-polarisation radar...
For radar simulations to play an important role in investigating hydrometeor scattering, they hav... more For radar simulations to play an important role in investigating hydrometeor scattering, they have to be validated against experimental measurements. If this can be achieved, then an existing database can be used to evaluate interference for any arbitrary scatter configuration, without undue restrictions to its validity. The authors describe, and present some preliminary results from, such a comparative study made at 17.8 GHz. The bistatic measurements were made on a 48 km rain scatter link and the corresponding radar data were obtained using the 3 GHz dual-polarisation radar based at Chilbolton. They include the methodology and discuss various factors which need consideration in the evaluation of bistatic scatter.
Radar can play two important roles in studies of rain-induced propagation effects on communicatio... more Radar can play two important roles in studies of rain-induced propagation effects on communications systems. Analysis of individual events an lead to a better understanding of the physical mechanisms involved, whilst a large database can be used to provide statistical information by simulating particular systems. Both approaches provide valuable information relevant to the modelling process. The successful launch of the Olympus satellite has provided a new opportunity to investigate the effects of rain and other hydrometeors on slant path propagation. Of particular interest will be the higher frequencies of 20 and 30 GHz, where even light precipitation can cause significant attenuation. The paper presents some early comparisons between radar estimates of attenuation along an actual satellite path, and direct measurements, both at 30 GHz. There are two general aims. One is to assess the ability of the Chilbolton radar to predict attenuation at this frequency, and the second is to ide...
IEE Colloquium on Remote Sensing of the Propagation Environment, 1996
The Rutherford Appleton Laboratory (RAL) is engaged in an experimental program to characterise pr... more The Rutherford Appleton Laboratory (RAL) is engaged in an experimental program to characterise precipitation in the tropics. We have developed and built a 3 GHz vertically pointing pulsed Doppler radar capable of measuring the co-polar reflectivity (Z), cross-polar reflectivity (LDR) and the full Doppler spectrum. The system has been installed at the University of Technology (Unitech) at Lae, Papua New Guinea. The radar system began a measurement campaign in December 1995. Unitech operates a receiver for the 12.75 GHz beacon of the Australian OPTUS-B satellite. The elevation angle of the satellite receiver is 72.8/spl deg/. The experiment yields valuable data on the slant path attenuation for comparison with radar predictions. The three principal parameters which are to be extracted from the radar data are the rainfall rate, the rain height and the rain drop-size distribution. The drop-size distribution is also being measured on the ground with a Jess distrometer. The rain events recorded with the radar can generally be classified into i) those which exhibit a clear, well defined bright band caused by the presence of the melting layer in stratiform precipitation, and ii) those which are convective with rain at heights often above 10 km and the Doppler data showing severe updrafts. The linear de-polarisation ratio (LDR) parameter is an excellent indicator of the melting layer which is an effective method of determining the top of the rain.
Accurate mathematical models of microwave propagation over Earth-space paths are essential for su... more Accurate mathematical models of microwave propagation over Earth-space paths are essential for successful design of satellite communications schemes. Whilst reliable models exist for temperate climates, little data are available to validate prediction procedures for the tropics. As satcomms terminals are rapidly proliferating in these regions, there is an urgent requirement to test current ITU-R recommendations against actual measurements. The most significant propagation impairments are attenuation, depolarisation and scattering, causing reduced circuit availability, and potentially resulting in cochannel interference. Though these effects are experienced at temperate latitudes, they are particularly severe in the tropics, due to the intensity of precipitation. We present design considerations for, and initial observations from, a polarimetric-Doppler radar deployed in Papua New Guinea for research on propagation effects caused by intense tropical precipitation. (5 pages)
This article presents the data collected and analyzed using the University of Iowa’s X-band polar... more This article presents the data collected and analyzed using the University of Iowa’s X-band polarimetric (XPOL) radars that were part of the spring 2013 hydrology-oriented Iowa Flood Studies (IFloodS) field campaign, sponsored by NASA’s Global Precipitation Measurement (GPM) Ground Validation (GV) program. The four mobile radars have full scanning capabilities that provide quantitative estimation of the rainfall at high temporal and spatial resolutions over experimental watersheds. IFloodS was the first extensive test of the XPOL radars, and the XPOL radars demonstrated their field worthiness during this campaign with 46 days of nearly uninterrupted, remotely monitored, and controlled operations. This paper presents detailed postcampaign analyses of the high-resolution, research-quality data that the XPOL radars collected. The XPOL dual-polarimetric products and rainfall are compared with data from other instruments for selected diverse meteorological events at high spatiotemporal r...
ABSTRACT Spatial correlations of two of the main rain drop-size distribution (DSD) parameters - n... more ABSTRACT Spatial correlations of two of the main rain drop-size distribution (DSD) parameters - namely the median-volume diameter (Do) and the normalized intercept parameter (Nw) - as well as rainfall rate (R) are determined from polarimetric radar measurements, with added information from 2D video disdrometer (2DVD) data. Two cases have been considered, (i) a widespread, long-duration rain event in Huntsville, Alabama, and (ii) an event with localized intense rain-cells within a convection line which occurred during the MC3E campaign. For the first case, data from a C-band polarimetric radar (ARMOR) were utilized, with two 2DVDs acting as 'ground-truth', both being located at the same site 15 km from the radar. The radar was operated in a special "near-dwelling" mode over the 2DVDs. In the second case, data from an S-band polarimetric radar (NPOL) data were utilized, with at least five 2DVDs located between 20 and 30 km from the radar. In both rain event cases, comparisons of Do, log10(Nw) and R were made between radar derived estimates and 2DVD-based measurements, and were found to be in good agreement, and in both cases, the radar data were subsequently used to determine the spatial correlations. For the first case, the spatial decorrelation distance was found to be smallest for R (4.5 km), and largest for Do (8.2 km). For log10(Nw) it was 7.2 km (Fig. 1). For the second case, the corresponding decorrelation distances were somewhat smaller but had a directional dependence. In Fig. 2, we show an example of Do comparisons between NPOL based estimates and 1-minute DSD based estimates from one of the five 2DVDs.
ABSTRACT Conference code: 90735, Export Date: 20 June 2013, Source: Scopus, Art. No.: 6206650, :d... more ABSTRACT Conference code: 90735, Export Date: 20 June 2013, Source: Scopus, Art. No.: 6206650, :doi 10.1109/EuCAP.2012.6206650, Language of Original Document: English, Correspondence Address: Capsoni, C.; Dipartimento di Elettronica e Informazione, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133, Milan, Italy; email: capsoni@elet.polimi.it, References: (2003), http://badc.nerc.ac.uk/data/nimrod/, Rain radar Products (NIMROD) British Atmospheric Data Centre. Accessed on January 2011Bringi, V.N., Chandrasekar, V., (2001) Polarimetric Doppler Weather Radar, , 1 st ed., New York, USA, Cambridge university press;
IEE Colloquium on Radio Communications at Microwave and Millimetre Wave Frequencies, 1996
New microwave or millimetre communication systems are designed to use dual-polarisation channels ... more New microwave or millimetre communication systems are designed to use dual-polarisation channels in order to increase the communication capacity without increasing the bandwidth. Even at 38 GHz, which is increasingly being brought into use, since its allocation for the interconnections of PCN base stations, the potential use of both horizontal and vertical polarisations has attracted much attention. A study of rain-induced depolarisation at 38 GHz is presented, including the effects of various rainfall rates, raindrop shape models, and water temperatures. The intervening medium between the two terminals is assumed to have constant rainfall rate and the cross-polar effects are evaluated for various link separations and for various rain intensities. Additionally, data obtained from the Chilbolton radar are used and the depolarisation effects due to typical precipitation events are assessed. (7 pages)
Comprehensive analysis of an unusual graupel-shower event recorded by an S-band polarimetric rada... more Comprehensive analysis of an unusual graupel-shower event recorded by an S-band polarimetric radar and two optical-imaging surface instruments is presented. The primary radar characteristic was negative differential reflectivity Zdr values along a vertical column. During the afternoon hours of 16 February 2015, a sequence of three showers that were composed primarily of small (8–15-mm diameter) graupel affected the ground instrumentation site that was established for the Multi-Angle Snowflake Camera and Radar (MASCRAD) experiment in the high plains of Colorado. While these showers passed the instrumentation site, the CSU–CHILL radar conducted high-time-resolution (~2.5-min cycle time) range–height indicator (RHI) scans from a range of 13 km. The RHI data show that the negative Zdr values extended vertically through much of the reflectivity cores, implying that the reflectivity-weighted mean axis ratios of the graupel particles in this event remained somewhat prolate throughout their...
Examines one aspect of the CCIR model, namely the difference in transmission loss between forward... more Examines one aspect of the CCIR model, namely the difference in transmission loss between forward and back scatter statistics. This difference is predicted by the model at low time percentages because of the difference in path attenuation inside the raincell. For the back scatter case, the transmission loss includes contributions from the scatter off the near-edge of the rain cell, which suffers very little attenuation within the cell itself. This contribution increases in importance for higher rain rates. The corresponding contribution for the forward scatter, however, will always include this component of attenuation, the magnitude of which generally increases with rain rate, and it is this factor which causes the predicted forward scatter transmission loss to be significantly higher than the back scatter transmission loss for high rain rates. The predicted asymmetry is examined by simulating hydrometeor scatter events using the data obtained from the 3 GHz dual-polarisation radar...
For radar simulations to play an important role in investigating hydrometeor scattering, they hav... more For radar simulations to play an important role in investigating hydrometeor scattering, they have to be validated against experimental measurements. If this can be achieved, then an existing database can be used to evaluate interference for any arbitrary scatter configuration, without undue restrictions to its validity. The authors describe, and present some preliminary results from, such a comparative study made at 17.8 GHz. The bistatic measurements were made on a 48 km rain scatter link and the corresponding radar data were obtained using the 3 GHz dual-polarisation radar based at Chilbolton. They include the methodology and discuss various factors which need consideration in the evaluation of bistatic scatter.
Radar can play two important roles in studies of rain-induced propagation effects on communicatio... more Radar can play two important roles in studies of rain-induced propagation effects on communications systems. Analysis of individual events an lead to a better understanding of the physical mechanisms involved, whilst a large database can be used to provide statistical information by simulating particular systems. Both approaches provide valuable information relevant to the modelling process. The successful launch of the Olympus satellite has provided a new opportunity to investigate the effects of rain and other hydrometeors on slant path propagation. Of particular interest will be the higher frequencies of 20 and 30 GHz, where even light precipitation can cause significant attenuation. The paper presents some early comparisons between radar estimates of attenuation along an actual satellite path, and direct measurements, both at 30 GHz. There are two general aims. One is to assess the ability of the Chilbolton radar to predict attenuation at this frequency, and the second is to ide...
IEE Colloquium on Remote Sensing of the Propagation Environment, 1996
The Rutherford Appleton Laboratory (RAL) is engaged in an experimental program to characterise pr... more The Rutherford Appleton Laboratory (RAL) is engaged in an experimental program to characterise precipitation in the tropics. We have developed and built a 3 GHz vertically pointing pulsed Doppler radar capable of measuring the co-polar reflectivity (Z), cross-polar reflectivity (LDR) and the full Doppler spectrum. The system has been installed at the University of Technology (Unitech) at Lae, Papua New Guinea. The radar system began a measurement campaign in December 1995. Unitech operates a receiver for the 12.75 GHz beacon of the Australian OPTUS-B satellite. The elevation angle of the satellite receiver is 72.8/spl deg/. The experiment yields valuable data on the slant path attenuation for comparison with radar predictions. The three principal parameters which are to be extracted from the radar data are the rainfall rate, the rain height and the rain drop-size distribution. The drop-size distribution is also being measured on the ground with a Jess distrometer. The rain events recorded with the radar can generally be classified into i) those which exhibit a clear, well defined bright band caused by the presence of the melting layer in stratiform precipitation, and ii) those which are convective with rain at heights often above 10 km and the Doppler data showing severe updrafts. The linear de-polarisation ratio (LDR) parameter is an excellent indicator of the melting layer which is an effective method of determining the top of the rain.
Accurate mathematical models of microwave propagation over Earth-space paths are essential for su... more Accurate mathematical models of microwave propagation over Earth-space paths are essential for successful design of satellite communications schemes. Whilst reliable models exist for temperate climates, little data are available to validate prediction procedures for the tropics. As satcomms terminals are rapidly proliferating in these regions, there is an urgent requirement to test current ITU-R recommendations against actual measurements. The most significant propagation impairments are attenuation, depolarisation and scattering, causing reduced circuit availability, and potentially resulting in cochannel interference. Though these effects are experienced at temperate latitudes, they are particularly severe in the tropics, due to the intensity of precipitation. We present design considerations for, and initial observations from, a polarimetric-Doppler radar deployed in Papua New Guinea for research on propagation effects caused by intense tropical precipitation. (5 pages)
This article presents the data collected and analyzed using the University of Iowa’s X-band polar... more This article presents the data collected and analyzed using the University of Iowa’s X-band polarimetric (XPOL) radars that were part of the spring 2013 hydrology-oriented Iowa Flood Studies (IFloodS) field campaign, sponsored by NASA’s Global Precipitation Measurement (GPM) Ground Validation (GV) program. The four mobile radars have full scanning capabilities that provide quantitative estimation of the rainfall at high temporal and spatial resolutions over experimental watersheds. IFloodS was the first extensive test of the XPOL radars, and the XPOL radars demonstrated their field worthiness during this campaign with 46 days of nearly uninterrupted, remotely monitored, and controlled operations. This paper presents detailed postcampaign analyses of the high-resolution, research-quality data that the XPOL radars collected. The XPOL dual-polarimetric products and rainfall are compared with data from other instruments for selected diverse meteorological events at high spatiotemporal r...
ABSTRACT Spatial correlations of two of the main rain drop-size distribution (DSD) parameters - n... more ABSTRACT Spatial correlations of two of the main rain drop-size distribution (DSD) parameters - namely the median-volume diameter (Do) and the normalized intercept parameter (Nw) - as well as rainfall rate (R) are determined from polarimetric radar measurements, with added information from 2D video disdrometer (2DVD) data. Two cases have been considered, (i) a widespread, long-duration rain event in Huntsville, Alabama, and (ii) an event with localized intense rain-cells within a convection line which occurred during the MC3E campaign. For the first case, data from a C-band polarimetric radar (ARMOR) were utilized, with two 2DVDs acting as 'ground-truth', both being located at the same site 15 km from the radar. The radar was operated in a special "near-dwelling" mode over the 2DVDs. In the second case, data from an S-band polarimetric radar (NPOL) data were utilized, with at least five 2DVDs located between 20 and 30 km from the radar. In both rain event cases, comparisons of Do, log10(Nw) and R were made between radar derived estimates and 2DVD-based measurements, and were found to be in good agreement, and in both cases, the radar data were subsequently used to determine the spatial correlations. For the first case, the spatial decorrelation distance was found to be smallest for R (4.5 km), and largest for Do (8.2 km). For log10(Nw) it was 7.2 km (Fig. 1). For the second case, the corresponding decorrelation distances were somewhat smaller but had a directional dependence. In Fig. 2, we show an example of Do comparisons between NPOL based estimates and 1-minute DSD based estimates from one of the five 2DVDs.
ABSTRACT Conference code: 90735, Export Date: 20 June 2013, Source: Scopus, Art. No.: 6206650, :d... more ABSTRACT Conference code: 90735, Export Date: 20 June 2013, Source: Scopus, Art. No.: 6206650, :doi 10.1109/EuCAP.2012.6206650, Language of Original Document: English, Correspondence Address: Capsoni, C.; Dipartimento di Elettronica e Informazione, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133, Milan, Italy; email: capsoni@elet.polimi.it, References: (2003), http://badc.nerc.ac.uk/data/nimrod/, Rain radar Products (NIMROD) British Atmospheric Data Centre. Accessed on January 2011Bringi, V.N., Chandrasekar, V., (2001) Polarimetric Doppler Weather Radar, , 1 st ed., New York, USA, Cambridge university press;
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