Comparative analysis of bright band data from TRMM and ground radar data in Malaysia
01 Jan 2013-Vol. 3, Iss: 4, pp 99-109
TL;DR: In this article, a comparative analysis of radar data sourced from both ground 3D RAPIC bistatic radar and space-borne precipitation radar above the Malaysian air space is presented.
Abstract: Good knowledge of the formation and recognition of the bright band is necessary to determine the location of the melting layer. This is partly because the melting layer is one of the major hydrometeors (others include as rain, hail, and cloud) responsible for signal degradations along the slant-path, in the tropical regions of the world. These may result in signal fading, amongst others, which may lead to errors in slant-path attenuation predictions. This paper involves the comparative analysis of radar data sourced from both ground 3D RAPIC bistatic radar and space-borne precipitation radar above the Malaysian air space. For this research work, the terrestrial meteorological radar data were sourced from the Meteorological Department of Malaysia, while the satellite radar data were obtained from the near-real-time TRMM Multi-Satellite Precipitation Analysis (TMPA-RT) version 7 products. Frozen hydrometeors are observed to exhibit peculiar characteristics in terms of increased radar reflectivity as they fall from the sky, transiting from solid to liquid, and manifesting in the popular bright band signature. The melting layer is the region where melting occur, just below the 0℃ isotherm height. It is a major factor responsible for the problems being encountered in characterization and modelling of microwave signal propagation along the earth-space link.
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TL;DR: In this paper, the effect of rain on a satellite link operating at a frequency above 10 GHz can be estimated using various parameters such as rain rate, drop size distribution, and rain height.
13 citations
01 Sep 2015
TL;DR: Comparison of the observed results show that the International Telecommunication Union - Recommendation (ITU-R) P.839 recommended values were underestimated, and recommends using the physical information about rain height derived from the local databases to improve in the rain attenuation prediction accuracy for this region.
Abstract: In this paper, 4-year precipitation data obtained from Tropical Rain Measuring Mission-Precipitation Radar (TRMM-PR) satellite were processed and used to determine the distribution of rain height based on 00C isotherm height over Durban in South Africa. The results show that there is a strong variation of bright-band height over the years of observation and will mostly lie between 3639 m and 4197 m above mean sea level. The observed rain height lies between 4517 m and 4803 m. Comparison of the observed results show that the International Telecommunication Union — Recommendation (ITU-R) P.839 recommended values were underestimated. Thus, the specific attenuation values are determined using ITU-R P.618 by incorporating the determined rain height for the location of Durban. It is noticed that the differences between the estimated attenuation based on the measured rain height and the established ITU-R rain height can be as high as 8 dB at Ka band. Thus, recommending using the physical information about rain height derived from the local databases to improve in the rain attenuation prediction accuracy for this region.
6 citations
Cites background from "Comparative analysis of bright band..."
...Attenuation beyond the rain height is generally considered insignificant, and thus neglected [8]....
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Dissertation•
01 Jan 2019
TL;DR: In the fulfilment of the requirements of the degree of Doctor of Engineering: Electronic Engineering, Durban University of Technology (DUET), Durban, South Africa, 2019.
Abstract: Submitted in the fulfilment of the requirements of the degree of Doctor of Engineering: Electronic Engineering, Durban University of Technology, Durban, South Africa, 2019.
5 citations
Cites background from "Comparative analysis of bright band..."
...ZDIH information can be obtained indirectly in the melting layer region of the atmosphere [84, 137, 138]....
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TL;DR: In this article, rain height and rain-induced attenuation contour maps for 1, 0.1%, and 0.01% of time exceedance are provided at 20 GHz and 40 GHz for Ka and V band signals respectively.
1 citations
01 Jan 1999
TL;DR: In this article, the authors deal with the characterisation and modelling of the melting layer in order to better predict its effects on the performance of spatial telecommunications systems in the EHF domain, and also assess radar performance for melting layer detection at a distance.
Abstract: The frequency bands, presently used by space telecommunications systems, are saturated, hence the need for using higher frequencies (EHF). However, for millimetre waves, the atmospheric propagation of electromagnetic waves is more perturbed than at lower bands. Precipitation, clouds and gases are responsible for that. The contribution of the melting layer, in terms of attenuation, is also no more negligible. This atmospheric layer, where ice particles melt into raindrops, still cause problems of characterisation and modelling. Furthermore, the melting layer can be responsible for the phenomenon of frost on the aircraft. Fortunately, this band can be easily detected because of its peak of reflectivity in the millimetre domain. It is for this reason that the melting layer is detected as a `bright band' by radar. This study deals with the characterisation and modelling of the melting layer in order to better predict its effects on the performance of spatial telecommunications systems in the EHF domain, and also to assess radar performance for melting layer detection at a distance. Some models already exist and are presented, but they are not entirely satisfactory. It is also for this reason that a new calculation for scattering by a particle is introduced. The results of simulations and a comparison with experimental data are presented.
References
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3,500 citations
"Comparative analysis of bright band..." refers background in this paper
...6 respectively, according to Marshall-Palmer[9]....
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...R) relationships, such as in[9], and with the expression: baRZ = (mm6m-3) (2) Where the values for a and b are 200 and 1.6 respectively, according to Marshall-Palmer[9]....
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...This may ultimately lead to a more accurate rain attenuation prediction by adopting appropriate reflectivity-rain rate (Z–R) relationships, such as in[9], and with the expression:...
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TL;DR: The Tropical Rainfall Measuring Mission (TRMM) was launched in November 1997 with fuel enough to obtain a four to five year data set of rainfall over the global tropics from 37 deg N to 37 deg S as mentioned in this paper.
Abstract: Recognizing the importance of rain in the tropics and the accompanying latent heat release, NASA for the U.S. and NASDA for Japan have partnered in the design, construction and flight of an Earth Probe satellite to measure tropical rainfall and calculate the associated heating. Primary mission goals are: 1) the understanding of crucial links in climate variability by the hydrological cycle, 2) improvement in the large-scale models of weather and climate, and 3) improvement in understanding cloud ensembles and their impacts on larger scale circulations. The linkage with the tropical oceans and landmasses are also emphasized. The Tropical Rainfall Measuring Mission (TRMM) satellite was launched in November 1997 with fuel enough to obtain a four to five year data set of rainfall over the global tropics from 37 deg N to 37 deg S. This paper reports progress from launch date through the spring of 1999. The data system and its products and their access is described, as are the algorithms used to obtain the data. Some exciting early results from TRMM are described. Some important algorithm improvements are shown. These will be used in the first total data reprocessing, scheduled to be complete in early 2000. The reader is given information on how to access and use the data.
455 citations
TL;DR: In this article, the melting layer in precipitation is physically modeled and compared with high resolution Doppler radar data, which includes a new formulation of the dielectric properties and can handle all ice particles with densities ranging from pure snow to hail.
Abstract: The melting layer in precipitation is physically modeled and compared with high resolution Doppler radar data. The model includes a new formulation of the dielectric properties and can handle all ice particles with densities ranging from pure snow to hail. The air temperature is calculated from the vertical air velocity. The model can simulate the aggregation and breakup of the melting particles. The melting layer is often observed as a bright band; the prominence of the bright band is related to the density of particles before melting. The width of the band increases with the rain intensity; according to the model this is mainly caused by an increase in the almost isothermal layer at the upper part of the melting layer. The results of the model are in good agreement with Doppler radar observations. According to the model, the reflectivity is very sensitive to the dielectric properties and density of the melting particles and the influence of aggregation is restricted. Because of the assumption o...
169 citations
"Comparative analysis of bright band..." refers background in this paper
...Wim Klaassen [20] Attenuation of radio waves in melting layer....
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...As a result, a handful of models have been developed and proposed by several researchers for predicting attenuation in the melting layer[8, 20-23]....
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TL;DR: In this paper, a methodology is developed that matches coincident precipitation radar and ground-based volume scanning weather radar observations in a common earth parallel three-dimensional Cartesian grid to minimize uncertainties associated with the type of weather seen by the radars, grid resolution, and differences in radar sensitivities, sampling volumes, viewing angles, and radar frequencies.
Abstract: Since the successful launch of the Tropical Rainfall Measuring Mission (TRMM) satellite, measurements of a wide variety of precipitating systems have been obtained with unprecedented detail from the first space-based radar [precipitation radar (PR)]. In this research, a methodology is developed that matches coincident PR and ground-based volume scanning weather radar observations in a common earth parallel three-dimensional Cartesian grid. The data matching is performed in a way that minimizes uncertainties associated with the type of weather seen by the radars, grid resolution, and differences in radar sensitivities, sampling volumes, viewing angles, and radar frequencies. The authors present comparisons of reflectivity observations from the PR and several U.S. weather surveillance Doppler radars (WSR-88D) as well as research radars from the TRMM field campaigns in Kwajalein Atoll and the Large Biosphere Atmospheric (LBA) Experiment. Correlation values above 0.8 are determined between PR and ground radar matched data for levels above the zero isotherm. The reflectivity difference statistics derived from the matched data reveal radar systems with systematic differences ranging from 1 2t o27 dB. The authors argue that the main candidate for systematic differences exceeding 1 to 1.5 dB is the ground radar system calibration bias. To verify this argument, the authors used PR comparisons against well-calibrated ground-based systems, which showed systematic differences consistently less than 1.5 dB. Temporal analysis of the PR versus ground radar systematic differences reveals radar sites with up to 4.5dB bias changes within periods of two to six months. Similar evaluation of the PR systematic difference against stable ground radar systems shows bias fluctuations of less than 0.8 dB. It is also shown that bias adjustment derived from the methodology can have significant impact on the hydrologic applications of ground-based radar measurements. The proposed scheme can be a useful tool for the systematic monitoring of ground radar biases and the studying of its effect.
135 citations
"Comparative analysis of bright band..." refers background in this paper
...The vertical resolution is 250 metres, while its nominal sensitivity is approximately 17 dBZ[3]....
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TL;DR: In this paper, a model of the scattering properties at microwave frequencies for snow, melting snow, and rain is implemented, running in tandem with a meteorological model, generating the reflectivity fields associated with the hydrometeors in the model to facilitate comparisons with available observations.
Abstract: To complement the meteorological modeling of the melting layer, a model of the scattering properties at microwave frequencies for snow, melting snow, and rain is implemented. The scattering model, running in tandem with a meteorological model, generates the reflectivity fields associated with the hydrometeors in the model to facilitate comparisons with available observations. Several existing and a few new approaches for the scattering of melting snow are attempted. In addition, the models are run using several relationships for the density of snowflakes as a function of their size. A large variability in the prediction of the brightband intensity is observed as a function of the scattering model. However, the scattering model whose melting snow morphology resembles most the one of real snowflakes reproduces the available observations with the highest accuracy. Sensitivity to the snowflake density relationship used is found to be less important. Other features like the melting-layer thickness, brightband peak position, and Doppler velocity are also correctly predicted.
134 citations
"Comparative analysis of bright band..." refers background in this paper
...Fabry & Szyrmer[21] Dynamics & Microphysics BB peak intensity varied by a factor of 10 between strongest models (0 and 1) and weakest (3 and 4)....
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...As a result, a handful of models have been developed and proposed by several researchers for predicting attenuation in the melting layer[8, 20-23]....
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