The Experts below are selected from a list of 101646 Experts worldwide ranked by ideXlab platform
Yu Song Meng - One of the best experts on this subject based on the ideXlab platform.
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High-Resolution ITU-R Cloud Attenuation Model for Satellite Communications in Tropical Region
IEEE Transactions on Antennas and Propagation, 2019Co-Authors: Feng Yuan, Shilpa Manandhar, Yee Hui Lee, Yu Song Meng, Jin Teong OngAbstract:In this paper, the precipitable water vapor (PWV) data from Global Navigation Satellite System (GNSS) is introduced into ITU-R cloud attenuation model for higher temporal and spatial resolution for a Tropical Region. The revised model incorporates PWV value for estimation of cloud integrated liquid water content (ILWC) and then determines the cloud attenuation. In this study, ILWC along the propagation path is obtained by processing radiosonde vertical profile using the combination of a water vapor pressure cloud detection model and the Salonen and Uppala liquid water density model. From the analysis of 2 years of radiosonde data from eight sites within the Tropical Region, the results show that the ILWC along the path can be approximated by a power function relationship with the PWV. The estimated cloud attenuation using the improved model is compared with the values calculated using the ITU-R model and the cloud attenuation derived from a Ka -band beacon data. The results show that the proposed model is in good agreement with the ITU-R model at high percentage of time exceedance for the thin layer of stratus clouds and matches well with cloud attenuation suffered from beacon signal at low percentage of time exceedance for the thick layer of cumulonimbus clouds.
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Characterization of S-Band Dual-Polarized Radar Data for the Convective Rain Melting Layer Detection in A Tropical Region
Remote Sensing, 2018Co-Authors: Feng Yuan, Yee Hui Lee, Yu Song Meng, Jin Teong OngAbstract:In the Tropical Region, convective rain is a dominant rain event. However, very little information is known about the convective rain melting layer. In this paper, S-band dual-polarized radar data is studied in order to identify both the stratiform and convective rain melting layers in the Tropical Region, with a focus on the convective events. By studying and analyzing the above-mentioned two types of rain events, amongst three radar measurements of reflectivity ( Z ), differential reflectivity ( Z DR ), and cross correlation coefficient ( ρ HV ), the latter one is the best indicator for convective rain melting layer detection. From two years (2014 and 2015) of radar and radiosonde observations, 13 convective rain melting layers are identified with available 0 °C isothermal heights which are derived from radiosonde vertical profiles. By comparing the melting layer top heights with the corresponding 0 °C isothermal heights, it is found that for convective rain events, the threshold to detect melting layer should be modified to ρ HV = 0.95 for the Tropical Region. The melting layer top and bottom heights are then estimated using the proposed threshold, and it is observed from this study that the thickness of convective rain melting layer is around 2 times that of stratiform rain melting layer which is detected by using the conventional ρ HV = 0.97 .
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Investigation of Melting Layer for Convective Rain in Tropical Region
2018 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), 2018Co-Authors: Feng Yuan, Shilpa Manandhar, Yee Hui Lee, Yu Song MengAbstract:Convective rain occurs quite often in Tropical Region, however, very little is known of the melting layer for convective rain. In this paper, the S band dual-polarization radar data are processed to identify the convective rain melting layer in the Tropical country of Singapore. By studying and isolating the convective rain Region, it is found out that among the three radar measurements of reflectivity, differential reflectivity, and cross-correlation coefficient, the crosscorrelation coefficient parameter is the most suitable indicator for convective rain melting layer detection. The reflectivity can be used to differentiate between stratiform rain and convective rain.
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GPS-Derived PWV for Rainfall Nowcasting in Tropical Region
IEEE Transactions on Geoscience and Remote Sensing, 2018Co-Authors: Shilpa Manandhar, Feng Yuan, Yee Hui Lee, Yu Song Meng, Jin Teong OngAbstract:In this paper, a simple algorithm is proposed to perform the nowcasting of rainfall in the Tropical Region. The algorithm applies global positioning system-derived precipitable water vapor (PWV) values and its second derivative for the short-term prediction of rainfall. The proposed algorithm incorporates the seasonal dependency of PWV values for the prediction of a rain event in the coming 5 min based on the past 30 min of PWV data. This proposed algorithm is based on the statistical study of four-year PWV and rainfall data from a station in Singapore and is validated using two-year independent data for the same station. The results show that the algorithm can achieve an average true detection rate and a false alarm rate of 87.7% and 38.6%, respectively. To analyze the applicability of the proposed algorithm, further validations are done using one-year data from one independent station from Singapore and two-year data from one station from Brazil. It is shown that the proposed algorithm performs well for both the independent stations. For the station from Brazil, the average true detection and false alarm rates are around 84.7% and 37%, respectively. All these observations suggest that the proposed algorithm is reliable and works well with a good detection rate.
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A constant conversion factor for retrieval of PWV from GPS signals in Tropical Region
2017 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), 2017Co-Authors: Shilpa Manandhar, Feng Yuan, Yee Hui Lee, Yu Song MengAbstract:In this paper, a constant conversion factor PI is proposed for retrieval of Precipitable Water Vapor (PWV) from Global Positioning System (GPS) signal delay in Tropical Region. The factor PI is calculated using water-vapor weighted mean temperature (Tm). For Tropical Region, Tm doesn't vary much and thus range of PI values is also small. Therefore, using the data obtained from 5 different sites of Tropical Region, a constant PI value of 0.163 is proposed for calculation of PWV from GPS signals in Tropical Region. The proposed conversion factor allows for the ease of PWV retrieval, which is useful in meteorological studies and also applicable in satellite communications.
Feng Yuan - One of the best experts on this subject based on the ideXlab platform.
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High-Resolution ITU-R Cloud Attenuation Model for Satellite Communications in Tropical Region
IEEE Transactions on Antennas and Propagation, 2019Co-Authors: Feng Yuan, Shilpa Manandhar, Yee Hui Lee, Yu Song Meng, Jin Teong OngAbstract:In this paper, the precipitable water vapor (PWV) data from Global Navigation Satellite System (GNSS) is introduced into ITU-R cloud attenuation model for higher temporal and spatial resolution for a Tropical Region. The revised model incorporates PWV value for estimation of cloud integrated liquid water content (ILWC) and then determines the cloud attenuation. In this study, ILWC along the propagation path is obtained by processing radiosonde vertical profile using the combination of a water vapor pressure cloud detection model and the Salonen and Uppala liquid water density model. From the analysis of 2 years of radiosonde data from eight sites within the Tropical Region, the results show that the ILWC along the path can be approximated by a power function relationship with the PWV. The estimated cloud attenuation using the improved model is compared with the values calculated using the ITU-R model and the cloud attenuation derived from a Ka -band beacon data. The results show that the proposed model is in good agreement with the ITU-R model at high percentage of time exceedance for the thin layer of stratus clouds and matches well with cloud attenuation suffered from beacon signal at low percentage of time exceedance for the thick layer of cumulonimbus clouds.
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Characterization of S-Band Dual-Polarized Radar Data for the Convective Rain Melting Layer Detection in A Tropical Region
Remote Sensing, 2018Co-Authors: Feng Yuan, Yee Hui Lee, Yu Song Meng, Jin Teong OngAbstract:In the Tropical Region, convective rain is a dominant rain event. However, very little information is known about the convective rain melting layer. In this paper, S-band dual-polarized radar data is studied in order to identify both the stratiform and convective rain melting layers in the Tropical Region, with a focus on the convective events. By studying and analyzing the above-mentioned two types of rain events, amongst three radar measurements of reflectivity ( Z ), differential reflectivity ( Z DR ), and cross correlation coefficient ( ρ HV ), the latter one is the best indicator for convective rain melting layer detection. From two years (2014 and 2015) of radar and radiosonde observations, 13 convective rain melting layers are identified with available 0 °C isothermal heights which are derived from radiosonde vertical profiles. By comparing the melting layer top heights with the corresponding 0 °C isothermal heights, it is found that for convective rain events, the threshold to detect melting layer should be modified to ρ HV = 0.95 for the Tropical Region. The melting layer top and bottom heights are then estimated using the proposed threshold, and it is observed from this study that the thickness of convective rain melting layer is around 2 times that of stratiform rain melting layer which is detected by using the conventional ρ HV = 0.97 .
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Investigation of Melting Layer for Convective Rain in Tropical Region
2018 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), 2018Co-Authors: Feng Yuan, Shilpa Manandhar, Yee Hui Lee, Yu Song MengAbstract:Convective rain occurs quite often in Tropical Region, however, very little is known of the melting layer for convective rain. In this paper, the S band dual-polarization radar data are processed to identify the convective rain melting layer in the Tropical country of Singapore. By studying and isolating the convective rain Region, it is found out that among the three radar measurements of reflectivity, differential reflectivity, and cross-correlation coefficient, the crosscorrelation coefficient parameter is the most suitable indicator for convective rain melting layer detection. The reflectivity can be used to differentiate between stratiform rain and convective rain.
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GPS-Derived PWV for Rainfall Nowcasting in Tropical Region
IEEE Transactions on Geoscience and Remote Sensing, 2018Co-Authors: Shilpa Manandhar, Feng Yuan, Yee Hui Lee, Yu Song Meng, Jin Teong OngAbstract:In this paper, a simple algorithm is proposed to perform the nowcasting of rainfall in the Tropical Region. The algorithm applies global positioning system-derived precipitable water vapor (PWV) values and its second derivative for the short-term prediction of rainfall. The proposed algorithm incorporates the seasonal dependency of PWV values for the prediction of a rain event in the coming 5 min based on the past 30 min of PWV data. This proposed algorithm is based on the statistical study of four-year PWV and rainfall data from a station in Singapore and is validated using two-year independent data for the same station. The results show that the algorithm can achieve an average true detection rate and a false alarm rate of 87.7% and 38.6%, respectively. To analyze the applicability of the proposed algorithm, further validations are done using one-year data from one independent station from Singapore and two-year data from one station from Brazil. It is shown that the proposed algorithm performs well for both the independent stations. For the station from Brazil, the average true detection and false alarm rates are around 84.7% and 37%, respectively. All these observations suggest that the proposed algorithm is reliable and works well with a good detection rate.
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A constant conversion factor for retrieval of PWV from GPS signals in Tropical Region
2017 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), 2017Co-Authors: Shilpa Manandhar, Feng Yuan, Yee Hui Lee, Yu Song MengAbstract:In this paper, a constant conversion factor PI is proposed for retrieval of Precipitable Water Vapor (PWV) from Global Positioning System (GPS) signal delay in Tropical Region. The factor PI is calculated using water-vapor weighted mean temperature (Tm). For Tropical Region, Tm doesn't vary much and thus range of PI values is also small. Therefore, using the data obtained from 5 different sites of Tropical Region, a constant PI value of 0.163 is proposed for calculation of PWV from GPS signals in Tropical Region. The proposed conversion factor allows for the ease of PWV retrieval, which is useful in meteorological studies and also applicable in satellite communications.
S Fraser - One of the best experts on this subject based on the ideXlab platform.
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Performance of an integrated solar absorption cooling system in a sub-Tropical Region
International Journal of Low-carbon Technologies, 2012Co-Authors: Jo Darkwa, S FraserAbstract:Evaluation of an integrated solar absorption cooling system located in a sub-Tropical Region has been carried out. Analysis of the results revealed an operational efficiency of 61% for the solar collectors at a mean differential temperature of 51°C when compared with the manufacturer's rating of 70% at 60°C. The absorption chiller did, however, perform quite satisfactorily and achieved a coefficient of performance of 0.69 when compared with the manufacturer's rating of 0.7. There is however the need for the hot water supply system to be optimized as well as provision for supplementary heat source in order to maintain the appropriate operating temperature during low solar radiation levels. Copyright , Oxford University Press.
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Performance of an integrated solar absorption cooling system in a sub-Tropical Region
International Journal of Low-Carbon Technologies, 2012Co-Authors: Jo Darkwa, S FraserAbstract:Evaluation of an integrated solar absorption cooling system located in a sub-Tropical Region has been carried out. Analysis of the results revealed an operational efficiency of 61% for the solar collectors at a mean differential temperature forumla of 51°C when compared with the manufacturer's rating of 70% at 60°C. The absorption chiller did, however, perform quite satisfactorily and achieved a coefficient of performance of 0.69 when compared with the manufacturer's rating of 0.7. There is however the need for the hot water supply system to be optimized as well as provision for supplementary heat source in order to maintain the appropriate operating temperature during low solar radiation levels.
Jin Teong Ong - One of the best experts on this subject based on the ideXlab platform.
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High-Resolution ITU-R Cloud Attenuation Model for Satellite Communications in Tropical Region
IEEE Transactions on Antennas and Propagation, 2019Co-Authors: Feng Yuan, Shilpa Manandhar, Yee Hui Lee, Yu Song Meng, Jin Teong OngAbstract:In this paper, the precipitable water vapor (PWV) data from Global Navigation Satellite System (GNSS) is introduced into ITU-R cloud attenuation model for higher temporal and spatial resolution for a Tropical Region. The revised model incorporates PWV value for estimation of cloud integrated liquid water content (ILWC) and then determines the cloud attenuation. In this study, ILWC along the propagation path is obtained by processing radiosonde vertical profile using the combination of a water vapor pressure cloud detection model and the Salonen and Uppala liquid water density model. From the analysis of 2 years of radiosonde data from eight sites within the Tropical Region, the results show that the ILWC along the path can be approximated by a power function relationship with the PWV. The estimated cloud attenuation using the improved model is compared with the values calculated using the ITU-R model and the cloud attenuation derived from a Ka -band beacon data. The results show that the proposed model is in good agreement with the ITU-R model at high percentage of time exceedance for the thin layer of stratus clouds and matches well with cloud attenuation suffered from beacon signal at low percentage of time exceedance for the thick layer of cumulonimbus clouds.
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Characterization of S-Band Dual-Polarized Radar Data for the Convective Rain Melting Layer Detection in A Tropical Region
Remote Sensing, 2018Co-Authors: Feng Yuan, Yee Hui Lee, Yu Song Meng, Jin Teong OngAbstract:In the Tropical Region, convective rain is a dominant rain event. However, very little information is known about the convective rain melting layer. In this paper, S-band dual-polarized radar data is studied in order to identify both the stratiform and convective rain melting layers in the Tropical Region, with a focus on the convective events. By studying and analyzing the above-mentioned two types of rain events, amongst three radar measurements of reflectivity ( Z ), differential reflectivity ( Z DR ), and cross correlation coefficient ( ρ HV ), the latter one is the best indicator for convective rain melting layer detection. From two years (2014 and 2015) of radar and radiosonde observations, 13 convective rain melting layers are identified with available 0 °C isothermal heights which are derived from radiosonde vertical profiles. By comparing the melting layer top heights with the corresponding 0 °C isothermal heights, it is found that for convective rain events, the threshold to detect melting layer should be modified to ρ HV = 0.95 for the Tropical Region. The melting layer top and bottom heights are then estimated using the proposed threshold, and it is observed from this study that the thickness of convective rain melting layer is around 2 times that of stratiform rain melting layer which is detected by using the conventional ρ HV = 0.97 .
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GPS-Derived PWV for Rainfall Nowcasting in Tropical Region
IEEE Transactions on Geoscience and Remote Sensing, 2018Co-Authors: Shilpa Manandhar, Feng Yuan, Yee Hui Lee, Yu Song Meng, Jin Teong OngAbstract:In this paper, a simple algorithm is proposed to perform the nowcasting of rainfall in the Tropical Region. The algorithm applies global positioning system-derived precipitable water vapor (PWV) values and its second derivative for the short-term prediction of rainfall. The proposed algorithm incorporates the seasonal dependency of PWV values for the prediction of a rain event in the coming 5 min based on the past 30 min of PWV data. This proposed algorithm is based on the statistical study of four-year PWV and rainfall data from a station in Singapore and is validated using two-year independent data for the same station. The results show that the algorithm can achieve an average true detection rate and a false alarm rate of 87.7% and 38.6%, respectively. To analyze the applicability of the proposed algorithm, further validations are done using one-year data from one independent station from Singapore and two-year data from one station from Brazil. It is shown that the proposed algorithm performs well for both the independent stations. For the station from Brazil, the average true detection and false alarm rates are around 84.7% and 37%, respectively. All these observations suggest that the proposed algorithm is reliable and works well with a good detection rate.
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Statistical Study of Cloud Attenuation on Ka-Band Satellite Signal in Tropical Region
IEEE Antennas and Wireless Propagation Letters, 2017Co-Authors: Feng Yuan, Yee Hui Lee, Yu Song Meng, Jun Xiang Yeo, Jin Teong OngAbstract:A two-year statistical study of cloud induced attenuation on Ka-band satellite communication link in the Tropical Region is presented. Different from other publications, experimental results from an 18.9-GHz beacon receiver is analyzed for cloud attenuation. Several new cloud detection methods are proposed in order to achieve accurate cloud attenuation estimation. These results are compared to the ITU-R model for the same frequency and elevation angle. The complementary cumulative distribution function of two-year cloud attenuation shows that at time exceedance of 0.01%, cloud attenuation in the Ka-band can reach up to 4 dB. It is found that the ITU-R model underestimate the cloud attenuation in the Tropical Region.
Yee Hui Lee - One of the best experts on this subject based on the ideXlab platform.
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High-Resolution ITU-R Cloud Attenuation Model for Satellite Communications in Tropical Region
IEEE Transactions on Antennas and Propagation, 2019Co-Authors: Feng Yuan, Shilpa Manandhar, Yee Hui Lee, Yu Song Meng, Jin Teong OngAbstract:In this paper, the precipitable water vapor (PWV) data from Global Navigation Satellite System (GNSS) is introduced into ITU-R cloud attenuation model for higher temporal and spatial resolution for a Tropical Region. The revised model incorporates PWV value for estimation of cloud integrated liquid water content (ILWC) and then determines the cloud attenuation. In this study, ILWC along the propagation path is obtained by processing radiosonde vertical profile using the combination of a water vapor pressure cloud detection model and the Salonen and Uppala liquid water density model. From the analysis of 2 years of radiosonde data from eight sites within the Tropical Region, the results show that the ILWC along the path can be approximated by a power function relationship with the PWV. The estimated cloud attenuation using the improved model is compared with the values calculated using the ITU-R model and the cloud attenuation derived from a Ka -band beacon data. The results show that the proposed model is in good agreement with the ITU-R model at high percentage of time exceedance for the thin layer of stratus clouds and matches well with cloud attenuation suffered from beacon signal at low percentage of time exceedance for the thick layer of cumulonimbus clouds.
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Characterization of S-Band Dual-Polarized Radar Data for the Convective Rain Melting Layer Detection in A Tropical Region
Remote Sensing, 2018Co-Authors: Feng Yuan, Yee Hui Lee, Yu Song Meng, Jin Teong OngAbstract:In the Tropical Region, convective rain is a dominant rain event. However, very little information is known about the convective rain melting layer. In this paper, S-band dual-polarized radar data is studied in order to identify both the stratiform and convective rain melting layers in the Tropical Region, with a focus on the convective events. By studying and analyzing the above-mentioned two types of rain events, amongst three radar measurements of reflectivity ( Z ), differential reflectivity ( Z DR ), and cross correlation coefficient ( ρ HV ), the latter one is the best indicator for convective rain melting layer detection. From two years (2014 and 2015) of radar and radiosonde observations, 13 convective rain melting layers are identified with available 0 °C isothermal heights which are derived from radiosonde vertical profiles. By comparing the melting layer top heights with the corresponding 0 °C isothermal heights, it is found that for convective rain events, the threshold to detect melting layer should be modified to ρ HV = 0.95 for the Tropical Region. The melting layer top and bottom heights are then estimated using the proposed threshold, and it is observed from this study that the thickness of convective rain melting layer is around 2 times that of stratiform rain melting layer which is detected by using the conventional ρ HV = 0.97 .
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Investigation of Melting Layer for Convective Rain in Tropical Region
2018 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), 2018Co-Authors: Feng Yuan, Shilpa Manandhar, Yee Hui Lee, Yu Song MengAbstract:Convective rain occurs quite often in Tropical Region, however, very little is known of the melting layer for convective rain. In this paper, the S band dual-polarization radar data are processed to identify the convective rain melting layer in the Tropical country of Singapore. By studying and isolating the convective rain Region, it is found out that among the three radar measurements of reflectivity, differential reflectivity, and cross-correlation coefficient, the crosscorrelation coefficient parameter is the most suitable indicator for convective rain melting layer detection. The reflectivity can be used to differentiate between stratiform rain and convective rain.
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GPS-Derived PWV for Rainfall Nowcasting in Tropical Region
IEEE Transactions on Geoscience and Remote Sensing, 2018Co-Authors: Shilpa Manandhar, Feng Yuan, Yee Hui Lee, Yu Song Meng, Jin Teong OngAbstract:In this paper, a simple algorithm is proposed to perform the nowcasting of rainfall in the Tropical Region. The algorithm applies global positioning system-derived precipitable water vapor (PWV) values and its second derivative for the short-term prediction of rainfall. The proposed algorithm incorporates the seasonal dependency of PWV values for the prediction of a rain event in the coming 5 min based on the past 30 min of PWV data. This proposed algorithm is based on the statistical study of four-year PWV and rainfall data from a station in Singapore and is validated using two-year independent data for the same station. The results show that the algorithm can achieve an average true detection rate and a false alarm rate of 87.7% and 38.6%, respectively. To analyze the applicability of the proposed algorithm, further validations are done using one-year data from one independent station from Singapore and two-year data from one station from Brazil. It is shown that the proposed algorithm performs well for both the independent stations. For the station from Brazil, the average true detection and false alarm rates are around 84.7% and 37%, respectively. All these observations suggest that the proposed algorithm is reliable and works well with a good detection rate.
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A constant conversion factor for retrieval of PWV from GPS signals in Tropical Region
2017 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), 2017Co-Authors: Shilpa Manandhar, Feng Yuan, Yee Hui Lee, Yu Song MengAbstract:In this paper, a constant conversion factor PI is proposed for retrieval of Precipitable Water Vapor (PWV) from Global Positioning System (GPS) signal delay in Tropical Region. The factor PI is calculated using water-vapor weighted mean temperature (Tm). For Tropical Region, Tm doesn't vary much and thus range of PI values is also small. Therefore, using the data obtained from 5 different sites of Tropical Region, a constant PI value of 0.163 is proposed for calculation of PWV from GPS signals in Tropical Region. The proposed conversion factor allows for the ease of PWV retrieval, which is useful in meteorological studies and also applicable in satellite communications.
