title: Enhancing rainfall measurement using microwave links at three scales

authors: Esmaeil Nia, Saeid

abstract: The application of microwave signals in telecommunication has advanced in recent decades. Hence the CMLs (Commercial Microwave Links) have been spread all over the lands. Meanwhile, the decrease in power of the signal due to rainfall has raised the idea of measuring rainfall with microwave attenuation. This PhD research delves into the challenges of these techniques and investigates potential solutions to enhance the accuracy of measuring rainfall. The objectives of the study set to three levels of raindrops’ impact, signal characteristics, and catchment evaluations.  

In the first stage, the cross-sections of different sizes of raindrops are calculated by solving Maxwell’s differential equations in COMSOL software. Rainfall is calculated from different Drop Size Distribution (DSD) models. Then, the correlation between the resulting attenuation and rainfall provided different coefficients for the power correlation between rainfall and attenuation. Regarding the variability in DSD with rainfall intensity, alterations in extinction cross-section play a role in establishing a fluid relationship between attenuation and rainfall. This necessitates adjusting constants for the correlation across different rainfall intensities. 

The results support the idea of having varying coefficients for different rainfall intensities.  At the second level, the signal characteristics were investigated to find a robust method for extracting attenuation from the received power. The study led to defining a reference signal level through signal denoising methods of moving average, Butterworth, and Chebyshev methods. The study showed the superior performance of the moving average in predicting rainfall, especially in 38 GHz links (H and V) indicated by NSE and KGE. Overall, the moving average also resulted in 2%, 16%, and 14% lower RMSE than the conventional method in microwave links 26H, 38H, and 38V, respectively. Butterworth and Chebyshev filters exhibited higher NSE and lower RMSE in 38 GHz links, with competitive accuracy in the 26 GHz link compared to conventional methods.  The effect of wet antenna also decreased and even vanished in some cases. 

At last, the catchment runoff was used to calibrate the relationship between rainfall and attenuation. In a study in 15 catchments in Melbourne, the suggested method established a relation between attenuation and the quick flow of 15 flow stations. Meanwhile, the coefficients of the rainfall-attenuation formula were calibrated to reach the highest accuracy of runoff prediction. The results indicate a more robust connection between attenuation and quick flow in contrast to conventional rain gauge data. The new suggested method achieved a maximum NSE of 0.78 and KGE of 0.86. Compared to rain gauges, the conventional CML model improved NSE by an average of 197%, while the new model showed an additional 50% enhancement. RMSE optimisation also demonstrated improvement, with a 15% enhancement using the conventional CML model and an additional 4% on average with the new model. Moreover, the revised flow calibration technique reduces the wet antenna effect by an average of 49%.

text: Enhancing rainfall measurement using microwave links at three scales The application of microwave signals in telecommunication has advanced in recent decades. Hence the CMLs (Commercial Microwave Links) have been spread all over the lands. Meanwhile, the decrease in power of the signal due to rainfall has raised the idea of measuring rainfall with microwave attenuation. This PhD research delves into the challenges of these techniques and investigates potential solutions to enhance the accuracy of measuring rainfall. The objectives of the study set to three levels of raindrops’ impact, signal characteristics, and catchment evaluations.  

In the first stage, the cross-sections of different sizes of raindrops are calculated by solving Maxwell’s differential equations in COMSOL software. Rainfall is calculated from different Drop Size Distribution (DSD) models. Then, the correlation between the resulting attenuation and rainfall provided different coefficients for the power correlation between rainfall and attenuation. Regarding the variability in DSD with rainfall intensity, alterations in extinction cross-section play a role in establishing a fluid relationship between attenuation and rainfall. This necessitates adjusting constants for the correlation across different rainfall intensities. 

The results support the idea of having varying coefficients for different rainfall intensities.  At the second level, the signal characteristics were investigated to find a robust method for extracting attenuation from the received power. The study led to defining a reference signal level through signal denoising methods of moving average, Butterworth, and Chebyshev methods. The study showed the superior performance of the moving average in predicting rainfall, especially in 38 GHz links (H and V) indicated by NSE and KGE. Overall, the moving average also resulted in 2%, 16%, and 14% lower RMSE than the conventional method in microwave links 26H, 38H, and 38V, respectively. Butterworth and Chebyshev filters exhibited higher NSE and lower RMSE in 38 GHz links, with competitive accuracy in the 26 GHz link compared to conventional methods.  The effect of wet antenna also decreased and even vanished in some cases. 

At last, the catchment runoff was used to calibrate the relationship between rainfall and attenuation. In a study in 15 catchments in Melbourne, the suggested method established a relation between attenuation and the quick flow of 15 flow stations. Meanwhile, the coefficients of the rainfall-attenuation formula were calibrated to reach the highest accuracy of runoff prediction. The results indicate a more robust connection between attenuation and quick flow in contrast to conventional rain gauge data. The new suggested method achieved a maximum NSE of 0.78 and KGE of 0.86. Compared to rain gauges, the conventional CML model improved NSE by an average of 197%, while the new model showed an additional 50% enhancement. RMSE optimisation also demonstrated improvement, with a 15% enhancement using the conventional CML model and an additional 4% on average with the new model. Moreover, the revised flow calibration technique reduces the wet antenna effect by an average of 49%.

year: 2024

title: Engineering of a polar crystal structure exclusively by π–π stacking between aryl and polyfluoroaryl groups

authors: Lane, Joseph R.

abstract: 1-(4-Nitrilo-2,3,5,6-tetrafluorophenyl)benzimidazole crystallizes in the polar space group Cc. The structure arises from the geometry of the molecule which gives columns of π-π stacked nitrilotetrafluorophenyl and benzimidazole groups in two almost orthogonal directions.

text: Engineering of a polar crystal structure exclusively by π–π stacking between aryl and polyfluoroaryl groups 1-(4-Nitrilo-2,3,5,6-tetrafluorophenyl)benzimidazole crystallizes in the polar space group Cc. The structure arises from the geometry of the molecule which gives columns of π-π stacked nitrilotetrafluorophenyl and benzimidazole groups in two almost orthogonal directions.

year: 2013

title: Maori Te Aroha before the opening of the goldfield (mostly through Pakeha eyes)

authors: Hart, Philip

abstract: The various names of the peaks of the mountain and the legends concerning it reflected a violent past. As proof, several pa have been located, both at Te Aroha and at Waiorongomai, and the names of some of the streams indicate the nature and consequences of the battles fought in this contested area.
Ngati Rahiri was subdivided into three hapu: Ngati Tumutumu, Hgati Hue, and Ngati Kopirimau, descendents of these ancestors. In the nineteenth century, when the population was small, Hou was the senior rangatira, with Tutuki being the subordinate rangatira of the plains. A pa (later known as Tui pa) was constructed at Omahu, to the north of the hot springs, which were prized by Maori and increasingly enjoyed by Pakeha. Some of the land was cultivated, though visiting Pakeha considered that settlers could do much more to develop the agricultural potential. Most Ngati Rahiri were regarded as being ‘friendly’, welcoming (and benefiting from) visitors. Elaborate welcoming ceremonies were held for officials and rangatira, and a hotel operated by a rangatira’s son provided basic accommodation. Under Maori auspices the first race day was held in January 1878. 
Also in 1878, negotiators obtained an agreement to make a road to Paeroa, using Maori workers, and as the benefits of such improvements became apparent there was increased willingness to permit the construction of more roads, a bridge, and the snagging of the river, over the objections of a minority. Pakeha disapproved of how money raised through land sales in particular were wasted on extravagant displays of mana, which were not possible after the end of the 1870s because of lack of money, necessitating seeking paid employment. Friendly contact increased steadily, apart from occasional worries prompted by such events as the shooting of Daldy McWilliams, and a football match in May 1880 reportedly revealed ‘the utmost friendly feeling’ existing between Maori and Pakeha.

text: Maori Te Aroha before the opening of the goldfield (mostly through Pakeha eyes) The various names of the peaks of the mountain and the legends concerning it reflected a violent past. As proof, several pa have been located, both at Te Aroha and at Waiorongomai, and the names of some of the streams indicate the nature and consequences of the battles fought in this contested area.
Ngati Rahiri was subdivided into three hapu: Ngati Tumutumu, Hgati Hue, and Ngati Kopirimau, descendents of these ancestors. In the nineteenth century, when the population was small, Hou was the senior rangatira, with Tutuki being the subordinate rangatira of the plains. A pa (later known as Tui pa) was constructed at Omahu, to the north of the hot springs, which were prized by Maori and increasingly enjoyed by Pakeha. Some of the land was cultivated, though visiting Pakeha considered that settlers could do much more to develop the agricultural potential. Most Ngati Rahiri were regarded as being ‘friendly’, welcoming (and benefiting from) visitors. Elaborate welcoming ceremonies were held for officials and rangatira, and a hotel operated by a rangatira’s son provided basic accommodation. Under Maori auspices the first race day was held in January 1878. 
Also in 1878, negotiators obtained an agreement to make a road to Paeroa, using Maori workers, and as the benefits of such improvements became apparent there was increased willingness to permit the construction of more roads, a bridge, and the snagging of the river, over the objections of a minority. Pakeha disapproved of how money raised through land sales in particular were wasted on extravagant displays of mana, which were not possible after the end of the 1870s because of lack of money, necessitating seeking paid employment. Friendly contact increased steadily, apart from occasional worries prompted by such events as the shooting of Daldy McWilliams, and a football match in May 1880 reportedly revealed ‘the utmost friendly feeling’ existing between Maori and Pakeha.

year: 2016