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Corona onset voltage gradient (COG) of bundled conductors is an important factor to be considered when designing extra-high voltage (EHV) and ultra-high voltage (UHV) transmission lines. For alternating current (AC) transmission lines, the electromagnetic environment degrades and the energy loss is greater on rainy days, which becomes more obvious with increasing altitude, therefore, it is particularly important to investigate corona onset characteristics of bundled conductors under rainy conditions in high-altitude areas. Based on an UHV corona cage established in Qinghai Province, China at an altitude of 2200 m, corona onset characteristics of nine types of bundled conductors generally used in EHV and UHV AC transmission lines were measured at a rainfall rate of up to 15 mm/h. Moreover, COG was obtained by using the tangent method. Changes in COG with rainfall intensity and corona characteristics with structural parameters of conductors at the saturated rainfall rate were investigated. Finally, considering sub-conductor radius, the number of sub-conductors, and rainfall rate, an empirical prediction equation for COG of bundled conductors with 4, 6 and 8 sub-conductors and cross-sectional areas of 400, 500, 630, and 720 mm2 was proposed, which could provide a reference for the design of overhead transmission lines in high-altitude areas.

In radar observations of hydrometeors, the 0°C isotherm in the atmosphere (i.e., the freezing level) usually appears as a region of enhanced reflectivity. This region is known as the bright band (BB). In this study, observations over 12 months from a vertically pointing 35-GHz radar and a collocated disdrometer at the Natural Environment Research Council (NERC) Facility for Atmospheric and Radio Research (NFARR) are used to identify and compare microphysical differences between BB and non-brightband (NBB) periods. From these observations, the relationship between radar reflectivity Z and rainfall intensity R is found to be Z = 772R0.57 for BB periods and Z = 108R0.99 for NBB periods. Additionally, the brightband strength (BBS) was calculated using a novel method derived from the Michelson contrast equation in an attempt to explain the observed variability in BB precipitation. A series of Z–R relationships are computed with respect to BBS. The coefficients increase with increasing BBS from 227 to 926, while the exponents decrease with increasing BBS from 0.85 to 0.38. The results also indicate that NBB periods identified in the presence of a 0°C isotherm in other studies may be misclassified due to their inability to identify weak brightband periods. As such, it is hypothesized that NBB periods are solely due to warm rain processes.

One-minute rain rate exceeded for 0.01% of an average year (known as R0.01) is an important parameter, which is required in rain fade models for planning both satellite and terrestrial links, especially in the microwave and millimeter-wave bands. This paper presents the development of a new global model for estimating high-resolution R0.01. The model is developed using the Climate Hazards Group Infrared Precipitation with Stations (CHIRPS), ERA-Interim reanalyzed total precipitable water, and the cumulative distribution functions of the measured R0.01 via genetic algorithm. The newly proposed model performs better than the International Telecommunication Union Radio Sector (ITU-R) recommendation and widely used ITU-R P.837-6 model, particularly over the tropical regions, where ITU-R P.837-6 strongly underestimates R0.01. Overall, when compared to ITU-R P.837-6, the estimated R0.01 by the proposed model is improved by ~15%. Furthermore, the proposed model can provide R0.01 with a much higher spatial resolution (~5 km) as compared to ITU-R P.837-6 (~110 km). Another key advantage of the proposed model over ITU-R P.837-6 is that the inputs required for this model are readily available from meteorological database as well as from space-based observing system. This paper also investigated the long-term (1981–2016) trends in R0.01. The analysis revealed significant increasing trends in R0.01 over most parts of the globe, India and northern part of Southern America exhibited the strongest ( $\sim 0.5\,\,\text {mm}\cdot \text {h}^{-1}\cdot $ year−1) increasing trends. It is anticipated that R0.01 obtained with the newly proposed model will have large implications in rain attenuation modeling for planning both terrestrial and earth–satellite microwave links.

Reliable rainfall rate complementary cumulative distributions are critical for the design of microwave communications systems operating above around 8 GHz. This Letter presents the results of the analysis of more than 5 years of 1-minute integrated rainfall accumulation data for 12 stations. This new dataset will prove useful considering the sharing analyses that must be executed for IMT services in the 24.25-27.5, 37-43.5, 45.5-47, 47.2-48.2 and 66-71 GHz spectrum bands. The resulting statistics can complement the entries in the database of ITU-R Study Group 3 for the region.

Method for rainfall rate estimation with satellite based microwave radiometer data is proposed. A method to consider the geometric relationship of the observed ice particles and microwave radiometer in the estimation of precipitation is shown, and its validity is shown by comparing it with precipitation radar data on the ground. Observations at high altitudes, such as ice particles, differ greatly in the location of the observation point projected on the ground surface and in the upper troposphere where the observations exist. This effect was insignificant when the precipitation was small because ice particles were often absent, but it was found that the effect was large when the precipitation was large. In other words, the proposed method is effective and effective for Advanced Microwave Scanning Radiometer (AMSR) data in Houston, which was shown as an example of a highly developed convective rain cloud with an In the case of Kwajalein, the effect is insignificant. In addition, the proposed method requires an assumption of ice particle height, and it is necessary to make assumptions based on climatic values. In addition, microwaves in the 89 GHz band, which are considered to be sensitive to ice particles, are not only sensitive to ice particles, so it must be taken into account that they are also affected by the presence of non-ice particles.

Reliable, cheap and accurate measurements of rainfall rate are growing to be more and more important in many sectors as: meteorology, agriculture, flood warning, and weather forecasting. Recently, indeed, the development of novel competitive techniques has been pushed in order to improve accuracy and reliability performance, such as commercial microwave links and broadcast satellite links. The aim of the current paper is to extend previous works of the literature based on land wireless links only. The basic idea consists in synergically employing both land and satellite based approaches together, by collecting and properly fusing the corresponding measurements. To this end, an iterative optimization procedure has been developed. As shown by numerical results, the proposed procedure gives the estimated rainfall map with a considerable accuracy and improved performance respect to the conventional algorithm based on terrestrial link only.

An analysis based on rainfall rate characteristics has been carried out to estimate flood occurance. In this paper, we analyzed the rain gauge data for 5 different rain gauge stations. 14 days acquired data covering events before, during and after the flood tragedy in Malaysia. The analysis of the rain gauge data was processed on precipitation phenomena observed in year 2014 in Kota Bharu, Kelantan (Malaysia) from 13 December until 26 December. The data was acquired from the Malaysian Drainage and Irrigation Department (DID). The objective of the research is to derive the tropical flood estimation model using rain gauge data in Malaysia. Among the preliminary result shows that the average rainfall rate at kota bharu is 204.5 mm/hr during the flood tragedy

The National Oceanic and Atmospheric Administration (NOAA) Geostationary Operational Environmental Satellite series R (GOES-R) will greatly expand the ability to observe the earth from geostationary orbit compared to the current-generation GOES, with more than 3 times as many spectral bands and a 75% reduction in footprint size. These enhanced capabilities are beneficial to rainfall rate estimation since they provide sensitivity to cloud-top properties such as phase and particle size that cannot be achieved using the limited channel selection of current GOES. The GOES-R rainfall rate algorithm, which is an infrared-based algorithm calibrated in real time against passive microwave rain rates, has been previously described in an algorithm theoretical basis document (ATBD); this paper describes modifications since the release of the ATBD, including a correction for evaporation of precipitation in dry regions and improved calibration updates. These improvements have been evaluated using a simplified version applicable to current-generation GOES to take advantage of the high-resolution ground validation data routinely available over the conterminous United States. Correcting for subcloud evaporation using relative humidity from a numerical model reduced false alarm rainfall by half and reduced the overall error by 35% for hourly accumulations validated against the National Centers for Environmental Prediction stage IV radar–gauge field; however, the number of missed events did increase slightly. Reducing the size of the calibration regions and increasing the training data requirements improved the consistency of the retrieved rates in time and space and reduced the overall error by an additional 4%.

The knowledge of adequate rainfall statistics will contribute greatly to the roll-out of emerging wireless technologies on the platform of Long-Term Evolution (LTE) and WiMax (IEEE 802.16). Therefore, it is important that rainfall measurements at shorter integration time are incorporated as useful inputs in the planning of Line-of-Sight (LOS) microwave and millimetre communication links for hosting these technologies. As compared to the use of one-minute rainfall data as suggested by International Telecommunication Union (ITU), the equivalent data measured at 30-second interval gives more information of temporal rain rates in the time domain. Therefore, in this study, rainfall rate measurements of 5-minute integration time representative of 10 locations in South Africa are evaluated to obtain their cumulative distributions. Results from these analyses are compared with rainfall data of one-minute and 30-second integration time data obtained over Durban (29°52'E, 30°55'S), South Africa. Consequently, rainfall rate models for conversion to one-minute and 30-second integration times were obtained over 10 locations in South Africa using the power-law regression functions. Our results obtained over these locations were used to estimate specific attenuation values in selected microwave and millimetric wave bands at 12 GHz, 30 GHz and 60 GHz for 10 locations under study. It is confirmed that the 30-second integration time provides more information needed for estimation of specific attenuation on microwave and millimeter-wave radio links in South Africa.

In Japan, there are many natural disasters that often expose residents to the risk of serious damage. To minimize such damage, the Japanese government has built a disaster information network using a radio system, and as part of it, an outdoor acoustic mass notification system is routinely operated. However, its intelligibility may be reduced by outdoor noise, which is increased by rainfall. In the present study, long-term surveys of rainfall rate and outdoor noise were conducted at four sites with different surrounding environments and the relationship between them was analyzed to clarify the effects of the rainfall rate on the physical characteristics of outdoor noise. The results indicated that the median sound pressure level for each 1/3 octave band increased with increasing rainfall rate, mainly above mid-frequencies of around 500 Hz to 1 kHz, though the frequency at which the level began to rise depended on the time period and site. Furthermore, a newly proposed macroscopic model for estimating the sound pressure level of outdoor noise under rainy conditions indicated that the distance from the loudspeaker of the system to ensure a certain speech-to-noise ratio could be significantly reduced by heavy rainfall.

187 p. Due to the need for an understanding of the rain structure and the effect of rainfall on the high frequency wireless communication links, several issues related to the characters of rainfall rates and rain attenuation in Singapore are studied. This will enable the development of a comprehensive rain attenuation model. MASTER OF ENGINEERING (EEE)

The convective rainfall rate from cloud physical properties (CRPh) algorithm for Meteosat second-generation satellites is a day-only precipitation algorithm developed at the Spanish Meteorological Agency (AEMET) for EUMETSAT’ Satellite Application Facility in support of nowcasting and very short-range forecasting (NWC SAF). It is therefore mainly intended to provide input for monitoring and near-real-time forecasts for a few hours. This letter critically discusses the theoretical basis of the algorithm with special emphasis on the empirical values and assumptions in the microphysics of precipitation, and compares the qualitative performances of the CRPh with its antecessor, the convective rainfall rate algorithm (CRR), using an object-based method applied to a case-study. The analyses show that AEMET’s CRPh is physically consistent and outperforms the CRR. The applicability of the algorithm for nowcasting and the challenges of improving the product to an all-day algorithm are also presented.