1-min Rain Rate Research Articles

On the conversion of a 3-hour integration time rain rate into one minute rain rate for forecast of attenuation due to rain

Degradation of satellite signal due to rain at Ku- band and higher frequencies are of much importance to the radio science community. This calls for a continuous effort in the development of a 1-min rain rate conversion model from 180-min (3 hours) integration time which would be helpful in the utilization of such data in the generation of 1-min rain rate towards rain attenuation calculation from the available attenuation models. This paper has therefore presented a formula that converts a 180-min (3 hours) rain rate to its 1-min equivalent rain rate.

The sensitivity of intense rainfall to aerosol particle loading – a comparison of bin-resolved microphysics modelling with observations of heavy precipitation from HyMeX IOP7a

Abstract. Over the Cévennes–Vivarais region in southern France 5 h intensive rainfall covering an area of 1000 km2 with more than 50 mm of rain accumulation was observed during IOP7a of HyMeX. This study evaluates the performance of a bin-resolved cloud model for simulating this heavy-precipitation event. The simulation results were compared with observations of rain accumulation, radar reflectivity, temporal and spatial evolution of precipitation, 5 min rain rates, and raindrop size distributions (RSDs). The different scenarios for aerosol number concentrations range from 1000 to 2900 cm−3 and represent realistic conditions for this region. Model results reproduce the heavy-precipitation event with respect to maximum rain intensity, surface area covered by intense rain and the duration, as well as the RSD. Differences occur in the short-term rainfall rates, as well as in the drop number concentration. The cloud condensation number concentration has a notable influence on the simulated rainfall, on both the surface amount and intensity but also on the RSD properties, and should be taken into account in microphysics parameterizations.

Estimation of Rainfall Rate Cumulative Distribution in Indonesia Using Global Satellite Mapping of Precipitation Data

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Rainfall rate and rain attenuation contour maps for preliminary “Simon Bolivar” satellite links planning in Venezuela

Predicting precipitation rate and rainfall attenuation are key aspects in planning and dimensioning of wireless communications systems operating at frequencies above 10 GHz, such as satellite communication systems at Ku and Ka bands. In this paper, contour maps of rainfall rate and rain attenuation are developed for the first time in Venezuela, based on 1-min rain rate statistics obtained from measurements carried out in Venezuela over at least 30 years period with a higher integration time and using Rice-Holmberg model, refined Moupfouma-Martin model and Recommendation ITU-R P.837-7, for rain rate estimation and Recommendation ITU-R P.618-13, Ramachandran-Kumar model, Yeo-Lee-Ong model and Rakshit-Adhikari-Maitra model, for rain attenuation prediction in “Simon Bolivar” satellite links in Venezuela. The overall results of both types of maps represent a useful tool for preliminary planning of those links in the country, specifically, in Ku and Ka bands

Estimating One-Minute Rain Rate Distributions in the Tropics From TRMM Satellite Data (October 2017)

Internationally recognized prognostic models of rain fade on terrestrial and Earth-space extremely high frequency (EHF) links rely fundamentally on distributions of 1-min rain rates. In Rec. ITU-R P.837-6, these distributions are estimated from the data provided by Numerical Weather Products (NWPs). NWP yields rain accumulations over regions typically larger than 100 km across and over intervals of 6 h. Over the tropics, the Tropical Rain Measuring Mission (TRMM) satellite data yield instantaneous rain rates over regions 5 km across. This paper uses TRMM data to estimate rain rate distributions for telecommunications regulation over the tropics. Rain rate distributions are calculated for each 1° square between 35° south to 35° north. These distributions of instantaneous rain rates over 5 km squares are transformed to distributions over 1 km squares using a correction calculated from U.K. Nimrod radar data. Results are compared to rain distributions in DBSG3, the database of ITU-R Study Group 3. A comparison with the new Rec. ITU-R P.837-7 is also presented. A table of 0.01% exceeded rain rates over the tropics is provided as associated data.

Statistical Modelling of 1-min Rain Rate Derived from 1-h Integration Time in Malaysia

Statistical analysis of 1 min rain rate used in estimation of rain attenuation is presented. In rainy condition, the electromagnetic signal tend to experience serious degradation in satellite communication system that operate above 10 GHz. Prediction of 1-min rain rate requires conversion method from longer integration time is important due to its limited 1 min availability in most places. A linear model was proposed in this paper and compared with few existing model in Malaysia. The proposed model achieved good result for Malaysia data which is at par with established models such as Segal, Burguẽno, and Chebil and Rahman.

Extension of ITU-R method for 1-h to 1-min conversion of rain rate statistics for satellite propagation in Malaysia

1-min rain rate is the key element to predict rain attenuation at a location precisely. However there is the limitation of 1-min rain rate availability in Malaysia for long term local measurement because rain rate statistics are commonly derived on the rain gauge recordings base with actual integration times of 10-min or longer. Therefore, conversion of available rain rate distributions with longer integration times to 1-min rain rate distributions is necessary. This paper proposes new set of coefficients to current ITU-R for Malaysia in order to improve the accuracy of conversion from 1-h to 1-min rain rate. From this study, the test shows the proposed set of coefficients performed better than Emiliani et al. (extension of ITU-R), Chebil and Rahman method in terms of accuracy. This study is important to provide more accurate regression coefficients to system designers when designing link margin.

Performance analysis of 60-min to 1-min integration time rain rate conversion models in Malaysia

Utilizing the frequency band above 10 GHz is in focus nowadays as a result of the fast expansion of radio communication systems in Malaysia. However, rain fade is the critical factor in attenuation of signal propagation for frequencies above 10 GHz. Malaysia is located in a tropical and equatorial region with high rain intensity throughout the year, and this study will review rain distribution and evaluate the performance of 60-min to 1-min integration time rain rate conversion methods for Malaysia. Several conversion methods such as Segal, Chebil & Rahman, Burgeono, Emiliani, Lavergnat and Gole (LG), Simplified Moupfouma, Joo et al., fourth order polynomial fit and logarithmic model have been chosen to evaluate the performance to predict 1-min rain rate for 10 sites in Malaysia. After the completion of this research, the results show that Chebil & Rahman model, Lavergnat & Gole model, Fourth order polynomial fit and Logarithmic model have shown the best performances in 60-min to 1-min rain rate conversion over 10 sites. In conclusion, it is proven that there is no single model which can claim to perform the best across 10 sites. By averaging RMSE and SC-RMSE over 10 sites, Chebil and Rahman model is the best method.

Study of 1-min rain rate integration statistic in South Korea

The design of millimeter wave communication links and the study of propagation impairments at higher frequencies due to a hydrometeor, particularly rain, require the knowledge of 1-min. rainfall rate data. Signal attenuation in space communication results are due to absorption and scattering of radio wave energy. Radio wave attenuation due to rain depends on the relevance of a 1-min. integration time for the rain rate. However, in practice, securing these data over a wide range of areas is difficult. Long term precipitation data are readily available. However, there is a need for a 1-min. rainfall rate in the rain attenuation prediction models for a better estimation of the attenuation. In this paper, we classify and survey the prominent 1-min. rain rate models. Regression analysis was performed for the study of cumulative rainfall data measured experimentally for a decade in nine different regions in South Korea, with 93 different locations, using the experimental 1-min. rainfall accumulation. To visualize the 1-min. rainfall rate applicable for the whole region for 0.01% of the time, we have considered the variation in the rain rate for 40 stations across South Korea. The Kriging interpolation method was used for spatial interpolation of the rain rate values for 0.01% of the time into a regular grid to obtain a highly consistent and predictable rainfall variation. The rain rate exceeded the 1-min. interval that was measured through the rain gauge compared to the rainfall data estimated using the International Telecommunication Union Radio Communication Sector model (ITU-R P.837–6) along with the empirical methods as Segal, Burgueno et al., Chebil and Rahman, logarithmic, exponential and global coefficients, second and third order polynomial fits, and Model 1 for Icheon regions under the regional and average coefficient set. The ITU-R P. 837-6 exhibits a lower relative error percentage of 3.32% and 12.59% in the 5- and 10-min. to 1-min. conversion, whereas the higher error percentages of 24.64%, 46.44% and 58.46% for the 20-, 30- and 60-min. to 1-min., conversion were obtained in the Icheon region. The available experimental rainfall data were sampled on equiprobable rain-rate values where the application of these models to experimentally obtained data exhibits a variable error rate. This paper aims to provide a better survey of various conversion methods to model a 1-min. rain rate applicable to the South Korea regions with a suitable contour plot at 0.01% of the time.

Estimating 1 min rain rate distributions from numerical weather prediction

AbstractInternationally recognized prognostic models of rain fade on terrestrial and Earth‐space EHF links rely fundamentally on distributions of 1 min rain rates. Currently, in Rec. ITU‐R P.837‐6, these distributions are generated using the Salonen‐Poiares Baptista method where 1 min rain rate distributions are estimated from long‐term average annual accumulations provided by numerical weather prediction (NWP). This paper investigates an alternative to this method based on the distribution of 6 h accumulations available from the same NWPs. Rain rate fields covering the UK, produced by the Nimrod network of radars, are integrated to estimate the accumulations provided by NWP, and these are linked to distributions of fine‐scale rain rates. The proposed method makes better use of the available data. It is verified on 15 NWP regions spanning the UK, and the extension to other regions is discussed.

Proposed One-Minute Rain Rate Conversion Method for Microwave Applications in Korea

Microwave and millimeter waves are considered suitable frequency ranges for diverse applications. The prediction of rain attenuation required the 1-min rainfall rate distribution, particularly for data obtained locally from experimental measurement campaigns over a given location. Rainfall rate data acquired from Korea Meteorological Administration (KMA) for nine major sites are analyzed to investigate the statistical stability of the cumulative distribution of rainfall rate, as obtained from a 10-year measurement. In this study, we use the following rain rate conversion techniques: Segal, Burgueno et al., Chebil and Rahman, exponential, and proposed global coefficient methods. The performance of the proposed technique is tested against that of the existing rain rate conversion techniques. The nine sites considered for the average 1-min rain rate derivation are Gwangju, Daegu, Daejeon, Busan, Seogwipo, Seoul, Ulsan, Incheon, and Chuncheon. In this paper, we propose a conversion technique for a suitable estimation of the 1-min rainfall rate distribution.

Rain rate modeling of 1-min from various integration times in South Korea

Rain plays a major impairment factor for propagation of electromagnetic waves in atmosphere for systems operating at frequencies above 10 GHz. Several effects are noted such as depolarization, scintillation, interference due to scattering and extra attenuation which seems to increase with frequency. To mitigate its effect in satellite communication, knowledge of local rainfall statistics is necessary which act as milestone for design of radio link. Rain attenuation is best visualize by the 1-min rainfall rate statistic but the measurement of this rain rate distribution is rare on a worldwide basis and observation of rain rate are done with longer integration times typically 30 min or more. In this paper, efforts have been made to develop model that can convert rain rate complementary cumulative distribution function to shorter integration times. The average relative error margin of about 5, 14, 43, 71 and 115 % are noted for 5 to 1-, 10 to 1-, 20 to 1, 30 to 1- and 60 to 1-min respectively from ITU-R P.837-6 method which have been analyzed in further section of this article. The empirical natures of conversion methods as such Segal method, Burgueno’s method, Chebil and Rahman method and Logarithmic model are studied along with the proposed new model that seems to be applicable in derivation of 1-min rain rate of the South Korea rain rate statistics. International Telecommunication Union-Radio communication Sector (ITU-R) has developed a recommendation ITU-R P.837-6 that enables the user to estimate the local 1-min rainfall rate statistical distribution which is compared with calculated 1-min rain rate distribution from experimental 1-min rainfall accumulation. Unfortunately, ITU-R P.837-6 estimated 1-min values show greater error percentages. In order to get better approximation of local 1-min rain rate estimation, a novel method is proposed and it’s efficiency have been compared with rainfall rate statistics obtained from nine different locations in the South Korea.

Dynamical Model for Deriving 1-Min Rain Rate from Various Integration Times in a Tropical Region

The congestion at the lower frequency bands has forced the telecommunication system engineers to move to higher frequencies. However, microwave signal tends to undergo fading effect at frequencies above 10 GHz due to rainfall. Consequently, the 1-min rain rate data needed for the prediction of rain-induced attenuation is still very scarce in most part of the world, Nigeria inclusive. Therefore, appropriate conversion method is needed to convert the available data to the required 1-min rain rate data. In this paper, an empirical and dynamic method for conversion of long integration time to 1-min integration time has been proposed and compared with other conversion methods. In overall, conversion factor modeled with a power law (CF-PL) is found suitable to be used in this region based on an average rms error less than 2%.

Validation of Empirical Rainrate Models Over a Tropical Coastal Station and an Inland Station in Southern India

Conversion of rainrate statistics from different integration times to 1 min is studied using 6 years (2007–2011, 2013) of disdrometric rainrate data over a tropical coastal station, Thiruvananthapuram ( ${8.5^{\circ}}{\rm N}$ , ${76.9^{\circ}}{\rm E}$ ), and an inland station, Gadanki ( ${13.5^{\circ}}{\rm N}$ , ${79.2^{\circ}}{\rm E}$ ), India. In this study, we used two established empirical models, namely Chebil and Segal, for deriving the conversion factors suitable for these stations. Results show that the Chebil model performs better than the Segal model over these locations for the conversion of different integration times to 1-min rainrate statistics. The 1-min rainrate statistics for the two sites are also estimated for different integration times using the ITU-R P. 837-6 method. Prediction performance of the Chebil model is assessed and is compared to ITU-R Rec P. 837-6. Chebil form is observed to be consistent up to ${\rm P} = 0.01\% $ time of the exceedance in a year. The results suggest that the ITU-R model needs to be suitably modified for the study region.

A method to estimate trends in distributions of 1 min rain rates from numerical weather prediction data

AbstractIt is known that the rain rate exceeded 0.01% of the time in the UK has experienced an increasing trend over the last 20 years. It is very likely that rain fade and outage experience a similar trend. This paper presents a globally applicable method to estimate these trends, based on the widely accepted Salonen‐Poiares Baptista model. The input data are parameters easily extracted from numerical weather prediction reanalysis data. The method is verified using rain gauge data from the UK, and the predicted trend slopes of 0.01% exceeded rain rate are presented on a global grid.

Space communications with variable elevation angle faded by rain: Radio links to the Sun-Earth first Lagrangian point L1

Summary How rain attenuation affects space links with variable elevation angles is not yet fully researched. The aim of this paper is to investigate this topic by simulating rain attenuation at Ka Band, in slant paths with variable elevation angles, with the Synthetic Storm Technique (SST), in links connected with spacecrafts at the Sun–Earth first Lagrangian point L1, viewed from Spino d'Adda (Italy), Tampa (Florida), White Sands (New Mexico). The input to the SST is a large database of time series of 1-min rain rate recorded on site, 10 years in Spino d'Adda, 4 years at Tampa and White Sands. After recalling known results on the elevation angle of the Sun (i.e. L1), θs (°), seen from latitude λ (°), I report what seems to be a new result: the mode of the probability density function of θs in a year, in the range 0 ≤ λ ≤ 90° − e (Earth axis tilt angle e = 23.44°), coincides with the peak angle found at the day of the Winter solstice at the site, a result valid also for other planets, once their tilt angle is used. Compared to the complementary probability distribution function (pdf) of rain attenuation calculated for a geostationary (GEO) link (fixed elevation angle), the pdf to L1 depends on the rain-rate pdf during the contact time with L1, according to the local climate. I show that, to obtain a good and easier estimate of the rain attenuation pdf in L1 links, we can consider a GEO link with elevation angle equal to the mean angle and rain rate pdf, both during the contact time, and that the mode angle gives an upper bound to the rain attenuation pdf in the sites considered. Copyright © 2015 John Wiley & Sons, Ltd.

Comparison of 1-min rain rate derived from TRMM satellite data and raingauge data for microwave applications in Nigeria

A comparative statistical study of derived 1-min rain rate using data obtained from Tropical Rainfall Measuring Mission (TRMM) satellite (3A12 V6 and 3B43V6) and raingauge measurements are presented. 30-years data of rainfall intensities obtained from the Nigerian Meteorological Agency rain-gauge network and 9-years rainfall data obtained from TRMM satellite are used. Cumulative distributions of rain rate were obtained using a combination of an improved version of the Moupfouma–Martin model for rain rate prediction in the tropical regions. Variations of rain rate of different integration time are compared for 28 stations across Nigeria. The Kriging interpolation method was used for spatial interpolation of rain accumulation values into a regular grid in order to obtain a highly consistent and predictable inter-gauge rainfall variation. Noticeable differences between rain rate estimated from rain-gauge and TRMM data were found to be a function of period and location. From quantitative comparison over each of the region, there are reasonably positive correlations between the two sets of data for different percentages of time with correlation coefficient varying from 0.84 to 0.99 at 99.99% availability of time. Comparison with ITU-R 837-5 shows that, ITU model underestimates rain rate as high as 51% from the mean value depending on the percentages of at which time rain rate is exceeded. The overall result shows that the gauge data perform better than TRMM data in most of the sites located in the SW, SE, SS, MB and NE regions, while TRMM data provided better results for sites in the NW region from the statistical perspective with the lower RMS values.

Undercatch of tipping-bucket gauges in high rain rate events

Abstract. We have investigated differences in rainfall accumulations for seven high rain rate events from three gauges: a Geonor T-200B vibrating-wire weighing gauge and two MetOne tipping-bucket gauges. The Geonor gauge and one tipping-bucket gauge are located in a pit so that their collection orifices are at ground level. Thus their measured rainfall accumulations are minimally affected by wind speed. The other tipping-bucket gauge is located 105 m from the pit and is surrounded by an Alter-type slatted wind screen. Its collection orifice is positioned 1 m above ground level. The results from the seven events show that the tipping-bucket gauges noticeably underestimated storm event rainfall totals relative to the weighing-bucket gauge when 1-min rain rates exceeded about 50 mm/h (2 in/h). In addition, we conclude that observable wind induced undercatch by the aboveground tipping bucket gauge begins when the wind speed at a height of 2 m exceeds around 5 m/s. In this paper we show and discuss time series of rain rates, differences in rain rates, and wind speeds for two of the seven events in an attempt to account for the lower storm totals from the two tipping bucket gauges relative to the weighing-bucket gauge.

Empirical Prediction Models of 1-min Rain Rate Distribution for Various Integration Time

In a wireless channel above microwave frequency, rain attenuation is very important. In order to predict rain attenuation, 1- min. rain rate distribution is required. This paper discusses appropriate conversion methods to estimate 1-minute rain rate from that of other integration time. Based on the measurement data filed in ITU-R WP3J including ETRI data for 6 consecutive years, distributions of rain rate with 1-, 5-, 10-, 20-, 30-minute integration time were analyzed, both on the global and regional basis, and the parametric relationship between the statistical characteristics of 1-minute and other measurement data were investigated to deduce the conversion methods. It is shown that the global model works good with good accuracy for 5-, 10-, 20-min integration time, and the global model is also applicable globally with good accuracy for 5-, 10-, 20-min integration time. The global conversion model was adopted last year as an ITU-R document for new recommendation. The regional conversion model would also be very useful for locations of similar climatic zone.

Rain precipitation in terrestrial and satellite radio links

This paper covers unavailability of terrestrial and satellite line-of-sight radio links due to rain. To evaluate the rain effects over communication system, it is essential to know the temporal and spatial evolution of rainfall rate. Longterm 1-min average rain-rate characteristics necessary for the design of microwave radio links are determined for central Poland. 1-min rain rate distributions are presented. It also describes comparison results of predicted attenuation obtained from ITU-R formula and empirical data at frequency bands 11 GHz and 18 GHz and satellite 12 GHz. The National Institute of Telecommunications stores 11-year long rain intensity characteristics (1985–1996), based on data derived on 15.4 km long experimental path. In this paper chosen experimental data are presented.