scholarly journals How Is the Intensity of Rainfall Events Best Characterised? A Brief Critical Review and Proposed New Rainfall Intensity Index for Application in the Study of Landsurface Processes

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 929 ◽  
Author(s):  
David Dunkerley
Keyword(s):  
Rainfall Intensity ◽  
Clock Period ◽  
Event Duration ◽  
Rainfall Events ◽  
Rainfall Characteristics ◽  
Convective Storms ◽  
Intensity Index ◽  
Rainfall Depth ◽  
Minute Interval ◽  
Event Based

In many studies of landsurface processes, the intensity of rainfall events is expressed with clock-period indexes such as I30, the wettest 30-minute interval within a rainfall event. Problematically, the value of I30 cannot be estimated for rainfall events shorter than 30 min, excluding many intense convective storms. Further, it represents a diminishing proportion of increasingly long rainfall events, declining to <2% of the duration of a 30-hour event but representing 25% of the duration of a two-hour event. Here, a new index termed EDf5 is proposed: It is the rainfall depth in the wettest 5% of the event duration. This can be derived for events of any duration. Exploratory determinations of EDf5 are presented for two Australian locations with contrasting rainfall climatologies—one arid and one wet tropical. The I30 index was similar at both sites (7.7 and 7.9 mm h−1) and was unable to differentiate between them. In contrast, EDf5 at the arid site was 7.4 mm h−1, whilst at the wet tropical site, it was 3.8 mm h−1. Thus, the EDf5 index indicated a greater concentration of rain at the arid site where convective storms occurred (i.e., the intensity sustained for 5% of event duration at that site is higher). The EDf5 index can be applied to short, intense events that can readily be included in the analysis of event-based rainfall intensity. I30 therefore appears to offer less discriminatory power and consequently may be of less value in the investigation of rainfall characteristics that drive many important landsurface processes.

scholarly journals How rainfall event characteristics affect the applicability of I<sub>30</sub> as an index of intense or erosive rainfall: a brief review with proposed new rainfall index

2019 ◽  
Author(s):  
David L. Dunkerley
Keyword(s):  
Rainfall Event ◽  
Average Intensity ◽  
Clock Period ◽  
Event Duration ◽  
Rainfall Events ◽  
Rainfall Characteristics ◽  
Convective Storms ◽  
Rainfall Index ◽  
Minute Interval ◽  
Erosive Rainfall

Abstract. In many fields, the intensity of rainfall events is expressed using indexes such as I30, the wettest 30-minute interval within a rainfall event. Various limitations attend this usage: I30 cannot be estimated for rainfall events shorter than 30 minutes, including many intense convective storms, and it represents a diminishing proportion of increasingly long rainfall events (representing 10 % of the duration of a 5-hour event but declining to < 2 % of the duration in a 30-hour event). These and other issues connected with I30 and related indices based on fixed clock periods (I15, I60, etc.) can be eliminated if instead, a nominated fraction of the event duration is used as an index, such as the wettest 5 % of the event duration. This index (termed EDf5) can be derived for both short and long rainfall events. Illustrative results are presented for two Australian locations having high-resolution rainfall data and contrasting rainfall climatologies, one arid and one wet tropical. The value of I30 is similar at both sites (7.7 mm h-1 and 7.9 mm h-1) and fails to differentiate between them. In contrast, the average intensity of the wettest 5 % of event durations (EDf5) at the arid site is 7.4 mm h-1, whilst at the wet tropical site, the corresponding value is 3.8 mm h-1. Thus, the EDf5 index indicates a greater concentration of rain at the arid site (i.e., intensity sustained for 5 % of event duration at the wet tropical site is lower). Results exemplify the capacity of the EDf5 index to be applied to short, intense events. The use of a fixed 30-minute clock period to describe intensity at the contrasting field locations has less discriminatory power and may be of less use in the investigation of rainfall characteristics that drive landsurface processes.

scholarly journals Selection of intense rainfall events based on intensity thresholds and lightning data in Switzerland

2014 ◽  
Vol 18 (5) ◽  
pp. 1561-1573 ◽  
Author(s):  
L. Gaál ◽  
P. Molnar ◽  
J. Szolgay
Keyword(s):  
Rainfall Intensity ◽  
Probability Distributions ◽  
Warm Season ◽  
Misclassification Rate ◽  
Event Duration ◽  
Rainfall Events ◽  
Lightning Strikes ◽  
Intense Storm ◽  
Rainfall Depth ◽  
Selection Of

Abstract. This paper presents a method to identify intense warm season storms with convective character based on intensity thresholds and the presence of lightning, and analyzes their statistical properties. Long records of precipitation and lightning data at 4 stations and 10 min resolution in different climatological regions in Switzerland are used. Our premise is that thunderstorms associated with lightning generate bursts of high rainfall intensity. We divided all recorded storms into those accompanied by lightning and those without lightning and found the threshold I* that separates intense events based on peak 10 min intensity Ip ≥ I* for a chosen misclassification rate α. The performance and robustness of the selection method was tested by investigating the inter-annual variability of I* and its relation to the frequency of lightning strikes. The probability distributions of the main storm properties (rainfall depth R, event duration D, average storm intensity Ia and peak 10 min intensity Ip) for the intense storm subsets show that the event average and peak intensities are significantly different between the stations. Non-parametric correlations between the main storm properties were estimated for intense storms and all storms including stratiform rain. The differences in the correlations between storm subsets are greater than those between stations, which indicates that care must be exercised not to mix events of different origin when they are sampled for multivariate analysis, for example, copula fitting to rainfall data.

scholarly journals Selection of intense rainfall events based on intensity thresholds and lightning data in Switzerland

2014 ◽  
Vol 11 (1) ◽  
pp. 593-628
Author(s):  
L. Gaal ◽  
P. Molnar ◽  
J. Szolgay
Keyword(s):  
Rainfall Intensity ◽  
Probability Distributions ◽  
Warm Season ◽  
Misclassification Rate ◽  
Event Duration ◽  
Rainfall Events ◽  
Lightning Strikes ◽  
Intense Storm ◽  
Rainfall Depth ◽  
Selection Of

Abstract. This paper presents a method to identify intense warm season storms of convective character based on intensity thresholds and lightning, and analyzes their statistical properties. Long records of precipitation and lightning data at 4 stations and 10 min resolution in different climatological regions in Switzerland are used. Our premise is that thunderstorms associated with lightning generate bursts of high rainfall intensity. We divided all storms into those accompanied by lightning and those without lightning and found the threshold I* that separates intense events based on peak 10 min intensity Ip ≥ I* for a chosen misclassification rate α. The performance and robustness of the selection method was tested by investigating the inter-annual variability of I* and its relation to the frequency of lightning strikes. The probability distributions of the main storm properties (rainfall depth R, event duration D, average storm intensity Ia and peak 10 min intensity Ip) for the intense storm subsets show that the event average and peak intensities are significantly different between the stations, and highest in Lugano in southern Switzerland. Non-parametric correlations between the main storm properties were estimated for the subsets of intense storms and all storms including stratiform rain. The differences in the correlations between storm subsets are greater than those between stations, which indicates that care must be exercised not to mix events when they are sampled for multivariate analysis, e.g. copula fitting to rainfall data.

Measurement properties of tipping bucket rain gauges and their influence on urban runoff simulation

1997 ◽  
Vol 36 (8-9) ◽  
pp. 7-12 ◽  
Author(s):  
R. Fankhauser
Keyword(s):  
Time Resolution ◽  
Rainfall Intensity ◽  
Depth Resolution ◽  
Urban Hydrology ◽  
Data Series ◽  
Runoff Simulation ◽  
Rainfall Events ◽  
Rain Gauges ◽  
Rainfall Depth ◽  
Bucket Size

Tipping bucket rain gauges (TBR) have become the most common device for measuring rainfall intensity in urban hydrology. Due to the measurement principle, the time resolution depends on rainfall intensity and bucket size. The present study investigated the influence of calibration uncertainties and bucket size on the accuracy of rainfall measurement and runoff simulation. Synthetic rainfall events with a time resolution of 6 seconds were generated from measured data. These rainfall series were taken as input to a model that simulated a TBR. Different TBR data series were produced by changing calibration parameters and bucket size of the simulated rain gauge. These data series together with the original rainfall events were used as input to a rainfall-runoff model. Computed runoff and overflow volume from a CSO weir were compared. The differences in rainfall depth, intensity peak and computed runoff due to the depth resolution of the TBR were smaller than expected. A depth resolution of the TBR of 0.2 - 0.3 mm per tip seems to fulfil the requirements in urban hydrology. Errors resulting from depth resolution are small compared to those of calibration (especially false rainfall depth per tip), site exposure, the influence of wind or disregarded areal rainfall distribution.

scholarly journals Effect of Multicollinearity on the Bivariate Frequency Analysis of Annual Maximum Rainfall Events

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 905 ◽  
Author(s):  
Yoo ◽  
Cho
Keyword(s):  
Frequency Analysis ◽  
Rainfall Intensity ◽  
Rainfall Event ◽  
Total Rainfall ◽  
Maximum Rainfall ◽  
Rainfall Events ◽  
Rainfall Duration ◽  
Rainfall Depth ◽  
The Mean ◽  
Annual Maximum Rainfall

A rainfall event, simplified by a rectangular pulse, is defined by three components: the rainfall duration, the total rainfall depth, and mean rainfall intensity. However, as the mean rainfall intensity can be calculated by the total rainfall depth divided by the rainfall duration, any two components can fully define the rainfall event (i.e., one component must be redundant). The frequency analysis of a rainfall event also considers just two components selected rather arbitrarily out of these three components. However, this study argues that the two components should be selected properly or the result of frequency analysis can be significantly biased. This study fully discusses this selection problem with the annual maximum rainfall events from Seoul, Korea. In fact, this issue is closely related with the multicollinearity in the multivariate regression analysis, which indicates that as interdependency among variables grows the variance of the regression coefficient also increases to result in the low quality of resulting estimate. The findings of this study are summarized as follows: (1) The results of frequency analysis are totally different according to the selected two variables out of three. (2) Among three results, the result considering the total rainfall depth and the mean rainfall intensity is found to be the most reasonable. (3) This result is fully supported by the multicollinearity issue among the correlated variables. The rainfall duration should be excluded in the frequency analysis of a rainfall event as its variance inflation factor is very high.

scholarly journals A Novel Approach for Delineation of Homogeneous Rainfall Regions for Water Sensitive Urban Design—A Case Study in Southeast Queensland

Water ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 570 ◽  
Author(s):  
Ashiq Rasheed ◽  
Prasanna Egodawatta ◽  
Ashantha Goonetilleke ◽  
James McGree
Keyword(s):  
Urban Design ◽  
Rainfall Intensity ◽  
Conventional Approach ◽  
Rainfall Characteristics ◽  
Novel Approach ◽  
Water Sensitive Urban Design ◽  
Event Based ◽  
Homogeneous Regions ◽  
Southeast Queensland

The delineation of homogeneous regions is primarily based on long-term overall rainfall characteristics and therefore does not necessarily consider the homogeneity of event-based rainfall characteristics. However, event-based rainfall characteristics including antecedent dry days, rainfall intensity, total rainfall and total duration of rainfall events are critical for Water Sensitive Urban Design (WSUD). Accordingly, this study presents a novel approach to objectively identify homogeneous rainfall regions based on event-based rainfall characteristics. This approach uses cluster analysis and Hosking–Wallis heterogeneous tests collectively to test the homogeneity of event-based rainfall characteristics. A case study conducted for southeast Queensland (SEQ), Australia is also presented in this article. This study compares the results of the novel modified approach against results of the conventional approach for the delineation of homogeneous regions. It was evident from the results that the entire SEQ could be treated as a homogeneous rainfall region based on the conventional approach. In contrast, based on the modified approach, the coast and the inland of SEQ were identified as separate homogeneous regions. Further, antecedent dry days and rainfall intensity were recognized as the deciding rainfall characteristics in the delineation of homogeneous rainfall regions.

scholarly journals Multiscale Evaluation of Extreme Rainfall Event Predictions Using Severity Diagrams

2012 ◽  
Vol 27 (1) ◽  
pp. 174-188 ◽  
Author(s):  
Davide Ceresetti ◽  
Sandrine Anquetin ◽  
Gilles Molinié ◽  
Etienne Leblois ◽  
Jean-Dominique Creutin
Keyword(s):  
Time Scales ◽  
Rainfall Intensity ◽  
Mesoscale Model ◽  
Extreme Rainfall ◽  
Space Time ◽  
Extreme Rainfall Event ◽  
Maximum Rainfall ◽  
Rainfall Events ◽  
Rainfall Depth ◽  
Heavy Rainfall Events

Abstract Observations and simulations of rainfall events are usually compared by analyzing (i) the total rainfall depth produced by the event and (ii) the location of the rainfall maximum. A different approach is proposed here that compares the mesoscale simulated rainfall fields with the ground rainfall observations within the multiscale framework of maximum intensity diagrams and severity diagrams. While the first simply displays the maximum rainfall intensity of an event at a number of scales, the second gives the frequency of occurrence of the maximum rainfall intensities as a function of the spatial and temporal aggregation scales, highlighting the space–time scales of the event severity. For use in a region featuring complex relief, severity diagrams have been generalized to incorporate the regional behavior of heavy rainfall events. To assess simulation outputs from a meteorological mesoscale model, three major storms that have occurred in the last decade over a mountainous Mediterranean region of southern France are analyzed. The severity diagrams detect the critical space–time scales of the rainfall events for comparison with those predicted by the simulation. This validation approach is adapted to evaluate the ability of the mesoscale model to predict various types of storms with different regional climatologies.

scholarly journals Storm event-based frequency analysis method

2017 ◽  
Vol 49 (3) ◽  
pp. 700-710 ◽  
Author(s):  
Changhyun Jun ◽  
Xiaosheng Qin ◽  
Yeou-Koung Tung ◽  
Carlo De Michele
Keyword(s):  
Conventional Method ◽  
Frequency Analysis ◽  
Return Period ◽  
Rainfall Data ◽  
Storm Event ◽  
Analysis Method ◽  
Rainfall Characteristics ◽  
Study Results ◽  
Rainfall Depth ◽  
Event Based

Abstract In this study, a storm event-based frequency analysis method was proposed to mitigate the limitations of conventional rainfall depth–duration–frequency (DDF) analysis. The proposed method takes the number, rainfall depth, and duration of rainstorm events into consideration and is advantageous in estimation of more realistic rainfall quantiles for a given return period. For the purpose of hydraulics design, the rainfall depth thresholds are incorporated to retrieve the rainstorm events for estimating design rainfalls. The proposed method was tested against the observed rainfall data from 1961 to 2010 at Seoul, Korea and the computed rainfall quantiles were compared with those estimated using the conventional frequency analysis method. The study results indicated that the conventional method was likely to overestimate the rainfall quantiles for short rainfall durations. It represented that the conventional method could reflect rainfall characteristics of actual rainstorm events if longer durations (like 24 hours) were considered for estimation of design rainfalls.

scholarly journals Assessment of the effect of rainfall dynamics on the storm overflow performance

2016 ◽  
Vol 48 (2) ◽  
pp. 123-139
Author(s):  
Bartosz Szeląg
Keyword(s):  
Rainfall Intensity ◽  
Research Study ◽  
Treatment Plant ◽  
Management Model ◽  
Model Program ◽  
Rainfall Characteristics ◽  
Storm Water Management Model ◽  
Rainfall Depth ◽  
Calculation Results ◽  
Discharge Duration

Abstract Assessment of the effect of rainfall dynamics on the storm overfl ow performance. This research study analyzes the effect of the rainfall characteristics (total and maximum 10-, 15- and 30-minute rainfall depth, its duration, the dry weather period) on the performance of the emergency overflow weir located at the inflow to an existing treatment plant. The analyses used the numerical calculation results of the inflow hydrographs performed in the SWMM (Storm Water Management Model) program on the basis of six-year-long rainfall measurement sequence. The obtained simulation results for the analysed catchment allowed for the performance of statistical analyses, which demonstrated that the volume of stormwater discharge, the maximum instantaneous flow and the share of stormwater volume discharged through the emergency overflow weir in relation to the total volume of the inflow hydrograph from the catchment are affected by the maximum 30-minute rainfall depth, whereas the discharge duration is affected by the depth of the catchment rainfall layer. Taking into account the results of statistical and hydraulic calculations it can be concluded that in the case of the analysed catchment the performance of the emergency overflow weir is affected to the greatest extent by the rainfall intensity distribution.

scholarly journals Soil Moisture Dynamics in Response to Precipitation and Thinning in a Semi-Dry Forest in Northern Mexico

Water ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 105
Author(s):  
Argelia E. Rascón-Ramos ◽  
Martín Martínez-Salvador ◽  
Gabriel Sosa-Pérez ◽  
Federico Villarreal-Guerrero ◽  
Alfredo Pinedo-Alvarez ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Forest Management ◽  
Water Availability ◽  
Dry Forest ◽  
Rainfall Events ◽  
Rainfall Characteristics ◽  
Northern Mexico ◽  
The Difference ◽  
The Impact ◽  
Moisture Dynamics

Understanding soil moisture behavior in semi-dry forests is essential for evaluating the impact of forest management on water availability. The objective of the study was to analyze soil moisture based in storm observations in three micro-catchments (0.19, 0.20, and 0.27 ha) with similar tree densities, and subject to different thinning intensities in a semi-dry forest in Chihuahua, Mexico. Vegetation, soil characteristics, precipitation, and volumetric water content were measured before thinning (2018), and after 0%, 40%, and 80% thinning for each micro-catchment (2019). Soil moisture was low and relatively similar among the three micro-catchments in 2018 (mean = 8.5%), and only large rainfall events (>30 mm) increased soil moisture significantly (29–52%). After thinning, soil moisture was higher and significantly different among the micro-catchments only during small rainfall events (<10 mm), while a difference was not noted during large events. The difference before–after during small rainfall events was not significant for the control (0% thinning); whereas 40% and 80% thinning increased soil moisture significantly by 40% and 53%, respectively. Knowledge of the response of soil moisture as a result of thinning and rainfall characteristics has important implications, especially for evaluating the impact of forest management on water availability.

Sign in / Sign up

Export Citation Format

Share Document