scholarly journals An analysis of temporal scaling behaviour of extreme rainfall in Germany based on radar precipitation QPE data

2021 ◽  
Vol 21 (4) ◽  
pp. 1195-1207
Author(s):  
Judith Marie Pöschmann ◽  
Dongkyun Kim ◽  
Rico Kronenberg ◽  
Christian Bernhofer

Abstract. We investigated the depth–duration relationship of maximum rainfall over all of Germany based on 16 years of radar-derived quantitative precipitation estimates (namely, RADKLIM-YW, German Meteorological Service) with a space–time resolution of 1 km2 and 5 min. Contrary to the long-term historic records that identified a smooth power law scaling behaviour between the maximum rainfall depth and duration, our analysis revealed three distinct scaling regimes of which boundaries are approximately 1 h and 1 d. A few extraordinary events dominated a wide range of durations and deviate to the usual power law. Furthermore, the shape of the depth–duration relationship varied with the sample size of randomly selected radar pixels. A smooth scaling behaviour was identified when the sample size was small (e.g. 10 to 100), but the original three distinct scaling regimes became more apparent as the sample size increases (e.g. 1000 to 10 000). Lastly, a pixel-wise classification of the depth–duration relationship of the maximum rainfall at all individual pixels in Germany revealed three distinguishable types of scaling behaviour, clearly determined by the temporal structure of the extreme rainfall events at a pixel. Thus, the relationship might change with longer time series and can be improved once available.

2020 ◽  
Author(s):  
Judith Marie Pöschmann ◽  
Dongkyun Kim ◽  
Rico Kronenberg ◽  
Christian Bernhofer

Abstract. We investigate the depth–duration relationship of maximum rainfall over the whole of Germany based on 16 yrs of radar derived Quantitative Precipitation Estimates (namely, RADKLIM–YW, German Meteorological Service) with a space–time resolution of 1 km and 5 min. Contrary to the long–term historic records that identified a smooth power law scaling behavior between the maximum rainfall depth and duration, our analysis revealed three distinct scaling regimes of which boundaries are approximately 1.5 h and 1 d. Few extraordinary events dominate a wide range of durations and deviate to the usual power law. Furthermore, the shape of the depth–duration relationship varies with the sample size of randomly selected radar pixels. A smooth scaling behavior were identified when the sample size is small (e.g. 10 to 100), but the original three distinct scaling regimes became more apparent as the sample size increases (e.g. 1000 to 10 000). Lastly, a pixel wise classification of the depth–duration relationship of the maximum rainfall at all individual pixels in Germany revealed three distinguishable types of scaling behavior, clearly determined by the temporal structure of the extreme rainfall events at a pixel. Thus, the relationship might change with longer time series and can be improved once available.


Author(s):  
Emanuele B. Manke ◽  
Claudia F. A. Teixeira-Gandra ◽  
Rita de C. F. Damé ◽  
André B. Nunes ◽  
Maria C. C. Chagas Neta ◽  
...  

ABSTRACT Although several studies have evaluated the intensity-duration-frequency relationships of extreme rainfall events, these relationships under different seasonal conditions remain relatively unknown. Thus, this study aimed to determine whether the intensity-duration-frequency relationships obtained seasonally from the rainfall records in the winter and summer represent the maximum rainfall events for the city of Pelotas, Rio Grande do Sul state, Brazil. Pluviographic data from 1982 to 2015 were used to create two seasonal series: one for the summer from December 21 to March 20 and the other for the winter from June 21 to September 22. These seasonal relationships were compared with the annual pluviographic data. The intensity, duration, and frequency relationships obtained from the summer rain data adequately represented the maximum rainfall in Pelotas, Rio Grande do Sul state, Brazil. The maximum intensity values of rainfall obtained from the relationship of intensity, duration, and frequency for the winter did not adequately encapsulate the occurrence of rain with greater intensities.


2020 ◽  
Vol 3 (1) ◽  
pp. 288-305
Author(s):  
Philip Mzava ◽  
Patrick Valimba ◽  
Joel Nobert

Abstract Urban communities in developing countries are one of the most vulnerable areas to extreme rainfall events. The availability of local information on extreme rainfall is therefore critical for proper planning and management of urban flooding impacts. This study examined the past and future characteristics of extreme rainfall in the urban catchments of Dar es Salaam, Tanzania. Investigation of trends and frequency of annual, seasonal and extreme rainfall was conducted, with the period 1967–2017 taken as the past scenario and 2018–2050 as the future scenario; using data from four key ground-based weather stations and RCM data respectively. Mann–Kendall trend analysis and Sen's slope estimator were used in studying changes in rainfall variability. Frequencies of extreme rainfall events were modeled using the Generalized Pareto model. Overall, the results of trend analysis provided evidence of a significant increase in annual and seasonal maximum rainfall and intensification of extreme rainfall in the future under the RCP4.5 CO2 concentration scenario. It was determined that extreme rainfall will become more frequent in the future, and their intensities were observed to increase approximately between 20 and 25% relative to the past. The findings of this study may help to develop adaptation strategies for urban flood control in Dar es Salaam.


2021 ◽  
Author(s):  
Ga Zhang ◽  
Chenge An ◽  
Xudong Fu

<p>Yellow River has long been suffered from floods and sedimentation in the history, and has brought great catastrophes to the Chinese nation. Therefore, the Yellow River is also called the “China’s sorrow”. From July 25 to 26 of 2017, most of the northern part of the Shanxi and Shannxi Province in the middle Yellow River basin encountered high intensity rainfall with the maximum rainfall of 223.6 mm. In the abstract below, we term this rainfall event as the “7.26 storm”. After the extreme rainfall, hyper-concentrated floods occurred in the Dali River and Wuding River, which are tributaries of the Yellow River. The objective of this research is to study the hyper-concentrated floods of the Wuding River (with a drainage area of 28460 km<sup>2</sup>) at hourly time-step with a numerical model. The model that we utilized is the Digital Yellow River Model (DYRIM), which a physically based spatially distributed model of watershed sediment dynamics. Due to lack of sub-daily observation data, we first calibrate and verify the model at daily time-step. Then we apply the model to simulate the 7.26 storm at hourly time-step. Results show the DYRIM could well reproduce the peak discharge, peak sediment concentration, flood timing and volume, when compared with the measured data. Furthermore, the DYRIM is able to (1) delineate spatial distribution of hillslope erosion intensity, maximum erosion intensity could reach 10000 t/km<sup>2</sup>; (2) provide information about proportion of different sources of sediment, channel erosion is the main source of the sediment to the outlet and (3) analysis the influence of check-dams on flow and sediment, the dam trapped about 40 millions tons sediment, their effect on water and sediment reduction under extreme rainfall events is limited though.</p>


2020 ◽  
Author(s):  
Jordan Richards ◽  
Jonathan Tawn

<div> <p>Fluvial flooding is caused by excessive rainfall sustained over extended periods of time and over spatial catchment areas. Although methodology for modelling excessive, or extreme, rainfall events is extensive and well researched, the same cannot be said about how the extremal properties of spatial and temporal aggregations of rainfall are related. We hope to rectify this by developing a methodology for modelling extremes at different spatio-temporal scales and which incorporates a wide range of dependence structures.</p> </div><div> <p>Research on modelling aggregated spatial extremes is ongoing, but here we present some interesting first-order behavior for the tails of aggregates of (dependent) variables. Marginally these variables are assumed to have GPD tails and we focus on exploring how properties of the dependence structure influence the tail properties of the aggregate. The implications of our theoretical results for statistical purposes will be discussed.</p> </div><div> <p> </p> </div>


2019 ◽  
Vol 58 (8) ◽  
pp. 1799-1819 ◽  
Author(s):  
Mengwen Wu ◽  
Yali Luo ◽  
Fei Chen ◽  
Wai Kin Wong

AbstractUnderstanding changes in subdaily rainfall extremes is critical to urban planners for building more sustainable and resilient cities. In this study, the hourly precipitation data in 1971–2016 from 61 rain gauges are combined with historical land-use change data to investigate changes in extreme hourly precipitation (EXHP) in the Pearl River delta (PRD) region of South China. Also, 120 extreme rainfall events (EXREs) during 2011–16 are analyzed using observations collected at densely distributed automatic weather stations and radar network. Statistically significant increase of hourly precipitation intensity leads to higher annual amounts of both total and extreme precipitation over the PRD urban cluster in the rapid urbanization period (about 1994–2016) than during the preurbanization era (1971 to about 1993), suggesting a possible link between the enhanced rainfall and the rapid urbanization. Those urbanization-related positive trends are closely related to more frequent occurrence of abrupt rainfall events with short duration (≤6 h) than the continuous or growing rainfall events with longer duration. The 120 EXREs in 2011–16 are categorized into six types according to the originating location and movement of the extreme-rain-producing storms. Despite the wide range of synoptic backgrounds and seasons, rainfall intensification by the strong urban heat island (UHI) effect is a clear signal in all the six types, especially over the inland urban cluster with prominent UHIs. The UHI thermal perturbation probably plays an important role in the convective initiation and intensification of the locally developed extreme-rain-producing storms during the daytime.


2021 ◽  
Author(s):  
Isabel Caballero-Leiva ◽  
Montserrat Llasat-Botija ◽  
María Carmen Llasat

<p>The Mediterranean coast of Spain is well known for its pleasant weather, which results in high population densities and large number of tourists. The littoral area is constituted by a rich variety of ecosystems combined with a well-developed industry and agricultural land. The attractive Mediterranean climate has another side of the story, due partially to the Spanish mountain ranges along the east coast. This results in extreme rainfall events that drive flash floods that carry significant economic, environmental and social impact to the affected areas. The mentioned scenario gets more complex when considering the climate change that is already experienced in the Mediterranean region. Among others, the increase in extreme precipitation events envisioned by global climate models. Considering that storms and flash floods are the highest occurrence and most expensive events, it is fair to analyse the adaptation measures in place for the studied area.</p><p>The present work shows the comparative analysis of three recent case studies of major compound hazard events happened in the Mediterranean coast of Spain with special focus on littoral impacts and within a short time frame of 4 months: September 2019, October 2019, and January 2020. The nearness of the events left short time for recovery between them, as well as added aggravation due to the accumulated environmental and economic impacts caused to the region and the Covid-19 pandemics. The work presents a wide range of data (meteorological, hydrological, economical, impact data, etc.), collected from the press and social media as well as from official sources such as CCS, Meteorological agencies, Civil Protection, and others. This allows developing a multidisciplinary approach from the point of view of hydrology, meteorology, sea sciences and social science.</p><p>The analysis of the events is made from a holistic point of view including details as varied as the geographical areas affected up to municipality level, circumstances of casualties, location of extreme hydrometeorological values recorded during the events, environmental impact and economic loss. Furthermore, the different factors driving to each compound hazard event (floods, windstorms, sea surges, ...) and cascade effects have been analysed. Moreover, an analysis of the adaptation measures present at the time is done, along with suggestions of complementary or better adaptation measures for the three cases. Even though the data collection and analysis are made for the entire affected area within the Iberian Peninsula, the impacts and adaptation measures considered in this communication have a focus on the coastal area, including its various littoral ecosystems, coastal infrastructures, tourist sector, etc.</p><p>This work has been done in the framework of the M-CostAdapt (CTM2017-83655-C2-1&2-R) research project, funded by the Spanish Ministry of Science and Innovation (MICINN-AEI/FEDER, UE).</p>


Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1397 ◽  
Author(s):  
Óscar E. Coronado-Hernández ◽  
Ernesto Merlano-Sabalza ◽  
Zaid Díaz-Vergara ◽  
Jairo R. Coronado-Hernández

Frequency analysis of extreme events is used to estimate the maximum rainfall associated with different return periods and is used in planning hydraulic structures. When carrying out this type of analysis in engineering projects, the hydrological distributions that best fit the trend of maximum 24 h rainfall data are unknown. This study collected maximum 24 h rainfall records from 362 stations distributed throughout Colombia, with the goal of guiding hydraulic planners by suggesting the probability distributions they should use before beginning their analysis. The generalized extreme value (GEV) probability distribution, using the weighted moments method, presented the best fits of frequency analysis of maximum daily precipitation for various return periods for selected rainfall stations in Colombia.


2020 ◽  
Author(s):  
Ming-Hsi Lee ◽  
Kun-Feng Chiang ◽  
Kuang-Jung Tsai

<p>There are almost 24% of total remoted mountainous communities located in Chiayi, Tainan, Kaohsiung and Pingtung counties/cities of southern Taiwan. During recent years, the extreme rainfall events brought huge amounts of rainfall and triggered severe environmental disasters such as landslides, debris flows, flooding and sediment disasters in southern Taiwan. The maximum rainfall of typhoon Morakot in August 2009 was approaching 3,000 mm during 4 days in mountainous area of Chiayi city. There are 359 landslides occurred nearby the remoted mountainous communities in the study area during the typhoon event. The landslide area was over 900 ha.</p><p>The potential assessments of environmental disasters for 38 remoted mountainous communities nearby the riverbank were analyzed. The landslide areas nearby the 38 communities in last 10 years (2007-2016) were identified. The numerical models (HEC-RAS, CCHE-2D and FLO-2D) were used to simulate the flooding level, scouring and deposition of river bed and the influence area of debris-flow occurrence under different return periods (25, 50 and 100 years). The results show that there are 5, 4 and 14 high potential communities of landslide, flooding and debris flow disasters, respectively. The results proposed by this study can provide the disaster risk management of administrative decisions to lessen the impacts of environmental disasters for remoted mountainous communities nearby the riverbank in southern Taiwan under climate change.</p>


2014 ◽  
Vol 33 (1) ◽  
pp. 13-19
Author(s):  
Amit Kumar Maheshwari

AbstractIn this study, hot workability aspect for modeling the flow stress at specified deformation level is investigated. The proposed model contains the basic parametric relationship of Arrhenius power law. The developed mathematical model is validated on Al 2024 alloy to check its feasibility over a wide range of strain rate, strain, and temperature. When compared with Johnson-Cook (JC) model, it is found to give a more perceptible experimental output by limited evaluation of arbitrary constants. The proposed model uses the input from hot compression test without the necessacity to go to torsion experiment. This proves its supremacy over JC model which require both the inputs. It also limits the number of constants, so produces a forwarding mark to N.S. Babu Model which needs 48 numbers of constants to define the constitutive aspect of deformation.


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