scholarly journals Analysis of diurnal, seasonal, and annual distribution of urban sub-hourly to hourly rainfall extremes in Germany

2021 ◽  
Author(s):  
Nasrin Haacke ◽  
Eva Nora Paton
Keyword(s):  
Extreme Events ◽  
Bimodal Distribution ◽  
Early Morning ◽  
Rainfall Regime ◽  
Circulation Types ◽  
Hourly Rainfall ◽  
Peak Over Threshold ◽  
Diurnal Distribution ◽  
Annual Distribution ◽  
June July

Abstract The timing of short extreme rainstorm, which was usually thought to occur on midsummer afternoons, was investigated to improve future mitigation options for infrastructure and safety from localised flash flooding. Using a peak-over-threshold approach, the timing of 10- and 60-min extreme events was filtered from high-resolution rainfall series assessing diurnal, seasonal, and annual distributions and analysed for spatial variations and prevailing atmospheric circulation types (CTs). The diurnal distribution showed a clear deviation from that of the entire rainfall regime. A complex spatial pattern was identified with distinct timing signatures of storms in the northern (mostly afternoon) and southern regions (a bimodal distribution with a second peak in the early morning) of Germany and a more homogenous diurnal distribution of events across the central regions. Most storms occurred in summer, but 42% of 10-min events occurred outside the summer months (June–July–August). A distinct annual clustering of extremes was identified, which varied distinctly between the 10- and 60-min extremes, indicating that the sub-hourly and hourly events were far from running conterminously. The timing of extreme events on the investigated time scales was not dominated by the occurrence of specific CTs in most cases, suggesting that other factors control these extremes.

scholarly journals Assessment of flash floods taking into account climate change scenarios in the Llobregat River basin

2013 ◽  
Vol 13 (12) ◽  
pp. 3145-3156 ◽  
Author(s):  
M. Velasco ◽  
P. A. Versini ◽  
A. Cabello ◽  
A. Barrera-Escoda
Keyword(s):  
River Basin ◽  
Extreme Events ◽  
Hydrological Model ◽  
Flash Flood ◽  
Flash Floods ◽  
Climate Change Scenarios ◽  
Whole Process ◽  
The Future ◽  
Peak Over Threshold ◽  
Llobregat River

Abstract. Global change may imply important changes in the future occurrence and intensity of extreme events. Climate scenarios characterizing these plausible changes were previously obtained for the Llobregat River basin (NE Spain). This paper presents the implementation of these scenarios in the HBV (Hydrologiska Byråns Vattenbalansavdelning) hydrological model. Then, the expected changes in terms of flash flood occurrence and intensity are assessed for two different sub-basins: the Alt Llobregat and the Anoia (Llobregat River basin). The assessment of future flash floods has been done in terms of the intensity and occurrence of extreme events, using a peak over threshold (POT) analysis. For these two sub-basins, most of the simulated scenarios present an increase of the intensity of the peak discharge values. On the other hand, the future occurrence follows different trends in the two sub-basins: an increase is observed in Alt Llobregat but a decrease occurs in Anoia. Despite the uncertainties that appear in the whole process, the results obtained can shed some light on how future flash floods events may occur.

Can climate models capture the high amplitudes circumglobal waves and their surface imprints?  

2021 ◽  
Author(s):  
Fei Luo ◽  
Kai Kornhuber ◽  
Frank Selten ◽  
Dim Coumou
Keyword(s):  
Soil Moisture ◽  
Climate Models ◽  
Phase Locking ◽  
Weather Conditions ◽  
Reanalysis Data ◽  
Circulation Types ◽  
Temperature And Precipitation ◽  
Wave Patterns ◽  
Precipitation Anomalies ◽  
June July

<p>Pronounced circumglobal waves can trigger and maintain persistent summer weather conditions by remaining in their preferred phase-locked positions for several weeks in a row. This phenomenon, especially important for wave numbers 5 and 7, has been observed in recent years, but it is unclear whether climate models can reproduce circulation types and their surface imprints.</p><p>Here we assess three climate models (EC-Earth3, CESM1.2, and MIROC5)  for their representation of amplified circumglobal waves and associated surface imprints in summer (June, July and August) over 1979-2016. ERA5 reanalysis data is used as reference to assess the models’ performance. We run a series of modeling experiments to understand the source of biases in the climate models: free interactive atmosphere and soil moisture runs (AISI), atmospheric nudged runs (AFSI), soil moisture prescribed runs (AISF), and both atmosphere and soil moisture nudged experiments (AFSF).</p><p>We show that all models reasonably well reproduce the climatological wave spectra. Further, both wave 5 and wave 7 are found to exhibit phase-locking behaviors across all models, resulting in similar wave patterns across the hemisphere as compared to reanalysis. The surface imprints are observed in the models as well, but depending on the model, the results vary in strength. We also found the biases in surface temperature and precipitation anomalies mainly come from the atmospheric circulation in the models as these biases reduced considerably from AISI runs to AFSI and AFSF runs where upper atmosphere levels were nudged. Nudging soil moisture also minimizes some biases in the models but not as obvious as nudging the atmosphere. </p><div> <div> <div> </div> </div> </div>

scholarly journals Circadian Variation of Migraine Attack Onset: A Review of Clinical Studies

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Daniel Baksa ◽  
Kinga Gecse ◽  
Sahel Kumar ◽  
Zsuzsanna Toth ◽  
Zsofia Gal ◽  
...  
Keyword(s):  
Migraine Attack ◽  
Circadian Variation ◽  
Early Morning ◽  
Sleep Stages ◽  
Shift Workers ◽  
Late Night ◽  
Diurnal Distribution ◽  
Pubmed Search ◽  
Migraine Triggers ◽  
The Moment

Several studies suggested that migraine attack onset shows a circadian variation; however, there has not been an overview and synthesis of these findings. A PubMed search with keywords “migraine” AND “circadian” resulted in ten studies directly investigating this topic. Results of these studies mostly show that migraine attacks follow a monophasic 24-hour cyclic pattern with an early morning or late night peak while other studies reported an afternoon peak and also a biphasic 24-hour cycle of attacks. The identified studies showed methodological variation including sample size, inclusion of medication use, comorbidities, and night or shift workers which could have contributed to the contradictory results. Several theories emerged explaining the diurnal distribution of migraine attacks suggesting roles for different phenomena including a morning rise in cortisol levels, a possible hypothalamic dysfunction, a circadian variation of migraine triggers, sleep stages, and a potentially different setting of the circadian pacemaker among migraineurs. At the moment, most studies show an early morning or late night peak of migraine attack onset, but a significant amount of studies reveals contradictory results. Further studies should investigate the arising hypotheses to improve our understanding of the complex mechanism behind the circadian variation of migraine attacks that can shed light on new targets for migraine therapy.

scholarly journals Diurnal Variation of Summer Precipitation across the Central Tian Shan Mountains

2017 ◽  
Vol 56 (6) ◽  
pp. 1537-1550 ◽  
Author(s):  
Jian Li ◽  
Tianru Chen ◽  
Nina Li
Keyword(s):  
Diurnal Variation ◽  
Summer Precipitation ◽  
Early Morning ◽  
Rainfall Events ◽  
Late Afternoon ◽  
Southern Basin ◽  
Hourly Rainfall ◽  
Tian Shan Mountains ◽  
Afternoon Peak ◽  
Tian Shan

AbstractThe climatic features of the diurnally varying summer precipitation over and around the central Tian Shan Mountains are investigated. Both the hourly rainfall data observed at eight stations along a transect across the mountains and the convective index derived from the satellite data show that there are three distinct regimes: the early morning peak at stations to the south of the mountains, the late afternoon peak at stations on the mountains, and the night peak at stations to the north of the mountains. The relation between regimes of diurnal variation is analyzed. By defining the regional rainfall event (RRE), the initial stations of each RRE are recorded. The early morning rainfall in the southern periphery of the mountains is triggered locally in the southern basin. Both the late afternoon peak over the mountains and the night peak in the northern periphery are influenced by mountain-originated rainfall events. These rainfall events appear over the mountains in the afternoon, and some of them move northward and lead to the nocturnal rainfall in the northern basin. The triggering of convection in the afternoon over the mountains and that in the early morning in the southern basin is related to the diurnally varying wind and thermodynamic conditions over and around the mountains. Low-level convergence with thermodynamic instability appears at noon (night) over the mountains (in the southern basin) just before the start of the convection.

scholarly journals Evaluation of Rainfall-Triggered Debris Flows under the Impact of Extreme Events: A Chenyulan Watershed Case Study, Taiwan

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2201
Author(s):  
Jinn-Chyi Chen ◽  
Wen-Shun Huang
Keyword(s):  
Debris Flow ◽  
Extreme Events ◽  
Debris Flows ◽  
Extreme Rainfall ◽  
Extreme Rainfall Event ◽  
Extreme Rainfall Events ◽  
Hourly Rainfall ◽  
Central Taiwan ◽  
The Impact

This study examined the conditions that lead to debris flows, and their association with the rainfall return period (T) and the probability of debris flow occurrence (P) in the Chenyulan watershed, central Taiwan. Several extreme events have occurred in the Chenyulan watershed in the past, including the Chi-Chi earthquake and extreme rainfall events. The T for three rainfall indexes (i.e., the maximum hourly rainfall depth (Im), the maximum 24-h rainfall amount (Rd), and RI (RI = Im× Rd)) were analyzed, and the T associated with the triggering of debris flows is presented. The P–T relationship can be determined using three indexes, Im, Rd, and RI; how it is affected and unaffected by extreme events was developed. Models for evaluating P using the three rainfall indexes were proposed and used to evaluate P between 2009 and 2020 (i.e., after the extreme rainfall event of Typhoon Morakot in 2009). The results of this study showed that the P‒T relationship, using the RI or Rd index, was reasonable for predicting the probability of debris flow occurrence.

Spatial and temporal dynamics of monsoon-induced landslides in Nepal in 2020

2021 ◽  
Author(s):  
Kaushal Raj Gnyawali ◽  
Dwayne D. Tannant ◽  
Yogesh Bhattarai ◽  
Rijan Jayana ◽  
Rocky Talchabhadel
Keyword(s):  
Temporal Dynamics ◽  
Monsoon Season ◽  
Warning System ◽  
Early Morning ◽  
Online News ◽  
Temporal Database ◽  
Rainfall Thresholds ◽  
Landslide Occurrence ◽  
Late Night ◽  
Hourly Rainfall

<p>In the monsoon season, landslides are major disasters in Nepal, causing loss of life and economic impacts. The landslides triggered in the 2020 monsoon (June – September) in Nepal caused more than 300 fatalities and affected about 800 families. A spatial and temporal database of landslides in this region does not exist, which has hindered an understanding of landslide dynamics and the development of a regional early warning system (EWS). In this study, we prepare a time-stamped (hourly) geo-referenced database of the landslides triggered by the 2020 monsoon in Nepal and investigate their dynamic trends. We track landslides from online news for each day during the monsoon to map their location and time. The database contains 332 mapped landslides, out of which accurate time stamps are available for 126 landslides. The spatial pattern shows a large concentration of landslides in central Nepal (districts of Parbat, Kaski, Myagdi, Baglung, Gulmi, and Syangja). The temporal pattern reveals that landslides in this region occur mostly during late night or early morning. We estimate hourly rainfall thresholds for landslide occurrence from the Integrated Multi-satellitE Retrievals for GPM (IMERG) rainfall product. The database and analysis provide a basis for estimating regional rainfall thresholds for Nepal and the design of an EWS.</p>

scholarly journals Using the UKCP09 probabilistic scenarios to model the amplified impact of climate change on drainage basin sediment yield

2012 ◽  
Vol 16 (11) ◽  
pp. 4401-4416 ◽  
Author(s):  
T. J. Coulthard ◽  
J. Ramirez ◽  
H. J. Fowler ◽  
V. Glenis
Keyword(s):  
Climate Change ◽  
Return Period ◽  
Extreme Events ◽  
Sediment Yield ◽  
Drainage Basin ◽  
Climate Change Scenarios ◽  
Hourly Rainfall ◽  
Baseline Values ◽  
The Impact ◽  
Emissions Scenario

Abstract. Precipitation intensities and the frequency of extreme events are projected to increase under climate change. These rainfall changes will lead to increases in the magnitude and frequency of flood events that will, in turn, affect patterns of erosion and deposition within river basins. These geomorphic changes to river systems may affect flood conveyance, infrastructure resilience, channel pattern, and habitat status as well as sediment, nutrient and carbon fluxes. Previous research modelling climatic influences on geomorphic changes has been limited by how climate variability and change are represented by downscaling from global or regional climate models. Furthermore, the non-linearity of the climatic, hydrological and geomorphic systems involved generate large uncertainties at each stage of the modelling process creating an uncertainty "cascade". This study integrates state-of-the-art approaches from the climate change and geomorphic communities to address these issues in a probabilistic modelling study of the Swale catchment, UK. The UKCP09 weather generator is used to simulate hourly rainfall for the baseline and climate change scenarios up to 2099, and used to drive the CAESAR landscape evolution model to simulate geomorphic change. Results show that winter rainfall is projected to increase, with larger increases at the extremes. The impact of the increasing rainfall is amplified through the translation into catchment runoff and in turn sediment yield with a 100% increase in catchment mean sediment yield predicted between the baseline and the 2070–2099 High emissions scenario. Significant increases are shown between all climate change scenarios and baseline values. Analysis of extreme events also shows the amplification effect from rainfall to sediment delivery with even greater amplification associated with higher return period events. Furthermore, for the 2070–2099 High emissions scenario, sediment discharges from 50-yr return period events are predicted to be 5 times larger than baseline values.

scholarly journals A chaotically driven model climate: extreme events and snapshot attractors

2011 ◽  
Vol 18 (5) ◽  
pp. 573-580 ◽  
Author(s):  
T. Bódai ◽  
Gy. Károlyi ◽  
T. Tél
Keyword(s):  
Extreme Events ◽  
Resonance Effect ◽  
Circulation Model ◽  
Extreme Value Statistics ◽  
Climate Extreme ◽  
Resonance Effects ◽  
System A ◽  
Peak Over Threshold ◽  
Global Atmospheric Circulation ◽  
Natural Measures

Abstract. In a low-order chaotic global atmospheric circulation model the effects of deterministic chaotic driving are investigated. As a result of driving, peak-over-threshold type extreme events, e.g. cyclonic activity in the model, become more extreme, with increased frequency of recurrence. When the characteristic time of the driving is comparable to that of the undriven system, a resonance effect with amplified variance shows up. For very fast driving we find a reduced enhancement of variance, which is also the case with white noise driving. Snapshot attractors and their natural measures are determined as a function of time, and a resonance effects is also identified. The extreme value statistics of group maxima is found to follow a Weibull distribution.

scholarly journals Association between Prevailing Circulation Patterns and Coarse Particles in Portugal

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 85
Author(s):  
Rui Cavaleiro ◽  
Ana Russo ◽  
Pedro M. Sousa ◽  
Rita Durão
Keyword(s):  
Extreme Events ◽  
Low Frequency ◽  
Coarse Particles ◽  
Time Data ◽  
Air Masses ◽  
Circulation Types ◽  
Pm10 And Pm2.5 ◽  
Circulation Patterns ◽  
Toxic Agents ◽  
Monitoring Service

Air pollution is one of the major environmental concerns today, with high socio-economic and public health impacts, which are expected to worsen in the future due to anthropogenic warming. Among the toxic agents present in the atmosphere, coarse particles (PM10 and PM2.5) are some of the most harmful for human health and the environment. Therefore, the study of these particles and their association with meteorological constraining factors is of utmost importance. The aim of this study is to analyze the circulation weather types (CWT) affecting PM10 and PM2.5 concentrations measured at background monitoring stations in Portugal between 2006 and 2018. PM10 and PM2.5 were analyzed in terms of their intra-annual and inter-annual variability, their relations with CWT and the characteristics of two major extreme events over Portugal. The analysis of the extreme events relied on both background stations and through the near-real time data from Copernicus Atmosphere Monitoring Service (CAMS) outputs. The inter-annual assessment showed a decrease in concentrations over the studied years, mainly for PM10. Intra-annual assessment pointed to higher concentrations during winter months. Higher PM concentrations were mostly associated with CWTs with easterly or southerly components, characterized by low frequency of rainfall and advection of dry air masses. The two analyzed extreme events, associated with mega wildfires (15–17 October 2017) and dust intrusion (1–10 August 2018) were analyzed in more detail. Prominent southerly and easterly circulations were observed during the onset and peak of the events, which then later decayed due to the change to maritime flows (westerly and northerly circulation types) which dispersed the particles.

Sign in / Sign up

Export Citation Format

Share Document