scholarly journals Changes in the occurrence of rainfall-induced landslides in Calabria, Southern Italy, in the 20th century

2015 ◽  
Vol 3 (6) ◽  
pp. 3579-3619
Author(s):  
S. L. Gariano ◽  
O. Petrucci ◽  
F. Guzzetti
Keyword(s):  
Southern Italy ◽  
Geographical Area ◽  
Daily Rainfall ◽  
Recent Period ◽  
Rainfall Events ◽  
Rain Gauges ◽  
Entire Observation Period ◽  
Geographical Variations ◽  
The Impact ◽  
Observation Period

Abstract. We exploit a catalogue of 1466 rainfall events with landslides in the 90 year period 1921–2010 to study temporal and geographical variations in the occurrence of landslides in Calabria, Southern Italy. We use daily rainfall records obtained by a network of 318 rain gauges to reconstruct 448 493 rainfall events. Combining the rainfall and the landslide information, we obtain a catalogue of 1466 rainfall events with landslides (REL) in Calabria from 1921 to 2010, where a REL is the occurrence of one or more landslide during or immediately after a rainfall event. We find that the geographical and the temporal distributions of the rainfall-induced landslides have changed in the observation period. The average and the maximum values of the cumulated event rainfall that have resulted in landslides in the recent-most 30 year period 1981–2010 are lower than the values necessary to trigger landslides in previous periods, whereas the duration of the rainfall events that triggered landslides has remained the same. This can be considered evidence of variations in rainfall conditions, but also an increase in the vulnerability of the territory. We further find that the yearly distribution of rainfall-induced landslides has changed in the observation period, analysing the variations in the number of rainfall events with landslides occurred in each month in three 30 year periods. To investigate variations in the impact of REL on the population, we compared the number of REL in each of the 409 municipalities in Calabria, with the size of the population in the municipalities, measured by national Censuses conducted in 1951, 1981, and 2011. For the purpose, we adopted two strategies. The first strategy considered impact as IREL = #REL/P and the second strategy measured impact as RREL = #REL × P, where #REL is the total number of REL in a period, and P is the size of the population in the same period and geographical area. Considering the entire observation period, IREL and RREL have both increased in Calabria. However, considering the changes between the recent period 1981–2010 and the previous period 1951–1980, results are more variegated with a number of municipalities where IREL and RREL have increased, or decreased. Municipalities where IREL has increased are mainly in the mountains, and municipalities where RREL has increased are mainly along the coasts.

scholarly journals Changes in the occurrence of rainfall-induced landslides in Calabria, southern Italy, in the 20th century

2015 ◽  
Vol 15 (10) ◽  
pp. 2313-2330 ◽  
Author(s):  
S. L. Gariano ◽  
O. Petrucci ◽  
F. Guzzetti
Keyword(s):  
Southern Italy ◽  
Environmental Changes ◽  
Geographical Area ◽  
Daily Rainfall ◽  
Temporal Variations ◽  
Landslide Risk ◽  
Rainfall Events ◽  
Lack Of Information ◽  
The Impact ◽  
Observation Period

Abstract. Only a few studies have investigated the geographical and temporal variations in the frequency and distribution of rainfall-induced landslides, and the consequences of the variations on landslide risk. Lack of information limits the possibility to evaluate the impact of environmental and climate changes on landslide frequency and risk. Here, we exploit detailed historical information on landslides and rainfall in Calabria, southern Italy, between 1921 and 2010 to study the temporal and the geographical variation in the occurrence of rainfall-induced landslides and in their impact on the population. We exploit a catalogue with information on historical landslides from June 1920 to December 2010, and daily rainfall records obtained by a network of 318 rain gauges in the same period, to reconstruct 448 493 rainfall events (RE). Combining the rainfall and the landslide information, we obtain a catalogue of 1466 rainfall events with landslides (REL), where an REL is the occurrence of one or more landslide during or immediately after a rainfall event. We find that (i) the geographical and the temporal distributions of the rainfall-induced landslides have changed in the observation period, (ii) the monthly distribution of the REL has changed in the observation period, and (iii) the average and maximum cumulated event rainfall that have resulted in landslides in the recent 30-year period 1981–2010 are lower than the rainfall necessary to trigger landslides in previous periods, whereas the duration of the RE that triggered landslides has remained the same. We attribute the changes to variations in the rainfall conditions and to an increased vulnerability of the territory. To investigate the variations in the impact of REL on the population, we compared the number of REL in each of the 409 municipalities in Calabria with the size of the population in the municipalities measured by national Censuses conducted in 1951, 1981, and 2011. We adopted two strategies; the first strategy considered impact as IREL = #REL / P, and the second strategy measured impact as RREL = #REL × P, where #REL is the total number of REL in a period, and P is the size of the population in the same period and geographical area. The analysis has revealed a complex pattern of changes in the impact of rainfall-induced landslides in Calabria in the recent past, with areas where IREL and RREL have increased, and other areas where they have decreased. Municipalities where IREL has increased are mainly in the mountains, and municipalities where RREL has increased are mainly along the coasts. The complexity of the changes in the frequency and impact of rainfall-induced landslides observed in Calabria suggests that it remains difficult and uncertain to predict the possible variations in the frequency and impact of landslide in response to future climatic and environmental changes.

Extreme rainfall events during and following heatwaves

2021 ◽  
Author(s):  
Christoph Sauter ◽  
Christopher White ◽  
Hayley Fowler ◽  
Seth Westra
Keyword(s):  
Natural Hazards ◽  
Rainfall Intensity ◽  
Daily Rainfall ◽  
Extreme Rainfall ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Rainfall Extremes ◽  
Average Rainfall ◽  
Time Of Year ◽  
The Impact

<p>Heatwaves and extreme rainfall events are natural hazards that can have severe impacts on society. The relationship between temperature and extreme rainfall has received scientific attention with studies focussing on how single daily or sub-daily rainfall extremes are related to day-to-day temperature variability. However, the impact multi-day heatwaves have on sub-daily extreme rainfall events and how extreme rainfall properties change during different stages of a heatwave remains mostly unexplored.</p><p>In this study, we analyse sub-daily rainfall records across Australia, a country that experiences severe natural hazards on a frequent basis, and determine their extreme rainfall properties, such as rainfall intensity, duration and frequency during SH-summer heatwaves. These properties are then compared to extreme rainfall properties found outside heatwaves, but during the same time of year, to examine to what extent they differ from normal conditions. We also conduct a spatial analysis to investigate any spatial patterns that arise.</p><p>We find that rainfall breaking heatwaves is often more extreme than average rainfall during the same time of year. This is especially prominent on the eastern and south-eastern Australian coast, where frequency and intensity of sub-daily rainfall extremes show an increase during the last day or the day immediately after a heatwave. We also find that although during heatwaves the average rainfall amount and duration decreases, there is an increase in sub-daily rainfall intensity when compared to conditions outside heatwaves. This implies that even though Australian heatwaves are generally characterised by dry conditions, rainfall occurrences within heatwaves are more intense.</p><p>Both heatwaves and extreme rainfall events pose great challenges for many sectors such as agriculture, and especially if they occur together. Understanding how and to what degree these events co-occur could help mitigate the impacts caused by them.</p>

scholarly journals The impact of atmospheric rivers on rainfall in New Zealand

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jingxiang Shu ◽  
Asaad Y. Shamseldin ◽  
Evan Weller
Keyword(s):  
New Zealand ◽  
Austral Summer ◽  
Daily Rainfall ◽  
Extreme Rainfall ◽  
Detection Algorithm ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Atmospheric Rivers ◽  
Hydrological Hazards ◽  
The Impact

AbstractThis study quantifies the impact of atmospheric rivers (ARs) on rainfall in New Zealand. Using an automated AR detection algorithm, daily rainfall records from 654 rain gauges, and various atmospheric reanalysis datasets, we investigate the climatology of ARs, the characteristics of landfalling ARs, the contribution of ARs to annual and seasonal rainfall totals, and extreme rainfall events between 1979 and 2018 across the country. Results indicate that these filamentary synoptic features play an essential role in regional water resources and are responsible for many extreme rainfall events on the western side of mountainous areas and northern New Zealand. In these regions, depending on the season, 40–86% of the rainfall totals and 50–98% of extreme rainfall events are shown to be associated with ARs, with the largest contributions predominantly occurring during the austral summer. Furthermore, the median daily rainfall associated with ARs is 2–3 times than that associated with other storms. The results of this study extend the knowledge on the critical roles of ARs on hydrology and highlight the need for further investigation on the landfalling AR physical processes in relation to global circulation features and AR sources, and hydrological hazards caused by ARs in New Zealand.

Impacts of the North Atlantic Subtropical High on Daily Summer Precipitation over the Conterminous United States

2021 ◽  
Author(s):  
Enrico Zorzetto ◽  
Laifang Li
Keyword(s):  
United States ◽  
North Atlantic ◽  
Daily Rainfall ◽  
Summer Precipitation ◽  
Subtropical High ◽  
Rainfall Events ◽  
North Atlantic Subtropical High ◽  
The North ◽  
The North Atlantic ◽  
The Impact

AbstractBy modulating the moisture flux from ocean to adjacent land, the North Atlantic Subtropical High (NASH) western ridge significantly influences summer-season total precipitation over the Conterminous United States (CONUS). However, its influence on the frequency and intensity of daily rainfall events over the CONUS remains unclear. Here we introduce a Bayesian statistical model to investigate the impacts of the NASH western ridge position on key statistics of daily-scale summer precipitation, including the intensity of rainfall events, the probability of precipitation occurrence, and the probability of extreme values. These statistical quantities play a key role in characterizing both the impact of wet extremes (e.g., the probability of floods) and dry extremes. By applying this model to historical rain gauge records (1948-2019) covering the entire CONUS, we find that the western ridge of the NASH influences the frequency of rainfall as well as the distribution of rainfall intensities over extended areas of the CONUS. In particular, we find that the NASH ridge also modulates the frequency of extreme rainfall, especially that over part of the Southeast and upper Midwest. Our analysis underlines the importance of including the NASH western ridge position as a predictor for key statistical rainfall properties to be used for hydrological applications. This result is especially relevant for projecting future changes in daily rainfall regimes over the CONUS based on the predicted strengthening of the NASH in a warming climate.

scholarly journals Extreme Daily Rainfall in Central-Southern Chile and Its Relationship with Low-Level Horizontal Water Vapor Fluxes

2019 ◽  
Vol 20 (9) ◽  
pp. 1829-1850 ◽  
Author(s):  
Raúl A. Valenzuela ◽  
René D. Garreaud
Keyword(s):  
Water Vapor ◽  
Daily Rainfall ◽  
Extreme Rainfall ◽  
Southern Chile ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Rain Gauges ◽  
The Andes ◽  
Synoptic Forcing ◽  
Moisture Fluxes

AbstractExtreme rainfall events are thought to be one of the major threats of climate change given an increase of water vapor available in the atmosphere. However, before projecting future changes in extreme rainfall events, it is mandatory to know current patterns. In this study we explore extreme daily rainfall events along central-southern Chile with emphasis in their spatial distribution and concurrent synoptic-scale circulation. Surface rain gauges and reanalysis products from the Climate Forecast System Reanalysis are employed to unravel the dependency between extreme rainfall and horizontal water vapor fluxes. Results indicate that extreme rainfall events can occur everywhere, from the subtropical to extratropical latitudes, but their frequency increases where terrain has higher altitude, especially over the Andes Mountains. The majority of these events concentrate in austral winter, last a single day, and encompass a north–south band of about 200 km in length. Composited synoptic analyses identified extreme rainfall cases dominated by northwesterly (NW) and westerly (W) moisture fluxes. Some features of the NW group include a 300-hPa trough projecting from the extratropics to subtropics, a surface-level depression, and cyclonic winds at 850 hPa along the coast associated with integrated water vapor (IWV) > 30 mm. Conversely, features in the W group include both a very weak 300-hPa trough and surface depression, as well as coastal westerly winds associated with IWV > 30 mm. About half of extreme daily rainfall is associated with an atmospheric river. Extreme rainfall observed in W (NW) cases has a strong orographic (synoptic) forcing. In addition, W cases are, on average, warmer than NW cases, leading to an amplified hydrological response.

scholarly journals Assessment of spatial uncertainty of heavy local rainfall using a dense gauge network

2018 ◽  
Author(s):  
Sungmin O ◽  
Ulrich Foelsche
Keyword(s):  
Heavy Rainfall ◽  
Extreme Rainfall ◽  
Rain Gauge ◽  
Spatial Uncertainty ◽  
Wet Season ◽  
Rainfall Events ◽  
Rain Gauges ◽  
Areal Rainfall ◽  
The Impact ◽  
Heavy Rainfall Events

Abstract. Hydrology and remote-sensing communities have made use of dense rain-gauge networks for studying rainfall uncertainty and variability. However, in most regions, these dense networks are only available at sub-pixel scales and over short periods of time. Just a few studies have applied a similar approach, employing dense gauge networks, to local-scale areas, which limits the verification of their results in other regions. Using 10-year rainfall measurements from a network of 150 rain gauges, we assess spatial uncertainty in observed heavy rainfall events. The network is located in southeastern Austria over an area of 20 km × 15 km with no significant orography. First, the spatial variability of rainfall in the region was characterised using a correlogram at daily and sub-daily scales. Differences in the spatial structure of rainfall events between wet and dry seasons are apparent and we selected heavy rainfall events, the upper 10 % of wettest days during the wet season, for further analyses because of their high potential for causing hazard risk. Secondly, we investigated uncertainty in estimating mean areal rainfall arising from a limited gauge density. The number of gauges required to obtain areal rainfall with > 20 % accuracy tends to increase roughly following a power law as time scale decreases. Lastly, the impact of spatial aggregation on extreme rainfall was examined using gridded rainfall data with horizontal grid spacings from 0.1° to 0.01°. The spatial scale dependence was clearly observed at high intensity thresholds and high temporal resolutions. Quantitative uncertainty information from this study can guide both data users and producers to estimate uncertainty in their own observational datasets, consequently leading to the rational use of the data in relevant applications. Our findings are generalisable to other plain regions in mid-latitudes, however the degree of uncertainty could be affected by regional variations, like rainfall type or topography.

scholarly journals Occurrence analysis of daily rainfalls through non-homogeneous Poissonian processes

2011 ◽  
Vol 11 (6) ◽  
pp. 1657-1668 ◽  
Author(s):  
B. Sirangelo ◽  
E. Ferrari ◽  
D. L. De Luca
Keyword(s):  
Southern Italy ◽  
Daily Rainfall ◽  
Seasonal Effects ◽  
Validation Period ◽  
Threshold Values ◽  
Fourier Law ◽  
Homogeneous Poisson Process ◽  
Rain Gauges ◽  
Rainfall Occurrence ◽  
Non Homogeneous Poisson Process

Abstract. A stochastic model based on a non-homogeneous Poisson process, characterised by a time-dependent intensity of rainfall occurrence, is employed to explain seasonal effects of daily rainfalls exceeding prefixed threshold values. The data modelling has been performed with a partition of observed daily rainfall data into a calibration period for parameter estimation and a validation period for checking on occurrence process changes. The model has been applied to a set of rain gauges located in different geographical areas of Southern Italy. The results show a good fit for time-varying intensity of rainfall occurrence process by 2-harmonic Fourier law and no statistically significant evidence of changes in the validation period for different threshold values.

scholarly journals SUPPORTING AGRICULTURAL INNOVATION IN UGANDA TO RESPOND TO CLIMATE RISK: LINKING CLIMATE CHANGE AND VARIABILITY WITH FARMER PERCEPTIONS

2011 ◽  
Vol 47 (2) ◽  
pp. 293-316 ◽  
Author(s):  
HENNY OSBAHR ◽  
PETER DORWARD ◽  
ROGER STERN ◽  
SARAH COOPER
Keyword(s):  
Climate Change ◽  
Methodological Approach ◽  
Regional Climate ◽  
Daily Rainfall ◽  
Significant Shift ◽  
Climate Data ◽  
Rainfall Events ◽  
Agricultural Innovation ◽  
Climate Change And Variability ◽  
The Impact

SUMMARYThis paper investigates farmers’ perceptions of climate change and variability in southwest Uganda and compares them with daily rainfall and temperature measurements from the 1960s to the present, including trends in daily rainfall and temperature, seasonality, changing probability of risk and intensity of rainfall events. Statistical analyses and modelling of rainfall and temperature were performed and contrasted with qualitative data collected through a semi-structured questionnaire. The fieldwork showed that farmers perceived regional climate to have changed in the past 20 years. In particular, farmers felt that temperature had increased and seasonality and variability had changed, with the first rainy season between March and May becoming more variable. Farmers reported detailed accounts of climate characteristics during specific years, with recent droughts in the late 1990s and late 2000s confirming local perceptions that there has been a shift in climate towards more variable conditions that are less favourable to production. There is a clear signal that temperature has been increasing in the climate data and, to a lesser extent, evidence that the reliability of rains in the first season has decreased slightly. However, rainfall measurements do not show a downward trend in rainfall amount, a significant shift in the intensity of rainfall events or in the start and end of the rainy seasons. We explore why there are some differences between farmers’ perceptions and the climate data due to different associations of risk between ideal rainfall by farmers, including the amount and distribution needed for production, meteorological definitions of normal rainfall or the long-term statistical mean and its variation, and the impact of higher temperatures. The paper reflects on the methodological approach and considers the implications for communicating information about risk to users in order to support agricultural innovation.

scholarly journals The Impact of Atmospheric Rivers on Rainfall in New Zealand

2021 ◽  
Author(s):  
Assad Shamseldin ◽  
Evan Weller ◽  
Jingxiang Shu
Keyword(s):  
New Zealand ◽  
Daily Rainfall ◽  
Extreme Rainfall ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Atmospheric Rivers ◽  
Hydrological Hazards ◽  
Synoptic Features ◽  
Western Side ◽  
The Impact

Abstract This study quantifies the impact of atmospheric rivers (ARs) on rainfall in New Zealand. Using daily rainfall records from 654 rain gauges and the ERA-Interim and ERA-5 reanalysis, we investigate the contribution of ARs to the annual and seasonal rainfall totals and extreme rainfall events between 1979–2018 across the country. Results indicate that these filamentary synoptic features play an essential role in regional water resources and are responsible for many extreme rainfall events on the western side of mountainous areas and northern New Zealand. Depending on the season in these areas, 40–86% of the rainfall totals and 50–98% of extreme rainfall events are shown to be associated with ARs, with the largest contributions predominantly occurring during the summer. Furthermore, the median daily rainfall associated with ARs is 2–3 times that associated with other storms. The results of this study extend the knowledge of the critical roles of ARs on hydrology and highlight the need for further investigation of the hydrological hazards caused by ARs in New Zealand.

scholarly journals Streamflow Intensification Driven by the Atlantic Multidecadal Oscillation (AMO) in the Atrato River Basin, Northwestern Colombia

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 216 ◽  
Author(s):  
Wilmar Loaiza Cerón ◽  
Mary Toshie Kayano ◽  
Rita Valeria Andreoli ◽  
Alvaro Avila ◽  
Teresita Canchala ◽  
...  
Keyword(s):  
River Basin ◽  
Climate Adaptation ◽  
Daily Rainfall ◽  
Atlantic Multidecadal Oscillation ◽  
Upward Movement ◽  
Central Pacific ◽  
Sea Level Pressure ◽  
Rainfall Events ◽  
Walker Cell ◽  
The Impact

The impact of the Atlantic Multidecadal Oscillation (AMO) on the variations in the streamflow in the Atrato River Basin (ARB) during the 1965–2016 period was analyzed here by considering the cold (1965–1994) and warm (1995–2015) phases of this oscillation. The mean streamflow increased after 1994 (AMO phase change). This increase is related to the strengthening of the zonal gradients of the sea surface temperature (SST) and sea level pressure (SLP) between the tropical central Pacific and the tropical Atlantic after 1994 (warm AMO phase). These gradients contributed to strengthen the Walker cell related upward movement over northern and northwestern South America, in particular during November-December (ND). Consistently, the frequency (R20 mm) and intensity (SDII) of extreme daily rainfall events increased during the 1995–2015 period. Our results show a connection between the AMO and the increase in the streamflow in the ARB during the last five decades. These results contribute to the studies of resilience and climate adaptation in the region.

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