scholarly journals Peaks-over-Threshold Study of Trends in Extreme Rainfall over the Iberian Peninsula

2011 ◽  
Vol 24 (4) ◽  
pp. 1089-1105 ◽  
Author(s):  
Francisco Javier Acero ◽  
José Agustín García ◽  
María Cruz Gallego
Keyword(s):  
Iberian Peninsula ◽  
Extreme Events ◽  
Atlantic Coast ◽  
Generalized Pareto Distribution ◽  
Extreme Rainfall ◽  
Mediterranean Coast ◽  
Return Level ◽  
Positive Trend ◽  
Peaks Over Threshold ◽  
Daily Scale

Abstract A peaks-over-threshold (POT) approach is used to study trends in extreme rainfall over the Iberian Peninsula (IP) at a daily scale. Records from 52 observatories regularly distributed over Iberia with no missing data were available for the common period from 1958 to 2004. The POT approach was used because it is particularly effective at extracting information concerning true extreme events. A generalized Pareto distribution fit was made to the data involving time-dependent parameters to account for possible temporal changes in the frequency distribution. These parameters were analyzed for trends in the return-level period, of importance for engineering purposes. A time-varying threshold was defined and an automatic declustering scheme was used to select independent extreme events exceeding the threshold. The results indicate a high variability of extreme events over the coastline of the IP, greater over the Mediterranean coast than over the Atlantic coast. The calculation of the trends for the 2-yr return level yielded a large proportion of negative trends for all three seasons considered: 58% for winter, 63% for spring, and 69% for autumn. The parametric approach also revealed an increase in the area with a positive trend of the 20-yr return level relative to the 2-yr return period, especially in autumn in the east of the IP.

scholarly journals ­Trends and Zonal Variability of Extreme Rainfall Events Over East Africa During 1960-2017

2021 ◽  
Author(s):  
Moses.A Ojara ◽  
Yunsheng Lou ◽  
Hasssen Babaousmail ◽  
Peter Wasswa
Keyword(s):  
Extreme Events ◽  
Heavy Rainfall ◽  
Rainwater Harvesting ◽  
Southern Oscillation ◽  
Extreme Rainfall ◽  
Mitigation Measures ◽  
Fluctuation Analysis ◽  
Positive Trend ◽  
Extreme Rainfall Events ◽  
Rainfall Events

Abstract East African countries (Uganda, Kenya, Tanzania, Rwanda, and Burundi) are prone to weather extreme events. In this regard; the past occurrence of extreme rainfall events is analyzed for 25 stations following the Expert Team on Climate Change Detection and Indices (ETCCDI) regression method. Detrended Fluctuation Analysis (DFA) is used to show the future development of extreme events. Pearson’s correlation analysis is performed to show the relationship of extreme events between different rainfall zones and their association with El Niño -Southern Oscillation (ENSO and Indian Ocean dipole (IOD) IOD-DMI indices. Results revealed that the consecutive wet day's index (CWD) was decreasing trend in 72% of the stations analyzed, moreover consecutive dry days (CDD) index also indicated a positive trend in 44% of the stations analyzed. Heavy rainfall days index (R10mm) showed a positive trend at 52% of the stations and was statistically significant at a few stations. In light of the extremely heavy rainfall days (R25mm) index, 56% of the stations revealed a decreasing trend for the index and statistically significant trend at some stations. Further, a low correlation coefficient of extreme rainfall events in the regions; and between rainfall extreme indices with the atmospheric teleconnection indices (Dipole Mode Index-DMI and Nino 3.4) (r = -0.1 to r = 0.35). Most rainfall zones showed a positive correlation between the R95p index and DMI, while 5/8 of the rainfall zones experienced a negative correlation between Nino 3.4 index and the R95p. In light of the highly variable trends of extremes events, we recommend planning adaptation and mitigation measures that consider the occurrence of such high variability. Measures such as rainwater harvesting, stored and used during needs, planned settlement, and improved drainage systems management supported by accurate climate and weather forecasts is highly advised.

scholarly journals Lacunarity, predictability and predictive instability of the daily pluviometric regime in the Iberian Peninsula

2007 ◽  
Vol 14 (2) ◽  
pp. 109-121 ◽  
Author(s):  
M. D. Martínez ◽  
X. Lana ◽  
A. Burgueño ◽  
C. Serra
Keyword(s):  
Spatial Distribution ◽  
Iberian Peninsula ◽  
Lyapunov Exponents ◽  
Atlantic Coast ◽  
Power Laws ◽  
Rain Gauge ◽  
Mediterranean Coast ◽  
Western Atlantic ◽  
Dry Spells ◽  
Dry Spell

Abstract. The complexity of the daily pluviometric regime of the Iberian Peninsula is analysed from the point of view of its lacunarity, predictability and predictive instability. The database consists of daily pluviometric records obtained from 43 rain gauges in Spain and Portugal for the period 1950–1990. Five different series are generated for every rain gauge. The first series is constituted by the consecutive daily amounts. The other four consist of dry spell lengths with respect to daily amount thresholds of 0.1, 1.0, 5.0 and 10.0 mm/day. A dry spell length is defined as the number of consecutive days with rainfall amounts below one of these thresholds. The empirical lacunarity for every rain gauge is well reproduced by two power laws, the exponents varying notably from one gauge to another. The spatial distribution of the lacunarity is characterised by a north to south or southeast gradient, thus suggesting that this parameter can be a useful tool to distinguish between different pluviometric regimes. The predictability of the five series is quantified by means of the rescaled analysis and the interpretation of the Hurst exponent. Its patterns reveal that most part of the Iberian Peninsula shows signs of persistence for the daily rainfall and the dry spell series, although persistence is only clearly manifested in some small domains. The instability of possible predictive algorithms is analysed through the Lyapunov exponents. They are only computed for the series of daily amounts and for dry lengths respect to the threshold level of 0.1 mm/day due to the short number of dry spells for larger threshold levels. The series of daily amounts depict the highest instability along the Mediterranean coast. The series of dry spells show an increasing instability from NE to SW Spain, with a relevant nucleus of high Lyapunov values in the south-western Atlantic coast. As a summary, lacunarity and Hurst and Lyapunov exponents depict a relevant spatial variation, which is in agreement with well known patterns of the pluviometric regime, such as annual amount spatial distribution and return periods of dry spells.

scholarly journals Trends in Block-Seasonal Extreme Rainfall over the Iberian Peninsula in the Second Half of the Twentieth Century

2007 ◽  
Vol 20 (1) ◽  
pp. 113-130 ◽  
Author(s):  
JoséAgustín García ◽  
María Cruz Gallego ◽  
Antonio Serrano ◽  
JoséManuel Vaquero
Keyword(s):  
Twentieth Century ◽  
Statistical Theory ◽  
Iberian Peninsula ◽  
Extreme Values ◽  
Extreme Rainfall ◽  
Kendall Test ◽  
Time Dependent ◽  
The West ◽  
Daily Scale ◽  
Dipolar Pattern

Abstract In this study trends in extreme rainfall over the Iberian Peninsula at a daily scale in the second half of the twentieth century have been detected and analyzed. For this goal 35 stations evenly distributed over the region of study covering the period 1958–97 have been studied. Two different approaches have been used. The first one consists of the nonparametric Mann–Kendall test and the Sen method. The second approach is based on the statistical theory of extreme values, involving time-dependent parameters in order to be able to reflect possible temporal changes in the frequency distribution. Results from both methods agree, confirming the reliability of the analysis. Negative trends are found for the west and southwest of the Iberian Peninsula in spring and winter. In autumn a spatial dipolar pattern appears, but trends are not so evident.

scholarly journals RETURN LEVEL ESTIMATION FOR EXTREME RAINFALL OVER THE IBERIAN PENINSULA: COMPARING METHODOLOGIES.

2017 ◽  
Author(s):  
Francisco Javier Acero ◽  
Sylvie Parey ◽  
José Agustín García ◽  
Didier Dacunha-Castelle
Keyword(s):  
Iberian Peninsula ◽  
Extreme Rainfall ◽  
Return Level

scholarly journals The spreading of the non-native caprellid (Crustacea: Amphipoda) Caprella scaura Templeton, 1836 into southern Europe and northern Africa: a complicated taxonomic history.

2013 ◽  
Vol 15 (1) ◽  
pp. 145 ◽  
Author(s):  
M. ROS CLEMENTE
Keyword(s):  
Iberian Peninsula ◽  
North Atlantic ◽  
Atlantic Coast ◽  
Mediterranean Coast ◽  
Strait Of Gibraltar ◽  
Fouling Communities ◽  
Morphological Form ◽  
The North ◽  
Survey Report ◽  
First Time

Caprella scaura, originally described by Templeton (1836) from Mauritius and later reported as several subspecies from numerous areas of the world, was found for the first time in the Mediterranean in 1994. Since this report, the species was found in several Mediterranean locations. To explore the current distribution of C. scaura in the Iberian Peninsula and adjacent areas, we surveyed marine fouling communities from 88 marinas along the whole Iberian Peninsula and North Africa, 3 from Italy, 1 from France, 1 from Malta and 1 from Greece between June 2011 and June 2012. The results of this survey report the first confirmed record of C. scaura in Corsica (France), Creta (Greece) and Morocco, and confirm an extensive distribution of C. scaura along the Spanish Mediterranean coast and the Strait of Gibraltar. The species was absent in the north Atlantic coast of Spain and the upper distribution limit in the eastern Atlantic coast is the locality of Cascais, in the south coast of Portugal. All populations studied belong to the same morphological form, with match with the subspecies C. scaura typica from Brazil and C. scaura scaura from Mauritius, suggesting that these two subspecies could correspond to the same “variety”.

scholarly journals Changes in the simulation of atmospheric instability over the Iberian Peninsula due to the use of 3DVAR data assimilation

2021 ◽  
Vol 25 (6) ◽  
pp. 3471-3492
Author(s):  
Santos J. González-Rojí ◽  
Sheila Carreno-Madinabeitia ◽  
Jon Sáenz ◽  
Gabriel Ibarra-Berastegi
Keyword(s):  
Data Assimilation ◽  
Iberian Peninsula ◽  
Mean Squared Error ◽  
Initial Conditions ◽  
Atlantic Coast ◽  
Convective Available Potential Energy ◽  
Mediterranean Coast ◽  
Dew Point ◽  
Atmospheric Instability ◽  
Convective Inhibition

Abstract. The ability of two downscaling experiments to correctly simulate thermodynamic conditions over the Iberian Peninsula (IP) is compared in this paper. To do so, three parameters used to evaluate the unstable conditions in the atmosphere are evaluated: the total totals index (TT), convective available potential energy (CAPE), and convective inhibition (CIN). The Weather and Research Forecasting (WRF) model is used for the simulations. The N experiment is driven by ERA-Interim's initial and boundary conditions. The D experiment has the same configuration as N, but the 3DVAR data assimilation step is additionally run at 00:00, 06:00, 12:00, and 18:00 UTC. Eight radiosondes are available over the IP, and the vertical temperature and moisture profiles from the radiosondes provided by the University of Wyoming and the Integrated Global Radiosonde Archive (IGRA) were used to calculate three parameters commonly used to represent atmospheric instability by our own methodology using the R package aiRthermo. According to the validation, the correlation, standard deviation (SD), and root mean squared error (RMSE) obtained by the D experiment for all the variables at most of the stations are better than those for N. The different methods produce small discrepancies between the values for TT, but these are larger for CAPE and CIN due to the dependency of these quantities on the initial conditions assumed for the calculation of a lifted air parcel. Similar results arise from the seasonal analysis concerning both WRF experiments: N tends to overestimate or underestimate (depending on the parameter) the variability of the reference values of the parameters, but D is able to capture it in most of the seasons. In general, D is able to produce more reliable results due to the more realistic values of dew point temperature and virtual temperature profiles over the IP. The heterogeneity of the studied variables is highlighted in the mean maps over the IP. According to those for D, the unstable air masses are found along the entire Atlantic coast during winter, but in summer they are located particularly over the Mediterranean coast. The convective inhibition is more extended towards inland at 00:00 UTC in those areas. However, high values are also observed near the southeastern corner of the IP (near Murcia) at 12:00 UTC. Finally, no linear relationship between TT, CAPE, or CIN was found, and consequently, CAPE and CIN should be preferred for the study of the instability of the atmosphere as more atmospheric layers are employed during their calculation than for the TT index.

scholarly journals Changes in the simulation of instability indices over the Iberian Peninsula due to the use of 3DVAR data assimilation

2020 ◽  
Author(s):  
Santos J. González-Rojí ◽  
Sheila Carreno-Madinabeitia ◽  
Jon Sáenz ◽  
Gabriel Ibarra-Berastegi
Keyword(s):  
Data Assimilation ◽  
Iberian Peninsula ◽  
Initial Conditions ◽  
Atlantic Coast ◽  
Wrf Model ◽  
R Package ◽  
Mediterranean Coast ◽  
Convective Precipitation ◽  
Seasonal Analysis ◽  
Instability Indices

Abstract. The ability of two downscaling experiments to correctly simulate the instability conditions that can trigger thunderstorms over the Iberian Peninsula is compared in this paper. To do so, three instability indices are evaluated: TT index, CAPE and CIN. The WRF model is used for the simulations. The N experiment is driven by ERA-Interim’s initial and boundary conditions; The D experiment has the same configuration as N, but the 3DVAR data assimilation step is additionally run at 00, 06, 12 and 18 UTC. Eight radiosondes are available over the IP, and the values for these indices calculated from the University of Wyoming were chosen as reference in the validation of both simulations. Additionally, measured variables at different pressure levels from the radiosondes provided byWyoming were used to calculate the three instability indices by our own methodology using the R package aiRthermo. According to the validation, the correlation, SD and RMSE obtained by the experiment D for all the indices in most of the stations are better than those for N. The different methodologies produce small discrepancies between the values for TT, but these are larger for CAPE and CIN due to the dependency of these indices on the initial conditions assumed for the calculation of an air parcel’s vertical evolution. Similar results arise from the seasonal analysis concerning both WRF experiments: N tends to overestimate or underestimate (depending on the index) the variability of the reference values, but D is able to capture it in most of the seasons. The heterogeneity of the indices is highlighted in the mean maps over the Iberian Peninsula. According to those from D, the ingredients for the development of convective precipitation during winter are found along the entire Atlantic coast, but in summer they are located particularly in the Mediterranean coast. The chances of developing thunderstorms in those areas at 12 UTC is much higher than at 00 UTC; The convective inhibition is more extended towards inland at 00 UTC in those areas, which prevents storms from developing. However, high values are observed near Murcia also at 12 UTC.

scholarly journals Return Level Estimation of Extreme Rainfall over the Iberian Peninsula: Comparison of Methods

Water ◽  
2018 ◽  
Vol 10 (2) ◽  
pp. 179 ◽  
Author(s):  
Francisco Acero ◽  
Sylvie Parey ◽  
José García ◽  
Didier Dacunha-Castelle
Keyword(s):  
Iberian Peninsula ◽  
Extreme Rainfall ◽  
Return Level ◽  
Comparison Of Methods

scholarly journals Vulnerability assessment of Central-East Sardinia (Italy) to extreme rainfall events

2010 ◽  
Vol 10 (1) ◽  
pp. 61-72 ◽  
Author(s):  
A. Bodini ◽  
Q. A. Cossu
Keyword(s):  
Extreme Events ◽  
Land Use Planning ◽  
Heavy Rainfall ◽  
Extreme Values ◽  
Generalized Pareto Distribution ◽  
Extreme Rainfall ◽  
Eastern Coast ◽  
Extreme Rainfall Events ◽  
Annual Scale ◽  
Future Work

Abstract. In Sardinia (Italy), the highest frequency of extreme events is recorded in the Central-East area (3–4 events per year). The presence of high and steep mountains near the sea on the central and south-eastern coast, causes an East-West precipitation gradient in autumn especially, due to hot and moist currents coming from Africa. Soil structure and utilization make this area highly vulnerable to flash flooding and landslides. The specific purpose of this work is to provide a description of the heavy rainfall phenomenon on a statistical basis. The analysis mainly focuses on i) the existence of trends in heavy rainfall and ii) the characterization of the distribution of extreme events. First, to study possible trends in extreme events a few indices have been analyzed by the linear regression test. The analysis has been carried out at annual and seasonal scales. Then, extreme values analysis has been carried out by fitting a Generalized Pareto Distribution (GPD) to the data. As far as trends are concerned, different results are obtained at the two temporal scales: significant trends are obtained at the seasonal scale which are masked at the annual scale. By combining trend analysis and GPD analysis, the vulnerability of the study area to the occurrence of heavy rainfall has been characterized. Therefore, this work might support the improvement of land use planning and the application of suitable prevention systems. Future work will consider the extension of the analysis to all Sardinia and the application of statistical methods taking into account the spatial correlation of extreme events.

scholarly journals Observed variability and trends in extreme rainfall indices and Peaks-Over-Threshold series

2013 ◽  
Vol 10 (5) ◽  
pp. 6049-6079 ◽  
Author(s):  
H. Saidi ◽  
M. Ciampittiello ◽  
C. Dresti ◽  
G. Ghiglieri
Keyword(s):  
Extreme Events ◽  
Extreme Rainfall ◽  
Heavy Precipitation ◽  
Historical Change ◽  
Average Intensity ◽  
Positive Trend ◽  
Hourly Precipitation ◽  
Intensity Index ◽  
Hourly Data ◽  
Yearly Maximum

Abstract. Intensification of heavy precipitation as discussed in climate change studies has become a public concern, but it has not yet been examined well with observed data, particularly with data at short temporal scale like hourly and sub-hourly data. In this research we digitalized sub-hourly precipitation recorded at the stations of Vercelli (since 1927), Bra (since 1933), Lombriasco (since 1939) and Pallanza (since 1950) in order to investigate historical change in extreme short precipitations. These stations are located in the northwest of Italy. Besides seasonal and yearly maximum of precipitation we adopted two indices of extreme rainfall: the number of events above an extreme threshold (extreme frequency), and the average intensity of rainfall from extreme events (extreme intensity). The results showed a statistically significant increase of the extreme frequency index and spring maximum precipitation for Bra and Lombriasco. The extreme intensity index presented by the means of events above 95th percentile is decreasing for Bra regarding hourly precipitation and increasing for Lombriasco regarding 20 min extreme events. In Pallanza, we noticed only a positive trend of the extreme frequency and extreme intensity indices of events with duration of 30 min. For the analyses presented in this paper, a peak-over-threshold approach was chosen. Investigation presented showed that extreme events have risen in the last 20 yr only for short duration. Here it cannot be said that in our study area recent sub-hourly and hourly precipitation have become unprecedently strong or frequent for all the stations and for all the extreme events duration.

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