scholarly journals Copula Based Spatial Analysis of Drought Return Period in Southwest of Iran

2020 ◽  
Author(s):  
Mohammadreza Kavianpour ◽  
Mohammadreza Seyedabadi ◽  
Saber Moazami ◽  
Omid Aminoroayaie Yamini
Keyword(s):  
Return Period ◽  
Probabilistic Approach ◽  
Standardized Precipitation Index ◽  
Joint Probability ◽  
Copula Functions ◽  
Khuzestan Province ◽  
Drought Characteristics ◽  
The North ◽  
Significant Difference ◽  
Southwest Of Iran

In the past years, Khuzestan province which is located in the southwest of Iran has experienced severe droughts. Drought can be explained by its characteristics known as duration or severity. However, combination of the two features by probabilistic approach is appeared to be a well improved method to describe the phenomena. The aim of this study is to provide a more accurate statistical method of determining drought based on simultaneous analysis of two drought characteristics. Here, precipitation data from twenty stations were used to determine drought characteristics, by Standardized Precipitation Index (SPI). Joint probability function of two variables were built via copula functions. The drought return period was calculated in the form of two scenarios. The first scenario is, based on an assumption that drought is recognized by at least one of the two specific characteristics. Drought in the second scenario is distinguished by the two characteristics in a joint probabilistic form. According to research results, there was no significant difference between the north and south of Khuzestan in the study of single characteristics of drought. While analyzing two characteristics of the drought, the return period in the north was shorter than the south. The return period of droughts in the east was always shorter than in the west. The drought return period varies from 30 to 52 months and 50 to 87 months for the first and second scenarios, respectively.

scholarly journals Multivariate drought risk analysis based on copula functions: a case study

2020 ◽  
Vol 20 (6) ◽  
pp. 2375-2388
Author(s):  
Mohammadreza Seyedabadi ◽  
Mohammadreza Kavianpour ◽  
Saber Moazami
Keyword(s):  
Return Period ◽  
Drought Index ◽  
Human Life ◽  
Standardized Precipitation Index ◽  
Drought Indices ◽  
Drought Risk ◽  
Severe Drought ◽  
Copula Functions ◽  
Drought Characteristics ◽  
Multiple Variables

Abstract Drought is asserted as a natural disaster that encompasses vast territories for a long time and affects human life. Indicators are powerful tools for understanding this phenomenon. However, in order to get more information about the drought, multivariate indices were introduced for simultaneous evaluation of multiple variables. In this study, a combined drought index (CDI) based on three drought indices, the Standardized Precipitation Index (SPI), Streamflow Drought Index (SDI), and Standardized Water-level Index (SWI), is defined. Then, the Entropy method is used to determine the weight of each indicator. Among the calculated weights, SDI and SPI had the highest and lowest weight, respectively. The CDI is utilized to identify drought characteristics, such as duration and severity. In addition, the joint distribution function of drought characteristics is formed by copula functions and consequently the probability of different droughts is calculated. For the study area, data and information from eight regions located in Golestan province in the northern part of Iran are used to evaluate the performance of the proposed index. Four categories of drought were defined and their return period calculated. The shortest return period of severe drought was observed in the east and then in the west. In the south and center, the return period of severe drought was longer. Over the course of 30 years, all parts of the province experienced all drought categories.

scholarly journals Prevalence of subclinical coccidiosis in river buffalo calves of southwest of Iran

2013 ◽  
Vol 58 (4) ◽  
Author(s):  
Somayeh Bahrami ◽  
Ali Alborzi
Keyword(s):  
Health Condition ◽  
Multiple Infections ◽  
River Buffalo ◽  
Negative Effects ◽  
Buffalo Calves ◽  
Khuzestan Province ◽  
Significant Difference ◽  
Eimeria Spp ◽  
Southwest Of Iran ◽  
Abundance And Distribution

AbstractDespite the importance of buffalo farming in Iran, little is known in this country about the abundance and distribution of Eimeria spp. in the animal species. The present study was designed to investigate the prevalence and species characterization of Eimeria oocysts in river buffalo calves of Khuzestan province, southwest of Iran. Of the total 108 fecal samples examined for Eimeria, 108 (100%) were found infected with 11 species of the parasite. Among the identified species of Eimeria, E. bovis was found to be the predominant etiological agent (76.85%), followed in order by E. canadensis (62.96%), E. zuernii (47.2%), E. ellipsoidalis (26.85%), E. subspherica (25.92%), E. brasiliensis (19.4%), E. auburnensis (18.51%), E. alabamensis (14.81%), E. pellita (11.1%), E. illinoisensis (5.5%) and E. bukidnonensis (2.7%). In most calves multiple infections with three species were present. While, 20.7% of calves showed heavy infection, 50.4 and 24.8% of calves showed weak and moderate infection, respectively. There was no significant difference in the OPG values between the calves of different localities. There was also no significant difference between the prevalence rate of infection in males and females. A total of 16.6% of all faecal samples were found to be diarrheic. A highly significant relationship could be identified between the occurrence of diarrhea and the level of E. bovis and E. zuernii oocysts excretion. Considering the pervasive occurrence and negative effects of the infection on the health condition and the growth performance of buffalo calves, infections should receive increased attention by both farmers and veterinarians.

Are the antecedent drought conditions magnifying the summer hot extremes in Australia

2020 ◽  
Author(s):  
Patrícia Páscoa ◽  
Célia Gouveia ◽  
Ana Russo ◽  
Andreia Ribeiro
Keyword(s):  
Probabilistic Approach ◽  
Joint Probability ◽  
Positive Trend ◽  
Standardized Precipitation Evapotranspiration Index ◽  
Copula Functions ◽  
Reanalysis Dataset ◽  
Temperature Trends ◽  
Drought Conditions ◽  
Hot Days ◽  
Climate Events

<p>The occurrence of extreme climate events such as droughts and heatwaves can have negative economic, environmental and social impacts. The simultaneous or sequential occurrence of these extreme events can increase these impacts, and their frequency is expected to increase in many regions of the world. Moreover, the occurrence of hot days/nights was shown to be correlated to drought conditions in Mediterranean areas. Recently the catastrophic fire seasons of 2019/2020 in Australia has been pointed out to be associated with a drought exacerbation of the summer hot conditions. Additionally, temperature trends In Australia since 1970 are positive in most of the territory, whereas annual precipitation presents a negative trend in the East and a positive trend in the West.</p><p>In this work, we propose to analyze the relation between summer hot days/nights and antecedent drought conditions in Australia. The Standardized Precipitation Evapotranspiration Index (SPEI) at time-scales of 1 to 6 months was used to assess drought conditions. The indices Number of Hot Days (NHD) and Number of Hot Nights (NHN) were computed as the number of days on each month that exceed the 90<sup>th</sup> percentile of maximum and minimum temperatures, respectively. Data to compute these indices were retrieved from the ERA5 climate reanalysis dataset, and from the CRU TS4.03 dataset. Temperature data from the ACORN-SAT dataset was also used. A correlation analysis was performed between SPEI and NHD/NHH, using the concurrent months, and also the SPEI values on the previous 1 to 3 months. Significant negative correlations were obtained in southern regions. A probabilistic approach was also used, using copula functions, which allowed to estimate the joint probability of occurrence of dry and hot events.</p><p>Acknowledgements: This work was partially supported by projects FireCast (PCIF/GRF/0204/2017), and IMPECAF (PTDC/CTA-CLI/28902/2017). Andreia Ribeiro thanks FCT for the grant PD/BD/114481/2016.</p>

scholarly journals Meteorological Drought Analysis and Return Periods over North and West Africa and Linkage with El Niño–Southern Oscillation (ENSO)

2021 ◽  
Vol 13 (23) ◽  
pp. 4730
Author(s):  
Malak Henchiri ◽  
Tertsea Igbawua ◽  
Tehseen Javed ◽  
Yun Bai ◽  
Sha Zhang ◽  
...  
Keyword(s):  
West Africa ◽  
Large Scale ◽  
Southern Oscillation ◽  
Standardized Precipitation Index ◽  
Joint Probability ◽  
Meteorological Drought ◽  
Socioeconomic Impacts ◽  
The North ◽  
The Standardized Precipitation Index ◽  
The North Atlantic Oscillation

Droughts are one of the world’s most destructive natural disasters. In large regions of Africa, droughts can have strong environmental and socioeconomic impacts. Understanding the mechanism that drives drought and predicting its variability is important for enhancing early warning and disaster risk management. Taking North and West Africa as the study area, this study adopted multi-source data and various statistical analysis methods, such as the joint probability density function (JPDF), to study the meteorological drought and return years across a long term (1982–2018). The standardized precipitation index (SPI) was used to evaluate the large-scale spatiotemporal drought characteristics at 1–12-month timescales. The intensity, severity, and duration of drought in the study area were evaluated using SPI–12. At the same time, the JPDF was used to determine the return year and identify the intensity, duration, and severity of drought. The Mann-Kendall method was used to test the trend of SPI and annual precipitation at 1–12-month timescales. The pattern of drought occurrence and its correlation with climate factors were analyzed. The results showed that the drought magnitude (DM) of the study area was the highest in 2008–2010, 2000–2003, and 1984–1987, with the values of 5.361, 2.792, and 2.187, respectively, and the drought lasting for three years in each of the three periods. At the same time, the lowest DM was found in 1997–1998, 1993–1994, and 1991–1992, with DM values of 0.113, 0.658, and 0.727, respectively, with a duration of one year each time. It was confirmed that the probability of return to drought was higher when the duration of drought was shorter, with short droughts occurring more regularly, but not all severe droughts hit after longer time intervals. Beyond this, we discovered a direct connection between drought and the North Atlantic Oscillation Index (NAOI) over Morocco, Algeria, and the sub-Saharan countries, and some slight indications that drought is linked with the Southern Oscillation Index (SOI) over Guinea, Ghana, Sierra Leone, Mali, Cote d’Ivoire, Burkina Faso, Niger, and Nigeria.

scholarly journals Probabilistic Fault Displacement Hazard Analysis for North Tabriz Fault

2021 ◽  
Author(s):  
Mohamadreza Hosseyni ◽  
Habib Rahimi
Keyword(s):  
Return Period ◽  
Hazard Analysis ◽  
Probabilistic Approach ◽  
Surface Displacement ◽  
Return Periods ◽  
Surface Rupture ◽  
Slip Mechanism ◽  
The North ◽  
North Tabriz Fault ◽  
Fault Displacement

Abstract. The probabilistic fault displacement hazard analysis is one of the new methods in estimating the amount of possible displacement in the area at the hazard of causal fault rupture. In this study, using the probabilistic approach and earthquake method introduced by Youngs et al., 2003, the surface displacement of the North Tabriz fault has been investigated, and the possible displacement in different scenarios has been estimated. By considering the strike-slip mechanism of the North Tabriz fault and using the earthquake method, the probability of displacement due to surface ruptures caused by 1721 and 1780 North Tabriz fault earthquakes has been explored. These events were associated with 50 and 60 km of surface rupture, respectively. The 50–60 km long section of the North Tabriz fault was selected as the source of possible surface rupture. We considered two scenarios according to possible displacements, return periods, and magnitudes which are reported in paleoseismic studies of the North Tabriz fault. As the first scenario, possible displacement, return period, and magnitude was selected between zero to 4.5; 645 years and Mw~7.7, respectively. In the second scenario, possible displacement, return period and magnitude were selected between zero to 7.1, 300 years, and Mw~7.3, respectively. For both mentioned scenarios, the probabilistic displacements for the rate of exceedance 5 % in 50, 475, and 2475 years for the principle possible displacements (on fault) of the North Tabriz fault have been estimated. For the first and second scenarios, the maximum probabilistic displacement of the North Tabriz fault at a rate of 5 % in 50 years is estimated to be 186 and 230 cm. Also, mentioned displacements for 5 % exceedance in 475 years and 2475 years in both return periods of 645 and 300 years, are estimated at 469 and 655 cm.

Dust storm frequency in relation to extreme droughts in arid regions of Iran

2021 ◽  
Author(s):  
reza modarres ◽  
Poria Mohit Esfahani
Keyword(s):  
Dust Storm ◽  
Arid Regions ◽  
Standardized Precipitation Index ◽  
Joint Probability ◽  
Climatic Conditions ◽  
Dust Storms ◽  
Drought Event ◽  
Drought Condition ◽  
Copula Functions ◽  
Dry Conditions

<p>Dust storms are frequent phenomenon in arid and semi arid regions of Iran which cover near 60 percent of the entire country in the center of Iran. Due to geographic and climatic conditions of prolonged dry conditions as well as poor land use management, dust storms occur in almost all seasons across the region. Drought is a major fator affecting the likelihood of dust storm occurrence across arid regions of Iran. We develop copula functions to investigate the effect of drought on dust storm frequency.The standardized precipitation Index (SPI) was caluclated and drought condition was defined based on SPI< -0.5. Dought severity and duration for each drought event were ca;culated and the number of dust days in each drought event ws also identified. The Archimedean copula families shoed that the probability of dust occurrence has a significant relationship to extreme drought conditions. The joint probability is then used to derive the joint return period of dust storms in relation to drought condition.</p>

scholarly journals Bivariate Assessment of Drought Return Periods and Frequency in Brazilian Northeast Using Joint Distribution by Copula Method

Geosciences ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 135 ◽  
Author(s):  
Rodrigo Lins da Rocha Júnior ◽  
Fabrício Daniel dos Santos Silva ◽  
Rafaela Lisboa Costa ◽  
Heliofábio Barros Gomes ◽  
David Duarte Cavalcante Pinto ◽  
...  
Keyword(s):  
Return Period ◽  
Probability Distributions ◽  
Standardized Precipitation Index ◽  
Bivariate Distribution ◽  
Drought Risk ◽  
Drought Event ◽  
Monthly Precipitation ◽  
Copula Functions ◽  
Spatially Distributed ◽  
The Standardized Precipitation Index

The Northeast region of Brazil (NRB) is the most populous semiarid area in the world and is extremely susceptible to droughts. The severity and duration of these droughts depend on several factors, and they do not necessarily follow the same behavior. The aim of this work is to evaluate the frequency of droughts in the NRB and calculate the return period of each drought event using the copula technique, which integrates the duration and severity of the drought in the NRB in a joint bivariate distribution. Monthly precipitation data from 96 meteorological stations spatially distributed in the NRB, ranging from 1961 to 2017, are used. The copula technique is applied to the Standardized Precipitation Index (SPI) on the three-month time scale, testing three families of Archimedean copula functions (Gumbel–Hougaard, Clayton and Frank) to reveal which model is best suited for the data. Averagely, the most frequent droughts observed in the NRB are concentrated in the northern sector of the region, with an observed duration varying from three and a half to five and a half months. However, the eastern NRB experiences the most severe droughts, lasting for 14 to 24 months. The probability distributions that perform better in modeling the series of severity and duration of droughts are exponential, normal and lognormal. The observed severity and duration values show that, for average values, the return period across the region is approximately 24 months. Still in this regard, the southernmost tip of the NRB stands out for having a return period of over 35 months. Regarding maximum observed values of severity and duration, the NRB eastern strip has the longest return period (>60 months), mainly in the southeastern portion where a return period above 90 months was observed. The northern NRB shows the shortest return period (~45 months), indicating that it is the NRB sector with the highest frequency of intense droughts. These results provide useful information for drought risk management in the NRB.

scholarly journals Analysis of Drought Characteristics in Northern Shaanxi Based on Copula Function

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1445
Author(s):  
Junhui Wang ◽  
Guangzhi Rong ◽  
Kaiwei Li ◽  
Jiquan Zhang
Keyword(s):  
Short Duration ◽  
Return Period ◽  
Copula Function ◽  
Recurrence Interval ◽  
Cumulative Probability ◽  
Severe Drought ◽  
The South ◽  
Drought Characteristics ◽  
The North ◽  
Northern Shaanxi

Precipitation is low and drought occurs frequently in Northern Shaanxi. To study the characteristics and occurrence and development of drought events in Northern Shaanxi is beneficial to the prevention and control of drought disasters. Based on the monthly rainfall data of 10 meteorological stations in Northern Shaanxi from 1960 to 2019, the characteristic variables of drought events at each meteorological station in Northern Shaanxi were extracted by using run theory and copula function. The joint probability distribution and recurrence period were obtained by combining the duration and intensity of drought, and the relationship between drought characteristics and crop drought affected area was studied. The results show that (1) from 1960 to 2019, drought events mainly occurred in Northern Shaanxi with long duration and low severity, short duration and high severity, or short duration and low severity, among which the frequency of drought events that occurred in Yuyang and Baota districts was higher. The frequency of light drought and extreme drought was more in the south and less in the north, while the frequency of moderate drought and severe drought was more in the north and less in the south. (2) The optimal edge distribution of drought intensity and drought duration in Northern Shaanxi is generalized Pareto distribution, and the optimal fitting function is Frank copula function. The greater the duration and intensity of drought, the greater the cumulative probability and return period. (3) The actual recurrence interval and the theoretical recurrence interval of drought events in Northern Shaanxi were close, and the error was only 0.1–0.3a. The results of the joint return period can accurately reflect the actual situation, and this study can provide effective guidance for the prevention and management of agricultural dryland in Northern Shaanxi.

scholarly journals Aflatoxin M1 Contamination in Raw Cow Milk of Dairy Farms in Behbahan area, Khuzestan province, Iran

2019 ◽  
Author(s):  
Seyedeh Ommolbanin Ghasemian
Keyword(s):  
Dairy Farms ◽  
Raw Milk ◽  
Cow Milk ◽  
Aflatoxin M1 ◽  
Natural Occurrence ◽  
Environmental Chemical ◽  
Khuzestan Province ◽  
Milk Samples ◽  
Significant Difference ◽  
Southwest Of Iran

Introduction: Mycotoxins are among the environmental chemical agents with toxic effects on animals and humans. Aflatoxins (AF) are a major group of mycotoxins produced following the growth of some species of Aspergillus flavus and Aspergillus parasiticus, particularly in agricultural products. Aflatoxin M1 (AFM1) is secreted to milk and remains there since the process of pasteurization and sterilization has little effect on this metabolite. The aim of this study was to investigate the natural occurrence of AFM1 in raw milk in Behbahan area, which is an area of high-density livestock production in southwest of Iran. The other aim was to compare these obtained levels with the accepted level recommended by the European community (50 ng/L). Methods: In the present study, 90 samples of raw milk were collected from five dairy farms in Behbahan region, Khuzestan province, Iran. The AFM1 was analyzed using the Enzyme Linked Immune Sorbent Assay (ELISA) method by ELISA kits from Euro Clone, Italy.  Data were analyzed by ANOVA and the results were reported as mean ± SE. The significant level was set at p ≤ 0.05.  Results: The concentration of aflatoxin M1 in (15)16.54% of raw milk was higher than maximum tolerance limit accepted by European Union /Codex Alimentarius Commission (50 ng/l). The results of this study showed that all 90 investigated raw milk samples were contaminated with AFM1 (100%). Conclusion: A significant difference was observed between concentration means of AFM1 in various studied farms at P < 0.05. Consequently, high occurrence of AFM1 in raw milk samples was considered as a possible hazard for human health. However, further longitudinal studies are required on milk samples and other dairy products in Behbahan as well as other regions of Iran to estimate the representative intake of AFM1 in Iran.

Plant diversity of Khuzestan and dust sources in the southwest of Iran, with a checklist of vascular plants

Phytotaxa ◽  
2020 ◽  
Vol 434 (3) ◽  
pp. 219-254
Author(s):  
MEHRI DINARVAND ◽  
ZIBA JAMZAD
Keyword(s):  
Vascular Plants ◽  
Life Form ◽  
Vascular Plant ◽  
Floristic Composition ◽  
Khuzestan Province ◽  
The North ◽  
Dust Sources ◽  
Terrestrial Habitats ◽  
Plant Families ◽  
Southwest Of Iran

Khuzestan province covers an area of 64236 square kilometers in the southwest of Iran and the border of Iraq. The area belongs to two regions, Irano-Turanian (IT) in the north and Sahara-Sindian in the south. An area with 349254 ha is the source of dust in Khuz province. We investigated the floristic composition, life-form spectrum and the phytogeography of the area during 2009–2018 by collecting vascular plants to provide an annotated checklist of the plants in Khuz province. In this time about two years focused on the vegetation of the septet areas of the source of dust and dune. Approximately 10,000 vascular plant specimens were collected from 13 types of terrestrial habitats and 15 types of wetlands. A total of 985 species and infraspecific taxa of vascular plants belonging to 487 genera and 93 plant families were recorded as native and naturalized in the study area. The richest families are Asteraceae (62 genera/132 species), Fabaceae (22/79), Poaceae (43/68), Brassicaceae (43/58), Lamiaceae (19/48), and Apiaceae (30/45). The genera Astragalus (20 species) and Convolvulus (14 species) are the most species-rich in Khuz. Raunkiaer’s plant life-form spectrum in the area is dominated by therophytes (33%) and hemicryptophytes (29%). The core flora of Khuz has the Irano-Turanian origin; the widespread elements are also well represented in the study area. The dust sources area includes four types of vegetation: wetland species, hygrophyte plants, terrestrial halophytes, and psammophytic plants. The main sources of dust rise are covered with two classes of vegetation (halophytes and pasmophytes), with 77 dune species, 43 species of salty soil places, and 28 species adapted to both climate and soil of the area.

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