Extreme Drought

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Variation of extreme drought and flood in North China revealed by document-based seasonal precipitation reconstruction for the past 300 years

Variation of extreme drought and flood in North China revealed by document-based seasonal precipitation reconstruction for the past 300 years

The chi-square test (χ 2 ) showed that there is a higher prob- ability of extreme drought with the El Niño occurrence in the same year or the previous year. For example, the chi- square value is 7.997 for the occurrence of extreme drought and El Niño in the previous year, which is significant at the p<0.01 level. Regarding the occurrence of extreme drought and El Niño in the same year, the chi-square value is 4.502, which passes the p<0.05 significant level. Hao et al. (2008, 2010b) found that the precipitation over the NCP in the El Niño year or the sequent year was below that in normal years, and the severe drought of 1876–1877 was associated with the strong El Niño episode. Chen and Yang (2013) and Q. Li et al. (2011) also found that most drought events or extreme dry years in northern China might have a close link with the occurrence of El Niño during historical times. In addition, many previous studies from observation found that the El Niño could usually cause precipitation evidently de- creasing in northern China not only simultaneously but also in the subsequent summer after an El Niño year (e.g., Wu et al., 2003; Lu, 2005, Zhang et al., 2017). Corresponding to the recent strong El Niño event in 2015–2016, the sum- mer precipitation decreased by 20 % to 50 % over northern China (Zhai et al., 2016). Our result confirmed their find- ings. As suggested by previous studies based on observations and simulations, the mechanism of impact of El Niño on pre-
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Are Northeastern U.S. forests vulnerable to extreme drought?

Are Northeastern U.S. forests vulnerable to extreme drought?

In the Northeastern U.S., drought is expected to increase in frequency over the next century, and therefore, the responses of trees to drought are important to understand. There is recent debate about whether land-use change or moisture availability is the primary driver of changes in forest species composition in this region. Some argue that fire suppression from the early twentieth century to present has resulted in an increase in shade-tolerant and pyrophobic tree species that are drought intolerant, while others suggest precipitation variability as a major driver of species composition. From this debate, an emerging hypothesis is that mesophication and increases in the abundance of mesophytic genera (e.g., Acer, Betula, and Fagus) resulted in forests that are more vulnerable to drought. This review examines the published literature and factors that contribute to drought vulnerability of Northeastern U.S. forests. We assessed two key concepts related to drought vulnerability, including drought tolerance (ability to survive drought) and sensitivity (short-term responses to drought), with a focus on Northeastern U.S. species. We assessed drought-tolerance classifications for species, which revealed both consistencies and inconsistencies, as well as contradictions when compared to actual observations, such as higher mortality for drought-tolerant species. Related to drought sensitivity, recent work has focused on isohydric/ anisohydric regulation of leaf water potential. However, based on the review of the literature, we conclude that drought sensitivity should be viewed in terms of multiple variables, including leaf abscission, stomatal sensitivity, turgor pressure, and dynamics of non-structural carbohydrates. Genera considered drought sensitive (e.g., Acer, Betula, and Liriodendron) may actually be less prone to drought-induced mortality and dieback than previously considered because stomatal regulation and leaf abscission in these species are effective at preventing water potential from reaching critical thresholds during extreme drought. Independent of drought-tolerance classification, trees are prone to dieback and mortality when additional stressors are involved such as insect defoliation, calcium and magnesium deficiency, nitrogen saturation, and freeze-thaw events. Overall, our literature review shows that multiple traits associated with drought sensitivity and tolerance are important as species may rely on different mechanisms to prevent hydraulic failure and depleted carbon reserves that may lead to mortality.
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Factors Determining Mortality of Adult Chaparral Shrubs in an Extreme Drought Year in California

Factors Determining Mortality of Adult Chaparral Shrubs in an Extreme Drought Year in California

We measured dieback and mortality in a chaparral shrub community at a chaparral/desert ecotone following four years of below-average rainfall. Ecotones are important systems in which to examine plant and community responses to extreme and prolonged drought conditions and the potential impact of global change on plant distributions and community composition. Following a particularly severe drought year, dieback and mortality were documented for seven co-dominant shrub species. We examined whether mortality was related to species ecology, leaf traits, or water relations. Dieback and mortality were greatest in two non-sprouting species. These species also had high xylem cavitation resistance and low specific leaf area compared to several sprouting species. Among two sprouting congeners, mortality was greater in the more shallowly rooted species, even though this species was more cavitation resistant. Across all species, those that were more resistant to cavitation had greater mortality. Evidently, high resistance to xylem cavitation does not prevent adult plant mortality at chaparral/desert ecotones. A series of extreme drought years could preferentially reduce or eliminate non-sprouting species from mixed chaparral populations, causing a shift in community structure and contributing to desertification.
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Extent and Intensity of Extreme Drought in Some Parts of the Savanna Region of Nigeria

Extent and Intensity of Extreme Drought in Some Parts of the Savanna Region of Nigeria

At regional level extreme drought occurred for eight years (100%) during the study period using sub-periods. The sub-period 1971 to 2000 experienced the highest number of years of extreme drought at three years (37.50%). Two sub-periods 1961 to 1990 and 1981 to 2010 had two years (25%) each of extreme droughts. The sub-period 1951 to1980 experienced one year (12.50%) of extreme drought while the sub-period 1941 to 1970 experienced no extreme drought at all. This may be due to low intensity of human activities like animal grazing and tree cuttings leading to more biogenic freezing nuclei in the air and therefore more rainfall (Table 4). Taking all the sub-periods into consideration (that is across the overlapping sub-periods) at regional level, Kano and Maiduguri experienced three (3) years (37.50%) of extreme drought. They were followed by Katsina with 2 years (25%) while other stations recorded no extreme drought during the study period. In Kano, The sub-periods with the three years of extreme drought were 1951 to 1980, 1961 to 1990 and 1971 to 2000 each with a (1)year (33.33%).Other sub-periods did not experienced extreme drought (Table 4). Maiduguri also had years of extreme drought like Kano but the drought sub-periods were 1961 to 1990, 1971 to2000 and 1981 to 2010 all with one (1) year (33.33%) of extreme drought each. Other sub-periods had no extreme drought. Katsina had the last two sub-periods of 1971 to 2000 and 1981 to 2010 with a (1) year (50%) each of extreme drought. Other sub-periods did not experience extreme drought (Table 4)
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Effects of high temperatures on threatened estuarine fishes during periods of extreme drought

Effects of high temperatures on threatened estuarine fishes during periods of extreme drought

We used an integrative approach to assess the impact of elevated water temperature on two fishes of immediate conservation concern in a large estuary ecosystem. The environmentally relevant exposure temperature of 20°C is more commonly reached and occurs earlier in the year during periods of extreme drought. Based on their physiological responses, longfin smelt may be more susceptible to increases in temperature, as this species appears to be near its upper thermal limits with relatively little room to tolerate persistent drought or future climate warming in California. Examination at multiple levels of biological organization (cellular to whole- organism) highlighted the potential vulnerability of longfin smelt relative to delta smelt. Longfin smelt aggregate in deeper water during peak seasonal temperatures, potentially to avoid extreme surface temperatures (Rosenfield and Baxter, 2007). Therefore, longfin smelt may respond behaviorally by seeking out suitable temperatures. Alternatively, longfin smelt may need to adjust the phenology of their spawning or migration to the cooler saltwater environment; otherwise, periods of high water temperature could be detrimental to segments of this population as regions of the Delta will no longer provide suitable habitat. With the delta smelt at a legitimate risk of extinction, longfin smelt could become a key indicator species of ecosystem health in the Delta, the epicenter of the debates surrounding water use in California. Understanding the physiological responses to environmental stressors of threatened and endangered species is crucial for conservation efforts in coastal systems and to effectively manage important estuary ecosystems.
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Are Northeastern U.S. forests vulnerable to extreme drought?

Are Northeastern U.S. forests vulnerable to extreme drought?

In the Northeastern U.S., drought is expected to increase in frequency over the next century, and therefore, the responses of trees to drought are important to understand. There is recent debate about whether land-use change or moisture availability is the primary driver of changes in forest species composition in this region. Some argue that fire suppression from the early twentieth century to present has resulted in an increase in shade-tolerant and pyrophobic tree species that are drought intolerant, while others suggest precipitation variability as a major driver of species composition. From this debate, an emerging hypothesis is that mesophication and increases in the abundance of mesophytic genera (e.g., Acer, Betula, and Fagus) resulted in forests that are more vulnerable to drought. This review examines the published literature and factors that contribute to drought vulnerability of Northeastern U.S. forests. We assessed two key concepts related to drought vulnerability, including drought tolerance (ability to survive drought) and sensitivity (short-term responses to drought), with a focus on Northeastern U.S. species. We assessed drought-tolerance classifications for species, which revealed both consistencies and inconsistencies, as well as contradictions when compared to actual observations, such as higher mortality for drought-tolerant species. Related to drought sensitivity, recent work has focused on isohydric/ anisohydric regulation of leaf water potential. However, based on the review of the literature, we conclude that drought sensitivity should be viewed in terms of multiple variables, including leaf abscission, stomatal sensitivity, turgor pressure, and dynamics of non-structural carbohydrates. Genera considered drought sensitive (e.g., Acer, Betula, and Liriodendron) may actually be less prone to drought-induced mortality and dieback than previously considered because stomatal regulation and leaf abscission in these species are effective at preventing water potential from reaching critical thresholds during extreme drought. Independent of drought-tolerance classification, trees are prone to dieback and mortality when additional stressors are involved such as insect defoliation, calcium and magnesium deficiency, nitrogen saturation, and freeze-thaw events. Overall, our literature review shows that multiple traits associated with drought sensitivity and tolerance are important as species may rely on different mechanisms to prevent hydraulic failure and depleted carbon reserves that may lead to mortality.
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Advances in the Research of Yunnan’s Arid Climate and Extreme Drought

Advances in the Research of Yunnan’s Arid Climate and Extreme Drought

In recent years, severe drought events happened in Yunnan and its neighboring zones continuously, particularly the drought in the autumn, winter and summer of2009/2010 and 2011/2012 aroused strong repercussion, and many scholars carried out the work of studying the causes of extreme drought. Sun Guowu et al . [33] compared and analyzed the atmospheric low-frequency change characteristics in these two extreme drought years and one non-drought year. Results hold that, there are two flow types for the at- mospheric low-frequency change in Yunnan region in the winter and spring: latitude in allow-frequency air flow and longitudinal low-frequency air flow. The former obstructs the north-south exchange of north (south) cold (warm) air flow; the latter ensures that there is no air flow convergence in the single north-south cold and warm air mass. Be- sides, in the drought year, the low-frequency anticyclone is far more than low-fre- quency cyclone in southwest region and India-Bay of Bengal region, the northerly air flow in front of the low-frequency anticyclone prevents the northward transportation of the vapor in the Bay of Bengal; in the non-drought year, the low-frequency air flow and the low-frequency system are opposite. Therefore, the change of atmospheric low-fre- quency air flow and low-frequency system might be one of the reasons resulting in the continuous drought in the winter and spring in Yunnan.
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The extreme drought of 1842 in Europe as described by both documentary data and instrumental measurements

The extreme drought of 1842 in Europe as described by both documentary data and instrumental measurements

The fact that no particularly outstanding price increases for base products occurred in either Prague or Vienna could re- sult from a number of factors and administrative strategies or decisions. One important influence was the mass stor- age of grain in royal or regional granaries; such a reserve could buffer the effects of at least one bad harvest (e.g. Je- lenkor, 3 September 1842). In similar fashion to that de- scribed for Hungary, this factor was also present at that time in other countries investigated (e.g. France, Germany, the Czech Lands, Austria) which had, for example, granaries and a burgeoning trade in basic agricultural products. It was also significant that the official market prices of major food prod- ucts (meat, cereals, etc.) were fixed by regional authorities. Despite actual market increases, these regulations may have had a positive impact and again could have buffered some of the immediate effects of the bad and very bad harvest re- sults of a dry year (e.g. Nemzeti Újság, 18 September 1842). Moreover, not all regions were affected to the same degree by drought and related natural extremes. There were areas that saw ample harvests in 1842 within the vast and geographi- cally varied Habsburg empire: for example, the major grain production regions of southern Hungary had a good harvest and its cereals were exported. Reports in the Jelenkor news- paper suggest regular shipping on the Danube towards Vi- enna all summer and autumn 1842, evidently not disturbed by low water levels. Further, despite less favourable (or even bad) hay harvests at country level, the export of hay from Hungary to Lower Austria (and Vienna) increased signifi- cantly in the dry years of 1841 and 1842; this may well have been due to the increased hay yields in the Fert˝o/Neusiedl and Hansag/Wasen wetlands during the dry years (Horváth, 2016).
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Impact of Temperature and Wetness of Summer Months on Autumn Vegetative Phenological Phases of Selected Species in Fageto‑Quercetum in the Years 2011–2015

Impact of Temperature and Wetness of Summer Months on Autumn Vegetative Phenological Phases of Selected Species in Fageto‑Quercetum in the Years 2011–2015

The work presents the result of the drought impact on the onset and the development of autumn phenological phases of tree species (Quercus robur L., Carpinus betulus L., Prunus avium L.) in the central part of Slovakia. The selected autumn phenological phases of tree species were observed in the years from 2011 to 2015. From meteorological parameters we examined precipitation, number of tropical days, and their periods from June to August. We revealed distinct differences in air temperature and precipitation between the years, which affected the onset of individual phenological phases. Based on the calculations of the Thornthwaite moisture index and climatic water balance, the year 2014 was wet (except for June) with the shortest periods of tropical days. The extreme drought and the longest 13‑day period of tropical days in the year 2015 shifted leaf colouring of hornbeam and cherry tree by 16 and 22 days earlier and the leaf fall by 5 and 16 days earlier than the average of the period from 2011 to 2015. Oak was the least sensitive to the weather extremes, which was documented by a balanced course of the phenological phases with the lowest variation. The 5‑year‑long average onset of the autumn phenophases of oak and hornbeam was shifted by 1 – 4 days later and of cherry tree by 4 days earlier than the 25‑year‑long average.
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Impact of climate change on the severity, duration, and frequency of drought in a semi-arid agricultural basin

Impact of climate change on the severity, duration, and frequency of drought in a semi-arid agricultural basin

Conclusions: This study applied the Standardized Precipitation Index (SPI) along with a combination of GCM-scenarios to create the severity-duration-frequency (SDF) curves of drought for the period 2020-2044. An average period of six months (ending in May) was used for the SPI, corresponding to the agricultural growing season of the region, to assess drought conditions under five plausible climate scenarios. The selected GCM-scenarios were GISS-ER A1B (warmer and drier), CSIROMk3.5 B1 (cooler and drier), INGV-SXG A1B (median conditions), ECHO-G A2 (warmer and wetter) and ECHAM5 B1 (cooler and wetter) and they were downscaled with an Artificial Neural Network (ANN) approach. Results reveal that most scenarios exhibit an increase in the duration of extreme drought while the duration of moderate drought decreases under all scenarios. The largest increases in the frequency of extreme droughts occur in the western portion of the basin in response to the warmer and drier climate scenario. An increase in the number of extreme (SPI < -2) drought conditions with a longer duration can influence the growing season.
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Evaluation of the Nature of Drought Experienced in Makueni County, Kenya

Evaluation of the Nature of Drought Experienced in Makueni County, Kenya

Drought events remain a major threat to lives and livelihoods in sub-Saharan Africa (SSA) due to the high exposure and vulnerability of populations. In the last three decades, Kenya experienced high frequency of drought events. The frequency of drought is projected to increase in the future more so due to anthropogenic climate change whose impacts include erratic seasonal rainfall and increased frequency of extreme rainfall events such as drought. Droughts present extreme conditions of water scarcity which have adverse effects on the physical environment and water resource systems particularly for arid and semi arid regions. The design and implementation of drought mitigation and response strategies requires an understanding of the nature and impacts of drought. Previous mitigation measures have been done randomly without establishing the nature of drought , reason as to why drought in Makueni County whether major or minor has severe impacts on this community.Makueni County of, Kenya has suffered many severe and extreme drought conditions the nature and impacts of which have however remained unknown and undocumented. The objective of this study was to examine the nature of drought in Makueni over the last three decades. Secondary data comprising of rainfall records from Makindu, Mavindini and Kibwezi areas was used to compute a drought index. The standardised precipitation index SPI was used to identify the nature of drought occurring in the study area. The results revealed that Makueni County experienced three episodes of extreme meteorological droughts in the last three decades. In the same period, Hydrological drought persisted for over 8 years while over five extreme and severe Agricultural droughts were analysed in the study area. Though the drought conditions in the study area are pathetic, the residents of Makueni County seemingly did not fathom the nature of drought that they experienced. The findings of this study are anticipated to inform decision makers and development actors in Kenya, whose interest is to mitigate, and respond to drought on Kenyans lives, economy and development as a whole.
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High-spatial-resolution probability maps of drought  duration and magnitude across Spain

High-spatial-resolution probability maps of drought duration and magnitude across Spain

Abstract. Assessing the probability of occurrence of drought is important for improving current drought assessment, man- agement and mitigation measures, and strategies across Spain. This study employed two well-established drought indices, the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI), to characterize drought duration and magnitude at different timescales over Spain. In order to map the drought hazard probability, we applied the extreme value theory and tested different thresholds to generate peak-over-threshold (POT) drought duration and magnitude series. Our results demon- strate that the generalized Pareto (GP) distribution performs well in estimating the frequencies of drought magnitude and duration. Specifically, we found a good agreement between the observed and modelled data when using upper percentiles to generate the POT series. Spatially, our estimations suggest a higher probability of extreme drought events in southern and central Spain compared to the northern and eastern re- gions. Also, our study found spatial differences in drought probability estimations as a function of the selected drought index (i.e. SPI vs. SPEI) and timescale (i.e. 1, 3, 6, and 12 months). Drought hazard probability maps can contribute to the better management of different sectors (e.g. agricul- ture, water resources management, urban water supply, and tourism) at national, regional, and even local scale in Spain.
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Droughts in the Amazon: Identification, Characterization and Dynamical Mechanisms Associated

Droughts in the Amazon: Identification, Characterization and Dynamical Mechanisms Associated

Drought events in 1998, 2005 and 2010 presented similar characteristics in the Tropical Pacific Ocean, with positive SST anomalies, followed by a transition to negative anomalies. The three extreme events were also marked by positive SST anomalies in the North Tropical Atlantic, contributing to the establishment of a meridional local circulation (Hadley cell), with vertical upward movement over the North Atlantic and downward vertical movement (subsidence) on the Ama- zon, cloud formation was inhibited by this pattern. The combination of the posi- tive SST anomalies observed in the Tropical Atlantic North and the Tropical Pa- cific Ocean reinforces the subsidence conditions on the Amazon are unfavorable to the occurrence of precipitation. The difference between the extreme drought events in 1998 for the 2005 and 2010 droughts was the action of both cells, Walker in the Pacific and Hadley in the North Atlantic, acting together in early 1998, this pattern intensified negative SPI values observed this year.
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Projecting future climate change effects on the extreme hydrological drought events in the Weihe River basin, China

Projecting future climate change effects on the extreme hydrological drought events in the Weihe River basin, China

Figure 6 shows the contours of joint probability for drought duration and severity for baseline and A1B drought events. It demonstrates large distances between the contours for baseline and A1B drought events with the higher joint probabilities, especially in the cases of the contours with the probabilities of 0.90, 0.95 and 0.99. On those contours at the same probability levels, if the same duration is given for both baseline and A1B events, the corresponding severity under A1B is found to be considerably higher than that under base- line. As a result, more severe extreme drought situations was projected under A1B scenario. This phenomena can be also illustrated by the conditional drought severity distributions given certain durations (Fig. 7). For example, given 3-month duration, the conditional probability of baseline events with severity less than or equal to 800 m 3 s −1 is approximately 0.91. However, for A1B events, the same probability cor-
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Monitoring droughts in Eswatini: A spatiotemporal variability analysis using the Standard Precipitation Index

Monitoring droughts in Eswatini: A spatiotemporal variability analysis using the Standard Precipitation Index

Estimating agriculture drought severity at a station or AEZ provides useful information for drought planning and management. It is therefore important to assess the drought over a specified agro-ecological region. This allows the administrative areas that fall within these regions to plan effectively. The drought analysis based on these zones is useful for determining the spatial distribution and characteristics of drought and for evaluating the most affected areas for a specific drought event. To provide a complete picture of the drought hotpots in Eswatini, spatial analysis was performed by plotting 3-month SPI values using ArcGIS 10.1. Figures 6–9 depict the spatial extent of selected drought years in Eswatini from 1986 to 2016. All the interpolated SPI maps were reclassified into four classes, that is, SPI value from -1 to 1 as no drought, -1.5 to -1.0 as moderate drought, ≤ 2 to -1.5 as severe drought and ≥ 2 as extreme drought category.
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Drought Analysis Based on Streamflow Drought Index (SDI) in Bhima sub-basin

Drought Analysis Based on Streamflow Drought Index (SDI) in Bhima sub-basin

The SDI values calculated from the time series of the monthly streamflow volume of the Bhima sub basin help to assess the temporal variation of hydrological drought and estimate the drought parameters. The calculated monthly SDI values were classified based on drought categories as presented in Table 1. The time scale series of occurrence of drought categories was calculated shown in graphs plotted year v/s SDI value for five hydrometric stations located in the basin. There is no extreme drought as occurred more frequently in 3, 6, and 9 month time scale. Whereas considering 12 month time scale there is a one extreme drought as occurred during 2008-09 to each station.
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The effects of persistent drought and waterlogging on the dynamics of nonstructural carbohydrates of Robinia pseudoacacia L. seedlings in Northwest China

The effects of persistent drought and waterlogging on the dynamics of nonstructural carbohydrates of Robinia pseudoacacia L. seedlings in Northwest China

Extreme event-induced tree mortality occurs globally and is likely to be exaggerated by future climate change, par- ticularly drought and flood (Patz et al. 2005; Bréda et al. 2006; Huntington et al. 2006; Adams et al. 2009; Allen et al. 2010; Pachauri et al. 2014). As is well known, the events of extreme drought and floods will affect forest ecosys- tems along with rising temperatures, heat waves, and changing interactions between pests/pathogens and hosts (Bonan 2008; Allen et al. 2010). However, the underlying mechanisms of drought-induced tree mortality remain un- clear (McDowell et al. 2008a, b; Sala 2009; Sala et al. 2010). In ideal condition over the time, tree mechanism is largely governed by the increasing stand level competition and social status on an individual tree (Saud et al. 2016, 2018), but under drought stress, trees are vulnerable to carbon starvation. Previous studies suggested that trees were vulnerable to carbon starvation under drought stress (Parker and Patton 1975; Bréda et al. 2006; McDowell et al. 2008a, b; Adams et al. 2009; Sala et al. 2010). However, there are the elusive and complex phenomena of non- structural carbohydrates (NSCs) in plants in response to drought that are induced by different drought features (i.e., intensity and duration) and tree species, size, age and tissues (Sala et al. 2012; Hartmann et al. 2013; Palacio et al. 2014). Therefore, the lack of consensus among these studies on the effect of water availability on the NSC dy- namics suggests that further studies are necessary to eluci- date the underlying mechanisms (McDowell et al. 2008a, b; O’Grady et al. 2013).
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Extreme Climatic Events Alter Aquatic Food Webs. A Synthesis of Evidence from a Mesocosm Drought Experiment

Extreme Climatic Events Alter Aquatic Food Webs. A Synthesis of Evidence from a Mesocosm Drought Experiment

p0435 We should be able to extrapolate from here to predict what might hap- pen in the food web, community or ecosystem as a whole. For example, in the immediate aftermath of an intense perturbation event, we might expect to see a short burst of intense and potentially destabilising predation followed by a more bottom-up dominated period, when r-selected species benefit from the subsequent loss of predators and the freeing-up of new habitat and food resources. This situation should eventually shift back to the pre- drought conditions as predator populations recover and top-down effects start to reassert themselves, and the rate at which this state is re-established represents the system’s resilience. However, if the perturba- tions do not cease then we might expect the system to persist in a transient state, akin to arrested succession in highly disturbed, human-modified envi- ronments, such as heathland or fen. This is reflective of the intermediate dis- turbance hypothesis, whereby, at moderate levels of disturbance, top-down effects are offset by bottom-up effects, with neither one being able to completely dominate (e.g. Connell, 1978). Although the IDH was never proposed with an explicitly food web perspective in mind, the parallels are notable. Thus, we might expect droughts to be reflected by pulses of ini- tially high mortality due to both density-dependent (i.e. intense competition or predation) and density-independent (e.g. mortality due to high temper- ature or desiccation) causes, followed by a relaxation of biotic control as predators run out of food and/or suffer disproportionately from increased metabolic demands and fragmentation of foraging patches. Subsequently, as the waters return (or the flood recedes), there is a dramatic increase in hab- itat and food availability for the survivors, which is likely to favour more r-selected species that are able to colonise and increase population sizes more rapidly than those towards the K-selected end of the gradient.
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Extreme Events (Flood & Drought) and Food Security Measures in the Aspects of Local Perception

Extreme Events (Flood & Drought) and Food Security Measures in the Aspects of Local Perception

Bangladesh as an agro-economy depended country, its food comes from agricultural sector but agriculture activities depends on climatic variables such as temperature, precipitation, pressure, wind, humidity and etc. Consecutively, Agricultural production rate gradually decreases due to imbalance condition of climate and food becomes insecure. Food security depends on regional natural activities and its variation, such as – natural hazards, climate changing pattern, distribution and quality of agricultural land, education, employment opportunities and food habits. Climatic variables and its changing pattern are expected negatively attribute to crop growth and take into further challenge to fulfill local and household food security [9-13]. Extreme events such as droughts, floods, cyclones etc. causes loss of crop yield that affects specially in food security and agricultural livelihood. As a result, agriculture dependent people do not get enough facilities of fundamental needs income, food, safe water, habitation, proper education and etc. and they are diverted themselves into other occupations for the better living standard. Climate change is directly focused to food security and social livelihood pattern. In summer season, temperature remains so high, it is one of the main causes of drought occurring. However, the soil becomes dry and does not able to make availability of necessary nutrients and reduces soil fertility. As a result, agricultural production profit is less than farmer expenditure. A number of factors such as low soil fertility, trade relationship, feeble infrastructure and institution, population growth and future climatic variation act as a key factor to remove poverty and achieve food security [14]. In addition, yearly drought damages enormous amount of crops, crop lands and fail to reach the target production. Mainly in char area like “chilmari” in Kurigram district of Bangladesh, agriculture dependent people lost their crop lands because of river bank erosion due to unexpected and/or uncertain flooding hazards. Nevertheless, Cyclone in coastal area increases salinity
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Application of the extreme learning machine algorithm for the prediction of monthly Effective Drought Index in eastern Australia

Application of the extreme learning machine algorithm for the prediction of monthly Effective Drought Index in eastern Australia

To be prepared for the detrimental consequences of drought on freshwater planning and water resource environments, the forecasting of future drought is a priori knowledge. For this purpose, basically two types of models are considered in literature: physical models which predict coupled effects of the ocean and the atmosphere, known as Global Circulation Model (GCM) and statistical models that assimilate observed values of hydro-meteorological properties (e.g. temperature or rainfall) to forecast future drought events. In Australia, the GCM frame- work implemented as the official model used by the Australian Bureau of Meteorology (BOM) is the Predictive Ocean Atmo- sphere Model for Australia (POAMA) (Hudson et al., 2011; Zhao and Hendon, 2009) and that by the Queensland Department of Environment and Resource Management is the statistical analysis of climate indices by the Seasonal Pacific Ocean Temperature Analysis (SPOTA-1) (Day et al., 2010). However the predictions of rainfall by GCMs on some occasions have failed to predict very wet or very dry conditions that produced significant economic consequences (van den Honert and McAneney, 2011). For example the floods between November 2010 and January 2011 that left three-quarters of Queensland, Australia a disaster zone (Hurst, 2011) were not predicted well in advance (Abbot and Marohasy, 2014; Inquiry, 2011; Seqwater, 2011). Despite improvements in the performance of numerical weather models, they do not provide quantitative precipitation forecasts at enough spatial and temporal scales
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