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This study proposes a quantitative approach for extreme drought hotspot assessment related to climate change, the hotspot drought risk index (HDRI), and evaluates the response of extreme drought to climate change in the five major river basins of the Korean Peninsula. According to an analysis of seasonal and regional drought characteristics on the Korean Peninsula, drought occurs most frequently in spring, and the central and southern areas are generally more vulnerable to drought. Drought risk analysis under various climate change scenarios indicates significant drought risk over the entire Korean Peninsula excepting some parts of the Han and Nakdong river basins from 2011 to 2040. Extreme drought may be particularly severe in the mid‐west area as these basins lack available water resources. Drought risk decreases in the southern Korean Peninsula in the 2011–2040 and 2071–2099 periods, during which the area vulnerable to drought also decreases. However, some parts of central Korea and the western and eastern coastlines remain susceptible to drought. The drought risk evaluation method suggested herein may be useful for predicting drought and establishing realistic coping strategies for extreme drought in a changing climate. [ABSTRACT FROM AUTHOR]

Future climate scenarios point to an increase in the frequency of extreme droughts events, even in humid biomes. Throughout the 21st century, large areas of the Amazon basin experienced the most severe droughts ever recorded with special emphasis on the 2005 and 2010 events due to their severity and extent. Currently, there is an increased demand to understand the geographic extent and seasonal variability of climate variables during drought events, especially with respect to the social and environmental impacts. In this study, we aim to compare the observed climate conditions during the drought episodes of 2005, 2010 and 2015. We perform a detailed assessment of the measured precipitation, land‐surface temperature (LST) and solar radiation anomalies. We provide evidence that the anomalous precipitation deficit during 2015 exceeded the amplitude and spatial extent of the previous events, affecting more than 80% of Amazon basin, particularly the eastern portion. The pronounced lack of rainfall availability during late spring and early summer, coincident with radiation and temperature surpluses during these years are significant and notable. Changed meteorological spatial patterns were observed, with precipitation and radiation being the most prominent parameters in 2005, whereas precipitation and LST were most relevant in 2010. Understanding the behaviour and interactions of pertinent meteorological variables, as well as identifying similar or divergent patterns over the region during distinct extreme events, is essential for the improvement of our knowledge of Amazon forest vulnerability to climate fluctuation changes. [ABSTRACT FROM AUTHOR]

ABSTRACT: Ocean and atmospheric patterns associated with the most severe and most persistent droughts in the Mexican Altiplano region are explored. The standardized precipitation index on a time scale of 12 months was used and compared with time series of other atmospheric conditions to identify major dry episodes from 1970 to 2012. The time series were derived from the second mode of a varimax‐rotated empirical orthogonal functional analysis from the mean summer rainfall series observed at weather stations located in the Mexican Altiplano from 1970 through 2000. The results showed that the longest and most persistent episode occurred from 1998 through 2001, while the most severe dry episode occurred in 2011–2012, when the Pacific Decadal Oscillation was in a negative phase and the Atlantic Multidecadal Oscillation in a positive phase, both in combination with a La Niña event. A large upper‐level anticyclone over the north‐central United States is related to droughts in the Altiplano. Under these conditions, the droughts were linked to a large anticyclone positioned over the central‐north of the United States, with consequent negative anomalies of specific humidity over central‐northern Mexico. Concurrent with droughts in the interior of Mexico, are positive rainfall anomalies along the central Pacific coast of Mexico near the study area. Under different atmospheric conditions, opposite anomalous behaviour between the coast and interior can exist. The mechanism driving this see‐saw behaviour between the west coast of Mexico and the Altiplano is explored. [ABSTRACT FROM AUTHOR]

ABSTRACT: A quasi‐stationary circumglobal teleconnection (CGT) in the Northern Hemisphere in summer is associated with summer droughts and floods and exhibits some vorticity anomalies. The CGT anomaly and its forcing sources were explored based on reanalysis data and the EI Nino 3.4 index. The term ∂v′/∂x was used to describe the multi‐scale variability of vorticity and the CGT anomaly, which had a 7‐wavenumber and a small interannual amplitude of ∂v′/∂x from 1987 to 2000 but a large amplitude from 2000 to 2010. The interannual CGT intensity was enhanced by an EI Nino sea surface temperature pattern in spring via key forcing sources that led to an enduring effect on the summer circulation; it was also a response to anomalies in Tibetan Plateau (TP) heating in spring–summer in two ways. First, increasing TP heating in the mid‐eastern TP caused an eastward shift and northerly extension of the South Asian High (SAH), which exhibited a Tibetan‐mode SAH as well as a 7‐wavenumber CGT anomaly. This enhanced the CGT over Eurasia and extended the wave pattern of the EI Nino contribution over the North Pacific and Eurasia. Second, increased snow cover in the west of the TP could have offset the TP heating effect and adjusted the position and intensity of the Tibetan‐mode SAH. This phenomenon weakened vorticity and wave amplitude and finally led to a weak CGT anomaly. This finding indicates a coupled effect of double‐mode TP heating (i.e. both heating and TP snow cover) on the CGT anomaly, which reveals the linkage of TP heating with weather over Eurasia and North America that could be predicted by TP heating and other factors. [ABSTRACT FROM AUTHOR]

ABSTRACT: Weather‐pattern, or weather‐type, classifications are a valuable tool in many applications as they characterize the broad‐scale atmospheric circulation over a given region. This study analyses the aspects of regional UK precipitation and meteorological drought climatology with respect to a new set of objectively defined weather patterns. These new patterns are currently being used by the Met Office in several probabilistic forecasting applications driven by ensemble forecasting systems. Weather pattern definitions and daily occurrences are mapped to Lamb weather types (LWTs), and parallels between the two classifications are drawn. Daily precipitation distributions are associated with each weather pattern and LWT. Standardized precipitation index (SPI) and drought severity index (DSI) series are calculated for a range of aggregation periods and seasons. Monthly weather‐pattern frequency anomalies are calculated for SPI wet and dry periods and for the 5% most intense DSI‐based drought months. The new weather‐pattern definitions and daily occurrences largely agree with their respective LWTs, allowing comparison between the two classifications. There is also broad agreement between weather pattern and LWT changes in frequencies. The new data set is shown to be adequate for precipitation‐based analyses in the UK, although a smaller set of clustered weather patterns is not. Furthermore, intra‐pattern precipitation variability is lower in the new classification compared to the LWTs, which is an advantage in this context. Six of the new weather patterns are associated with drought over the entire UK, with several other patterns linked to regional drought. It is demonstrated that the new data set of weather patterns offers a new opportunity for classification‐based analyses in the UK. [ABSTRACT FROM AUTHOR]

ABSTRACT Projected changes in regional characteristics of drought throughout the 21st century can help inform climate change assessments across drought-sensitive sectors. However, the ability of global climate models ( GCMs) to reproduce statistical attributes of observed drought at regional scales has not typically been considered. We present a framework for evaluating the fidelity of GCMs to simulate regional drought to help guide model selection for users of regional climate projections where drought plays a key climate impact, and elucidate shortcomings of model simulations of hydroclimate variability. Monthly precipitation (Pr) and potential evapotranspiration ( ETo) from 24 GCMs of the Coupled Model Intercomparison Project Phase 5 were compared to observations, with a focus on the northwestern United States ( NWUS), using a suite of statistics for capturing multi-scalar aspects of drought and both supply (Pr) and atmospheric demand ( ETo). Model fidelity was generally higher for drought metrics evaluated with ETo versus Pr, and for seasonal and annual time scales versus multi-year time scales. While some GCMs performed well across the suite of drought metrics and time scales, models systematically underestimated the severity of regional drought in the NWUS defined by precipitation deficits, particularly for multi-year time scales. [ABSTRACT FROM AUTHOR]

ABSTRACT Drought may occur in almost every climatic region on Earth at any time. Understanding the nature and magnitude of the dryness and drought events are crucial mainly in semi-arid regions characterized by water shortage and warm/hot and dry Mediterranean type climate. The present article analyses the major patterns of the spatial and temporal characteristics of the climatological dryness in Turkey. This study adopts a relatively new approach for characterizing the dryness over a certain region; dry days since last rain ( DDSLR). The DDSLR in a certain place can be evaluated using three different metrics; its severity, consistency and temporal uncertainty enabling to present intra- and inter-annual variations of the dryness. The DDSLR is also coupled with the Mediterranean Climate Index ( MCI) approach, measuring the seasonality of rainfall. Analyses were based on daily precipitation data recorded at 69 principal climatological and synoptic meteorological stations of the Turkish Meteorological Service network during the period 1970-2011. The spatial distributions of the MCI and the various DDSLR metrics are presented and analysed. Overall, the three metrics of the DDSLR show their highest values in southern parts of Turkey along the Mediterranean and the borders with Syria and Iraq. These dryness indices are even larger than in central Turkey which receives less annual rainfall. On the other hand, dryness is at its minimum along the Black Sea in northern Turkey. Logarithmic equations of the type f( DDSLR) = a × ln( MCI) + b were fitted to describe the dependence of these metrics on the MCI. All regressions are highly significant and enable to evaluate these metrics even in regions without daily data. Finally, linear trends of the longest DDSLR in each year were calculated and reveal trends toward more severe dry conditions in north-western Turkey and less severe dry conditions in east Turkey. [ABSTRACT FROM AUTHOR]

ABSTRACT Agro-climatic classification helps to determine the different features of a region. This climatic classification provides a useful insight for a farmer to grow their crops according to the conditions of their region. This study identifies the shifting of moisture index from average values in different agro-climatic zones of Pakistan. Unpredictable climate remains dominant over long periods. Observational data of precipitation and evapotranspiration were used to determine the agro-climatic zone during the period 1951-2010. This study reveals that almost 87% of Pakistan is in extremely arid to semi-arid zones, a 5% decrease in over the last 30 years (1981-2010). The largest decrease of 8% and increase of 5% were observed in the extremely arid and humid zones, respectively. The semi-arid zone is more vulnerable to drought, while intensity and severity are greater in the extremely arid region. An agro-climatic regional analysis identifies 1952, 1969, 2000, 2001 and 2002 as years when the most severe droughts were observed during the study period. The trends of precipitation and temperature were performed at 95% significance level on a monthly, seasonal and annual basis over the entire agro-climatic zone of Pakistan during 1951-2014. The annual precipitation trends show a significant increase of 0.828 mm year−1 in arid regions, whereas the maximum temperature trends shows a significant increase of 0.014 °C year−1 and 0.018 °C year−1 in extremely arid and humid regions, respectively. The trend of minimum temperature shows an increase over the whole region, which may place pressure on the water demands of crops. [ABSTRACT FROM AUTHOR]

ABSTRACT Monthly gridded (0.5° × 0.5°) standardized precipitation-evapotranspiration index ( SPEI) data of 1901-2008 were used to detect spatial pattern of temporal trend in meteorological drought during the Indian summer monsoon period. The SPEI data were converted into drought duration, magnitude and types of occurrence to capture overall drought scenario. A non-parametric (Mann-Kendall test) method was used to test for monotonic trend at each grid level, whereas the magnitude was estimated using Sen's method. Further, a field significance test was performed at major meteorological regions level to assess whether the individual trends identified could occur by chance in an analysis of large number of time series analysed. Significant ( α = 0.05) increasing trend of both drought duration and magnitude during the monsoon was found over parts of eastern, central and north-eastern region of India, whereas the parts of west coast, arid western region and north India showed significantly decreasing trend. The trends in mid- as well as late-season drought were contributing towards significant increase in drought condition, whereas trends in early-season drought were responsible for decrease in drought events. The time series analysis of rainfall and potential evapotranspiration ( PET) illustrated that over eastern part of India the increase in drought was attributed due to decrease in rainfall, whereas the decrease in drought occurrence over western arid region was mainly because of decrease in PET. [ABSTRACT FROM AUTHOR]

ABSTRACT A spatiotemporal analysis of two well-known agricultural drought indices, the Palmer Drought Severity Index ( PDSI) and the Standardized Precipitation Index at a 9-month scale ( SPI-9), is presented for Sri Lanka. The analysis was conducted based on monthly precipitation and temperature data from January 1881 to December 2010 using 13 stations distributed across the three climatic zones of the country. Principal component analysis shows that the first two principal components of PDSI and SPI-9 are spatially comparable and could physically represent the two main monsoons. A wavelet analysis of these principal components' scores for both indices indicates a stronger association between the Northeastern monsoon and El-Niño in recent decades. Correlation analysis with agricultural metrics suggests that different indices might be appropriate for each of the climatic zones in Sri Lanka. PDSI correlated best with the intermediate zone districts; SPI-9 correlated best with the dry zone districts; but neither index correlated well with the wet zone districts. [ABSTRACT FROM AUTHOR]

The Standardized Precipitation Index ( SPI), a well-reviewed meteorological drought index recommended by the World Meteorological Organization ( WMO), and its more recent climatic water balance variant, the Standardized Precipitation-Evapotranspiration Index ( SPEI), both rely on selection of a univariate probability distribution to normalize the index, allowing for comparisons across climates. Choice of an improper probability distribution may impart bias to the index values, exaggerating or minimizing drought severity. This study compares a suite of candidate probability distributions for use in SPI and SPEI normalization using the 0.5° × 0.5° gridded Watch Forcing Dataset ( WFD) at the continental scale, focusing on Europe. Several modifications to the SPI and SPEI methodology are proposed, as well as an updated procedure for evaluating SPI/ SPEI goodness of fit based on the Shapiro-Wilk test. Candidate distributions for SPI organize into two groups based on their ability to model short-term accumulation (1-2 months) or long-term accumulation (>3 months). The two-parameter gamma distribution is recommended for general use when calculating SPI across all accumulation periods and regions within Europe, in agreement with previous studies. The generalized extreme value distribution is recommended when computing the SPEI, in disagreement with previous recommendations. [ABSTRACT FROM AUTHOR]

ABSTRACT The weather conditions from August 2011 to May 2012 produced an extreme drought in the eastern Czech Republic (Moravia), whereas the patterns were nearly normal in its western region (Bohemia). The Southern and Central Moravia regions, which represent the most important agricultural areas, were most affected by the drought. The precipitation totals for the studied period were 50-70% of the long-term mean, which was calculated for 1961-2000. In autumn 2011, the total precipitation accounted for 10-30% of the long-term mean for most of Moravia, increasing to 30-50% in spring 2012. Moreover, 7.5% of the Czech Republic experienced a 100-year drought; 20% of the country experienced a 20-year drought. According to the Palmer Drought Severity Index, the 2012 drought was classified as the worst in the past 130 years. The drought patterns were related to the prevailing high-pressure systems over Central Europe and the occurrence of weather types with different precipitation amounts in Bohemia and Moravia. The most substantial drought effects occurred in the agricultural sector. A decrease in cereal yields was observed in the analysed production areas in Moravia, which was unprecedented in the past 52 years. Moreover, winter crops were affected more than spring crops. An increased risk of fire occurred due to the drought conditions; the largest forest fire in the past 15 years was recorded during this period. Furthermore, signs of hydrological drought were also reported in rivers. The 2011-2012 drought was compared with the significant droughts in 2000, 2003 and 2007. Austria and Slovakia, which neighbour the Czech Republic, experienced a similar drought. Global circulation model sensitivity experiments appear to indicate that droughts similar to this episode may be occurring at a recurrence interval of 20 years by the 2050s. [ABSTRACT FROM AUTHOR]

ABSTRACT In this study, the spatial distribution of the potential drought hazard areas in Korea was estimated by conducting frequency analysis with the Standardized Precipitation Index ( SPI), and the changes in potential drought hazard areas that appeared because of climate changes were predicted. In an attempt to estimate the changes in the spatial distribution of potential drought hazard areas, past observed data (1976-2010) from 54 automated weather stations under the Korea Meteorological Administration ( KMA) and projected precipitation data (2011-2099) by four global climate models ( GCMs). CNRM:CM3, CSIRO:MK3, CONS:ECHOG and UKMO:HADCM, were used. The severity-duration-frequency ( SDF) curves were derived for the 54 weather stations in order to estimate the potential drought hazard areas by employing the potential drought hazard mapping approach. The spatial distribution analysis for the potential drought hazard areas showed that the drought in the Nakdong River basin, which was a frequent drought hazard area in the past, was more aggravated, and more severe droughts were predicted for the future in the Han River basin (Han River, Anseong Stream, West of Han River), which is located in the middle part of the country. From the analysis results of the four GCMs, more severe drought is expected throughout the Korean Peninsula in the future, by using the CONS:ECHOG model compared with the projected data from the four GCMs. Additionally, potential drought areas would shift from the south toward the east and central parts of the country, as projected by the UKMO:HADCM model. [ABSTRACT FROM AUTHOR]

West Africa includes a semi-arid zone between the Sahara Desert and the humid Gulf of Guinea coast, approximately between 10°N and 20°N, which is irrigated by summer monsoon rains. This article refers to the region as the Sahel. Rain-fed agriculture is the primary sustenance for Sahel populations, and severe droughts (in the 1970s and 1980s), therefore, have devastating negative societal impacts. The future frequency of Sahel droughts and the evolution of its hydrological balance are therefore of great interest. The article reviews 10 recent research studies that attempt to discover how climate changes will affect the hydrology of the Sahel throughout the 21st century. All 10 studies rely on atmosphere-ocean global climate model (AOGCM) simulations based on a range of greenhouse gas emissions scenarios. Many of the simulations are contained in the Intergovernmental Panel on Climate Change archives for Assessment Reports #3 and #4. Two of the studies use AOGCM data to drive regional climate models. Seven studies make projections for the first half of the 21st century and eight studies make projections for the second half. Some studies make projections of wetter conditions and some predict more frequent droughts, and each describes the atmospheric processes associated with its prediction. Only one study projects more frequent droughts before 2050, and that is only for continent-wide degradation in vegetation cover. The challenge to correctly simulate Sahel rainfall decadal trends is particularly daunting because multiple physical mechanisms compete to drive the trend upwards or downwards. A variety of model deficiencies, regarding the simulation of one or more of these physical processes, taints models' climate change projections. Consequently, no consensus emerges regarding the impact of anticipated greenhouse gas forcing on the hydrology of the Sahel in the second half of the 21st century. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The article presents the study that examines the impact of climatic changes Bani basin in Niger River and Mali. It states that study focuses on drought hazards and its indicators obtained from the climatic moisture index using the monthly data for the period to examine the vulnerability of Bani basin to water stress. It indicates that the standardized precipitation index was used to address water deficit.

The article studies the tropical rainbelt in West Africa in relation to the patterns of rainfall anomalies in the said area. According to the author, the years 1955 and 1950 were anomalously wet in Sahel while the years 1983 and 1984 were anomalously dry. Moreover, the author mentions of abnormally high rainfall that occurs in Sahelian latitudes while drought is experienced in the Guinea Coast latitudes. In the study, the author compares the wet and dry years and associates it with the activities in the tropical rainbelt. Moreover, the author provided connection between the global scale phenomena and Sahel.