Drought Climatology Research Articles

Multivariate Evaluation of Flash Drought Across the United States

AbstractThis study uses the flash drought intensity index (FDII) to develop a multivariate flash drought climatology for the contiguous U.S. using data from 2001 to 2021. The FDII method uses the rate of intensification (FD‐INT) and subsequent drought severity (DRO‐SEV) to determine when a flash drought occurred and the strength of the event. Overall, the results showed that flash drought occurrence and severity varied with season and region and were sensitive to the drought indicator used to compute the FDII. Precipitation‐based indicators identified more flash droughts across the western U.S. whereas soil moisture (SM) and evapotranspiration indicators identified more flash droughts across the central and eastern U.S. When assessed over the entire U.S., the most flash droughts were found when using an evaporative demand indicator. Though FD‐INT was larger than DRO‐SEV across the U.S. for most indicators, regional patterns were also evident in their relative importance. For example, a distinct east‐west gradient was present in the SM and evapotranspiration FD‐INT, with relatively large values in the central and eastern U.S. A combined data set synthesizing information from multiple indicators showed that the strongest flash droughts from a multivariate perspective were located in the central and southeastern U.S. A seasonal analysis revealed a distinct seasonal cycle in flash drought onset across the western and central U.S. Together, the results illustrate the need to use a multivariate framework to identify and characterize the occurrence and severity of flash droughts.

Assessing decadal- to centennial-scale nonstationary variability in meteorological drought trends

Abstract. There are indications that the reference climatology underlying meteorological drought has shown nonstationarity at seasonal, decadal, and centennial timescales, impacting the calculation of drought indices and potentially having ecological and economic consequences. Analyzing these trends in meteorological drought climatology beyond 100 years, a time frame which exceeds the available period of observation data, contributes to a better understanding of the nonstationary changes, ultimately determining whether they are within the range of natural variability or outside this range. To accomplish this, our study introduces a novel approach to integrate unevenly scaled tree-ring proxy data from the North American Seasonal Precipitation Atlas (NASPA) with instrumental precipitation datasets by first temporally downscaling the proxy data to produce a regular time series and then modeling climate nonstationarity while simultaneously correcting model-induced bias. This new modeling approach was applied to 14 sites across the continental United States using the 3-month standardized precipitation index (SPI) as a basis. The findings showed that certain locations have experienced recent rapid shifts towards drier or wetter conditions during the instrumental period compared to the past 1000 years, with drying trends generally found in the west and wetting trends in the east. This study also found that seasonal shifts have occurred in some regions recently, with seasonality changes most notable for southern gauges. We expect that our new approach provides a foundation for incorporating various datasets to examine nonstationary variability in long-term precipitation climatology and to confirm the spatial patterns noted here in greater detail.

The evolution of “Hot” droughts in Southern California, USA from the 20th to the 21st century

Drought intensity and duration in southern California, USA during the 21st century has been exceptional, and the changing climate dynamics of drought in this arid and semiarid region have been linked to anthropogenic warming. We examine the frequency, intensity, and persistence of drought in southern California's two climatic divisions during 1900–2022 and use the monthly instrumental record of the Palmer Drought Severity Index (PDSI) to track how drought events have changed. We introduce an empirical definition of “hot drought” by combining mean summer PDSI values with standardized scores of mean summer minimum temperature. Droughts in southern California, USA have become increasingly more severe, frequent, and long-lived in the 21st century. Moderate drought conditions (PDSI < −2) were recorded during more than half of the months in the decade ending in 2020. Similarly, hot droughts, droughts associated with both water deficits and significantly above-normal temperatures, have become increasingly frequent in recent decades. By the 21st century, hot droughts were occurring in approximately half of the summers. Our findings support the idea that anthropogenic warming results in a changing drought climatology for arid and semiarid regions of southern California and that hot droughts will likely become the dominant drought type.

Evolution of Drought Climatology and Variability in the Central Anatolia Region, Turkey, for the Period 1970–2020

Evolution of Drought Climatology and Variability in the Central Anatolia Region, Turkey, for the Period 1970–2020

Determination of the Intensity of Hydrological and Climatological Drought in the Južna Morava River Sub-Basin

Determination of the Intensity of Hydrological and Climatological Drought in the Južna Morava River Sub-Basin

Analysis of the critical components of flash drought using the standardized evaporative stress ratio

Flash droughts develop rapidly (∼1 month timescale) and produce significant ecological, agricultural, and socioeconomical impacts. Recent advances in our understanding of flash droughts have resulted in methods to identify and quantify flash drought events. However, few studies have been done to isolate the individual rapid intensification and drought components of flash drought, which could further determine their causes, evolution, and predictability. This study utilized the standardized evaporative stress ratio (SESR) to quantify individual components of flash drought from 1979 – 2019, using evapotranspiration (ET) and potential evapotranspiration (PET) data from the North American Regional Reanalysis (NARR) dataset. The temporal change in SESR was utilized to quantify the rapid intensification component of flash drought. The drought component was also determined using SESR and compared to the United States Drought Monitor. The results showed that SESR was able to represent the spatial coverage of drought well for regions east of the Rocky Mountains. Furthermore, the rapid intensification component agreed well with previous flash drought studies, with the overall climatology of rapid intensification events showing similar hotspots to the flash drought climatology east of the Rocky Mountains. The rapid intensification climatology suggested areas west of the Rocky Mountains experience rapid drying more often than east of the Rocky Mountains.

Rainfall trends and district-wise drought climatology during southwest monsoon season over Bundelkhand region of Uttar Pradesh, India

Drought is a climatic anomaly that can occur in all regions with vastly different climate. A persistent lack of precipitation over an extended period scaling usually a season or more results water stress that significantly impacts economic, agricultural, environmental and social aspects. For an effective monitoring of drought condition, drought indices play major role which are region specific and have limitation of applicability in different climatic condition. Hence, the present study aims to analyse the climatology and drought by two drought indices viz. Standard Precipitation Index (SPI) and standardized precipitation evapotranspiration index (SPEI)) for Bundelkhand region, the most drought prone area of Central India by using 48 years (1969-2016) rainfall and temperature data. The trend analysis was performed at a significance level of 5% by using non parametric Mann-Kendall (MK) test and Sen’s slope estimator with the help of XLSTAT 2021 software. The SPI and SPEI were calculated with the SPEI R package in R-Studio software. The study revealed that i) the southwest monsoon (June to September) contributed 88.8-91.8% of total annual rainfall with coefficient of variation (CV) of 29.9-39.5%. ii) A non- significant decreasing trend in rainfall was noticed for almost all the districts during July, August and September. However, a significant (0.05 level) and decreasing trend was observed in July (4.03 mm rainfall/year) and August rainfall (4.03 mm rainfall/year) for Hamirpur. iii) The frequency of moderate drought events increased followed by severe and extreme drought events. The decreasing trends of SPI-3 and SPEI-3 were also observed which indicates more dry spells during southwest monsoon season. iv) A good correlation (r= value of 0.88 to 0.91) was observed between SPI-3 and SPEI-3 during southwest monsoon season which indicates the importance of theses indices for assessment of drought in the study region.

Climatological Drought Monitoring in Switzerland Using EUMETSAT SAF Satellite Data

Climatological drought monitoring in Switzerland relies heavily on station-based precipitation and temperature data. Due to the high spatial variability and complexity of droughts, it is important to complement station-based drought indices with gridded information and to couple multiple drought indicators within the monitoring system. Here, long-term satellite-based drought parameters from the EUMETSAT SAF network are analyzed in terms of dry anomalies within their climatology’s, namely ASCAT soil water index (SWI), CM SAF land surface temperature (LST), complemented with NOAA vegetation data, and LSA SAF Meteosat evapotranspiration data. The upcoming EUMETSAT SAF climate data records on land surface temperature and evapotranspiration will cover for the first time the WMO climatological 30-year reference period. This study is the first study investigating the potential of those long-term data records for climate monitoring of droughts in Europe. The satellite datasets are compared with the standardized precipitation index (SPI), soil moisture observations from the SwissSMEX measurement network, with a modelled soil moisture index (SMI) based on observations, and with evapotranspiration measurements, focusing on the temporal dynamics of the anomalies. For vegetation and surface temperature, the dry years of 2003, 2015, and 2018 are clearly visible in the satellite data. CM SAF LSTs show strong anomalies at the beginning of the drought period. The comparison of in situ and modelled soil moisture and evapotranspiration measurements with the satellite parameters shows strong agreement in terms of anomalies. The SWI indicates high anomaly correlations of 0.56 to 0.83 with measurements and 0.63 to 0.76 with the SMI at grassland sites. The Meteosat evapotranspiration data strongly agree with the measurements, with anomaly correlations of 0.63 and 0.67 for potential and actual evapotranspiration, respectively. Due to the prevailing humid climate conditions at the considered sites, evapotranspiration anomalies during the investigated dry periods were mostly positive and thus not water limited, but were also a driver for soil moisture drought. The results indicate that EUMETSAT SAF satellite data can well complement the station-based drought monitoring in Switzerland with spatial information.

Hot Extremes and Climatological Drought Indicators in the Transitional Semiarid-Subtropical Region of Sinaloa, Northwest Mexico

Hot Extremes and Climatological Drought Indicators in the Transitional Semiarid-Subtropical Region of Sinaloa, Northwest Mexico

Quantification of leaf wax and cutin monomer composition in Pima (Gossypium barbadense L.) and upland (G. hirsutum L.) cotton

Climatological drought is a historic problem that limits agricultural production worldwide. Reducing transpirational water loss can conserve soil moisture and confer drought tolerance to crops by delaying their dehydration during periods of drought stress. Transpiration can be regulated by the hydrophobic plant cuticle, which coats the aerial surfaces of plants and limits water loss through non-stomatal transpiration. The cuticle is composed primarily of two lipid classes, free cuticular wax components and the polymerized cutin polyester. Many studies suggest that both waxes and cutin are important in maintaining plant water status during periods of drought. Five varieties of Pima cotton (Gossypium barbadense) and six varieties of upland cotton (G. hirsutum) were examined for variation in leaf wax and cutin composition. Wax and cutin monomers were analyzed using an Agilent 7890A gas chromatograph and a 5975C mass spectrometer (GC–MS). Results show that upland cotton produces more total wax than Pima varieties, whereas Pima cotton produces more total cutin than upland varieties. In both species, alcohols were the most abundant wax compounds and dihydroxy monobasic acids were the most abundant cutin monomers.

Begging for Rain: Economic and Social Effects of Climate in the Early Koryŏ Period

Abstract As in other premodern societies, the economy and society of Koryŏ Korea (918–1392) were greatly affected by climatological phenomena, particularly rain and drought. However, climate played a critical role in the early formation of Koryŏ, especially in reinforcing a sociocultural belief system that supported monarchical authority. The kings utilized a “menu” of rituals designed to appease Heaven and create favorable climate conditions, which legitimated the temporal and spiritual power of the king. The different rituals can be categorized as personal rituals, private rituals, and public rituals. While climate crises threatened the economic and social stability of Koryŏ society, they were also opportunities for the Koryŏ rulers to display and reaffirm their supreme economic and juridical authority. The kings demonstrated their power by reducing corvée labor and taxes, postponing or eliminating monastery construction, and commuting judicial punishments. While weather and climate were natural phenomena, the social responses to weather were encapsulated in a ritual system that reinforced both the personal responsibility of the king and popular belief in the power and authority of the king to affect the physical and metaphysical environment.

Building an Improved Drought Climatology Using Updated Drought Tools: A New Mexico Food-Energy-Water (FEW) Systems Focus

Drought is a familiar climatic phenomenon in the United States Southwest, with complex human-environment interactions that extend beyond just the physical drought events. Due to continued climate variability and change, droughts are expected to become more frequent and/or severe in the future. Decision-makers are charged with mitigating and adapting to these more extreme conditions and to do that they need to understand the specific impacts drought has on regional and local scales, and how these impacts compare to historical conditions. Tremendous progress in drought monitoring strategies has occurred over the past several decades, with more tools providing greater spatial and temporal resolutions for a variety of variables, including drought impacts. Many of these updated tools can be used to develop improved drought climatologies for decision-makers to use in their drought risk management actions. In support of a Food-Energy-Water (FEW) systems study for New Mexico, this article explores the use of updated drought monitoring tools to analyze data and develop a more holistic drought climatology applicable for New Mexico. Based upon the drought climatology, droughts appear to be occurring with greater frequency and magnitude over the last two decades. This improved drought climatology information, using New Mexico as the example, increases the understanding of the effects of drought on the FEW systems, allowing for better management of current and future drought events and associated impacts.

Drought Risk Analysis in the Eastern Cape Province of South Africa: The Copula Lens

This research study was carried out to investigate the characteristics of drought based on the joint distribution of two dependent variables, the duration and severity, in the Eastern Cape Province, South Africa. The drought variables were computed from the Standardized Precipitation Index for 6- and 12-month accumulation period (hereafter SPI-6 and SPI-12) time series calculated from the monthly rainfall data spanning the last five decades. In this context, the characteristics of climatological drought duration and severity were based on multivariate copula analysis. Five copula functions (from the Archimedean and Elliptical families) were selected and fitted to the drought duration and severity series in order to assess the dependency measure of the two variables. In addition, Joe and Gaussian copula functions were considered and fitted to the drought duration and severity to assess the joint return periods for the dual and cooperative cases. The results indicate that the dependency measure of drought duration and severity are best described by Tawn copula families. The dependence structure results suggest that the study area exhibited low probability of drought duration and high probability of drought severity. Furthermore, the multivariate return period for the dual case is found to be always longer across all the selected univariate return periods. Based on multivariate analysis, the study area (particularly Buffalo City, OR Tambo and Alfred Zoo regions) is determined to have higher/lower risks in terms of the conjunctive/cooperative multivariate drought risk (copula) probability index. The results of the present study could contribute towards policy and decision making through e.g., formulation of the forward-looking contingent plans for sustainable management of water resources and the consequent applications in the preparedness for and adaptation to the drought risks in the water-linked sectors of the economy.

Development of drought hazard index for vulnerability assessment in Pakistan

Drought is a silent meteorological disaster that spreads over time, affecting water availability for agriculture and livelihood in any region. The prediction of drought is a complex phenomenon; however, the negative impacts of drought are mitigated by monitoring drought events over a region. The present study provides spatial and temporal drought climatology over Pakistan, using 60-years (1951–2010) observational gridded data (0.5° × 0.5°) of precipitation from Global Precipitation Climatological Center and soil moisture from Climate Prediction Center. Using precipitation and soil moisture datasets, a novel drought hazard index is developed to determine drought vulnerability across different districts of Pakistan. Our findings identified 19 districts that are extremely vulnerable to drought, with northern regions being vulnerable to mild drought, whereas central and southern districts are vulnerable to high drought events. By using standardized precipitation index and soil moisture anomaly, six severe drought years were identified as 1952, 1969, 1971, 2000, 2001, and 2002 in different parts of the country. Deficiency of monsoon rainfall is a major cause of droughts in southern and rain-fed regions. This study is helpful for drought managers, hydrologists, and contingency planners to prepare mitigation and adaptation plans toward sustainable development in Pakistan.

Recent wetting trend in China from 1982 to 2016 and the impacts of extreme El Niño events

AbstractClimate warming generally is expected to increase drought, but arguments about China's past drought trends persist. PDSIARTS, a revised self‐calibrating Palmer Drought Severity Index, was computed for China over 1982–2016 using satellite leaf‐area indices combined with monthly climate data interpolated from 2000 high‐density stations. Drought climatology was analysed against climate factors. The results show that temperature has increased at a rate of 0.38°C per decade (p &lt; .001) in China in the past 35 years (1982–2016). However, over the same interval, China and the northern China region became wetter. PDSIARTS increased at a rate of 0.03 yr−1 (p &lt; .001) across China during 1982–2016. The analogous increase of PDSIARTS in northern China was 0.05 yr−1 (p &lt; .001). In China, the 5‐year interval from 2012 to 2016 was the wettest 5 years in the 35‐year interval. This arises from the coupled effects of decreased potential evaporation (Ep) and increased precipitation (Pr). The implication is that temperature increase does not necessarily indicate increased drought. A potential complication is that the 2015/16 El Niño event induced the highest Pr in southern China for 1982–2016, and northern China still had plentiful Pr in 2015/16, which further contributed to the wettest 2‐years (2015/16) during the past 35 years in the whole of China. This study highlights the joint impacts of Pr and Ep on the dry/wet changes and the possibility of extremely wet events in the warming future.

Assessment of meteorological droughts over Saudi Arabia using surface rainfall observations during the period 1978\u20132017

This paper discusses the preliminary results of meteorological drought analysis over Saudi Arabia for the period 1978–2017. In conjunction with meteorological observations, datasets from the Climate Prediction Center (CPC), the Merged Analysis of Precipitation (CMAP), the Climatic Research Unit (CRU), and the Tropical Rainfall Measuring Mission (TRMM) are utilized to understand the impact of the spatial distribution of rainfall on drought events. Applying precipitation thresholds allows rainfall classifications such as deficit, scanty, and surplus. Precipitation thresholds are also used to define meteorological droughts in the country, which are categorized as usual, moderate, and severe. It is found that drought events occur in Saudi Arabia due to shortfalls in the dry season, even though there is above normal rainfall in the wet season. There is no case of a shortfall in both the wet and dry seasons causing drought. Saudi Arabian droughts of all categories occurred mostly in the dry season, with fewer in the wet season. Results show that in Saudi Arabia, the last month of the wet season (April) is less prone to drought while the first and last months of the dry season (June and September respectively) are more prone to drought. Spatial distribution of drought climatology is obtained by calculating the Standardized Precipitation Index (SPI) and the Palmer Drought Severity Index (PDSI). Further application-driven studies of projections are needed based on drought indices and climate model output.

Analysis of the Climatological Drought Trend Variations Using Mann-Kendall, Sen and Pettitt Tests in Isfahan Province

Analysis of the Climatological Drought Trend Variations Using Mann-Kendall, Sen and Pettitt Tests in Isfahan Province

Assessing the Remotely Sensed Evaporative Drought Index for Drought Monitoring over Northeast China

Many existing satellite evapotranspiration (ET)-based drought indices have characterized regional drought condition successfully, but the relatively short time span of ET products limits their use in long-term climatological drought assessment. In this study, we assess Evaporative Drought Index (EDI) as a drought monitoring indicator over Northeast China through a retrospective comparison with drought-related indicators. After verifying its utility for detecting documented regional drought events and impacts of drought on crop production, we apply it to improve our understanding of the variation in dryness over Northeast China from 1982 to 2015. Our results illustrate that EDI is generally effective for characterizing terrestrial moisture condition and its standardized formula, namely, Standardized Evaporative Drought Index (sEDI) corresponds well with historical drought events and inter-annual grain crop yields over Northeast China. Although the calculation of sEDI does not directly incorporate precipitation and soil moisture, statistical analyses indicate sEDI can detect drought in accordance with the Standardized Precipitation Index (SPI) and Palmer Drought Severity Index (PDSI), with the highest correlations found in the west part of Northeast China (R &lt; −0.7). Further analysis illustrates sEDI is more related to commonly-used drought metrics over areas with short canopy vegetation (R &lt; −0.5) than woodland (R &lt; −0.2), which suggests precipitation may not be a good representative of drought condition over areas with deep-rooted vegetation. Then, we find 56.5% of Northeast China shows an upward dry trend from 1982 to 2015, which mainly concentrates in the west part of the study area. Conversely, 14.4% of Northeast China shows a significant wetted trend and most of them locate at cropland areas, due to the improved water management. This study suggests that EDI is a feasible method to monitor spatially distributed drought condition and can provide unique drought information not reflected by rainfall deficits, which also can be used to evaluate traditional precipitation-based indicators.

A Methodology for Flash Drought Identification: Application of Flash Drought Frequency across the United States

Abstract With the increasing use of the term “flash drought” within the scientific community, Otkin et al. provide a general definition that identifies flash droughts based on their unusually rapid rate of intensification. This study presents an objective percentile-based methodology that builds upon that work by identifying flash droughts using standardized evaporative stress ratio (SESR) values and changes in SESR over some period of time. Four criteria are specified to identify flash droughts: two that emphasize the vegetative impacts of flash drought and two that focus on the rapid rate of intensification. The methodology was applied to the North American Regional Reanalysis (NARR) to develop a 38-yr flash drought climatology (1979–2016) across the United States. It was found that SESR derived from NARR data compared well with the satellite-based evaporative stress index for four previously identified flash drought events. Furthermore, four additional flash drought cases were compared with the U.S. Drought Monitor (USDM), and SESR rapidly declined 1–2 weeks before a response was evident with the USDM. From the climatological analysis, a hot spot of flash drought occurrence was revealed over the Great Plains, the Corn Belt, and the western Great Lakes region. Relatively few flash drought events occurred over mountainous and arid regions. Flash droughts were categorized based on their rate of intensification, and it was found that the most intense flash droughts occurred over the central Great Plains, Corn Belt, and western Great Lakes region.

A drought climatology for Mauritius using the standardized precipitation index

ABSTRACTThis study presents a high-resolution and multi-temporal drought climatology for Mauritius based on calculated standardized precipitation index (SPI) using mean monthly rainfall for the period 1953–2007. A monthly mean SPI varying from +3.4 to −2.7 indicates the occurrence of extremely wet and dry conditions, and collocated SPI indicates more frequent mild drought conditions. Spatial maps of rainfall trends and SPI show mostly neutral to severely dry conditions, but sparse regions of extremely wet and dry conditions are also observed. An increase in the frequency of dry years after the 1990s is noted, while most of the extreme wet conditions are found to have occurred between 1972 and 1988. More frequent short-duration wet events are observed on the 3- and 6-month time scales compared to dry events. On the 12- and 24-month time scales the frequency of both dry and wet periods is almost the same, with the dry events lasting longer.