drought intensity
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2022 ◽  
Vol 314 ◽  
pp. 108809
Author(s):  
Ying Yao ◽  
Bojie Fu ◽  
Yanxu Liu ◽  
Yan Li ◽  
Shuai Wang ◽  
...  

Author(s):  
Swatantra Kumar Dubey ◽  
Rakesh Kumar Ranjan ◽  
Anil Kumar Misra ◽  
Nishchal Wanjari ◽  
Santosh Vishwakarma

2022 ◽  
Author(s):  
Mehdi Mohammadi Ghaleni ◽  
Saeed Sharafi ◽  
Seyed-Mohammad Hosseini-Moghari ◽  
Jalil Helali ◽  
Ebrahim Asadi Oskouei

Abstract The present study compares the main characteristics (intensity, duration, and frequency) of meteorological drought events in the four climates (Hyperarid, Arid, Semiarid, and Humid) of Iran. For this purpose, three drought indices, including Standardized Precipitation Index (SPI), Reconnaissance Drought Index (RDI), and Standardized Precipitation Evapotranspiration Index (SPEI), were employed at the timescales of 1-, 3-, 6-, 9- and 12-months. These indices were compared by utilizing long-term data of 41 synoptic meteorological stations for the recent half century, 1969–2019. The long-term analysis of drought indices indicates that the duration and intensity of drought events have temporally risen after the 1998–99 period. Iran has experienced the longest duration (40 months) of extreme drought during Dec 98–Mar 02 and Jan 18–Mar 18, respectively. Spatial patterns demonstrate that drought intensity uniformly increased in SPI1 to SPI12, and SPEI3 to SPEI12, from humid and semiarid to arid and hyperarid regions. The average drought duration in studied stations for SPI, SPEI and RDI indices equaled 9, 12, and 9 months, respectively. In addition, mean drought frequencies are calculated at 14, 17, and 13 percent for SPI, SPEI and RDI indices, respectively. Generally, SPEI compared to SPI and RDI shows greater duration and frequency of drought events, particularly in arid and hyperarid regions. The research shows the crucial role of climatic variables in detecting drought characteristics and the importance of selecting appropriate drought indices in various climates.


Abstract Under the new background of climate change, it is very important to identify the characteristics of drought in North China. Based on the daily Meteorological Drought Comprehensive Index from 494 national meteorological stations in North China during 1961–2019, the drought processes and their intensity are identified by applying the ‘extreme’ intensity-duration theory. Then, the stage variation characteristics of the drought trend, the average drought intensity and the drought frequency are analyzed. The results show that among the five drought intensity indexes the process maximum intensity demonstrates the greatest correlation coefficient with the disaster rate of drought in North China. Therefore, the process maximum intensity of drought is selected as the annual drought intensity to analyze the drought characteristics in North China. According to the climate warming trends, the study period is divided into three stages, i.e., 1951–1984 (stage I), 1985–1997 (stage II) and 1998–2019(stage III). The comprehensive results show that the drought intensity in North China has significant stage characteristics. In stage I, the drought shows an increasing trend in most parts of North China, but its average intensity is relatively weaker, with a lower severe drought frequency. The drought also shows an increasing trend in most parts in stage II, with a more significant increase rate than that in stage I, and the average drought intensity is the strongest and the severe drought frequency is the highest. In stage III, the drought shows a decreasing trend in some areas, and the average intensity is the weakest, with a lower severe drought frequency.


Water ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 71
Author(s):  
Serhii Nazarenko ◽  
Jūratė Kriaučiūnienė ◽  
Diana Šarauskienė ◽  
Darius Jakimavičius

The problem of droughts is acute due to climate change. The study aims to assess the temporal and spatial drought patterns in Lithuanian lowland rivers in the past and to project these phenomena according to climate scenarios and models. Drought analysis was based on Standardized Precipitation Index (SPI), Reconnaissance Drought Index (RDI) and Streamflow Drought Index (SDI). To evaluate the past patterns, the hydrometeorological data of 17 rivers were used from 1961–2020. Future drought changes were analyzed in 2021–2100 according to the selected RCPs (Representative Concentration Pathways) using the hydrological model HBV. There were different patterns of droughts in three hydrological regions of Lithuania (Western, Central and Southeastern). The Southeastern region was more prone to extreme summer hydrological droughts, and they had a shorter accumulation period compared to the other two regions. SPI and RDI indices showed that the number of dry months and the minimum value of the index increased, extending the accumulation period. The highest correlation was recorded between RDI-12/SPI-12 and SDI-12. The amplitude between extremely wet and dry values of river runoff will increase according to RCP8.5. The projections indicated that hydrological drought intensity in the Central region is expected to increase under both analyzed RCPs.


2021 ◽  
Vol 12 ◽  
Author(s):  
Li Ji ◽  
Yue Liu ◽  
Jun Wang ◽  
Zhimin Lu ◽  
Lijie Zhang ◽  
...  

Non-structural carbohydrates (NSCs) facilitate plant adaptation to drought stress, characterize tree growth and survival ability, and buffer against external disturbances. Previous studies have focused on the distribution and dynamics of NSCs among different plant organs under drought conditions. However, discussion about the NSC levels of fine roots in different root branch orders is limited, especially the relationship between fine root trait variation and NSC content. The objective of the study was to shed light on the synergistic variation in fine root traits and NSC content in different root branch orders under different drought and soil substrate conditions. The 2-year-old Fraxinus mandshurica Rupr. potted seedlings were planted in three different soil substrates (humus, loam, and sandy–loam soil) and subjected to four drought intensities (CK, mild drought, moderate drought, and severe drought) for 2 months. With increasing drought intensity, the biomass of fine roots decreased significantly. Under the same drought intensity, seedlings in sandy–loam soil had higher root biomass, and the coefficient of variation of 5th-order roots (37.4, 44.5, and 53% in humus, loam, and sandy–loam soil, respectively) was higher than that of lower-order roots. All branch order roots of seedlings in humus soil had the largest specific root length (SRL) and specific root surface area (SRA), in addition to the lowest diameter. With increasing drought intensity, the SRL and average diameter (AD) of all root branch orders increased and decreased, respectively. The fine roots in humus soil had a higher soluble sugar (SS) content and lower starch (ST) content compared to the loam and sandy–loam soil. Additionally, the SS and ST contents of fine roots showed decreasing and increasing tendencies with increasing drought intensities, respectively. SS and ST explained the highest degree of the total variation in fine root traits, which were 32 and 32.1%, respectively. With increasing root order, the explanation of the variation in root traits by ST decreased (only 6.8% for 5th-order roots). The observed response in terms of morphological traits of different fine root branch orders of F. mandshurica seedlings to resource fluctuations ensures the maintenance of a low cost-benefit ratio in the root system development.


2021 ◽  
Author(s):  
Hang Xu ◽  
Zhiqiang Zhang ◽  
Ram Oren ◽  
Xiaoyun Wu

Abstract Increased drought intensity with rising atmospheric demand for water (hereafter VPD) increases the risk of tree mortality worldwide. Ecosystem-scale water-use strategy (WUSe), quantified here by canopy stomatal sensitivity to VPD (Sc), is increasingly recognized as a factor in drought-related ecosystem dysfunction. However, the links between Sc and ecosystem adaptation to and stability following droughts are poorly established. We examined how Sc regulates carbon sequestration, identifying ecosystems potentially susceptible to drought-induced mortality based on data from the global flux network, remote-sensing products, and plant functional-traits archive. We found that Sc is higher where ecosystem water availability is low in arid regions, reflecting conservative WUSe (i.e., hypersensitivity), but ecosystems of all regions converge on permissive WUSe (i.e., hyposensitivity) under ample water supply. During extreme droughts, hyposensitive and hypersensitive ecosystems achieved similar net ecosystem productivity employing considerably different structural-functional strategies. However, hyposensitive ecosystems, risking their hydraulic system with permissive WUSe, did not recover from extreme droughts as quickly. Models predicting current performance and future distributions of vegetation types should account for the greater vulnerability of hyposensitive ecosystems to intensifying atmospheric and soil drought.


2021 ◽  
Vol 28 (4) ◽  
pp. 14-24
Author(s):  
Omar M. A. Mahmood Agha

This paper deals with the study of drought in the Nineveh region usingthe Chinese Z index (CZI) for a time scale (1 month). Historical data wereused from 1981 to 2018 for Mosul, Sinjar, and Tal Afar stations. Thereturn period and probability event for the moderate drought werecalculated for each month separately. The results indicated that allstations experienced the highest drought intensity in March comparedwith the other months. The average probability of moderate droughtranged between 0-0.31 for all months, and the maximum severity of thedrought was found in December from 2004 to 2008 for all stations. Inaddition, the results showed that the region's climate during the studyperiod was within the mild drought and humidity (closest to normal).This paper is the first study using the Chinese Z-index (CZI) in the studyarea and the Iraq region


Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1274
Author(s):  
Suping Wang ◽  
Qiang Zhang ◽  
Jinsong Wang ◽  
Yuanpu Liu ◽  
Yu Zhang

Based on daily meteorological data from 55 meteorological stations in eastern Gansu from 1960 to 2017, the characteristics of the drought process and precipitation heterogeneity were analyzed, and the relationship between drought and precipitation heterogeneity was evaluated. Results showed that there were 1–3 drought processes in the study area every year. Drought processes in the eastern and north-central regions were more frequent than those in other regions. Droughts were mainly manifested as intra-seasonal droughts, especially across the spring and summer. PCD (Precipitation Concentration Degree, the concentration degree of the precipitation at a certain time) ranged from 0.2 to 0.7 in the area. PCD increased in spring and autumn but decreased in summer and winter for most regions from 1960 to 2017. PCP (Precipitation Concentration Period, the shortest time which the precipitation was concentrated in) was from late April to early May in spring, mid-to-late July in summer, mid-September in autumn, and late January in winter. In the last 58 years, PCP has remained consistent in most regions, varying by approximately 10 days. In addition to insignificant changes in winter, the days with light and moderate rain presented a declining trend, especially in summer and autumn. The larger the PCD, the fewer the days with light and moderate rain, and the stronger the drought intensity. However, in the east-central region, the larger the PCD in autumn, the weaker was the drought intensity. This difference is related to the PCP and the evapotranspiration. Additionally, the later the PCP, the stronger was the drought intensity, particularly in summer and autumn. When PCD was ≥0.5 in spring and ≥0.4 in summer, the PCP was after May and August in spring and summer, respectively. Droughts appeared in 28–56% of periods when seasonal precipitation was above normal. When PCD was ≥0.5 in autumn and PCP was in early and middle September, droughts appeared in 7% of periods when precipitation was above normal. Our results show that although less precipitation is the leading influencing factor of drought in the dry rain-fed agricultural areas, the influence of precipitation heterogeneity should be also considered for the prediction and diagnosis of seasonal drought.


Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1259
Author(s):  
Anita Bokwa ◽  
Mariusz Klimek ◽  
Paweł Krzaklewski ◽  
Wojciech Kukułka

Mountains are highly sensitive to the effects of climate change, including extreme short- and long-term weather phenomena. Therefore, in spite of relatively high annual precipitation totals, mountains might become endangered by droughts. The paper presents drought trends in the Polish Carpathians located in Central Europe. Data from the period 1991–2020 from 12 meteorological stations located in various vertical climate zones of the mountains were used to define drought conditions using the following indices: Standardized Precipitation (SPI), Standardized Precipitation Evapotranspiration (SPEI), Relative Precipitation (RPI) and Sielianinov. Additionally, four forest drought indices were used in order to estimate the impact of drought on beech as a typical Carpathian tree species, i.e., the Ellenberg (EQ), Forestry Aridity (FAI), Mayr Tetratherm (MT) and De Martonne Aridity (AI) indices. Statistically significant but weak trends were obtained for the 6-month SPI for four stations (indicating an increase in seasonal to mid-term precipitation), for the 1-month SPEI for three stations, for the 3-month SPEI for four stations, and for MT for all stations (indicating an increase in drought intensity). The analysis of dry month frequency according to particular indices shows that at most of the stations during the last decade of the study period, the frequency of dry months was much higher than in previous decades, especially in the cold half-year. Two zones of the Polish Carpathians are the most prone to drought occurrence: the peak zone due to the shift in climatic vertical zones triggered by the air temperature increase, and the forelands and foothills, together with basins located about 200–400 m a.s.l., where the mean annual air temperature is the highest in all the vertical profile, the annual sums of precipitation are very diversified, and the conditions for beech are already unfavorable.


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