scholarly journals Evaluation and Forecasting Meteorological Drought, Case Study: Kohgilooyeh and Boyer Ahmad

2021 ◽  
Author(s):  
Homa Razmkhah ◽  
Eshagh Rostami ◽  
Amin Rostami Ravari ◽  
Alireza Fararouie
Keyword(s):  
Spatial Variation ◽  
Average Duration ◽  
Meteorological Drought ◽  
Threshold Level ◽  
Performance Measure ◽  
Lead Times ◽  
Neural Network Models ◽  
Drought Duration ◽  
Drought Characteristics ◽  
Increasing Trend

Abstract The SPI is the most widely used drought index to provide an acceptable estimation of drought characteristics. The objective of this study was to compare different threshold levels effect on derived drought characteristics, assessment of the spatial variation of meteorological drought properties as well as drought frequency, duration, and value in Kohgilooyeh and Boyer Ahmad Province, Iran, using SPI for 1, 3, 6, 12, 24 and 48 months lead-times, and finally SPI forecasting using Artificial Neural Networks (ANNs). For the first threshold level (scenario), drought properties are extracted based on the standard level of zero, and for the second one, -1 is considered. Results showed that the frequency of drought and wet periods decreased from SPI-1 to 48 for both scenarios in all stations. Max drought duration of stations had an increasing trend from SPI-1 to 48. The average duration of dry periods changed as a function of the time scales; it increased from SPI-1 to 48. Spatial variation of the drought average duration was considerable for long-term drought. Max SPI value did not follow any spatial variation, as it was constant for all lead times in all stations. Average SPI values had a decreasing trend from SPI-1 to 9 but increased from SPI-9 to 48 in all stations. Max average of SPI value observed in short-term drought and min value in medium-term. SPI value general trend was similar in both scenarios, therefore drought threshold level did not affect the results. The third objective was to develop neural network models for drought forecasting. Different architectures are applied to find the best models to forecast SPI over various lead times. The best forecasting results for SPI-3 and 6, obtained from the Quasi-Newton training algorithm, when for SPI-1, 9, 12, 24, and 48, Levenberg-Marquardt was the best. There was an increasing trend in performance measure R2 from SPI-1 to 48 and a decreasing trend in Root Mean Square Error (RMSE). The best input lead-time for SPI-1 to 48 decreased from 11 to 1, the number of hidden layers decreased, but there was no significant trend in hidden neurons. Drought properties could be considered in water resources management to supply water for various demands.

scholarly journals Climate Change Effects on Spatiotemporal Patterns of Hydroclimatological Summer Droughts in Norway

2011 ◽  
Vol 12 (6) ◽  
pp. 1205-1220 ◽  
Author(s):  
Wai Kwok Wong ◽  
Stein Beldring ◽  
Torill Engen-Skaugen ◽  
Ingjerd Haddeland ◽  
Hege Hisdal
Keyword(s):  
Climate Change ◽  
General Circulation ◽  
Dominant Role ◽  
Summer Precipitation ◽  
Meteorological Drought ◽  
Threshold Level ◽  
General Circulation Models ◽  
Drought Duration ◽  
Drought Characteristics ◽  
The Impact

Abstract This study examines the impact of climate change on droughts in Norway. A spatially distributed (1 × 1 km2) version of the Hydrologiska Byråns Vattenbalansavdelning (HBV) precipitation-runoff model was used to provide hydrological data for the analyses. Downscaled daily temperature and precipitation derived from two atmosphere–ocean general circulation models with two future emission scenarios were applied as input to the HBV model. The differences in hydroclimatological drought characteristics in the summer season between the periods 1961–90 and 2071–2100 were studied. The threshold level method was adopted to select drought events for both present and future climates. Changes in both the duration and spatial extent of precipitation, soil moisture, runoff, and groundwater droughts were identified. Despite small changes in future meteorological drought characteristics, substantial increases in hydrological drought duration and drought affected areas are expected, especially in the southern and northernmost parts of the country. Reduced summer precipitation is a major factor that affects changes in drought characteristics in the south while temperature increases play a more dominant role for the rest of the country.

scholarly journals Hydrological Drought Characteristics Based on Groundwater and Runoff Across Europe

2020 ◽  
Vol 383 ◽  
pp. 281-290
Author(s):  
Samuel Jonson Sutanto ◽  
Henny A. J. Van Lanen
Keyword(s):  
Hydrological Model ◽  
Meteorological Drought ◽  
Hydrological Drought ◽  
Weather Data ◽  
Model Resolution ◽  
Southeast Europe ◽  
Annual Average ◽  
Drought Duration ◽  
Drought Characteristics ◽  
Groundwater Drought

Abstract. Hydrological drought often gets less attention compared to meteorological drought. For water resources managers, information on hydrological drought characteristics is prerequisite for adequate drought planning and management. Therefore, the aim of this study is to analyse hydrological drought characteristics in the pan-European region based on past drought events from 1990 to 2017. The annual average drought duration, deficit volume, onset, termination, and intensity during drought years were calculated using daily runoff and groundwater data. All data were simulated with the LISFLOOD hydrological model (resolution 5×5 km) fed with gridded time series of observed weather data. Results based on runoff and groundwater data show that regions in Northeast to Southeast Europe, which stretched out from Poland to Bulgaria, were identified as profound regions to severe hydrological drought hazards. The most severe droughts during our study period were observed in 1992 to 1997, where on average Europe experienced drought events, which lasted up to 4 months. Long average drought durations up to 4 and 8 months in runoff and groundwater occurred in a few parts of the European regions (around 10 % area). Longer drought durations and a lower number of drought events were found in groundwater drought than in runoff, which proved that slow responding variables (groundwater) are better in showing extreme drought compared to fast responding variables (runoff). Based on our results, the water managers can better prepare for upcoming drought and foster drought adaptation actions.

scholarly journals Evidence of anthropogenic impacts on global drought frequency, duration, and intensity

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Felicia Chiang ◽  
Omid Mazdiyasni ◽  
Amir AghaKouchak
Keyword(s):  
Anthropogenic Impacts ◽  
Extreme Temperature ◽  
Meteorological Drought ◽  
Drought Frequency ◽  
Anthropogenic Aerosol ◽  
Drought Duration ◽  
Anthropogenic Forcing ◽  
Drought Characteristics ◽  
Detection And Attribution ◽  
Frequency Maximum

AbstractMost climate change detection and attribution studies have focused on mean or extreme temperature or precipitation, neglecting to explore long-term changes in drought characteristics. Here we provide evidence that anthropogenic forcing has impacted interrelated meteorological drought characteristics. Using SPI and SPEI indices generated from an ensemble of 9 CMIP6 models (using 3 realizations per model), we show that the presence of anthropogenic forcing has increased the drought frequency, maximum drought duration, and maximum drought intensity experienced in large parts of the Americas, Africa, and Asia. Using individual greenhouse gas and anthropogenic aerosol forcings, we also highlight that regional balances between the two major forcings have contributed to the drying patterns detected in our results. Overall, we provide a comprehensive characterization of the influence of anthropogenic forcing on drought characteristics, providing important perspectives on the role of forcings in driving changes in drought events.

scholarly journals Temporal-Spatial Characteristics of Drought in Guizhou Province, China, Based on Multiple Drought Indices and Historical Disaster Records

2018 ◽  
Vol 2018 ◽  
pp. 1-22 ◽  
Author(s):  
Qingping Cheng ◽  
Lu Gao ◽  
Ying Chen ◽  
Meibing Liu ◽  
Haijun Deng ◽  
...  
Keyword(s):  
Drought Index ◽  
Meteorological Drought ◽  
Guizhou Province ◽  
Drought Indices ◽  
Drought Severity ◽  
Severe Drought ◽  
Drought Event ◽  
Drought Duration ◽  
Increasing Trend ◽  
Western Guizhou

Guizhou Province, China, experienced several severe drought events over the period from 1960 to 2013, causing great economic loss and intractable conflicts over water. In this study, the spatial and temporal characteristics of droughts are analyzed with the standard precipitation index (SPI), comprehensive meteorological drought index (CI), and reconnaissance drought index (RDI). Meanwhile, historical drought records are used to test the performance of each index at identifying droughts. All three indices show decreasing annual and autumn trends, with the latter particularly prominent. 29, 30, and 32 drought events were identified during 1960–2013 by the SPI, CI, and RDI, respectively. Continuous drought is more frequent in winter–spring and summer–autumn. There is a significant increasing trend in drought event frequency, peak, and strength since the start of the 21st century. Drought duration indicated by CI shows longer durations in the higher-elevation region of central and western Guizhou. The corresponding drought severity is high in these regions. SPI and RDI indicate longer drought durations in the lower elevation central and eastern regions of Guizhou Province, where the corresponding drought severity is also very strong. SPI shows an increasing trend in drought duration and drought severity across most of the regions of Guizhou. In general, SPI and RDI show an increasing trend in the western Guizhou Province and a decreasing trend in central and eastern Guizhou. Comparing these three drought indices with historical records, the RDI is found to be more objective and reliable than the SPI and CI when identifying the periods of drought in Guizhou.

scholarly journals Robust Future Changes in Meteorological Drought in CMIP6 Projections Despite Uncertainty in Precipitation

2021 ◽  
Author(s):  
Anna Ukkola ◽  
Martin De Kauwe ◽  
Michael Roderick ◽  
Gab Abramowitz ◽  
Andy Pitman
Keyword(s):  
Climate Models ◽  
Water Security ◽  
Meteorological Drought ◽  
Resource Planning ◽  
Climate Projections ◽  
Land Area ◽  
Natural Ecosystems ◽  
Drought Duration ◽  
Drought Intensity ◽  
Projected Changes

<p>Understanding how climate change affects droughts guides adaptation planning in agriculture, water security, and ecosystem management. Earlier climate projections have highlighted high uncertainty in future drought projections, hindering effective planning. We use the latest CMIP6 projections and find more robust projections of meteorological drought compared to mean precipitation. We find coherent projected changes in seasonal drought duration and frequency (robust over >45% of the global land area), despite a lack of agreement across models in projected changes in mean precipitation (24% of the land area). Future drought changes are larger and more consistent in CMIP6 compared to CMIP5. We find regionalised increases and decreases in drought duration and frequency that are driven by changes in both precipitation mean and variability. Conversely, drought intensity increases over most regions but is not simulated well historically by the climate models. These more robust projections of meteorological drought in CMIP6 provide clearer direction for water resource planning and the identification of agricultural and natural ecosystems at risk.</p>

scholarly journals Detection of signals of moving objects based on the time selection method

2021 ◽  
Vol 66 (3) ◽  
pp. 335-342
Author(s):  
V. M. Artemiev ◽  
S. M. Kostromitsky ◽  
A. O. Naumov
Keyword(s):  
Moving Objects ◽  
Average Duration ◽  
Threshold Level ◽  
Selection Method ◽  
Probability Of Detection ◽  
False Alarms ◽  
Threshold Method ◽  
Detection Of Signals ◽  
Two Stages ◽  
Time Selection

To increase the efficiency of detecting moving objects in radiolocation, additional features are used, associated with the characteristics of trajectories. The authors assumed that trajectories are correlated, that allows extrapolation of the coordinate values taking into account their increments over the scanning period. The detection procedure consists of two stages. At the first, detection is carried out by the classical threshold method with a low threshold level, which provides a high probability of detection with high values of the probability of false alarms. At the same time uncertainty in the selection of object trajectory embedded in false trajectories arises. Due to the statistical independence of the coordinates of the false trajectories in comparison with the correlated coordinates of the object, the average duration of the first of them is less than the average duration of the second ones. This difference is used to solve the detection problem at the second stage based on the time-selection method. The obtained results allow estimation of the degree of gain in the probability of detection when using the proposed method.

scholarly journals Study on the spatial-temporal variation in evapotranspiration in China from 1948 to 2018

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Feng Zhang ◽  
Mengqing Geng ◽  
Qiulan Wu ◽  
Yong Liang
Keyword(s):  
Spatial Variation ◽  
Temporal Variation ◽  
Basic Research ◽  
Variation Coefficient ◽  
Data Sets ◽  
The North ◽  
Mk Test ◽  
Increasing Trend ◽  
Land Data Assimilation System ◽  
Almost All

Abstract It is of great significance for the efficient utilization of water resources and the construction of the ecological environment in China to fully understand the evolution process of the spatial-temporal pattern of evapotranspiration (ET). With the use of the v2.0 and v2.1 ET data sets combined with the Global Land Data Assimilation System and Noah model, this paper selects pixels as the basic research object to analyse the spatial-temporal variation in ET in China during the 71 years from 1948 to 2018. We first applied the TFPW-MK test to study the annual ET trend in China throughout the 71-year period, including the ET trend of each month from January to December and the annual total ET trend. Moreover, we examined the spatial variation in these trends. In addition, we calculated the variation coefficient of the time series of each pixel’s ET throughout the 71-year period and the variation coefficient of the spatial distribution of ET in each year to analyse the spatial-temporal fluctuations in ET in the study area. Finally, the Hurst index was adopted to evaluate the future ET trend. Based on these analyses, we observed the following novel spatial-temporal characteristics of ET: from 1948 to 2018, (1) the ET in most regions covered by 89.5% of all pixels in China exhibits an increasing trend. (2) The ET trend in China varies greatly with the change in months, and many regions show the most or least obvious increasing trend (or decreasing trend) at different times. (3) The area with an increasing trend is the largest in May and the smallest in December, and more than half of the pixels in all months of a year reveal an increasing trend. (4) In the northeast, west and south regions of China, the monthly fluctuation in the ET trend is relatively large, which indicates that the ET trend in these regions is greatly affected by the month. (5) The fluctuation in ET in China is larger in the north than it is in the south and larger in the west than it is in the east. The most stable fluctuation occurs in East China. (6) The ET trend of almost all the pixels in the study area remains consistent from 1948 to 2018, and there are large areas with a notable continuity. This results in the spatial variation in ET in the study area increasing.

scholarly journals Elucidating Diverse Drought Characteristics from Two Meteorological Drought Indices (SPI and SPEI) in China

2020 ◽  
Vol 21 (7) ◽  
pp. 1513-1530 ◽  
Author(s):  
Lingcheng Li ◽  
Dunxian She ◽  
Hui Zheng ◽  
Peirong Lin ◽  
Zong-Liang Yang
Keyword(s):  
Clustering Algorithm ◽  
Potential Evapotranspiration ◽  
Standardized Precipitation Index ◽  
Three Dimensional ◽  
Meteorological Drought ◽  
Drought Indices ◽  
Drought Severity ◽  
Severe Drought ◽  
Small Areas ◽  
Drought Characteristics

AbstractThis study elucidates drought characteristics in China during 1980–2015 using two commonly used meteorological drought indices: standardized precipitation index (SPI) and standardized precipitation–evapotranspiration index (SPEI). The results show that SPEI characterizes an overall increase in drought severity, area, and frequency during 1998–2015 compared with those during 1980–97, mainly due to the increasing potential evapotranspiration. By contrast, SPI does not reveal this phenomenon since precipitation does not exhibit a significant change overall. We further identify individual drought events using the three-dimensional (i.e., longitude, latitude, and time) clustering algorithm and apply the severity–area–duration (SAD) method to examine the drought spatiotemporal dynamics. Compared to SPI, SPEI identifies a lower drought frequency but with larger total drought areas overall. Additionally, SPEI identifies a greater number of severe drought events but a smaller number of slight drought events than the SPI. Approximately 30% of SPI-detected drought grids are not identified as drought by SPEI, and 40% of SPEI-detected drought grids are not recognized as drought by SPI. Both indices can roughly capture the major drought events, but SPEI-detected drought events are overall more severe than SPI. From the SAD analysis, SPI tends to identify drought as more severe over small areas within 1 million km2 and short durations less than 2 months, whereas SPEI tends to delineate drought as more severe across expansive areas larger than 3 million km2 and periods longer than 3 months. Given the fact that potential evapotranspiration increases in a warming climate, this study suggests SPEI may be more suitable than SPI in monitoring droughts under climate change.

scholarly journals Drought Propagation Patterns under Naturalized Condition Using Daily Hydrometeorological Data

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Jianzhu Li ◽  
Yuangang Guo ◽  
Yixuan Wang ◽  
Shanlong Lu ◽  
Xu Chen
Keyword(s):  
Early Warning ◽  
Assessment Tool ◽  
Swat Model ◽  
Meteorological Drought ◽  
Threshold Level ◽  
Hydrological Drought ◽  
Propagation Pattern ◽  
Drought Early Warning ◽  
Hydrological Droughts

Drought propagation pattern forms a basis for establishing drought monitoring and early warning. Due to its regional disparity, it is necessary and significant to investigate the pattern of drought propagation in a specific region. With the objective of improving understanding of drought propagation pattern in the Luanhe River basin, we first simulated soil moisture and streamflow in naturalized situation on daily time scale by using the Soil and Water Assessment Tool (SWAT) model. The threshold level method was utilized in identifying drought events and drought characteristics. Compared with meteorological drought, the number of drought events was less and duration was longer for agricultural and hydrological droughts. The results showed that there were 3 types of drought propagation pattern: from meteorological drought to agricultural/hydrological drought (M-A/H), agricultural/hydrological drought without meteorological drought (NM-A/H), and meteorological drought only (M). To explain the drought propagation pattern, possible driven factors were determined, and the relations between agricultural/hydrological drought and the driven factors were built using multiple regression models with the coefficients of determination of 0.4 and 0.656, respectively. These results could provide valuable information for drought early warning and forecast.

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