scholarly journals Comparison of Nine Meteorological Drought Indices Over Middle Euphrates Region During Period from 1988 To 2017

2018 ◽  
Vol 7 (4.20) ◽  
pp. 602 ◽  
Author(s):  
Imzahim A. Alwan ◽  
Abdul Razzak T. Ziboon ◽  
Alaa G. Khalaf
Keyword(s):  
Correlation Coefficient ◽  
Time Scale ◽  
Pearson Correlation ◽  
Meteorological Drought ◽  
The Other ◽  
Drought Indices ◽  
Annual Time Scale ◽  
Maximum Value ◽  
Seasonal Time Scale ◽  
Annual Time

The aim of this research is compare between nine drought indices and evaluate their performance with respect to predict and monitoring drought over Middle Euphrates region during period from 1988 to 2017.These indices are RDI, Normal SPI, Gamma SPI, Log SPI, CZI, MCZI, RAI, PN, and DI.Season and annual time scale were used to calculate all indices at Dewaniya, Hilla, Karbala, Najaf, and Semawa stations. The Pearson correlation coefficient between nine drought indices were analyzed. Annual and seasonal results illustrated that the maximum value of correlation between RDI and the other indices was noted with Gamma SPI and Log SPI at all stations. In annual time scale, the correlation coefficient reached to (0.99) at all stations except Hilla station, where it reached to (0.98), while in seasonal time scale the correlation coefficient reached to (0.98) at all stations. The RDI, Gamma SPI and Log SPI indices have similarity of classes and frequencies for drought. They also have similarity of frequencies for wet but there are minimum differences between wet classes compared to other indices. The RDI, Gamma SPI and Log SPI are good indices to predict and monitoring drought in study area in comparison to other indices which mentioned above.  

scholarly journals Assessment of the Dissimilarities of EDI and SPI Measures for Drought Determination in South Africa

Water ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 82
Author(s):  
Omolola M. Adisa ◽  
Muthoni Masinde ◽  
Joel O. Botai
Keyword(s):  
South Africa ◽  
South African ◽  
Correlation Coefficient ◽  
Pearson Correlation ◽  
Standardized Precipitation Index ◽  
Drought Monitoring ◽  
Drought Indices ◽  
Drought Severity ◽  
Pearson Correlation Coefficient ◽  
Drought Duration

This study examines the (dis)similarity of two commonly used indices Standardized Precipitation Index (SPI) computed over accumulation periods 1-month, 3-month, 6-month, and 12-month (hereafter SPI-1, SPI-3, SPI-6, and SPI-12, respectively) and Effective Drought Index (EDI). The analysis is based on two drought monitoring indicators (derived from SPI and EDI), namely, the Drought Duration (DD) and Drought Severity (DS) across the 93 South African Weather Service’s delineated rainfall districts over South Africa from 1980 to 2019. In the study, the Pearson correlation coefficient dissimilarity and periodogram dissimilarity estimates were used. The results indicate a positive correlation for the Pearson correlation coefficient dissimilarity and a positive value for periodogram of dissimilarity in both the DD and DS. With the Pearson correlation coefficient dissimilarity, the study demonstrates that the values of the SPI-1/EDI pair and the SPI-3/EDI pair exhibit the highest similar values for DD, while the SPI-6/EDI pair shows the highest similar values for DS. Moreover, dissimilarities are more obvious in SPI-12/EDI pair for DD and DS. When a periodogram of dissimilarity is used, the values of the SPI-1/EDI pair and SPI-6/EDI pair exhibit the highest similar values for DD, while SPI-1/EDI displayed the highest similar values for DS. Overall, the two measures show that the highest similarity is obtained in the SPI-1/EDI pair for DS. The results obtainable in this study contribute towards an in-depth knowledge of deviation between the EDI and SPI values for South Africa, depicting that these two drought indices values are replaceable in some rainfall districts of South Africa for drought monitoring and prediction, and this is a step towards the selection of the appropriate drought indices.

scholarly journals Attribution Analysis of Long-Term Trends of Aridity Index in the Huai River Basin, Eastern China

2020 ◽  
Vol 12 (5) ◽  
pp. 1743
Author(s):  
Meng Li ◽  
Ronghao Chu ◽  
Abu Reza Md. Towfiqul Islam ◽  
Yuelin Jiang ◽  
Shuanghe Shen
Keyword(s):  
River Basin ◽  
Time Scale ◽  
Aridity Index ◽  
Growing Season ◽  
Dominant Factor ◽  
Annual Time Scale ◽  
Huai River ◽  
Autumn And Winter ◽  
Annual Time ◽  
The Huai River Basin

This paper aims to combinedly investigate the spatiotemporal trends of precipitation (Pre), reference evapotranspiration (ET0), and aridity index (AI) by employing nonparametric methods based on daily datasets from 137 meteorological stations during 1961–2014 in the Huai River Basin (HRB). The dominant factors influencing ET0 and AI trends were also explored using the detrended and differential equation methods. Results show that (1) Pre, ET0, and AI were much larger in summer than in other seasons, and AI had a nonsignificant increasing trend in annual time scale, while Pre and ET0 exhibited decreasing trends, but AI showed a downward trend in spring and autumn (becoming drier) and an upward trend during summer and winter due to increased Pre (becoming wetter); (2) lower AI values were identified in north and higher in south, and lower ET0 was identified in south and higher in north in annual time scale, growing season and spring, while ET0 decreased from west to east in summer and winter, the spatial distribution of Pre was similar to that of AI; (3) for ET0 trends, in general, wind speed at two-meter height (u2) was the dominant factor in spring, autumn, winter, and annual time scale, while in other seasons, solar radiation (Rs) played a dominant role; (4) for AI trends, AI was mostly contributed by Pre in spring, autumn, and winter, the Rs contributed the most to AI trend in growing season and summer, then in annual time scale, u2 was the dominant factor; (5) overall, the contribution of Pre to AI trends was much larger than that of ET0 in spring, autumn, and winter, while AI was mostly contributed by ET0 in annual time scale, growing season and summer. The outcomes of the study may improve our scientific understanding of recent climate change effects on dry–wet variations in the HRB; moreover, this information may be utilized in other climatic regions for comparison analyses.

scholarly journals TWIG: A model to simulate the gravitropic response of a tree axis in the frame of elasticity and viscoelasticity, at intra-annual time scale

2011 ◽  
Vol 273 (1) ◽  
pp. 115-129 ◽  
Author(s):  
Catherine Coutand ◽  
Jean-Denis Mathias ◽  
Georges Jeronimidis ◽  
Jean-François Destrebecq
Keyword(s):  
Time Scale ◽  
Gravitropic Response ◽  
Annual Time Scale ◽  
Annual Time

scholarly journals Investigating the Meteorological Drought Using CZI in Nineveh Governorate, Iraq.

2021 ◽  
Vol 28 (4) ◽  
pp. 14-24
Author(s):  
Omar M. A. Mahmood Agha
Keyword(s):  
Time Scale ◽  
Historical Data ◽  
Meteorological Drought ◽  
The Other ◽  
Drought Intensity ◽  
Moderate Drought ◽  
Average Probability ◽  
Mild Drought

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

scholarly journals Prediction of Seasonal Meteorological Drought Onset and Termination over the Southern Great Plains in the North American Multimodel Ensemble

2020 ◽  
Vol 21 (10) ◽  
pp. 2237-2255
Author(s):  
Richard Seager ◽  
Jennifer Nakamura ◽  
Mingfang Ting
Keyword(s):  
Great Plains ◽  
North American ◽  
Time Scale ◽  
Meteorological Drought ◽  
Atmospheric Variability ◽  
Multimodel Ensemble ◽  
Southern Great Plains ◽  
The North ◽  
Seasonal Time Scale ◽  
North American Multimodel Ensemble

AbstractThe predictability on the seasonal time scale of meteorological drought onsets and terminations over the southern Great Plains is examined within the North American Multimodel Ensemble. The drought onsets and terminations were those identified based on soil moisture transitions in land data assimilation systems and shown to be driven by precipitation anomalies. Sea surface temperature (SST) forcing explains about a quarter of variance of seasonal mean precipitation in the region. However, at lead times of a season, forecast SSTs only explain about 10% of seasonal mean precipitation variance. For the three identified drought onsets, fall 2010 is confidently predicted and spring 2012 is predicted with some skill, and fall 2005 was not predicted at all. None of the drought terminations were predicted on the seasonal time scale. Predictability of drought onset arises from La Niña–like conditions, but there is no indication that El Niño conditions lead to drought terminations in the southern Great Plains. Spring 2012 and fall 2000 are further examined. The limited predictability of onset in spring 2012 arises from cool tropical Pacific SSTs, but internal atmospheric variability played a very important role. Drought termination in fall 2000 was predicted at the 1-month time scale but not at the seasonal time scale, likely because of failure to predict warm SST anomalies directly east of subtropical Asia. The work suggests that improved SST prediction offers some potential for improved prediction of both drought onsets and terminations in the southern Great Plains, but that many onsets and terminations will not be predictable even a season in advance.

scholarly journals Impact of Meteorological Drought in Upper Blue Nile Basin on the Hydrological Drought of Nile River in Egypt

2020 ◽  
Vol 9 (6) ◽  
pp. 50-55
Keyword(s):  
Water Resources ◽  
Pearson Correlation ◽  
Meteorological Drought ◽  
Hydrological Drought ◽  
Drought Indices ◽  
Nile River ◽  
Nile Basin ◽  
Blue Nile ◽  
Blue Nile Basin ◽  
Upper Blue Nile Basin

Precipitation over the Upper Blue Nile Basin in Ethiopia contributes with 85% of the Nile river which provides 93% of Egypt’s conventional water resources. This study aims at assessing the meteorological drought in different locations in the Upper Blue Nile Basin and their relationship with the hydrological drought of Nile river in Egypt. The metrological drought was calculated by the Standard Precipitation Index (SPI) at five stations inside and close to the Upper Blue Nile Basin in Ethiopia, whereas the hydrological drought was calculated by the Streamflow Drought Index (SDI) at Dongola station at Nasser lake entrance. Both indices were calculated using the Drought Indices Calculator (DrinC) software. The selected study period was from 1973 to 2017 based on the availability of recorded data for meteorological stations in Ethiopia, and the streamflow for Dongola station. The data was categorized for each station by considering time periods of 1, 3, 6, 9, and 12 months based on their homogeneity. The correlation between SPI and SDI was evaluated using the Pearson correlation coefficient. The results showed a correlation between SPI for the five stations in the Upper Blue Nile Basin and SDI for Dongola station, where Gore station represented the highest frequency of significance at different time scales especially at the 3-months’ scale. The results confirm the relationship between SPI at Gore Station and SDI at Dongola Station, which means that the hydrological drought in Egypt is highly affected by the meteorological drought in the area surrounding Gore station. The paper recommends improving techniques for monitoring and overseeing drought hazards and assessing more meteorological stations to accurately predict climate change variations in Upper Blue Nile Basin and its effect on Egypt’s water resources.

scholarly journals Estimating the flood frequency distribution at seasonal and annual time scale

2012 ◽  
Vol 9 (6) ◽  
pp. 7947-7967 ◽  
Author(s):  
E. Baratti ◽  
A. Montanari ◽  
A. Castellarin ◽  
J. L. Salinas ◽  
A. Viglione ◽  
...  
Keyword(s):  
Objective Function ◽  
Frequency Analysis ◽  
Time Scale ◽  
Peak Flow ◽  
Flood Frequency ◽  
Cumulative Distribution ◽  
Annual Time Scale ◽  
Frequency Regime ◽  
Seasonal Flood ◽  
Annual Time

Abstract. We propose an original approach to infer the flood frequency distribution at seasonal and annual time scale. Our purpose is to estimate the peak flow that is expected for an assigned return period T, independently of the season in which it occurs (i.e. annual flood frequency regime), as well as in different selected sub-yearly periods (i.e. seasonal flood frequency regime). While a huge literature exists on annual flood frequency analysis, few studies have focused on the estimation of seasonal flood frequencies despite the relevance of the issue, for instance when scheduling along the months of the year the construction phases of river engineering works directly interacting with the active river bed, like for instance dams. An approximate method for joint frequency analysis is presented here that guarantees consistency between fitted annual and seasonal distributions, i.e. the annual cumulative distribution is the product of the seasonal cumulative distribution functions, under the assumption of independence among floods in different seasons. In our method the parameters of the seasonal frequency distributions are fitted by maximising an objective function that accounts for the likelihoods of both seasonal and annual peaks. Differently from previous studies, our procedure is conceived to allow the users to introduce subjective weights to the components of the objective function in order to emphasize the fitting of specific seasons or of the annual peak flow distribution. An application to the time series of the Blue Nile daily flows at Sudan-Ethiopia border is presented.

Testing the influence of snow and meteorological conditions on snow avalanche deposit volumes

2021 ◽  
Author(s):  
Hippolyte Kern ◽  
Vincent Jomelli ◽  
Nicolas Eckert ◽  
Delphine Grancher
Keyword(s):  
Time Scale ◽  
Snow Depth ◽  
Snow Avalanche ◽  
Wet Snow ◽  
The Mean ◽  
Seasonal Time Scale ◽  
Snow Conditions ◽  
Complex Relationships ◽  
The Relationship ◽  
Annual Time

<p>Snow avalanche deposit volume is an important characteristic that determines vulnerability to snow avalanche. However, there is insufficient knowledge about snow and meteorological variables controlling deposit volumes. Our study focuses on the analysis of 1986 deposit volumes from 182 paths located in different regions of the French Alps including Queyras, and Maurienne valleys, between 2003 and 2017. This work uses data from the Permanent Avalanche Survey (EPA) database, an inventory of avalanche events occurring at well-known, delineated and mapped paths in France. We investigated relationships between snow deposit volumes and meteorological quantities, such as precipitation and temperature determined from SAFRAN reanalyses and snow-depth and wet snow-depth estimated from CROCUS reanalyses at a daily time scale at 2100m a.s.l. Analysis was conducted at an annual and seasonal time scale considering winter (November-February) and spring (March-May) between the mean deposit volumes and the mean meteorological and snow conditions.<span> </span></p><p>Results do not show any significant relationship between deposit volumes and meteorological or snow conditions at an annual time scale or for spring season. However, correlations between deposit volumes and meteorological and snow variables are high in winter (R<sup>2</sup>=0.78). The best model includes two snow variables: mean snow-depth and maximal wet snow-depth. We suggest that these two important snow variables reflect variations in the snow cover characteristics later influencing the nature of the flow and the deposit volumes. Dividing the studied paths sample into several classes according to their morphology (i.e: surface area or mean slope) increases the significance of the relationship for both seasons and highlights more complex relationships with meteorological and snow variables.</p>

scholarly journals Evaluation of the similarity between drought indices by correlation analysis and Cohen's Kappa test in a Mediterranean area

2021 ◽  
Author(s):  
L. Vergni ◽  
F. Todisco ◽  
B. Di Lena
Keyword(s):  
Correlation Analysis ◽  
Pearson Correlation ◽  
Central Italy ◽  
Meteorological Drought ◽  
Drought Indices ◽  
Drought Severity ◽  
Cohen’S Kappa ◽  
Kappa Test ◽  
Cohen's Kappa ◽  
Standardised Precipitation Index

AbstractIn the literature, numerous papers report comparative analyses of drought indices. In these types of studies, the similarity between drought indices is usually evaluated using the Pearson correlation coefficient, r, calculated between corresponding severity time series. However, it is well known that the correlation does not describe the strength of agreement between two variables. Two drought indices can exhibit a high degree of correlation but can, at the same time, disagree substantially, for example, if one index is consistently higher than the other. From an operational point of view, two indices can be considered in agreement when they indicate the same severity category for a given period (e.g. moderate drought). In this work, we compared six meteorological drought indices based on both correlation analysis and Cohen's Kappa test. This test is typically used in medical or social sciences to obtain a quantitative assessment of the degree of agreement between different methods or analysts. The indices considered are five timescale-dependent indices, i.e. the Percent of Normal Index, the Deciles Index, the Percentile Index, the Rainfall Anomaly Index, and the Standardised Precipitation Index, computed at the 1-, 3-, and 6-month timescales, and the Effective Drought Index, a relatively new index, which has a self-defined timescale. The indices were calculated for 15 stations in the Abruzzo region (central Italy) during 1951–2018. We found that the strength of agreement depends on both the criteria of drought severity classification and the different indices' calculation method. The Cohen's Kappa test indicates a prevailing moderate or fair agreement among the indices considered, despite the generally very high correlation between the corresponding severity times series. The results demonstrate that the Cohen's Kappa test is more effective than the correlation analysis in discriminating the actual strength of agreement/disagreement between drought indices.

Sign in / Sign up

Export Citation Format

Share Document