Showing 18 results for Drought
Shamsallah Asgari, Tayeb Razi, Mohamadreza Jafari, Ali Akbar Noroozi,
Volume 0, Issue 0 (3-1921)
Abstract
Due to the importance of forests in natural and anthropogenic environment, the effects of meteorological drought on the dryness of oak forests in Ilam province were investigated. The main purpose of this study was to determine the relationship of Zagros forests with drought occurring in the area. The results of the Standard Precipitation Index (SPI) for the time periods showed that the most drought occurred in 2007, 2008, 2011, 2015 and 2016. Remote sensing data (MODIS images) were used to investigate the vegetation trend (NDVI) of trees during the period 2016–2016. The vegetation trend (NDVI) was significant over the period with the index drought index (SPI) with R2 = 0.9999. Ground harvesting of oak drying points and simulation using Landsat satellite imagery with 15 m pixel output from GIS software showed that 17894 hectares of area forests from 2000 to 2016 were dried and destroyed and prepared with oak forest and integrated layer. The output layers from the drought zoning were shown visually and the statistical analysis was performed in three 5-year time series. The results of these analyzes from 2002 to 2006 showed that the correlation coefficient between meteorological drought and oak drought 96.6% with a coefficient of determination R2 = 0.985, for the time series of 2007 to 2011 the correlation coefficient between scratches Meteorological and oak dryness of 95.4% with R2 = 0.980 and coefficient of correlation for meteorological drought and oak drought of 98.8% and R2 = 0.995 of coefficient respectively. Its fluctuations in time series show the intensity and duration of the drying up of oak forests in the region. According to the results of this study, it is predicted that if the drought goes through this process, 1118.4 hectares of oak forests in Ilam province will be dried and destroyed annually.
Mr Danesh Nasiri, Dr Reza Borna, Dr Manigheh Zohorian Pordel,
Volume 0, Issue 0 (3-1921)
Abstract
Widespread and frequent droughts in recent decades in Khuzestan province have become one of the most important challenges of this province. The use of remote sensing products in temporal and spatial monitoring of drought can play a key role in managing this risk and reducing and adjusting its destructive effects. The main goal of this research is to provide a remote sensing index for temporal and spatial monitoring of drought in Khuzestan province and its validation using station meteorological drought indices. In this research, by using the products of vegetation (MOD13C2) and land surface temperature (MOD11C3) of MODIS sensor, a drought index based on vegetation called VHI plant health index was produced. SPI Meteorological Drought Index, which was based on station rainfall data during the statistical period of 2000-2012, was used to evaluate and quantify this index. The comparison of VHI drought index with three-month SPI meteorological drought index values showed a significant correlation between 0.68 and 0.75. By identifying 4 years with widespread and relatively severe drought in Khuzestan province (based on both VHI and SPI indices), which included the years 2000, 2005, 2012, 2015, the spatial distribution pattern of meteorological drought and VHI plant drought to In general, it indicated that the northern parts of the province were generally involved in mild to moderate droughts and the southern parts were generally involved in moderate to severe droughts. The spatial correlation matrix based on the number of 2500 pixels with dimensions of 5x5 km, which included VHI and SPI values of selected drought years, indicated the existence of a significant spatial correlation between the two mentioned indicators. In the widespread drought of 2000, at the level of Khuzestan province, two drought indices VHI and SPI, the correlation was equal to 0.47, and in 2005, equal to 0.35, and
Zahra Hedjazizadeh, Sayyed Mohammad Hosseini, Ali Reza , Shokofe Layeghi,
Volume 0, Issue 0 (3-1921)
Abstract
Drought is a natural hazard that annually causes significant economic, social, environmental, and life-threatening damage in vast areas of the Earth. The damages caused by this phenomenon are intangible but very extensive and costly, which, if necessary, remote sensing techniques can be a useful tool in monitoring drought due to high temporal accuracy, wide spectral coverage, ease of access, no need for atmospheric correction and ground referencing. In recent years, the province of Hamedan has faced many problems due to frequent droughts. Therefore, the present study focused on investigating and monitoring drought in Hamedan province using the Temperature Condition index and its impact on the vegetation cover of the province using Advanced Very High Resolution Radiometer (AVHRR) and National Oceanic and Atmospheric Administration (NOAA) remote sensing data. First, the relevant data was extracted from the Nova star database, and finally, the spatiotemporal behavior of the vegetation cover drought index was examined on 1528 pixels in Hamedan province. The spatial resolution of the data used in this study is 4 kilometers. First, the relevant data were extracted from the Navstar database and ultimately, the spatiotemporal behavior of the drought index and vegetation cover was examined. The results indicate that drought has significantly increased the vegetation cover of Hamedan province based on remote sensing data. Kendall's coefficients indicate the presence of decreasing trends in vegetation cover at a 95 Percent confidence level. Only in May, June, and December has there been a slight decrease in vegetation cover within the extent of drought in the province. The spatial behavior analysis of the drought index on vegetation cover showed that February, March, as well as April have experienced more severe droughts within Hamedan province.
Firooz Mojarad, Razieh Kheiri, Zahra Noorisameleh,
Volume 14, Issue 35 (3-2015)
Abstract
Iran's Potential for the occurrence of drought at various severities illuminates the need to examine this phenomenon with new indexes. The major deficiency of the current indexes is that they cannot monitor the droughts in daily scale. Effective Drought Index (EDI) overcomes this defect. The goal of this study is to analyze the frequency of daily droughts by EDI in 43 synoptic stations in a 30-year period. Accordingly, the frequency of daily droughts in the stations was calculated by EDI during the seasons and the year. Then the stations were divided into five groups using cluster analysis based on total frequency of mild to most severe droughts (categories 1 to 4), and frequency patterns in each group were examined. The results showed that the most severe droughts have not happened in the stations except for Gorgan, Zanjan and Torbat-Heydariyeh. In contrast, the frequencies of mild, moderate and severe droughts, all being equal, are much more than most severe droughts, and their frequencies are almost equal. In 56 percent of the days, a variety of droughts (mild to most severe) has occurred in the whole country. Based on the output maps, frequency distribution of droughts in the country does not follow a certain geographical pattern, so it could be cocluded that all types of droughts have happened in all regions of the country. However, maximum total frequency of daily droughts (mild to most severe) is observed in the east and center parts. The decrease in the EDI values over time shows the tendency of the most stations towards drought.
Behroz Sobhani, Ata Gafarigilandeh, Akbar Goldost,
Volume 15, Issue 36 (6-2015)
Abstract
Drought defined as a climatic phenomenon with the humidity and rainfall shortage as compared with normal conditions. This phenomenon affects on all of aspects of human activities, severely. while, studies associated with this phenomenon on the basis of appropriate methods are very low. In the present study, effort has been made to analyze the drought state in Ardabil province by means of software system capabilities in MATLAB and SEPI index in two temporal scales of 6 and 12 months. The climatic data of synoptically stations of Ardabil were used, Parsabad and khalkhal countian in Ardabil province. Results of study show that SEPI index reflects the features of two SPI and SEI indices well. And also enters temperature in the studying of drought conditions as one of the effective parameters in changing of drought intensity. Therefore, the investigation into drought with SEPI index is better than SPI index. Studies associated to drought on the basis of SEPI index shows that drought process is increasing in Ardabil province. Temperature also has an increasing flow with higher intensity. Longest temporal continuation of drought in province, has occurred in Parsabad station in temporal scale of 12 months, from June, 1998 to November, 1999 in 18 month period. The greatest percentage of drought occurrence is in Parsabad station and the minimum of that is observed in Khalkhal station.
[1] - Akbar Goldust: PhD student's of climatology in environmental planning Mohaggeg Ardabil University
Arash Malekian, Mahro Dehbozorgi, Amir Hoshang Ehsani,
Volume 15, Issue 36 (6-2015)
Abstract
Drought is one of the most destructive natural disasters in human societies that cause irreparable impacts on agriculture, environment, society and economics. So, awareness of occurrence of droughts can be effective in reducing losses. In this study, in order to modeling and forecasting drought severity in a 37 year time period (1971-2007) in 21 meteorological stations, located in the cold semi-arid region of north-west Iran, artificial neural networks was used. The input data was annual rainfall data and annual drought precipitation index for all stations that 80% of the data (1971-2000) used for training the network and other 20% (2001-2007) used for testing it and in the next step drought severity predicted for the years 2008 to 2012 by the trained algorithm without using actual and existed data in this period. The appropriate structure for the network, based on Multi Layer Perceptron with three hidden layer, Back Propagation algorithm, Sigmoid transfer function and 10 neurons in middle layer. The results show that the artificial neural networks are well able to predict the non-linear relationship between rainfall and drought as it can simulate drought precipitation index values largely consistent with the real values with more than 97% regression and less than 5% error. So, drought can be predicted by this method in future and also it is useful in water resources management, drought management and climate change.
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Volume 16, Issue 41 (9-2016)
Abstract
Drought phenomenon with different goals including planning, water sources management and dealing with the problems due to water shortage has been investigated by most scholars. This research examined the relationship between drought and the normalized difference vegetation index (NDVI)in Qorveh and Dehgolan region in Kurdistan, Iran. To determine years with meteorological drought, index of Standard Z during a 20 year period time (1387-1368) has been applied. The results of the statistical data in Ghorveh station in 2008 with total annual rainfall of 155 mm and Z index of -2.31, in 2000 with total rainfall of 253.1 and Z index of -1.5 and in 2001 with 239.5 rainfall and Z index of -1.22. Were determined as drought indeces. MODIS satellite images were used to assess the ecological drought. Associated with each image to a randomly selected sample of 500 places in the software ERDAS, NDVI values were calculated for these images. satellite image processing results and Normalized Difference Vegetation Index (NDVI) indicates a low index values in the years 2000, 2001 and 2008 Were determined as ecological drought years of 2001 samples had the lowest NDVI and central parts of the area under irrigation has almost lost its vegetation.
Meysam Toulabi Nejad, Dr Zahra Hejazizadeh, Mrs Atefeh Bosak, Mrs Nasrin Bazmi,
Volume 18, Issue 49 (5-2018)
Abstract
The purpose of this study was to investigate the effects of the North Atlantic Oscillation on the middle levels of Atmosphere and precipitation changes in the West of country. To do this, first monthly rainfall data of 17 synoptic stations of the West Country in period of 30 years from 1984 to 2014 of country were collected from Meteorological Organization. As well as North Atlantic Oscillation data and anomalies geopotential height data, sea level pressure and precipitation were received from NOAA. To clarify the relationship between the NAO index phase with precipitation of west of Iran used Pearson correlation coefficient was at least 95%, (P_value = 0.05). Finally, using synoptic maps, spatial relationships among data, were analyzed. The results indicate that between North Atlantic Oscillation changes with middle level height anomalies of the Atmosphere and the amount of precipitation in West of Iran in January, March, April and November there is communication and concurrency. The results showed that , at a time of sovereignty positive phase of the North Atlantic oscillation , an average of height atmospheric middle level in mid - western Iran 17 meters long - term and less than the average rainfall per month 23.5 mm increased and wetly sovereign. But when phase of governance is negative, high atmospheric middle level anomaly to an average of 20 meters more than normal. As a result, the drought will prevail in the west and precipitation in the region each month will face a reduction of 30 mm. In general, we can say that droughts more severe than wet coincide with the negative phase of the North Atlantic Oscillation is positive phase.
Adel Nabi Zadeh Balkhanloo, Zahra Hejazizadeh, Parviz Zeaiean Firoozabadi,
Volume 18, Issue 50 (6-2018)
Abstract
Continuous decline in Lake Urmia water levels In recent years, the decline of rainfall and river flows and constant droughts has become the main concern of the people and the people. To study climate change and increase of temperature in the catchment area of Lake Urmia, two factors for measuring the temperature and properties of satellite images were used which indicate the importance of land surface temperature changes (LST) and normalized vegetation differences (NDVI). This study was carried out using the satellite data of the periodic watershed (2008-2008) to investigate the spatial relationship between NDVI-Ts and NDVI-ΔT to investigate the actual agricultural drought occurrence. The goal is to extract the VTCI (vegetation temperature index) index, which is capable of identifying drought stress at regional scale. The results showed that the slope is negative for the warm edge, where it is positive for the cold edge. The gradient gradient shows that the maximum temperature is reduced when the NDVI value increases for any interval. The slope on the cold edge indicates that the minimum temperature rises when the NDVI value rises. Overall, at the warm and cold edges, it has been observed that the drought trend over 2009-2008 is higher than in 2010. In the days of Julius Day 257, the slope of the cold edge from 2008 to 2010 is decreasing. But at the hot edge, intercept pixels for 2008 is more than 323 degrees Kelvin, where in 2009-2010 it is less than 323 degrees Kelvin. In general, the correlation coefficient (R2) is different in the TS-NDVI spacing between (0.90-0.99). The present study showed that with the integration of satellite satellite data with meteorological data, the VTCI threshold for drought stress varies from year to year depending on the data conditions.
Saeed Javizadeh, Zahra Hejazizadeh,
Volume 19, Issue 53 (7-2019)
Abstract
Drought is one of the environmental events and an inseparable part of climatic fluctuations. This phenomenon is one of the main characteristics of the various climates. Awareness of spatiotemporal behavior is effective in land planning. The spatial statistical methods provide the means by which they analyze the spatial patterns of random variables such as precipitation. In this study, using the rainfall data of 84 selected synoptic stations during the period of 30 years (1985 to 2014) in Iran, the spatial analysis of drought has been investigated. Initially, using SPI values (timescales 3, 6, 12, 24 and 48 months), drought and traumatic periods of the area were identified and using the Geostatistic Analyst extension, the drought was zoned by interpolation methods. Moran statistics were used to explain the pattern of drought in Iran. The results of Moran index for drought showed that the values for different years during the statistical period have a positive and close to one, indicating that the SPI drought index data has spatial self-correlation and cluster pattern. Also, the results of Z score and P-value values, clustering of a spatial distribution of drought, were confirmed.
Dr Bahman Shafii, Dr Hamid Barghi, Dr Yusef Ghanbari,
Volume 19, Issue 55 (12-2019)
Abstract
The purpose of this paper is to investigate the social, economic, and environmental effects of drought from the viewpoint of villagers, with the structural equation modeling approach. The purpose of this study is of applied research type, and is essentially a descriptive-correlation research. The population of the study, 1762 heads of households and sample size were determined according to Cochran formula, 316 people. Data analysis was performed using SPSS22 software and Structural Equation Modeling (SEM). In this research, the observed variables were obtained for three components: economic, social, and environmental. Three first-factor factor analysis models were designed, measured, and validated for measuring three sub-scale droughts. Finally, the role and effect of observed variables and their triple components derived from the drought, as the main hidden dependent variable, and the relationships between them, were analyzed with the help of a structural model of the factor-factor analysis (CFA) of the quadratic factor of the second order. The results of the fitting and validation of all three models of drought measurement, and the realization of goals, as well as the quadratic model of second order, were evaluated based on the data for drought evaluation. Finally, drought affected by socioeconomic and social indicators of 0. 97, and environmental index was 0. 87, so the drought in the studied villages areas had the greatest impact on economic and social indicators, and As a result, it has been placed on an environmental index.
Dr Parviz Zeaiean Firoozabadi,
Volume 20, Issue 59 (1-2021)
Abstract
Various satellite remote sensing data, images and products have proven their place in drought, drought and agriculture studies since the production of this type of information resource. Visible, near-infrared and thermal bands are among the most widely used in the production of products such as vegetation and surface temperature. In this study, from MODIS sensor data to investigate and find the coefficients of spatial relationship between vegetation-surface temperature index (NDVI-TS) and NDVI-ΔTS to extract the time of agricultural drought from June to October 2007 to 2010 in the catchment Siminehrood has been extracted from the Temperature-Vegetation Condition Index (VTCI) and the Water Lack Index (WDI), which are able to detect drought stress on a regional scale. The results of this study showed that in both indicators, the drought stress situation was higher in 2007 and 2008. Also based on the NDVI-TS space relationship in all the years 2007 to 2010 the high slope of the triangular space for the hot edge is negative. This means that with increasing NDVI, the LST level decreases while for the cold edge the slope is positive. In addition, the slope obtained from the NDVI-ΔTS space relationship is negative for the dry line, ie the dry line or the minimum transpiration-sweat line (ETR) shows a negative correlation with NDVI. While for the wet line, especially in 2010, the slope is positive and in other years, no significant change is seen. The present study showed that the VTCI threshold for drought stress was severe in 2007 and 2008.
Saideh Eiyni, Dr Saeide Eini,
Volume 21, Issue 60 (3-2021)
Abstract
The aim of this research is to investigate drought stress in rangeland rangelands in Ardabil province. According to the monthly rainfall data, 4 synoptic stations of Ardebil province (Ardebil, Khalkhal, Meshgin Shahr and Parsabad Moghan) during the statistical period of 2016-1996 were used to calculate drought index (SEPI) index for 4 periods of 1, 3, 6 and 9 months. Landsat TM and OLI satellite imagery was also used to prepare landslide classification maps based on the maximum probability model and calculation of vegetation indices NDVI, EVI, SAVI and LAI. In order to investigate the relationship between the studied indices, Pearson correlation coefficient (R) and root mean square error (RMSE) have been used. The results of the classification showed that the extent of the rangelands of Ardebil province in 1394 in the year 1377, both in the rangeland and in the rangelands, is a significant decrease. According to the results of SPI, the drought condition during 2011-2015 is more than the other periods studied. Vegetation dispersal maps were based on decision tree tree classification algorithm and according to NDVI index for the studied months. Also, according to the results of the evaluation, the highest correlation was observed between the NDVI index and the 6-month SEPI index, and the lowest mean squared error was found between the SAVI index and the 6-month SEPI index, but in general, the most suitable indicator for Drought monitoring in Ardebil province pastures is a 6-month NDVI and SEPI indicator.
Mrs Zahra Ebadi Nehari, Dr Mahdi Erfanian, Mrs Sima Kazempour Choursi,
Volume 23, Issue 68 (4-2023)
Abstract
Drought is a complex phenomenon caused by the breaking of water balance and it has always an impact on agricultural, ecological and socio-economic spheres. Although the drought indices deriving from remote sensing data have been used to monitor meteorological or agricultural drought, there are no indices that can suitably reflect the comprehensive information of drought from meteorological to agricultural aspects. In this study, the synthesized drought index (SDI) as a synthesized index from the vegetation condition index (VCI), temperature condition index (TCI) and precipitation condition index (PCI) were used for comprehensive drought monitoring in the Urmia Lake Basin (ULB) based on the Principal Component Analysis (PCA). For this purpose, MOD13A3, MOD11A2 and TRMM 3B43 data series were downloaded y for the period of 2001–2012. After initial processing, drought indicators were calculated using LST NDVI and TRMM data, and monthly drought severity maps were prepared. In order to validate SDI index, the Correlation relationship between SDI and SPI indices was obtained in the 3 month period during the growing season. As well as, SDI correlation relationships were investigated with wheat and barley crop yields. The results indicate that drought occurred in 2008 and 2001 in the ULB. The results of validation show that there is a correlation of 80% between the two SDI and SPI indicators. Also, the results of this study showed that the SDI index, as a comprehensive index of drought monitoring, reflects the effects of drought on agriculture.
Fatemeh Yadegarifar, Mohammadreza Poodineh, Morteza Esmaelnejad,
Volume 23, Issue 68 (4-2023)
Abstract
In the meantime it can cause serious and irreparable damage to other social, economic and structural sectors of society. A look at the history of human life on Earth shows that human beings have always been exposed to all kinds of natural hazards. Natural hazards have many types, one of which is drought and water crisis. The recent droughts in Iran and the severity of the damage indicate the continued vulnerability of urban and rural areas. At present, drought management in our country is based on crisis management and thus less attention is paid to drought impacts and preparedness. Therefore, the purpose of this study is to evaluate the resilience of Zahedan city against water crisis and drought. The present study is applied in terms of purpose and in terms of research, descriptive and analytical. The statistical population of the study is all households in Zahedan city based on the census of 1395 168480 households (672589 people). From the household heads, a sample size of 383 people was selected randomly using Cochran formula. Descriptive statistics and inferential statistics were used to analyze the findings. The results of one-sample t-test show that the economic, social and institutional resiliency status in Zahedan city is lower than the average (2.815, 2.873 and 2.886, respectively); The results showed that Zahedan city is not in a good position in terms of resilience to drought and water crisis and this city has many water problems in rural areas and Zahedan city. Rural water shortages and droughts have caused extensive damage to farmers and ranchers. The effects of the water crisis on the economic, social and environmental structure of the villages have been very negative and these negative effects have ultimately led to the migration of villagers to Zahedan
Hadi Zare Khormizie, Hamid Reza Ghafarian Malamiri,
Volume 23, Issue 69 (7-2023)
Abstract
Knowledge of rangeland vegetation characteristics as well as factors affecting it in environmental planning, land management and sustainable development is very important. However, regional and up-to-date maps of pasture vegetation cover are not always available. In this study, in order to plot the vegetation cover percentage of the rangelands and monitor its changes in drought and wet periods, NDVI products of MODIS sensor during the years from 2000 to 2017 with a spatial resolution of 250 m and a 16-day time resolution, and The SPI drought index were used. The study area is the part of the rangelands located in the Southern province of Yazd. In 2013, in order to provide ground truth data, a field work was done to take the sampling rate of vegetation from the rangeland level in the study area. According to the results, the NDVI index has a good ability to map vegetation cover, so the coefficient of determination (R2) between this index and the sample points was 0.71. Based on the results, the average vegetation cover of the studied area was 11.3% during the years 2000 to 2017. The highest and lowest amount of vegetation cover in the study area was in 2000 and 2002, with moderate mild conditions and very severe drought, respectively (14.6% and 9.2% respectively). The most important factors influencing the vegetation cover in the study area are rainfall and drought periods, so that the coefficient of determination (R2) between the SPI drought index and the average vegetation percentage was 0.85. In general, based on the results there is a high potential for assessing and monitoring rangeland vegetation changes using satellite data and remote sensing technique.
Dr Raoof Mostafazadeh, Engr. Roghayeh Asiabi-Hir, Engr. Seyed Saied Nabavi,
Volume 23, Issue 69 (7-2023)
Abstract
Drought is the main causes of significant water imbalance, increase of crop losses or limitation in water consumption, and finally large number of socioeconomic and environmental problems. Precipitation amount is the most important climatic variables that its spatiotemporal variability has a great influence on water resources availability along with the effects of climate change. The Angot index is an indicator to determine the climatic cycles of precipitation as the ratio between the average values of multiannual precipitation over wet and dry periods which highlights the climate significance of monthly precipitation to detect dry or rainy intervals. The aim of this study is to assess and calculation of the Angot inxed in analysis of dry and wet periods of monthly rainfall in rain gauge stations of Ardabil province. The maximum values of Angot index were observed in November and May months. The results proved the suitability of the Angor index in determining wet and dry months and the comparison of the employed index with other common drought indices (e.g. Standardized Precipitation Index) and also different climatic zones of Iran needs further investigations.
Masood Safari Aliakbari, Mohammad Reza Poodineh, Mohammad Azadpour,
Volume 23, Issue 70 (10-2023)
Abstract
The drought occurs in a large number of livelihoods of rural households, especially in villages of border areas facing livelihoods. To deal with these effects, the use of coping strategies in rural areas is essential. Therefore, considering the importance of this issue, the purpose of this study was to investigate the effects of drought on rural communities and identify strategies for coping with its implications in border villages in Zahedan. The present research is in terms of purpose, applied and method of combined (quantitative and qualitative). The data collection tool and questionnaire were observed and interviewed with farmers and villagers. The statistical society is related to rural households in Zahedan (10278 households), which uses a simple quota and random quota sampling 380 Household was selected as the first instance. In order to analyze quantitative data, Johansson's exploratory test was used. Exploratory interviews were used to investigate and analyze qualitative analyzes. The results showed that drought in Zahedan city villages had the greatest effect on reducing water resources, cultivation, employment, income, rural poverty, number of livestock or animal products, rural migration, vegetation loss, erosion and soil salinity and reduced price Had land and land. The results of the use of coping practices among farmers in the region showed that the status of using these actions is not suitable, and more than half of the farmers do not use these methods. However, some farmers have used more relatively simple and low cost methods that do not need to specialize and with the characteristics of border villages. In terms of farmers, such as smuggling fuel and goods, leaving the village and migrate to the city, addressing non-agricultural jobs, flooring or lyrics of Qanat and manual nutrition of livestock as the most important methods for compatibility with drought and decrease The effects are it.
