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Showing 8 results for AliAkbar
Mohammad Ali Saghafi, Abbas Ali Aliakbari Bidokhti,
Volume 1, Issue 1 (4-2014)
Volume 1, Issue 1 (4-2014)
Abstract
Nowadays air pollution in large cities such as Tehran have dramatic effects on public health, hence study of the way air pollutions varies with meteorological parameters appears to be important. One important aspect of sustainability of large cities such as Tehran, is controlling the emissions of pollutants as the meteorological (climatic) conditions are becoming more acute in terms of air pollution and temperature rise. In this paper some recent records of near surface meteorological parameters as well as some pollutants records are examine to observe how they change daily, monthly and annually and how they are correlated. Considering the variations of winds and temperature (extracted from a 2D sonic anemometer at 10 m at the Institute of Geophysics, Tehran University in the northern part of central Tehran, with one minute intervals) and hurly data of CO and PM10 concentrations for the same station for 2007, their relations were investigated. Also using upper air meteorological data (at 00.00 and 12.00 UTC) from Mehrabad Airport station, the stability of the atmosphere during this period was analysed. Here the buoyancy frequencies that are measure of stability of air column were calculated. For averaging of winds two methods based on the real wind vectors and wind unit vectors were used. By correlations between the pollutants concentrations and meteorological parameters, their relationships were considered. Based on the probability distributions of winds for 2007, it was found that most of the time wind speeds were in the range of 0.5 and 2 m/s. Hence most of the time due to this weak wind there was a condition of air pollution accumulations over the city and only local winds could move the polluted air over the area. Annual cycle of variations of mean surface winds had small amplitude that appears to be due to high mountain ranges that surround the city from north and east. The annual cycle of CO variations showed a peak in autumn and winter while PM10 amounts showed a trough in winter and spring. The higher values of CO in winter seems to be due to the surface temperature inversions and improper burnings of the fuel of vehicles as well as the domestic heating systems. This was indicated in the correlations between temperature and CO concentration. In annual cycle the correlation between CO and PM10 concentrations was about 0.4 which increased to 0.7 for spring time. This may indicate that in this season the sources of these two are similar and one of them may be used to estimate the others is the sources are not changed. There are two maxima in the daily variations of CO which coincides with minima of wind in morning and evening transition times. In this study it was found that due to calm meteorological conditions (often od local origin, called mountain breezes) over the city air pollution problem is a serious problem requiring more emission control. Also trend factors as the pollutant sources (traffic) and the depth of the atmospheric surface layer are important. It is particularly noticeable that during the midday as the depth of the mixed layer increases, the air pollution concentration is reduced substantially. At night surface drainage flow from north of the city and surface radiation cooling creates near surface inversions that can limit mixing and ventilation of the polluted air from the area leading to higher values of gaseous pollutant over the city. Also lager stability in the air over the city at higher levels in autumn and winter is due to subsidence inversions as a result of the prevailing meteorological conditions of high pressure systems over this area in these months. Such conditions seem to have increased the creation of more acute conditions for air pollution over the city. For a more resilient city in terms of air pollution, some mitigation need to be undertaken in the face of climate change effects that are deteriorating the atmosphere of the city.
Khadijeh Karimi, Vahid Riahi, Farhad Azizpour, Aliakbar Taghilo,
Volume 4, Issue 2 (7-2017)
Volume 4, Issue 2 (7-2017)
Abstract
Human settlements as local -spatial systems are subject to continuous dynamism and transformation. In the meantime, rural settlements including; in Iran, as the most important establishment of population and activity, are exposed to the deepest environmental, ecological, social, economic and cultural changes. It is evident that in these developments, a variety of different and different forms of internal and external interactions Are creative However, most of these factors are somehow influenced by the management system that plays a role in the rural areas. This system, having different patterns, has a different effect on spatial systems.
The issue of drought has recently been the major concern all over the country and particularly in Urmia Basin. This is considered as a key factor in Urmia Lake crisis. Urmia's rural settlements are also affected by the management factor in a variety of spatial dimensions. The crisis of the dramatic decrease in Urmia Lake water and its management (decisions making) has posed a serious challenge to rural areas. This article to pursue to base management as a foreign factor on the basis of a good governance approach to the analysis and analysis of the role It focuses on the transformation of rural settlements in Urmia.
This research is applied in terms of its purpose and based on descriptive-analytical method. The statistical population of the study was the experts in the institutions related to the county crisis management. Experts from sample target communities were 70 people who were identified by a sample size determination method with an unknown community. A sample sampling method was used to select the samples. Data and information was collected using library and information technology. The questionnaire was used to assess the role of the management system in the framework of the components of a good governance approach and Referring to related research backgrounds, they were identified. To measure the normal distribution of data and appropriate regression selection, Kolmogorov-Smirnov and Dorbin Watson's tests were used. Also, for measuring the direct and indirect effects and the correlation between the components, Pearson's path analysis and Pearson correlation tests were used in SPSS software.
The findings of the research shows that the villages affected by the disaster management system in facing the risk of drying the Lake Urmia have encountered inappropriate environmental, social, economic and physical changes. These changes are influenced by the military mechanism that It is not due to being state-owned, focused, and open-minded; they are not accountable, legitimate, and efficient. In the meantime, the weakness of the legitimacy of failure in effective performance has had a direct impact on the disaster management inefficiency. Of course, other components such as weakness of pivotal justice, weakness of accountability, weakness of orientation affect the components of the weakness of legitimacy and weakness of the role Effectiveness has doubled disaster management inefficiencies.
The assessment of the disaster management system of Lake Urmia, based on the governance framework, indicates that the management system has not been efficient. This ineffectiveness, however, is heavily influenced by the weakness of legitimacy. But, indirectly influenced by other factors, including weakness of orientation, weakness of justice, and weakness of accountability. The important thing in this regard is the impact of the indirect factors on the legitimacy factor. By considering the nature of their direct and indirect factors, it is clear that the weak role of the villagers and the means to participate in disaster management, the cause of all problems In the countryside. Restoring Lake Urmia without paying attention to the villagers living around the Lake Urmia will be difficult. Therefore, giving villagers the role of the main beneficiaries of Lake Urmia Basin can help restore Lake Urmia.infact,Communities are the first responders in case of a disaster. Therefore, community-based disaster risk management should be the core of any risk reduction approach. community based Disaster risk management focuses more on community participation and reducing underlying risk, encouraging preventive action before a disaster. and focuses on participation on design, decision and performance for better management of disasters.
The issue of drought has recently been the major concern all over the country and particularly in Urmia Basin. This is considered as a key factor in Urmia Lake crisis. Urmia's rural settlements are also affected by the management factor in a variety of spatial dimensions. The crisis of the dramatic decrease in Urmia Lake water and its management (decisions making) has posed a serious challenge to rural areas. This article to pursue to base management as a foreign factor on the basis of a good governance approach to the analysis and analysis of the role It focuses on the transformation of rural settlements in Urmia.
This research is applied in terms of its purpose and based on descriptive-analytical method. The statistical population of the study was the experts in the institutions related to the county crisis management. Experts from sample target communities were 70 people who were identified by a sample size determination method with an unknown community. A sample sampling method was used to select the samples. Data and information was collected using library and information technology. The questionnaire was used to assess the role of the management system in the framework of the components of a good governance approach and Referring to related research backgrounds, they were identified. To measure the normal distribution of data and appropriate regression selection, Kolmogorov-Smirnov and Dorbin Watson's tests were used. Also, for measuring the direct and indirect effects and the correlation between the components, Pearson's path analysis and Pearson correlation tests were used in SPSS software.
The findings of the research shows that the villages affected by the disaster management system in facing the risk of drying the Lake Urmia have encountered inappropriate environmental, social, economic and physical changes. These changes are influenced by the military mechanism that It is not due to being state-owned, focused, and open-minded; they are not accountable, legitimate, and efficient. In the meantime, the weakness of the legitimacy of failure in effective performance has had a direct impact on the disaster management inefficiency. Of course, other components such as weakness of pivotal justice, weakness of accountability, weakness of orientation affect the components of the weakness of legitimacy and weakness of the role Effectiveness has doubled disaster management inefficiencies.
The assessment of the disaster management system of Lake Urmia, based on the governance framework, indicates that the management system has not been efficient. This ineffectiveness, however, is heavily influenced by the weakness of legitimacy. But, indirectly influenced by other factors, including weakness of orientation, weakness of justice, and weakness of accountability. The important thing in this regard is the impact of the indirect factors on the legitimacy factor. By considering the nature of their direct and indirect factors, it is clear that the weak role of the villagers and the means to participate in disaster management, the cause of all problems In the countryside. Restoring Lake Urmia without paying attention to the villagers living around the Lake Urmia will be difficult. Therefore, giving villagers the role of the main beneficiaries of Lake Urmia Basin can help restore Lake Urmia.infact,Communities are the first responders in case of a disaster. Therefore, community-based disaster risk management should be the core of any risk reduction approach. community based Disaster risk management focuses more on community participation and reducing underlying risk, encouraging preventive action before a disaster. and focuses on participation on design, decision and performance for better management of disasters.
Aliakbar Anabestani, Mahdi Javanshiri, Hamideh Mahmoudi, Mohammad-Reza Darban Astaneh,
Volume 5, Issue 1 (6-2018)
Volume 5, Issue 1 (6-2018)
Abstract
Spatial Analysis of Villagers’ Resilience Against Environmental Hazards
(A Case Study of Central District of Faruj County)
Statement of the problem
The concept of resilience is the outcome of changes in risk managing in current decade. Today, the views and theories of disaster management and sustainable development seek to create societies resilient against natural disasters. Natural disasters such as earthquakes, droughts, floods, etc. are inevitable phenomenon which always pose a serious threat to development, especially in rural areas. This reflects the need to pay more attention to resilience in local level (rural areas). Resilience is the ability of a social or ecological system to absorb and deal with disorder or disturbance, so that the basic functional structure, can maintain the capacity of reorganization and adapting to changes and tensions. Carpenter defines resilience as the capacity of an environmental and social system to absorb a disruption, reorganize and thereby maintain essential functions. Thus, in order to reduce damage caused by natural disasters, the capacity of rural areas to deal with these events should be increased. Increased level of resilience against natural hazards is possible through accurately identifying the factors affecting resilience. Therefore, the aim of this study is the spatial analysis of factors affecting the promotion of rural environmental resilience in the face of natural hazards in rural areas of Faruj County.
In fact, the present study seeks to answer the following questions: what are the factors which may increase the level of resilience in the sample communities exposed to natural hazards, and how resilient are the sample villages of the study?
Research Methodology
This study is an applied research conducted in a descriptive-analytical method based on questionnaires. Data were collected through library research and field works which required completing questionnaires and conducting interviews with villagers living in the Central District of Faruj County.
Validity of the questionnaires was confirmed based on experts' views and its reliability was calculated using Cronbach alpha for different dimensions. The population consisted of 4591 households from the villages suitable for temporary accommodation. Based on the Cochran formula, 252 were obtained from these samples. They were selected by stratified random sampling.
Using statistical analysis methods in SPSS software, we analyzed the data to measure resilience in sample villages of the study area. We also used Excel and GIS in various parts of the study. To determine the best option, we used the VIKOR models, Gray relational analysis and Additive Ratio Assessment (ARAS).
Results and discussion
The results showed that infrastructure dimension with a mean of 2.92 and the economic dimension with a mean of 2.58 respectively had the highest and least impact on increased resilience which suggest that these villages compared to sample villages have relatively good infrastructure facilities. However, due
to the lack of proper institutional framework and poor performance of crisis management institutions, villagers are less satisfied with these organizations. Accordingly, based on t-test, the actual mean of the total respondents’ views was less than 3 and at the moderate level, and the economic index with the t statistics of -10.38 had the most negative impact on the resilience of the villagers.
It should be noted that according to the results of the resilience correlation with the individual characteristics of the respondents, it became clear that the gender and marital status has a direct and weak relationship with each dimension of resilience, which means men and the married people compared to the women and the singles believe their villages are more resilient. Besides, there is a weak and reverse relationship between the education of the individuals and their resilience, meaning that people with lower education compared to educated people, believe their villages are more resilient. There was no relationship between age and the dimensions of resilience.
In order to assess the impact of each index of the study on the level of resilience in the villages of the study, the confirmatory factor analysis test was used which revealed that among the indices of the study, "the villagers’ satisfaction with the performance of the Rural Council and administers (Dehyars)", "the role of institutions in educating people about various incidents" and "the use of new and durable materials to prevent the damaging effects of the incidents" had the greatest effect on the resilience of the samples villages.
Eventually, to determine the best village in terms of resilience for establishing a temporary settlement site in crisis management, we use three techniques: additive ratio assessment (ARSA),- VIKOR and Gray relational analysis. We prioritized the villages based on the mean rank method. -Considering the indices of resilience in the rural areas of the study, the villages of Mefrangah, Ostad and Pirali have the highest ranks, and the villages of Rizeh and Roshavanlou have the lowest ranks.
Key words: resilience, environmental hazards, organizational-institutional dimension, additive ratio assessment (ARSA), Faruj Central District
Dr. Aliakbar Shamsipour, Mr. Ayoub Jafari, Mr. Hesam Bostanchi,
Volume 7, Issue 2 (8-2020)
Volume 7, Issue 2 (8-2020)
Abstract
Occurrence conditions for severe snow blizzard in the west-north of Iran
Abstract
The blizzard incident is one of the climatic hazards that occurs due to the combination of other climatic factors such as temperature (below zero), snow and wind (at 15 m/s). In this research, the conditions of blizzard in Northwest of Iran are carried out using statistical methods. By analyzing all the meteorological codes of the blizzard (36, 37, 38 and 39) during the statistical period from 1987 to 2016 for 11 synoptic stations of the study area, codes with severe blizzard (37, 39) were selected. Then, using the geopotential height, wind and Leveling temperature of 500 and 850 hpa, obtained from the NCEP/NCAR open source database, the synoptic patterns of blizzard incident analyzed. Statistical analysis of the relationship between the effects of geographic factors on severe blizzard has shown that the factor of height has the greatest effect on intensity, increase and incident spatial differences of this phenomenon. The study of the synoptic patterns of the incident of the blizzard phenomenon showed that five main patterns play a role in creating it in the region. The synoptic patterns of development include the formation of a low cut-off center, a long landing passage from Iran, the formation of a relatively deep and drawn Mediterranean East, The rectangular system is a rex-shaped system and is an umbilical bundle system. Among the patterns obtained, the patterns that were bundled were, the most important role in the survival and transfer of flows associated with cold, and other patterns, despite the frequency they had, were periodically of severity and weakness.
Keywords: Blizzard; North West; Wind speed; Temperatures below zero; Synoptic patterns
Human life is always affected by climatic phenomena, especially the hazards of the two variables of temperature and wind. One of the most important simultaneous phenomena of these two variables is the blizzard, which is caused by heavy snow, stormy winds, and very low temperatures. This climate risk can cause damage to various areas of horticulture, agriculture, urbanization, transportation, and so on. This phenomenon is present in regions such as Canada and North America with a cold weather wave that results from turbulence in the winters and damages the lawns in these areas. There are plenty of local storm in the polar regions and it lasts for a few days. For example, the wind in the Adelie land in the Antarctic is so severe that the area is known as the storm Land. In Iran, the most significant blizzard occurred in mid-February 1350, resulting in the deaths of more than 4,000 people across the country. In this research, considering the characteristics of the blizzard phenomenon at the time of occurrence (severity, continuity, expansion, and time of occurrence), the study has been conducted to determine the statistical synoptic patterns in the northwest region.
In this research, the studied area is northwest of Iran, which includes 6 provinces (Ardebil, West Azarbaijan, East Azarbaijan, Zanjan, Kurdistan, Kermanshah, Hamedan). In order to study, the days with the blizzard phenomenon in the form of 3 hours and in codes of this phenomenon (36, 37, 38 and 39), were obtained from the establishment of the stations studied by 2016. In the following, for precise examination, stations with 30 years of statistic from 1987 to 2016 were identified and the statistical (frequency, daily, monthly and annual frequency) codes 39 and 37 were studied. Finally, the relationship between blizzard with the latitude and elevation in the studied stations was determined. To assess the statistical results, the correlation coefficients (R) and coefficient of determination (R2) were used.
In the second part, the identification of synoptic patterns was done by Principal Component Analysis in MATLAB software and ocular method. The criterion for identifying synoptic patterns, the days where codes 37 and 39 are more than 1 time (3 hours) within 24 hours or two days behind each other at the stations studied. In order to determine the patterns, at first, the average geopotential data of the 500-hpa level from 1987 to 2016 were obtained from a range of 10-70 degrees north latitude and 0-80 degrees east longitude with a spatial resolution of 2.5 * 2.5 from the NCEP / NCAR data.
Statistical analyzes on the relationship between the effect of geographic factors on severe blizzard showed that the factor of height had the greatest effect on the intensity, magnitude and spatial differences of this phenomenon. In sum, the most important factor in the occurrence of this phenomenon is due to atmospheric conditions and synoptic patterns of the region. In this study, the most frequent occurrence of codes 37 and 39 in all stations studied was at Sardasht station and Khalkhal station, respectively. Also, the statistical study of the frequency of the annual and monthly occurrence of each code showed that code 39 in 1990 and code 37 in the years 1989 and 1990, as well as in January, had the highest frequency of each of the two codes.
Investigating the patterns of the occurrence of the blizzard phenomenon showed that five main patterns have contributed to its creation in the region, the first pattern due to the formation of a low cut-off center, which, with the cold weather in Central and Eastern Europe, has reduced the temperature in the northwest. The second pattern is due to the high landing passage from Iran, which has crossed the descent from a cold and cold weather zone from Europe to Iran. The third pattern is the location of the studied area in the relatively moderate, dragged, eastern Mediterranean wavelength, causing cold weather to fall to the northwest. The fourth pattern, with the formation of a Rex-type blockade on the Mediterranean, has led to the transfer of cold air from Eastern Europe, Kazakhstan, and high latitudes to Iran. The fifth pattern, with the formation of a blockade, has caused cold weather in northern Europe and Central Asia to enter the country from the north, causing a drop in temperature in the region.
Among the known patterns, the patterns that were blocked (pattern 4 and 5) played the most important role in the survival and transfer of cold fluxes and even drawn to lower latitudes. Other patterns, despite frequent periods, provide conditions for the occurrence of this phenomenon and, unlike the blocking patterns, have had severity and weakness.
Keywords: Blizzard; North West; Wind speed; Temperatures below zero; Synoptic patterns
Geographical-Synoptic Characteristics of Arabian Anticyclone in the Heavy Precipitation Days on Iran
Dr. Mostafa Karimi, Norouzi Fahimeh, Dr. Mahnaz Jafari, Dr. Khoshakhlagh Faramarz, Dr. Shamsipour Aliakbar,
Volume 9, Issue 1 (5-2022)
Volume 9, Issue 1 (5-2022)
Abstract
Vulnerability assessment of Miangaran wetland ecosystem
To support the proper management of ecosystems, vulnerability analysis of ecosystems is very important. Vulnerability analysis of ecosystems provides information about weaknesses and capacity of the studied ecosystem for recovery after damage. Considering the degradation status of Miangaran wetland, vulnerability evaluation of this wetland is one of the most important management methods in the region. For this purpose, in this study, after identifying and evaluating the threatening factors of Miangaran wetland, these factors were scored using evaluation matrices. Then, the interaction between these values and threatening factors was examined and the vulnerability of wetland values was obtained by multiplying the scores of all studied factors. Finally, management solutions were presented to deal with the most important threatening factors. According to the results, the most vulnerability is to the hydrological and ecological values of the wetland. The highest effects of threats on the ecological value are also on the birds of Miangaran wetland. The results of the evaluation of Miangaran Wetland show that this wetland has a high potential for ecosystem functions of the wetland. These functions have been neglected in the planning and managing of wetlands at the local, regional and national levels. As a result, ecosystem-based management is suggested as the best management approach. The management in these areas should take action to prevent the vulnerability of Miangaran wetland. Also, the vulnerability evaluation method used in this study can provide a good understanding of the relationship between wetland functions and the resulting services for the management of the ecosystem of Miangaran Wetland.
Key words: Miangaran wetland, ecosystem management, vulnerability assessment
Ms. Sousan Heidari, Dr. Mostafa Karimi, Dr. Ghasem Azizi, Dr. Aliakbar Shamsipour,
Volume 9, Issue 4 (3-2023)
Volume 9, Issue 4 (3-2023)
Abstract
Explaining the spatial patterns of drought intensities in Iran
Abstract
Recognition of spatial patterns of drought plays an important role in monitoring, predicting, confronting, reducing vulnerability, and increasing adaptation to this hazard. This study aims to identify the spatial distribution and analyze the spatial patterns of annual, seasonal, and monthly drought intensities in Iran. For this purpose, the European center Medium-Range Weather Forecast (ECMWF) data for the period 1979-2021 and the ZSI index were used to extract the drought intensities. To achieve the research goal and explain the spatial pattern of the frequency of drought intensities (Extreme, severe, moderate, and weak), spatial statistical methods such as global Moran’s I, Anselin local Moran’s Index, and hot spots were used. The results of the global Moran’s I showed that with increasing intensity, the spatial distribution of drought events has become clustered. The spatial distribution of the local Moran’s Index and hot spots also confirms this. Very clear contrast was observed in the local clusters of high (low) occurrence as well as hot (cold) spots of severe (Extreme) yearly droughts in the south, southeast, and east. In autumn, weak to Extreme droughts show a southeast-northwest pattern. But in spring and winter, the spatial pattern of drought is very strong as opposed to severe and moderate drought. Despite the relatively high variability of maximum positive spatial Autocorrelation of severe and Extreme monthly droughts, their spatial pattern is almost similar. The spatial clusters of severe and very severe droughts in the northwest, northeast, and especially on the Caspian coast, are a serious warning for the management of water resources, especially for precipitation-based activities, such as agriculture.
Introduction
Drought or lack of precipitation over some time is the most widespread natural hazard on the earth compared to its long-term average. This risk negatively affects various sectors such as hydropower generation, health, industry, tourism, agriculture, livestock, environment, and economy. To reduce these negative or destructive effects, it must be determined how often drought occurs during the period and in which areas it is most severe. Doing so requires determining the characteristics of the drought. These characteristics include area, intensity, duration, and frequency of drought. Discovering the geographical focus, recognizing the pattern governing the frequency of occurrence and temporal-spatial distribution as well as changes in the dynamics of this hazard facilitate an important role in drought monitoring, early warning, forecasting, and dealing with these potential hazards; this information can be used to create a drought plan by providing analysts and decision-makers with ideas about drought, helping to reduce the negative and vulnerable effects and ultimately make it easier to protect or replace for greater adaptation. Many researchers have been led by these approaches to the use of statistical analysis. Numerous studies have been conducted in the study of climatic phenomena such as drought with space statistics techniques in various regions, including China, India, South Korea, and even Iran. Part of the domestic research on spatial patterns of drought is without the use of spatial statistics and a limited number of others who have used these analyzes have only studied the overall intensity of drought and have not studied the spatial patterns of different drought intensities. The main purpose of this study is to identify the distribution and spatial patterns of drought intensities in Iran using spatial analysis functions of spatial statistics based on the frequency of drought intensities (Extreme, severe, moderate, and weak) with yearly, seasonal and monthly multi-scale approach. Therefore, this study will answer the questions: a) What is the spatial distribution of drought intensity data in Iran? And b) What is the variability of spatial patterns of Iranian droughts at different time scales?
Material &Method
ERA5 monthly precipitation data for a period of 43 years from 1979 to 2021 were used for this study. an array of dimensions of 78×59×504 of data were formed in MATLAB software in which 78×59 is the number of nodes with a spatial resolution of 0.25 degrees and 504 represents the month. After creating the database, the ZSI index was used to calculate the severity of drought in annual, seasonal, and monthly comparisons. Finally, to achieve the research goal and explain the spatial pattern governing the frequency of drought intensities (Extreme, severe, moderate, and weak), spatial statistical methods such as global Moran’s I, Anselin local Moran I and hot spots was used.
Discussion of Results
Due to its ecological conditions, geographical location, and location in an arid and semi-arid region of the world, Iran is among the most vulnerable countries due to natural hazards, including drought. It has experienced many severe droughts in the last century. The occurrence of drought and its effects is one of the major challenges of water resources management in this century. The results of the Global Moran’s Index for all three annual, seasonal, and monthly scales showed a highly clustered pattern of drought events in the country. Spatial clustering of the occurrence of severe and Extreme yearly droughts in the eastern, southeastern, and southern regions is also an interesting result. These conditions are due to low precipitation and high spatial variation coefficient in these areas. This contrast of spatial clusters of drought intensities indicates the relationship between drought and temporal-spatial anomalies of precipitation so that with increasing precipitation, spatial variability of precipitation decreases, and consequently spatial homogeneity of precipitation increases. severe and moderate-intensity spots in the south-southeast in autumn and spring can be affected by fluctuations in the beginning and end of the monsoon season in South Asia due to the high variability of atmospheric circulation at the beginning and end of precipitation in these areas. Some studies have also shown the relationship between precipitation in these areas and the monsoon behavior of South Asia. Extreme drought events in winter and spring have had a positive spatial correlation pattern in the southwest, west, and northwest. However, precipitation at this time of year is concentrated in these areas. Warm clusters or concentrations of very severe drought events in the northern strip of the country, especially in the Caspian region, can be due to the high variability of precipitation at the beginning of the annual precipitation season (late summer and early autumn). Observations of these conditions in the northern strip indicate that an event with a high frequency of severe droughts, even in rainy areas, should not be unexpected. Spatial clusters of Extreme, severe, moderate, and weak drought every month using both local Moran and hot spots statistics show the fact that in Iran, the most severe droughts have occurred in the western, northwestern, and coastal areas of the Caspian Sea. However, the absence of severe droughts or spatial clusters has been the occurrence of low drought in the southeast and to some extent in the south. On a yearly scale, the south, southeast, and east have played a significant role in the spatial cluster of severe and extreme droughts. So that these areas of the country have had positive spatial solidarity. However, in these areas, negative spatial correlation prevailed in the autumn for severe drought. This may indicate an anomaly and a tendency to concentrate more precipitation in Iran, as well as many changes in seasonal and local precipitation regimes. According to the research results, a high incidence of severe and extreme drought on all three scales (monthly, seasonal and annual) even in the wettest climate of the country (northern Iran, especially the southern shores of the Caspian Sea) shows that High-intensity droughts can occur in all parts of the country, regardless of the weather conditions.
Keywords: Natural hazards, spatial patterns, Moran statistics, spatial autocorrelation, hot spots
Dr. Aliakbar Shamsipour, Dr. Hadis Sadeghi, Prof. Hosein Mohammadi, Dr. Mostafa Karimi,
Volume 9, Issue 4 (3-2023)
Volume 9, Issue 4 (3-2023)
Abstract
Climate is one of the determining factors in the quantity and quality of agricultural products, therefore, in this study, the relationship between precipitation and temperature (as explanatory variables) with rice yield in 40 cities and wheat yield in 30 cities (as dependent variables) was investigated in the Caspian coastal area during 2000-2017. Spatial statistical analyses were performed with using the Moran autocorrelation test and geographically weighted regression. Based on the results (Moran index, z = 0.4342121 for rice and z = 0.719571 for wheat, respectively), it was revealed that the spatial distribution pattern of rice and wheat yield had a cluster pattern. The results of the geographic weighted regression analysis showed that the temperature increase was more desirable than the precipitation increase so the increasing temperature could lead to yield increases. In the eastern parts of the study area, the positive effect of precipitation on rice yield (with 0.020 to 0.540 regression coefficients) was remarkable; the results also revealed a negative relationship between temperature and rice yield in the southeast and eastern parts and a positive effect on rice yield in other areas. Also, the effect of precipitation on wheat yield was negative in the west and central parts of the study area (with -0.481 to -0.871 regression coefficients). According to the results, a negative relationship was dominant between temperature and wheat yield in the east and southeastern parts of the study area and a positive relationship was detected in other areas. Finally, the results indicated that in the western and central parts, due to heavy rainfall and a low number of sunny hours, an increase in temperature is more favourable than an increase in rainfall. In the eastern and southeastern regions of the region, where the amount of precipitation is lower than the threshold required for rice and wheat, an increase in precipitation is more desirable.
Mr. Aliakbar Mirshafie, , ,
Volume 11, Issue 2 (8-2024)
Volume 11, Issue 2 (8-2024)
Abstract
Assessment of the measurement statistics of model accuracy and the appropriate
use of them (Case study: Interpolation of Precipitation in Fars province)
Abstract
In many scientific researches, error measurement statistics are often used without taking notices into account
when selecting a model or method for the spatial analysis of environmental hazards. In order to assess the
accuracy of precipitation interpolation methods in Fars province, the performance of widely used error
measurement statistics and some comments were implemented. Spatial interpolation of precipitation was
accomplished using inverse distance weighting, kriging, co-kriging, and radial basis functions methods with 161
weather stations (22 synoptic and 139 rain gauge stations) for 2018 as a rainy year. The results of MBE statistic
evaluation indicated that the researcher may have chosen the incorrect interpolation method in certain cases
where the sum of the positive and negative values became zero. In addition, this statistic is limited to indicating
overestimation or underestimation and should not be used for assessing accuracy or selecting interpolation
techniques. Regarding the coefficient of determination (r 2 ), the results revealed that due to the lack of
compatibility in the magnitude of the range of this coefficient (0 to 1) with error values (100 to 400 mm for the
interpolation of precipitation in Fars province), its use in evaluation of the accuracy of a method is not
recommended. In terms of NRMSE, the results showed that samples with a small number of observations (n=3),
its value increased excessively (NRMSE=0.35) when compared to samples with a bigger number of data (n=20,
NRMSE=0.097). Therefore, it is not advised to use this statistic. In conclusion, since MAE and RMSE statistics
provide a more realistic error value, it is advised to use them for assessing the accuracy of interpolation
methods.
Keywords: Precipitation, Error evaluation statistics, Interpolation methods, Fars province
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