Showing 14 results for Rainfall
Mr Ebrahim Bairanvand, Dr Amir Gandomkar, Dr Alireza Abbasi, Dr Morteza Khodaghoi,
Volume 0, Issue 0 (3-1921)
Abstract
The occurrence of torrential rains in April 2017 in Lorestan province was a clear example of heavy rains that left very heavy damage to agricultural, urban, transportation and communications infrastructure. The purpose of this study is to investigate and reveal the relationship between the physical structure of clouds producing two waves of heavy rainfall in April 2017 in the Doroud catchment area of Boroujerd. In this regard, the statistical characteristics of two precipitation waves on March 25 and April 1, 2019 were analyzed. The supernatural properties of the clouds producing these two heavy rainfall waves were investigated using the Madis superconductor product, MOD06. 4 Microphysical factors of generating clouds These two waves of heavy rainfall in the Doroud-Borujerd basin, including cloud peak temperature (CTT), cloud peak pressure (CTO), optical cloud thickness (COT) and cloud cover ratio (CF) were analyzed. Statistics of these two waves of heavy rainfall showed that in the first wave of heavy rainfall, ie the wave of March 25, 2019, (5 April 1398) 15% of the total annual rainfall and in the second wave, the wave of April 1, 2019 (April 12, 1398) 20% of the total The total average annual rainfall of the region was recorded in these two days. The results of analyzing the microphysical structure of the generating clouds of these two precipitation waves using the MODSI cloud sensor product data showed that the four microphysical factors of the cloud showed a significant spatial correlation with the recorded precipitation values of these two heavy precipitation waves. The two factors of temperature and pressure of cloud peak, which show a vertical expansion of clouds in the area, showed a significant inverse relationship with the amount of precipitation in the basin, while the two factors of cloud ratio and cloud optical thickness have a direct and significant spatial correlation with values. Recorded rainfall showed. The results of this study showed that in these two events of heavy rainfall, a significant and strong relationship was established between the microphysical structure of the cloud and the amount of rainfall recorded in the region.
Faramarz Khoshakhlagh, Mohammad Amin Heydary,
Volume 15, Issue 37 (9-2015)
Abstract
Climate control centers in each area are diverse and understanding how they relate to the atmospheric components of the Earth's surface contribute to prediction of climate fluctuations. In this study, by using Pearson's correlation and multivariate regression in a thirty-year period (1961-2010), the relationship between widespread rainfall anomalies in entire of Iran west with temperature and pressure of atmospheric centers in East and West of Mediterranean Sea in 5 atmospheric levels (SLP, 850, 500 and 300 Hpa) were analyzed and modeled. Based on the results, the correlation of atmospheric control centers in the East and West Mediterranean Sea with anomalies of rainfall in West of Iran is inverse and meaningful in 95% level. In this study, statistical indicators such as temperature differences and standardized pressure between West and East Mediterranean sea were identified as the most important indicators in relation to changes of rainfall in the study area. Based on the designed indicators, whenever indicators DT and DH is positive, this means higher temperature and higher atmospheric standardized pressure in the Western parts of Mediterranean sea in compare with its East and therefore the wet spells (Monthly) occur in the study area, and If the above mentioned index is negative, means that the occurrence of drought in West Iran. As for the indicators introduced for lower levels of the atmosphere, especially in the case of temperature, meaningful strong and direct correlation is seen with rainfall abnormalities in entire West of Iran. Modeling provided some indicator for Mediterranean region using multivariate regression that they showed a relatively strong correlation in this regard of the selected components that include the pressure difference in sea level, the temperature difference in 925 and 850 hPa level in the West (Compared to its East) Mediterranean sea. Also check the regression model using real data confirm the accuracy of the relative performance of the model.
Yadollah Balyani, Mohammad Saligheh, Hossein Asakereh, Mohammad Hossein Nasserzadeh,
Volume 15, Issue 37 (9-2015)
Abstract
Precipitation is one of the most intractable elements. The oscillating behavior of the crucial environmental planning (explicit and tacit knowledge of the behavior), is the key variable. Spectrum analysis techniques to understand the behavior of overt or covert methods suitable for the extraction and analysis of climate oscillations with different wave lengths. The size range of the distribution variance across all wave lengths may provide time series. In this study, data from 37 stations Heleh and Mond watershed (both rain and synoptic) from its inception until 2011, who had over 30 years of data, to analyze the cycle of annual rainfall, interest has been taken. So that the space is 3-2 year cycles in every area of study, the highest annual rainfall events are returned. On this basis, the Story of annual precipitation 95 percent for each of the stations under study and cycle meaningful estimate of the time series of basin data were extracted.
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Volume 16, Issue 42 (9-2016)
Abstract
There are numerous methods to estimate missing values of which some are used depending on the data type and regional climatic characteristics. In this research, part of the monthly precipitation data in Sarab synoptic station, east Azerbaijan province, Iran was randomly considered missing values. In order to study the effectiveness of various methods to estimate missing data, by seven classic statistical methods and M5 model tree as one of efficient data mining methods, hypothetical missing values were estimated using precipitation data from neighbor station. The results showed that multiple imputation, Delta Learning Rule, and Multivariable Linear Regression (MLR) yield relatively more accurate results with fewer errors. The results also indicate the fact that, developing if-then rules, M5 tree model, as one of modern data mining methods, has been able to give the most accurate results among the mentioned methods with four simple linear relationship and statistical values including correlation coefficient (0.974), Nash-Sutcliffe model efficiency coefficient (0.948), RMSE (5.11), and MAE (4.189). Therefore, taking simple modeling process, functionality, comprehensibility, and high accuracy of this method into account, this method is proposed to estimate monthly precipitation missing values.
Somayeh Soltani Gerdfaramarzi, Aref Saberi, Morteza Gheisouri ,
Volume 17, Issue 44 (3-2017)
Abstract
Rainfall is one of the most important components of the water cycle and plays a very important role in the measurement of climate characteristic in any area. Limitations such as lack of sufficient information about the amount of rainfall in time and space scale and complexity of the relationship between meteorological elements related to rainfall, causes the calculation of these parameters using the conventional method not to be implemented. One method of evaluating and forecasting of rainfall in each region is time series models. In this research, to predict the average annual rainfall synoptic station at Mahabad, Uromiya and Mako in West Azarbayejan provience during 1984-2013, linear time series ARIMA was used. To investigate model static, Auto Correlation Function (ACF) and Partial Auto Correlation Function (PACF) was applied and with differencing method, the non-static data transformed to static data. In next step, stochastic models to estimate the annual rainfall average were used. With regard to the evaluation criterion such as T, P-VALUE < 0.05 and Bayesian Information Creterion (BIC), ARIMA (1,0,0), ARIMA (0,1,1) and ARIMA (0,1,1) models was determined as a suitable model for predicting annual rainfall in the three selected stations at Uromiya, Makoo and Mahabad. In the following, the annual rainfall for 3 (2013-2016) years is forecasted which based on rainfall data in that time, the adjusted model was acceptable.
Alimohammad Khorshiddoust, Behrooz Sarraf, Bagher Ghermez Cheshmeh, Mrs Fatemeh Jafarzadeh,
Volume 17, Issue 47 (12-2017)
Abstract
In recent years, the severe fluctuations in precipitation have affected various parts of the country. On the southern coasts of the Caspian Sea, precipitation as one of the important climatic parameters has undergone changes due to global climate change. In the present study, we tried to evaluate the effect of climate change on rainfall in this region by applying a suitable model. In this study, observational period rainfall (1961-2001) was analyzed. the output of the HadCM3 model was used. At first, seven synoptic stations were selected and their data were analyzed in terms of accuracy, and length of statistical period, and lost data was restored. The AOGCM data were simulated using the SDSM model and the rainfall values were simulated for the observation period. After confirming the matching of the simulated data with observational data, the values of the Future (2039-2011) is estimated. The estimation errors of the SDSM model were calculated monthly by MBE and MAE criteria, and then compared. The output of the SDSM model was used to study the total annual precipitation in days with rainfall of more than 1 mm in the observation period and the upcoming period (2011-2039) by the R-Climdex model and the values of the PRCPTOT index Became zoning in the Future. The results showed that the model error in season with high rainfall is more than seasons with low rainfall. On a monthly scale, the maximum error occurred in the months of September, October, November and December. The maximum error in the fall and the minimum error was calculated in the spring and April and May months. According to the results, the total annual rainfall in the period of 2039-2011 will decrease in Anzali, Babolsar, Gorgan and Noshahr stations and rainfall will increase in stations of Astara, Ramsar and Rasht. Geographical distribution of selected were 5 sites in the Khuzestan, 20 sites in Bushehr, 24 sites in Hormozghan and 12 sites in Sistan and Baluchistan provinces. In total, 9000 sites were selected with a 2 km2 were suitable for large scale microalgae cultivation. The total area of these sites were estimated to be 18000 km2. The highest number of proper sites were found in Hormozghan province and lowest numbers of sites were found in Khuzestan province. The availability of technical service, carbon dioxide point resources from oil and gas units are an advantages for microalgae related activities in the Bushehr and Khuzestan provinces. The higher quality of water in the Sistan and Baluchistan province is an advantages for development of microalgae biomass production in the area.
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Mr Ali Mohammadpourzeidi, Professor Bohloul Alijani, Associate Professor of Climatology Mohammad Saligheh, Mr Mohammadsaleh Gerami,
Volume 19, Issue 52 (3-2019)
Abstract
owledge of spatial rainfall behavior in environmental, land planning is effective. These changes in the later place in the form of time later and in the climate of the area. The Target of this study was to reveal the presence or absence of precipitation trend in the ratio of the height of local precipitation behavior and identify province mazandarn. Therefore, the purpose of the rainfall data station 32 (Meteorological Agency and Department of energy), the statistical period 1988-2010. To get the regression analysis of precipitation process was used to identify the local behavior of precipitation, the method of spatial statistics were used. The results obtained from the behavior of precipitation, the existence of the process within the scope of the study and the emphasis is most consistent with the Be modified regression model at adjustment indicate. According to the regional behavior of precipitation, using local spatial statistics, spatial Moran well hot spots check this behavior. The results showed that precipitation in the province of Mazandaran has the pattern of clusters with high value. According to the local hot spots and methods Moran, West Coast up to a height of 700 m has positive z score and clusters with high value, 99% confidence level. This range includes 15% of the total of the province. The range of the Southern Highlands as well as the negative z score and clusters with low value with a confidence level shows 99%. This range is also about 20 per cent of the province's total. About 65 percent of the total area of the province as well as the lack of a significant trend show.
Hosseinali Roohbakhsh Sigaroodi, Mostafa Karampoor, Hooshang Ghaemi, Mohammad Moradi, Majid Azadi,
Volume 19, Issue 55 (12-2019)
Abstract
Investigating the variability of the spatial-temporal pattern of rainfall, which can lead to climate change, due to its strong impact, is of interest to various scientists. For this purpose, after receiving the daily precipitation data of 27 stations for the period of 60 years (2010-1951), its quality and the total monthly precipitation and statistics necessary for the continuation of the research process such as mean, coefficient of variation, skewness, probability estimate of 20% The upper limit of the maximum and minimum rainfall average were calculated experimentally for a period of 60 years and two 30-year periods (1951-1980 and 1981-2010) and two periods of 10 years (1951-1960 and 2010-2001) for each of the spring and summer seasons Was calculated. The studies show relatively modest variations in spring and summer precipitation patterns on the Caspian coast, Northwest-West, 30 and 10 years old, compared to the 60-year, 30-year, and 10-year periods. In general, the mean of precipitation decreases from north and northwest to south and south east and increases the amount of coefficient of change and skidding. Except for the Caspian Basin, in the remaining stations, the average spring precipitation is higher than the average summer rainfall. There is a clear difference in the long-term characteristics of precipitation and its changes. It is worth mentioning that the increase in the coefficient of variation of the 30-year and 10-year periods is comparable to the corresponding periods at all stations, which indicates a decrease in the monthly and seasonal mean of spring and summer precipitation, which confirms the results of the decade and the first decade of the second decade. The greatest decrease occurred in the northern and western parts. In the second 30 years, the incidence of dry sunshine and drought-affected stations has increased. Therefore, it confirms the climate change for the Caspian and the Southwest coast.
Ms Mahboobeh Pouratashi, Dr Mohammad Moradi, Dr Ebrahim Fattahi,
Volume 20, Issue 57 (6-2020)
Abstract
This research aims to study the impact of temperature and wind in the southern low-pressure system and its associated precipitation in the southern regions of Iran. As The southern low pressure system moves eastward, it crosses the southern regions of Iran, causing medium and heavy rainfall in these areas. In this study, two southern low-pressure systems that caused heavy rainfall on March 11, 2015 and January 17, 2000 in southern Iran were selected, analyzed and simulated using the numerical Weather Research and Forecasting (WRF) model. Since the wind and temperature fields play a significant role in the southern low-pressure systems, four experiments were performed for investigating the effects of temperature and wind on the intensification and weakening of the southern system. The simulation results showed that the simulation for the increased (decreased) temperature caused the weakened (intensified) the southern low pressure in the studied area. This result showed that the vertical structure of the southern low-pressure and its physical characteristics are similar to the mid-latitudes cyclones, and these systems were different from the thermal low pressures. The results of wind speed changes showed that the increased (decreased) wind speed simulation caused an increase (decrease) in relative vorticity, thus the southern low pressure was intensified (weakened). In both cases, the rainfall was decreased by the increased temperature simulation, and decreased temperature caused an increase in rainfall. It was also seen that the increase in wind speed caused the special humidity advection to be increased and then the rainfall increased. Also the amount of rainfall decreased when conditions did not provide for the advection of specific humidity or the wind speed reduced.
H Hossain Asakereh, M Mehdi Doustkamian, M Mohammad Darand,
Volume 21, Issue 60 (3-2021)
Abstract
The purpose of this study is to investigate and analyze turbulence, fluctuations and jumps of Iranian regions. For this purpose, environmental data has been gathered in two parts. In the first part of the data, the results of the interpolation of the daily precipitation observations of 1434 stations of climate and climate were used from the beginning of 1340 to 1383. After the formation of a database to identify the Iranian regions, a cluster analysis was used on average data and annual and monthly rainfall variation coefficients. Silhouette analysis has been used to validate the Iranian rainy areas. In order to investigate disturbances, mutations and fluctuations in Iran's rainy areas, this study was carried out. The results of cluster analysis indicate that Iran's peripheral areas are divided into six classes. In the meantime, the Caspian region (area 4) has the highest rainfall and the lowest coefficient of variation. The distribution of rainfall regime in each of the six areas shows that Iran's precipitation regime is more frequent in winter and spring and sometimes in autumn. Investigation and analysis of rainfall turmoil has shown that rainfall, except in the 4th district (Caspian region), in other areas of distribution of rainfall occurred along with disturbance. Although most disturbances occur in the zagros area, the highest sequence of disturbances is related to the fifth load region. The least sequence of disturbances occurred in the central and eastern part of the country. The results of mutation analysis and fluctuations indicate that rainfall disturbances, except in the early years of precipitation regions two and five in other regions of the other regions, have no significant mutation, while short-term fluctuations of 3-5 years on rainfall Each of the six domains has dominated.
- Nesa Sepandar, Professor Kamal Omidvar,
Volume 21, Issue 61 (6-2021)
Abstract
In this study, we tried to identify the sources of moisture and its direction of heavy rainfall in south and southwest of Iran by using a new algorithm based on atmospheric rivers. For this purpose, daily rainfall of 17 synoptic stations in the period 1986 to 2015 in south and southwestern Iran that have a common time span and fully cover the study area is used.Also from the data set of the National Center for Environmental Prediction / National Center for Atmospheric Research (NCEP / NCAR) European Mid-Term Forecast Center (ECMWF) and ERA-interim data with spatial resolution of 0.75 It was used at 0.75 latitude and longitude with 6 hour resolution. The variables used are integrated water vapor (IWV), specific humidity (q), and orbital and meridional components (u, v). In this research, an algorithm based on the calculation of Vertical Horizontal Vapor Transfer Integral (IVT) is used to identify and navigate atmospheric rivers. The results show that the main source of rainfall moisture is in south and southwestern Iran, south of Red Sea and Gulf of Aden. Of course, the maps show that the Arabian Sea was not affected by the humidity.The Arabian Peninsula also, due to the high moisture transfer rate, as a transitional route, transmits a large amount of moisture to the study area.Finally, the path of moisture to the study area was mapped and identified, and thus considering the three main conditions for the atmospheric river, it can be said that the path obtained is the same as the atmospheric river.
Ali Saadat, Mohamad Saligheh, Mohamadhosin Nassrzadeh,
Volume 21, Issue 63 (12-2021)
Abstract
The goal of this research is studying the effect of recent climate changes, espeeially heat rise on the amount of effective rainfall in the lorestan peovince. Effective rainfall is the amount of fall which, after evaporation, is absorbed in the ground. in the ground.in USDA method and the us agriculture, the amount of rain abstorbed in a growth perlod of a plant and available for its consumption is called effective raifoll. The results showed that the amouent of rainfall in the first period is more than that of the second. The frequency of raining days got reduced in the after-climate- change period. Heat got increased in the second period. Evaporation was more in the second period. Relation humidity got decreased in the second compared to the first period, and wind speed increased by studying the process of the data changes, it became evident that climate change leads to the increased inconsistent rainfalls in the studied climate variables indicate that under the effect of climate change , Based on Vibol method, droughts caused by effective rainfalls were calculated, and the probability of effective rainfalls in 5 time periods was accounted for. It was shown that in the years 1369 to 1396, effective rainfall in the region was scarce, so it was very influential. With Dobif Model, effective rainfall was analyzed, and years with the least effective rainfall for dry farming with positive signal, that is, appropriate conditions, and negative, that is, inappropriate conditions were recorded. Based on linear coefficient, rainfall trends in the three stations of Khorramabad, Aligudarz and Borujerd. Geographical distribution analysis of effective rainfall showed that in the south and south-east of the province, the coefficient of effective rainfall was more than the rest of the province. This coefficient was decreasing when it comes to the south-west of the province. Effective rainfall decrease was more due to increasing evaporation happening in this part. the effective rainfall in the studied region got decreased, therefore, preserving underground water resources, on which natural life depend, should be considered more than ever.
Zahra Hejazizadeh, Sharifeh Zarei, ,
Volume 23, Issue 69 (6-2023)
Abstract
Abstract
In recent years, attention has been paid to climate change, which could be the result of economic, social, and financial losses associated with extreme weather events. The purpose of this study is to investigate the variation of extreme temperature and precipitation in Kurdistan province. For this purpose, daily rainfall data, minimum temperature and maximum temperature of 6 stations were used during the statistical period (1990-1990). And their changes during the period (2041-2060) using the universal HadGEM2 model under two scenarios RCP2.6 and RCP8.5 and the LARS-WG6 statistical downscaling were investigated. In order to study the trend of climatic extreme indexes, rainfall and temperature indices were analyzed using RClimdex software. The results showed that during the period (2016-1990), hot extreme indicators have a positive and incremental trend. This trend is significant for the "number of summer days" and "maximum monthly of maximum daily temperature" indicators. This is while the cold extreme indexes had a decreasing and negative trend. This trend was significant only for the "cold days" index. Extreme precipitation in Kurdistan province has a negative trend in most stations. ،this trend is significant at most stations, that indicates a reduction in the severity, duration and frequency of precipitation during the study period. The results of the climate change outlook also indicate that the temperature will increase over the next period and rainfall will decrease.
Ms Elaheh Ghasemi Karakani, Mr Ebrahim Fattahi, Mrs Loabat Salehi Pak, Mr Hooshang Ghaemi,
Volume 23, Issue 69 (6-2023)
Abstract
During the rainfall, the intensity of precipitation varies. Changes in the amount of precipitation during an event of rainfall are effective in the resulting of flood and its intensity. Knowledge of how rainfall changes over time during rainfall is determined by temporal distribution pattern of rainfall. For this purpose, availability of short-term time scales rainfalls data are important that obtained by rain gauge stations. However, the low density of the rain gauge network and the lack of sufficient data from the time pattern of rainfall have always been a problem in determining storm patterns for executive plans. Therefore, the simulation of WRF numerical weather models can be used. The WRF model is one of the most responsive models for predicting precipitation, temperature and atmospheric elements that used in this study. In this paper, three great storm events on 15 December 2003, 24 - 26 December 2006 and 6-7 March 2007 have been selected in the Parsian dam basin and surrounding areas in south west of Iran. The result of WRF numerical weather prediction model for these great storms compared with data loggers. It showed that the WRF model was able to performance the heavy rainfall and simulates the rainfall pattern in these dates.
