Javad Bazrafshan

University of Tehran | UT · Department of Irrigation and Reclamation Engineering

One major characteristic of the Standardized Precipitation Index (SPI) is its flexibility to be calculated in a variety of time scales and hence being aware of different types of droughts. However, various time scales may result in confusion of the water resources’ researchers, decision makers and users in identifying and specifying drought periods...

Effective monitoring of drought plays an important role in water resources planning and management, especially under global warming effect. The aim of this paper is to study the effect of air temperature on historical long-term droughts in regions with diverse climates in Iran. To this end, monthly air temperature (T) and precipitation (P) data wer...

Traditionally, drought indices are calculated under stationary condition, the assumption that is not true in a changing environment. Under non-stationary conditions, it is assumed the probability distribution parameters vary linearly/non-linearly with time or other covariates. In this study, using the GAMLSS algorithm, a time-varying location param...

Climate change projections were evaluated over both the whole Iran and six zones having different precipitation regimes considering the CORDEX South Asia dataset, for assessing space-time distribution of drought occurrences in the future period 2070-2099 under RCP4.5 scenario. Initially, the performances of eight available CORDEX South Asia Regiona...

Precipitation is one of the most complex weather phenomena that its successful spatiotemporal modeling provides substantial information for designing water management systems. This research aimed to seek the relationship of sixteen large-scale climate signals with weather types (WTs) as well as precipitation amounts over Iran during the winter seas...

The nonstationary hydrologic processes due to climate variability and intensification of human activities are challenging and questionable for researchers. This study investigates nonstationary partial duration series (PDS) records for the period 1971–2017 at 14 hydrological stations across the Gorganrood River Basin, Iran. The Gorganrood Basin is...

This study was aimed at evaluating the application of the canonical correlation analysis (CCA) to predict monthly precipitation amounts (predictands) by benefitting from 17 large-scale climate indices (predictors) in Iran. Monthly precipitation data, covering the period of 1987–2017, were collected from 100 weather stations across the country. Mont...

The impact of the dust phenomenon in Iran is so vast that it has involved more than half of the country's provinces in some way with the issues and limitations of this natural phenomenon, which, in addition to the environmental effects, has disrupted the implementation of national sustainable development plans and So far, it has and will have many...

Dust has always been one of the most important environmental hazards and has adverse environmental consequences. The purpose of this study is to investigate the relationship between temperature extreme variables and dust storms and evaluate the best model for predicting the FDSD index in the west of the country. We used hourly visibility data, Worl...

Global space coverage of the TRMM satellite imagery has provided a good opportunity to use the precipitation data estimated by this satellite in the country. Various studies have been conducted in the country to evaluate the accuracy of the above data in comparison to the measured data at ground stations. However, few studies have examined the effi...

Global warming has changed rainfall patterns and reduced snow sources. The main target of this research study was to evaluate the impact of temperature increase on snowmelt and river runoff in hot months of the year along with analysis of climate variables in Tamar basin, Iran, and its sensitivity analysis. To achieve this aim, the snow cover area...

Expanded abstract De Martonne climate classification is one of the first generation of classifications that are mainly aimed to assess plant ecology and the degree of aridity of areas in relation to their natural vegetation. This classification is quantitative and its climatic ranks are defined based on the values of the aridity index" a=P/(T+10)"...

Aras Dam Lake is a strategic aquatic ecosystem in Iran and there are reports of toxic phytoplankton blooms in this reservoir. This study was performed to determine the effect of meteorological variables on the formation and expansion of toxic phytoplankton communities in Aras dam reservoir. The data of this project have been obtained using field st...

In a changing climate, drought indices as well as drought definitions need to be revisited because some statistical properties, such as the long-term mean, of climate series may change over time. This study aims to develop a Non-stationary Standardized Precipitation Evapotranspiration Index (NSPEI) for reliable and robust quantification of drought...

Sea-surface temperature anomalies (SSTA) and precipitation forecasts from the National Centers for Environmental Prediction-Climate Forecast System Version 2 (NCEP-CFSv2) model are combined to produce probabilistic forecasts of standardized precipitation index (SPI) phases at the seasonal time scales over Iran. The hybrid statistical-dynamical mode...

One of the most crucial issues in water and food security is to assess the impacts of climate change on virtual water content (VWC) and crop yield of agricultural products. The objective of this study is to efficiently predict the VWC patterns and yields of different crops under various climate change conditions using three data mining approaches i...

The present research has been conducted to parameterize and evaluate the APSIM-Wheat model for winter wheat and to use the model for evaluation of climate change effects on grain yield. The model is used to simulate leaf area index, dry matter, and grain yield of Roshan cultivar winter wheat in Karaj and Khomein regions between 2014 and 2015, under...

Precipitation and seasonal streamflow are the two major sources of water for vegetation cover in arid and semi-arid regions. A simple and novel hybrid drought index is presented in this study to assess the joint effects of precipitation and streamflow on vegetation cover in seven coastal sub-basins in southern Iran. To this end, the Standardized Pr...

Short-term prediction of heavy precipitation events is especially crucial in flood warning and mitigation. This study offered a novel concept of the regional heavy precipitation based on the probability pattern of a typical rainstorm. Daily precipitation data of 12 synoptic stations located over southwestern Iran were used for this purpose. In addi...

Surface water, especially rivers, is one of the most important water resources that play an important role in supplying water for various activities. The purpose of this study was to investigate the temporal and spatial variability of water quality parameters in three different basins, in terms of land use, at 50 hydrometric stations in 9 rivers in...

Introduction The North Atlantic Oscillation (NAO) is one of the large climate signals that affect partly climate variabilities in northern hemisphere. Various studies have considered covariation between precipitation in Iran with NAO mainly at monthly timescale. No research has been conducted on a weekly time scale. In this study, the covariate bet...

The impact of the dust phenomenon in Iran is so great that it has involved more than half of the country's provinces in some way with the problems and limitations of this natural phenomenon, which in addition to environmental impacts, has disrupted the implementation of sustainable national development plans and so far it has had and will have many...

The increasing incidence of dust storms indicates the dominance of desert ecosystems in each region. Therefore, in order to properly control and manage dust storms, it is necessary to be aware of the temporal-spatial changes of this phenomenon and the need to predict and model it. In this study, in order to predict the variable frequency of days wi...

Climate time series may exhibit abrupt or gradual shift, due to non-climatic changes (e.g., the station relocation) or actual climate change of a region. This study presented a step-by-step methodology for detecting the climatic and non-climatic changes in annual precipitation (P) and maximum (T_x) and minimum (T_n) air temperature data related to...

Madden and Julian (MJO), a large-scale climate signals, is one of the factors that affect the tropical and even subtropical areas. The effect of MJO on precipitation has generally been investigated in the southern parts of Iran. The purpose of this study is to investigate the spatial distribution of probability of precipitation occurrence(PPO) over...

The increase in dust storms occurrence in recent years in southwestern Iran, especially in Khuzestan province, and consequently the decrease in air quality in these areas, has doubled the importance of forecasting and linking this phenomenon with climate variations. The aim of this study was to investigate the efficiency of hybrid Genetic-Annealing...

The increase in dust storms occurrence in recent years in southwestern Iran, especially in Khuzestan province, and consequently the decrease in air quality in these areas, has doubled the importance of forecasting and linking this phenomenon with climate variations. The aim of this study was to investigate the efficiency of hybrid Genetic-Annealing...

Stream flow forecasting on a monthly time scale is essential for optimal water resources management and planning. In this paper using the predictions obtained from the ECMWF climate model, monthly stream flow forecast was made in Shahroud river Subbasin, part of Sefidrood basin northwest of Iran. To achieve this aim, using monthly precipitation for...

Precipitation forecasting is one of the most important tools in water resources planning and management. Recently, new methods called atmospheric dynamic models have been used to predict many hydro-climate variables including precipitation. Before using the predictions of these models in planning and decision making, the accuracy of the mentioned p...

Hyrcanian forests play an important role in absorbing carbon dioxide and reducing the severity of climate change and global warming. The accurate estimation of actual evapotranspiration can help to plan for conservation and management of these forests and their water resources. Direct measurement methods for evapotranspiration have limitations, one...

Comparison of the Performance of ClimGen and LARS-WG Models in Simulating the Weather Factors for Diverse Climates of Iran J. Bazrafshan 1*, A. Khalili2 , A. Hoorfar3 , S. Torabi4 and S. Hajjam Volume 5, No. 1, Spring 2009 (IR-WRR) تحقيقات منابع آب ايران Iran-Water Resources Research Abstract Comparison of the Performance of ClimGen and LARS-WG M...

Evaluation of drought duration risk using annual secular precipitation data in ancient stations of Iran Abstract The aim of the study is to evaluate the return period and risk of drought duration in five ancient and unique stations of Iran, having more than one-hundred annual precipitation data. For determining the return period and risk of drough...

Different regions have different potentials in dust release, and the increase in dust storms indicates the dominance of the desert ecosystem in each region. Prediction of the occurrence of dust storms in critical regions allow desion-makers to efficiently manage and to mitigate its probable damages to landscape. This study aims to predict the frequ...

Displaying and quantifying how large-scale climatic signals affect the regional and global climate is one of the issues of interest to researchers. New approach of Network Analysis enables us to study a complex system such as the climate more effectively. In this study, the effect of NAO on precipitation in Iran was investigated using the method of...

The purpose of this study is to evaluate the effects of meteorological droughts on vegetation cover using satellite images. For this purpose, vegetation images were extracted from MODIS sensor of AQUA satellite on a 16-days timescale, during the growing season for three years of Wet (2006), Normal (2009) and Dry (2008) for different land uses, i.e....

This study aims to conduct a thorough investigation to compare the abilities of quantile mapping (QM) techniques as a bias correction method for the raw outputs from general circulation model (GCM)/regional climate model (RCM) combinations. The Karkheh River basin in Iran was selected as a case study, due to its diverse topographic features, to tes...

In this study, with the aim of improving river flow simulation, the effect of coupling between Atmosphere-Land Surface Interaction Scheme (ALSIS) and HBV hydrological model in Karkheh Basin and its sub basins without considering South Karkheh basin was investigated. Before coupling, comparison between soil moisture of HBV model and ALSIS scheme was...

According to numerous reports about the global warming process and the fluctuations of rainfall, the study of climate change, especially in semi-arid regions of the country's dryland, is necessary in order to adapt to this phenomenon. The purpose of this study was to investigate the current process of climate change and the projection of CMIP5 (Cou...

North Atlantic Oscillation (NAO) is one of large-scale signal that affects the north hemisphere. Various studies have investigated the correlations between Iran’s precipitations and North Atlantic Oscillation from monthly to yearly scales. This study has considered weekly time scale. The daily precipitation variable was obtained from the ERA-Interi...

Net primary production (NPP) is an important indicator of ecosystem production potential, which is heavily affected by climate change. The purpose of this study was to investigate the effect of climate change on-trend and sensitivity of NPP in the Hyrcanian region of northern Iran using long-term (31 years, 1987-2017) meteorological data recorded i...

مدیریت منابع آب زیرزمینی، نیازمند شناخت عملکرد آن و پیش بینی تاثیر عوامل مختلف اقلیمی و انسانی می باشد. در این تحقیق، به منظور شناخت و شبیه سازی ویژگی های آبخوان دشت مهاباد از مدل GMS10.05 استفاده شد. پس از واسنجی و صحت سنجی مدل، عوامل تاثیرگذار بر تراز آب زیرزمینی مورد بررسی قرار گرفت و به این منظور مدل با حذف کلیه عوامل انسانی تاثیرگذار اجرا شد ک...

Monthly rainfall forecasting plays a major role in the water resources management and agroclimatic studies. The main purpose of this study is to assess the accuracy of NMME (North American Multi-Model Ensemble) in forecasting monthly rainfall in Sefidrood basin, North of Iran. For this purpose, the historical predicted data of NMME models for the p...

Drought is one of the most important weather-induced phenomena which may have severe impacts on different areas, such as agriculture, economy, energy production, and society. From a meteorological point of view, drought can be induced by lack of precipitation, hot temperatures, and enhanced evapotranspiration. The efficiency of the drought monitori...

The HBV (Hydrologiska Byråns Vattenbalansavedlning) is a conceptual model widely used for hydrological forecasting and water resource studies. In this study, sensitivity analysis of parameters of the HBV model is investigated for Karkheh basin and its sub-basins for four different periods 1, 5, 10 and 25 years with four methods including FAST (Four...

This study evaluates the application of Atmosphere-Land Surface Interaction System (ALSIS) scheme in simulating the streamflow in Karkheh river basin. The Climate Forecast System Reanalysis (CFSR) data for the period 1982-2011 are used as atmospheric forcing data and sub-grid scale heterogeneity of the land-surface is represented by soil-vegetation...

The purpose of this study was to evaluate the role of rainfall during wet periods and meteorological droughts in recent years to decrease the impact of river flow droughts in the Karkheh basin. To this end, the hydrology-land surface coupled model ALSIS-HBV was used. The application of this model to an undisturbed period (when the system is only af...

Groundwater plays a significant role in domestic, agricultural, and industrial water supply in semi-arid regions. In such areas, rapid growth of population and water demand in conjunction with climate change negatively impacts groundwater quantity and quality. In this research, human activities and climate change effects on groundwater quality in a...

The first effects of climate change are visible on temperature and precipitation; changing these variables will disrupt the current order of the hydrological cycle. The new state of the hydrological cycle causes a change in the flow regime. Natural flow regime plays a major role in sustaining native biodiversity and ecosystem integrity in rivers (P...

Introduction: Different regions have various dust production; and the increase of dust storms illustrates the arid ecosystem dominance in each region. Analyzing and identifying of dust storms and its association with climatic parameters is one of the crucial approaches to reduce the caused damage of this phenomenon. Since besides determining the po...

In recent years, the determination of the uncertainty of hydrological models in the hydrological research has been very much taken into consideration. Although the parameters of the hydrological model are usually determined by calibration, but there is considerable uncertainty in the model parameters. In this study, with the aim of calibration and...

Remote sensing-based methods were developed for resolving the limits of direct measurement methods for evapotranspiration. The purpose of this study was to investigate the capability of Landsat 8 satellite imagery and the SEBAL model for estimating actual instantaneous (ETins) and daily (ET24) evapotranspiration in the forest ecosystem. For this re...

In this study, the water balance component of the Palmer Drought Severity Index (PDSI) was replaced by the Atmosphere-Land Surface Interaction Scheme (ALSIS) and the modified Palmer Drought Severity Index (AL-PDSI) was compared with the self-calibrating version of Palmer Drought Severity Index (SC-PDSI). The evaluation of drought indices in Karkheh...

Gamasiab River is one of the five main branches of the Karkheh River and plays a basic role in preserving the life and ecosystem of the region. The first step in the adoption of proper and sustainable methods for managing the water resources of the Gamasiyab river is to gain continuous knowledge of the quantitative and qualitative status of the wat...

One of the natural characteristics of the Gamasiab River is the probability of occurrence of the flood and its hazard. Hydrological studies under climate change conditions are required to organize and manage it. Because of the necessity of using CMIP5 series models in new researches due to their high accuracy and lack of research using these models...

Precipitation is a major component of the hydrological cycle and is a crucial forcing data for hydrological and agricultural models. Great efforts have been made to generate gridded precipitation products, thereby leading to the increased availability of precipitation datasets at different spatial and temporal resolutions over the globe. This study...

Mediterranean Sea temperature information (SST-M) to predict droughts. Agro-metrological drought i ndex addressing seasonality and autocorrelation (AMDI-SA) was used in a Markov model i n Urmia l ake basin, North West of Iran. Markov chain i s adopted to model drought for joint occurrence of different classes of drought severity and sea surface tem...

Drought is a temporary status of water deficit with respect to its long term average condition. Combined Drought Indices (CDIs) are new tools to evaluate general status of drought in a region. In this study, we focus on the integrated monitoring of meteorological droughts (based on temperature and precipitation data) and hydrological droughts (only...

Drought is a complex, multi-dimensional, and recurrent natural hazard that impacts on the Earth hydrological and biological systems. The cause–effect relationship of meteorological and hydrological droughts induced the study to aim at evaluating capability of a copula-based joint meteorological–hydrological drought index (MHDI) in identifying overa...

Late spring frosts (LSFs) play a key role in the evaluation of climate suitability for agricultural and horticultural crop production and are considered to be one of the main components of food security. It is expected that future climate change will affect the occurrence of LSFs and its damages. In order to quantify these changes, this study aims...

Drought indices are statistical tools used for monitoring the departure from normal conditions of water availability. Recently, the multivariate nature of droughts has been addressed through composite indices, capable of including different factors contributing to the occurrence of a drought. However, some issues (like the auto-correlation or the p...

Frost damage, especially in spring, can have profound effects on agricultural and horticultural crops so that in some years, Iranian insurance companies have to pay millions of dollars of cost to the farmers. It seems that the costs tend to change due to changing in frost features under future climate scenarios. Therefore, the purpose of the study...

The monitoring of drought is the most important factor in water resources management. This study focuses on evaluation of the drought characteristics such as intensity, frequency and duration drought using Standardized Precipitation Index (SPI) in different time scales such as: SPI1, SPI3 months, during 1980-2012. The results show that selection of...

Introduction: There have been several indices for agricultural drought monitoring such as Palmer Drought Severity Index (PDSI), Crop Moisture Index (CMI) and Reconnaissance Drought Index (RDI). These indices model the general conditions of soil moisture as a function of climatic parameters such as temperature and rainfall and they are not appropria...

در سال هاي اخير، تغيير رفتار رويدادهاي حدي اقليمي (نظير يخبندان هاي زودرس پاييزه و ديررس بهاره) به علت تغيير اقليم مورد توجه محققان زيادي قرارگرفته است. هدف از اين تحقيق، ارزيابي تغييرات تاريخ شروع و خاتمه يخبندان با استفاده از داده هاي مدل گردش عمومي جو HadCM3 است كه با به كارگيري مدل SDSM تحت دو سناريوي A2 و B2 ريز مقياس شده اند. براي اين منظور،...

Alternatively, to other studies that used parametric distributions (e.g. Gamma) in the estimation of the Standardized Precipitation Index (SPI), this study aims to apply a nonparametric method based on Kernel Density Estimator (KDE) for calculating the SPI. Results of the proposed method were compared with the ones from the most widely used paramet...

Predicting soil erosion change is an important strategy in watershed management. The objective of this research was to evaluate land use change effects on soil erosion in the north of Iran using five land use scenarios. Three land use maps were created for a period of 25 years (1986–2010) to investigate land use transition and to simulate land use...

The late spring frost (LSF), as one of the main climatic disasters, has significant negative impacts on agricultural and horticultural crops production. It is expected that the features of its occurrence will be altered by climate change and global warming. Hence, the present study was performed to quantify these changes under two scenarios of A2 a...

Daily minimum air temperature data are greatly needed in climatic studies of first-fall and last-spring frosts, frost periods, evaluation and improvement of crop production potentials, and eventually their effects upon food security. Despite the fact that climate stations, set up at high elevations play important roles in accurate estimate of tempe...

Climate change is known as the long-term average changes of weather conditions in an area with significant effects on the ecosystem of the region. Climate change is believed to have significant impacts on the water basin and region, such as in a runoff and hydrological system, erosion, environment as well as agriculture. Climate change simulation a...

In this study, we examine the relationship between short- and long-term effects of precipitation deficits, integrated in a drought index called ‘Joint Deficit Index (JDI)’, and tree-ring growth of oak trees (Quercus infectoria) in the Javan-Roud region,Kermanshah province (Iran). Precipitation data from regional climate stations cover the period 19...