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Papers by Farahnaz Taghavi

Research paper thumbnail of The Identification of Climatic Patterns of Iran Based on Spectral Analysis and Clustering of Precipitation and Temperature Extreme Values

Introduction Extreme weather events are rare events from intensity and frequency perspective and ... more Introduction Extreme weather events are rare events from intensity and frequency perspective and at the time of their occurrence, ecosystem and human societies hardly can adapt themselves to occurred changes. Some examples of these events are Heat waves, Cold waves, Floods, Tropical cyclones, Tornadoes, Wildfires and Dust storms. Since extreme weather events occur when precipitation and temperature have extreme values, studying the extreme climatic data is a matter of vital importance. An important issue in the climatological studies is the identification of regions with the same climatic behavior. The results of regionalization based on extreme climatic events can aid decision-makers and planners in dealing with crises aroused from extreme weather events, especially in the development of management policies.

Research paper thumbnail of Determination of the Elastic Thickness of the Crust using GOES and LIDAR images

Research paper thumbnail of Land Surface Temperature Forecasting using spectral observations of MODIS and Modular Neural Networks

Research paper thumbnail of Forecasting and Simulation of Floods in Western Boundary Basin Ilam,Iran

Research paper thumbnail of Lorentz Force Contribution to Thunderstorm's Electrical Characteristics

In this paper, the exerted electric and geomagnetic forces on the electrified hydrometeors in thu... more In this paper, the exerted electric and geomagnetic forces on the electrified hydrometeors in thunderclouds are compared. The parameters of geomagnetic field are acquired from International Geomagnetic Reference Field (IGRF) model. First, the calculations showed that the magnitude of the electric force exerted on a charged hydrometeor dominated the magnitude of the geomagnetic force in troposphere. These results revealed the significance of electric force in the formation of thunderclouds’ charge structure. Moreover, as the electric field increases in thunderstorm conditions, (regarding the dependence of the induction mechanism of cloud electrification to the intensity of the electric field), the increased electric field strengthens the induction mechanism of cloud electrification and influences the electrical properties of thunderstorm. Second, using satellite-based/ground-based data and reports, an inverse relation has been revealed between the total geomagnetic field and the mean...

Research paper thumbnail of Investigation of spatiotemporal behavior of annual precipitation based on EOF and fuzzy EOF: Ghazvin Province area

Introduction: The pattern of annual precipitation in developing areas and the related industries ... more Introduction: The pattern of annual precipitation in developing areas and the related industries is known as one of the most important infrastructure in such studies. This investigation is based on statistical analysis of the frequency of the total annual amount of precipitation using Empirical Orthogonal Function (EOF). The long time statistical studies support the effectiveness of the implemented statistical EOF in the area. Fuzzy logic is a new fold of logical reasoning that is estimated rather than a fixed and exact * ﻂﺑار هﺪﻧرﺎﮕﻧ

Research paper thumbnail of Investigation of multi-scale and unsteady characteristics of deep Foehn events over Alborz Mountains

Research paper thumbnail of Latitudinal and Longitudinal Variations of Earth’s Magnetic Force on Electrified Hydrometeors

Geomagnetism and Aeronomy

In this study, a hypothesis is proposed about the possible effect of Geomagnetic field (GMF) on t... more In this study, a hypothesis is proposed about the possible effect of Geomagnetic field (GMF) on the charge structure of a thundercloud based on Lorentz force equation and Fleming’s right-hand rule. To prove this hypothesis, a simulation using the12th International Geomagnetic Reference Field (IGRF) model has been made. In this simulation, latitudinal and longitudinal variations of Earth’s magnetic force on electrified hydrometeor are considered. With regard to the simulation results, the electrified hydrometeor’ velocity vector is noteworthy to consider GMF effect on charge structure of thundercloud. Furthermore, the influence of GMF on charge separation could clarify the reason of some real thunderstorm observations. Finally, the effect of GMF on charge structure of thunderclouds might be a mechanism for electric field development and lightning initiation.

Research paper thumbnail of Short range precipitation forecasts evaluation of WRF model over IRAN

Research paper thumbnail of The use of Satellite Images to monitor the position of Dust Storm over Persian Gulf region

37Th Cospar Scientific Assembly, 2008

The frequency and intensity of dust storms may likely to change in southwest of Iran near to Pers... more The frequency and intensity of dust storms may likely to change in southwest of Iran near to Persian Gulf region .Dust and sand storms occur when the sub-tropical jet stream pushing up from south of the Arabian peninsula and a polar front jet stream pushing down from the European continent .These events sometimes unrecognized by weather observers and satellite images provide a useful means for detect and monitor of dust storm. In recent years, several complex dust storms occurred (e.g. March 24 2003, April 17 2003, April 17 2007, May 17 2007) which caused huge damage in this region. In this study, the behavior of dust storm was investigated using satellite images. The meteorological observations and numerical models are also going to use to study the dynamics of this phenomenon in order to investigate evolution and mechanism of the meteorological system and its physical effects, such as visibility reduction, heavy winds, red sky, continuous heavy precipitation, and severe lightning. Keywords: Dust storm, Persian Gulf, Satellite Image, Weather models.

Research paper thumbnail of Dust Storm Monitoring Using Satellite Observatory and Numerical Modeling Analysis

In recent years, the frequency of dust pollution events in the Iran Southwest are increased which... more In recent years, the frequency of dust pollution events in the Iran Southwest are increased which caused huge damage and imposed a negative impacts on air quality, airport traffic and people daily life in local areas. Dust storms in this area usually start with the formation of a low-pressure center over the Arabian Peninsula. The main objectives of this study is to asses and monitor the movement of aerosols and pollutions from origin source to local areas using satellite imagery and numerical modeling analysis. Observational analyses from NCEP such as synoptic data (Uwind,Vwind,Vorticity and Divergence Fields), upper air radiosonde, measured visibility distributions, land cover data are also used in model comparisons to show differences in occurrence of dust events. The evolution and dynamics of this phenomena are studied on the based a method to modify the initial state of NWP output using discrepancies between dynamic fields and WV imagery in a grid. Results show that satellite images offers a means to control the behavior of numeric models and also the model using land cover data improving the wind-blown dust modeling.

Research paper thumbnail of Application of wavelet analysis to investigate precipitation variability in western regions of Iran

Research paper thumbnail of Enhancement of Southwest Asia dust using spectral properties of MODIS

Research paper thumbnail of Hybrid model for weather forecasting using ensemble of neural networks and mutual information

2014 IEEE Geoscience and Remote Sensing Symposium, 2014

The chaotic and dynamic nature of weather makes weather forecasting a challenging and controversi... more The chaotic and dynamic nature of weather makes weather forecasting a challenging and controversial task. Various numerical models have been developed and applied for this purpose, however usually they do not provide accurate predictions. Although artificial neural networks have been considerably applied for weather forecasting, they are not able to provide precise results. Consequently some researchers proposed to use ensemble models of neural networks for the prediction task. When considering multiple neural networks, the redundancy caused by having multiple models and also combining the results of different networks are still the main challenges. In this paper we propose a new hybridmodel for weather forecasting, which is based on an ensemble of neural networks. We address the redundancy issue by introducing a modular model in which a feature selection module is first applied to the data. We also, introduce a mutual information approach to tackle the challenge of combining the results of different networks and reducing the redundancy in the hybrid model. The evaluation results presented at the end of paper shows an outperformance of the proposed method compared to the similar methods in the literature.

Research paper thumbnail of Evaluation of spatial and spatiotemporal estimation methods in simulation of precipitation variability patterns

Theoretical and Applied …, 2012

Identification of spatial and spatiotemporal precipitation variations plays an important role in ... more Identification of spatial and spatiotemporal precipitation variations plays an important role in different hydrological applications such as missing data estimation. In this paper, the results of Bayesian maximum entropy (BME) and ordinary kriging (OK) are compared for modeling spatial and spatiotemporal variations of annual precipitation with and without incorporating elevation variations. The study area of this research is Namak Lake watershed located in the central part of Iran with an area of approximately 90,000 km 2. The BME and OK methods have been used to model the spatial and spatiotemporal variations of precipitation in this watershed, and their performances have been evaluated using cross-validation statistics. The results of the case study have shown the superiority of BME over OK in both spatial and spatiotemporal modes. The results have shown that BME estimates are less biased and more accurate than OK. The improvements in the BME estimates are mostly related to incorporating hard and soft data in the estimation process, which resulted in more detailed and reliable results. Estimation error variance for BME results is less than OK estimations in the study area in both spatial and spatiotemporal modes.

Research paper thumbnail of Dust Storm Monitoring Using Satellite Observatory and Numerical Modeling Analysis

In recent years, the frequency of dust pollution events in the Iran Southwest are increased which... more In recent years, the frequency of dust pollution events in the Iran Southwest are increased which caused huge damage and imposed a negative impacts on air quality, airport traffic and people daily life in local areas. Dust storms in this area usually start with the formation of a low-pressure center over the Arabian Peninsula. The main objectives of this study is to asses and monitor the movement of aerosols and pollutions from origin source to local areas using satellite imagery and numerical modeling analysis. Observational analyses from NCEP such as synoptic data (Uwind,Vwind,Vorticity and Divergence Fields), upper air radiosonde, measured visibility distributions, land cover data are also used in model comparisons to show differences in occurrence of dust events. The evolution and dynamics of this phenomena are studied on the based a method to modify the initial state of NWP output using discrepancies between dynamic fields and WV imagery in a grid. Results show that satellite i...

Research paper thumbnail of Dust Storm Monitoring Using Satellite Observatory and Numerical Modeling Analysis

In recent years, the frequency of dust pollution events in the Iran Southwest are increased which... more In recent years, the frequency of dust pollution events in the Iran Southwest are increased which caused huge damage and imposed a negative impacts on air quality, airport traffic and people daily life in local areas. Dust storms in this area usually start with the formation of a low-pressure center over the Arabian Peninsula. The main objectives of this study is to asses and monitor the movement of aerosols and pollutions from origin source to local areas using satellite imagery and numerical modeling analysis. Observational analyses from NCEP such as synoptic data (Uwind,Vwind,Vorticity and Divergence Fields), upper air radiosonde, measured visibility distributions, land cover data are also used in model comparisons to show differences in occurrence of dust events. The evolution and dynamics of this phenomena are studied on the based a method to modify the initial state of NWP output using discrepancies between dynamic fields and WV imagery in a grid. Results show that satellite i...

Research paper thumbnail of The Identification of Climatic Patterns of Iran Based on Spectral Analysis and Clustering of Precipitation and Temperature Extreme Values

Introduction Extreme weather events are rare events from intensity and frequency perspective and ... more Introduction Extreme weather events are rare events from intensity and frequency perspective and at the time of their occurrence, ecosystem and human societies hardly can adapt themselves to occurred changes. Some examples of these events are Heat waves, Cold waves, Floods, Tropical cyclones, Tornadoes, Wildfires and Dust storms. Since extreme weather events occur when precipitation and temperature have extreme values, studying the extreme climatic data is a matter of vital importance. An important issue in the climatological studies is the identification of regions with the same climatic behavior. The results of regionalization based on extreme climatic events can aid decision-makers and planners in dealing with crises aroused from extreme weather events, especially in the development of management policies.

Research paper thumbnail of Determination of the Elastic Thickness of the Crust using GOES and LIDAR images

Research paper thumbnail of Land Surface Temperature Forecasting using spectral observations of MODIS and Modular Neural Networks

Research paper thumbnail of Forecasting and Simulation of Floods in Western Boundary Basin Ilam,Iran

Research paper thumbnail of Lorentz Force Contribution to Thunderstorm's Electrical Characteristics

In this paper, the exerted electric and geomagnetic forces on the electrified hydrometeors in thu... more In this paper, the exerted electric and geomagnetic forces on the electrified hydrometeors in thunderclouds are compared. The parameters of geomagnetic field are acquired from International Geomagnetic Reference Field (IGRF) model. First, the calculations showed that the magnitude of the electric force exerted on a charged hydrometeor dominated the magnitude of the geomagnetic force in troposphere. These results revealed the significance of electric force in the formation of thunderclouds’ charge structure. Moreover, as the electric field increases in thunderstorm conditions, (regarding the dependence of the induction mechanism of cloud electrification to the intensity of the electric field), the increased electric field strengthens the induction mechanism of cloud electrification and influences the electrical properties of thunderstorm. Second, using satellite-based/ground-based data and reports, an inverse relation has been revealed between the total geomagnetic field and the mean...

Research paper thumbnail of Investigation of spatiotemporal behavior of annual precipitation based on EOF and fuzzy EOF: Ghazvin Province area

Introduction: The pattern of annual precipitation in developing areas and the related industries ... more Introduction: The pattern of annual precipitation in developing areas and the related industries is known as one of the most important infrastructure in such studies. This investigation is based on statistical analysis of the frequency of the total annual amount of precipitation using Empirical Orthogonal Function (EOF). The long time statistical studies support the effectiveness of the implemented statistical EOF in the area. Fuzzy logic is a new fold of logical reasoning that is estimated rather than a fixed and exact * ﻂﺑار هﺪﻧرﺎﮕﻧ

Research paper thumbnail of Investigation of multi-scale and unsteady characteristics of deep Foehn events over Alborz Mountains

Research paper thumbnail of Latitudinal and Longitudinal Variations of Earth’s Magnetic Force on Electrified Hydrometeors

Geomagnetism and Aeronomy

In this study, a hypothesis is proposed about the possible effect of Geomagnetic field (GMF) on t... more In this study, a hypothesis is proposed about the possible effect of Geomagnetic field (GMF) on the charge structure of a thundercloud based on Lorentz force equation and Fleming’s right-hand rule. To prove this hypothesis, a simulation using the12th International Geomagnetic Reference Field (IGRF) model has been made. In this simulation, latitudinal and longitudinal variations of Earth’s magnetic force on electrified hydrometeor are considered. With regard to the simulation results, the electrified hydrometeor’ velocity vector is noteworthy to consider GMF effect on charge structure of thundercloud. Furthermore, the influence of GMF on charge separation could clarify the reason of some real thunderstorm observations. Finally, the effect of GMF on charge structure of thunderclouds might be a mechanism for electric field development and lightning initiation.

Research paper thumbnail of Short range precipitation forecasts evaluation of WRF model over IRAN

Research paper thumbnail of The use of Satellite Images to monitor the position of Dust Storm over Persian Gulf region

37Th Cospar Scientific Assembly, 2008

The frequency and intensity of dust storms may likely to change in southwest of Iran near to Pers... more The frequency and intensity of dust storms may likely to change in southwest of Iran near to Persian Gulf region .Dust and sand storms occur when the sub-tropical jet stream pushing up from south of the Arabian peninsula and a polar front jet stream pushing down from the European continent .These events sometimes unrecognized by weather observers and satellite images provide a useful means for detect and monitor of dust storm. In recent years, several complex dust storms occurred (e.g. March 24 2003, April 17 2003, April 17 2007, May 17 2007) which caused huge damage in this region. In this study, the behavior of dust storm was investigated using satellite images. The meteorological observations and numerical models are also going to use to study the dynamics of this phenomenon in order to investigate evolution and mechanism of the meteorological system and its physical effects, such as visibility reduction, heavy winds, red sky, continuous heavy precipitation, and severe lightning. Keywords: Dust storm, Persian Gulf, Satellite Image, Weather models.

Research paper thumbnail of Dust Storm Monitoring Using Satellite Observatory and Numerical Modeling Analysis

In recent years, the frequency of dust pollution events in the Iran Southwest are increased which... more In recent years, the frequency of dust pollution events in the Iran Southwest are increased which caused huge damage and imposed a negative impacts on air quality, airport traffic and people daily life in local areas. Dust storms in this area usually start with the formation of a low-pressure center over the Arabian Peninsula. The main objectives of this study is to asses and monitor the movement of aerosols and pollutions from origin source to local areas using satellite imagery and numerical modeling analysis. Observational analyses from NCEP such as synoptic data (Uwind,Vwind,Vorticity and Divergence Fields), upper air radiosonde, measured visibility distributions, land cover data are also used in model comparisons to show differences in occurrence of dust events. The evolution and dynamics of this phenomena are studied on the based a method to modify the initial state of NWP output using discrepancies between dynamic fields and WV imagery in a grid. Results show that satellite images offers a means to control the behavior of numeric models and also the model using land cover data improving the wind-blown dust modeling.

Research paper thumbnail of Application of wavelet analysis to investigate precipitation variability in western regions of Iran

Research paper thumbnail of Enhancement of Southwest Asia dust using spectral properties of MODIS

Research paper thumbnail of Hybrid model for weather forecasting using ensemble of neural networks and mutual information

2014 IEEE Geoscience and Remote Sensing Symposium, 2014

The chaotic and dynamic nature of weather makes weather forecasting a challenging and controversi... more The chaotic and dynamic nature of weather makes weather forecasting a challenging and controversial task. Various numerical models have been developed and applied for this purpose, however usually they do not provide accurate predictions. Although artificial neural networks have been considerably applied for weather forecasting, they are not able to provide precise results. Consequently some researchers proposed to use ensemble models of neural networks for the prediction task. When considering multiple neural networks, the redundancy caused by having multiple models and also combining the results of different networks are still the main challenges. In this paper we propose a new hybridmodel for weather forecasting, which is based on an ensemble of neural networks. We address the redundancy issue by introducing a modular model in which a feature selection module is first applied to the data. We also, introduce a mutual information approach to tackle the challenge of combining the results of different networks and reducing the redundancy in the hybrid model. The evaluation results presented at the end of paper shows an outperformance of the proposed method compared to the similar methods in the literature.

Research paper thumbnail of Evaluation of spatial and spatiotemporal estimation methods in simulation of precipitation variability patterns

Theoretical and Applied …, 2012

Identification of spatial and spatiotemporal precipitation variations plays an important role in ... more Identification of spatial and spatiotemporal precipitation variations plays an important role in different hydrological applications such as missing data estimation. In this paper, the results of Bayesian maximum entropy (BME) and ordinary kriging (OK) are compared for modeling spatial and spatiotemporal variations of annual precipitation with and without incorporating elevation variations. The study area of this research is Namak Lake watershed located in the central part of Iran with an area of approximately 90,000 km 2. The BME and OK methods have been used to model the spatial and spatiotemporal variations of precipitation in this watershed, and their performances have been evaluated using cross-validation statistics. The results of the case study have shown the superiority of BME over OK in both spatial and spatiotemporal modes. The results have shown that BME estimates are less biased and more accurate than OK. The improvements in the BME estimates are mostly related to incorporating hard and soft data in the estimation process, which resulted in more detailed and reliable results. Estimation error variance for BME results is less than OK estimations in the study area in both spatial and spatiotemporal modes.

Research paper thumbnail of Dust Storm Monitoring Using Satellite Observatory and Numerical Modeling Analysis

In recent years, the frequency of dust pollution events in the Iran Southwest are increased which... more In recent years, the frequency of dust pollution events in the Iran Southwest are increased which caused huge damage and imposed a negative impacts on air quality, airport traffic and people daily life in local areas. Dust storms in this area usually start with the formation of a low-pressure center over the Arabian Peninsula. The main objectives of this study is to asses and monitor the movement of aerosols and pollutions from origin source to local areas using satellite imagery and numerical modeling analysis. Observational analyses from NCEP such as synoptic data (Uwind,Vwind,Vorticity and Divergence Fields), upper air radiosonde, measured visibility distributions, land cover data are also used in model comparisons to show differences in occurrence of dust events. The evolution and dynamics of this phenomena are studied on the based a method to modify the initial state of NWP output using discrepancies between dynamic fields and WV imagery in a grid. Results show that satellite i...

Research paper thumbnail of Dust Storm Monitoring Using Satellite Observatory and Numerical Modeling Analysis

In recent years, the frequency of dust pollution events in the Iran Southwest are increased which... more In recent years, the frequency of dust pollution events in the Iran Southwest are increased which caused huge damage and imposed a negative impacts on air quality, airport traffic and people daily life in local areas. Dust storms in this area usually start with the formation of a low-pressure center over the Arabian Peninsula. The main objectives of this study is to asses and monitor the movement of aerosols and pollutions from origin source to local areas using satellite imagery and numerical modeling analysis. Observational analyses from NCEP such as synoptic data (Uwind,Vwind,Vorticity and Divergence Fields), upper air radiosonde, measured visibility distributions, land cover data are also used in model comparisons to show differences in occurrence of dust events. The evolution and dynamics of this phenomena are studied on the based a method to modify the initial state of NWP output using discrepancies between dynamic fields and WV imagery in a grid. Results show that satellite i...