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Öğe Downscaling of the Land Surface Temperature Data Obtained at four Different Dates in a Year Using the GWR Model: A Case Study in Antakya, Turkey(Springer, 2023) Irvem, Ahmet; Ozbuldu, MustafaLand surface temperature (LST) is a major factor that affects many biophysical processes in the land-atmosphere relationship. This factor is obtained from satellite images having different temporal and spatial resolutions. This study applied the geographically weighted regression (GWR) model for four different dates representing each season a year to improve the LST images obtained in coarse resolution. In this study, MODIS LST images that are available having fine temporal but coarse spatial resolution were modeled using NDBI and NDVI indices, and their spatial resolution is improved. In addition, LANDSAT 8 images were used as reference images to evaluate the accuracy of the images obtained from the models. Results of the GWR model have been evaluated by comparing it statistically with TsHARP and DisTradother commonly used methods. As a result of the comparison by using the average of four dates outputs, the GWR model (R-2 = 0.73, RMSE = 0.78) was more successful than the TsHARP (R-2 = 0.56, RMSE = 1.00) and DisTrad (R-2 = 0.49, RMSE = 1.09) methods. The most successful downscaling performance in the GWR model was obtained in the spring season (RSR = 0.48). According to these findings, the GWR model can be used for downscaling LST images in urban areas. However, before applying this algorithm to scenarios outside of urban areas, it is recommended to use the required parameters and optimize their combinations.Öğe Evaluation of flood simulation for zeyzoun dam-break in Syria using hec-ras model(Parlar Scientific Publications, 2020) Irvem, Ahmet; Ozbuldu, MustafaDams are the storage structure constructed across the river to store water in the upstream and release it to downstream as and when the demand arises. It is necessary to carry out dam-break analysis to study the behavior of the flood wave generated from the dam-break. It is necessary to prepare the inundation maps as a part of the emergency action plan to evacuate the population during the flood event. In this study, a simulation of the flood event that resulted in the Zeyzoun dam-break in Syria has been conducted using the HEC-RAS software. The simulation results were evaluated by considering flood risk areas, flood lag time, which is an important information for early warnings, and performance of the HEC-RAS model. Simulations were performed using different inlet hydrograph values until accurate results obtained, based on observed streamflow data. When, 286 m3/s inlet flow-rate is used as an input, a relatively better simulation outflow 109 m3/s is obtained in comparison with an observed flow of 143 m3/s. Flood lag time, which is an important information for early warnings, was found to be 50 hours. These observations from the simulation model gave relatively correct results. Also, this study indicates that flood simulation and peak discharge forecasting can be easily performed using the HEC-RAS model. © 2020 Parlar Scientific Publications. All rights reserved.Öğe EVALUATION OF FLOOD SIMULATION FOR ZEYZOUN DAM-BREAK IN SYRIA USING HEC-RAS MODEL(Parlar Scientific Publications (P S P), 2020) Irvem, Ahmet; Ozbuldu, MustafaDams are the storage structure constructed across the river to store water in the upstream and release it to downstream as and when the demand arises. It is necessary to carry out dam-break analysis to study the behavior of the flood wave generated from the dam-break. It is necessary to prepare the inundation maps as a part of the emergency action plan to evacuate the population during the flood event. In this study, a simulation of the flood event that resulted in the Zeyzoun dam-break in Syria has been conducted using the HEC-RAS software. The simulation results were evaluated by considering flood risk areas, flood lag time, which is an important information for early warnings, and performance of the HEC-RAS model. Simulations were performed using different inlet hydrograph values until accurate results obtained, based on observed streamflow data. When, 286 m(3)/s inlet flow-rate is used as an input, a relatively better simulation outflow 109 m(3)/s is obtained in comparison with an observed flow of 143 m(3)/s. Flood lag time, which is an important information for early warnings, was found to be 50 hours. These observations from the simulation model gave relatively correct results. Also, this study indicates that flood simulation and peak discharge forecasting can be easily performed using the HEC-RAS model.Öğe Evaluation of Satellite and Reanalysis Precipitation Products Using GIS for All Basins in Turkey(Hindawi Ltd, 2019) Irvem, Ahmet; Ozbuldu, MustafaUse of the satellite and reanalysis precipitation products, as supplementary data sources, are steadily rising for hydrometeorological applications, especially in data-sparse areas. However, the accuracy of these data sets is often lacking, especially in Turkey. This study evaluates the accuracy of satellite precipitation product (TRMM 3B42V7) and reanalysis precipitation product (NCEP-CFSR) against rain gauge observations for the 1998-2010 periods. Average annual precipitation for the 25 basins in Turkey was calculated using rain gauge precipitation data from 225 stations. The inverse distance weighting (IDW) method was used to calculate areal precipitation for each basin using GIS. According to the results of statistical analysis, the coefficient of determination for the TRMM product gave satisfactory results (R-2 > 0.88). However,R(2)for the CFSR data set ranges from 0.35 for the Eastern Black Sea basin to 0.93 for the West Mediterranean basin. RMSE was calculated to be 95.679 mm and 128.097 mm for the TRMM and CFSR data, respectively. The NSE results of TRMM data showed very good performance for 6 basins, while the PBias value showed very good performance for 7 basins. The NSE results of CFSR data showed very good performance for 3 basins, while the PBias value showed very good performance for 6 basins.Öğe Evaluation of the performance of CFSR reanalysis data set for estimating reference evapotranspiration (ET0) in Turkey(Firenze Univ Press, 2022) Irvem, Ahmet; Ozbuldu, MustafaEvapotranspiration is a key process and a necessary parameter for hydrological, meteorological, and agricultural studies. However, the calculation of actual evapotranspiration is very challenging and costly. Therefore, reference evapotranspiration (ET0) calculated using meteorological data is generally preferred over actual evapotranspiration. However, it is challenging to get complete and accurate data from meteorology stations in rural and mountainous regions. This study examined the suitability of the Climate Forecast System Reanalysis (CFSR) reanalysis data set as an alternative to meteorological observation stations to compute seasonal reference evapotranspiration for seven different climatic regions of Turkey. The ET0 calculations using the CFSR reanalysis dataset for 1987-2017 were compared to data at 259 weather stations observed in Turkey. As a result of statistical evaluations, it has been determined that the most successful predicted season is winter (C' = 0.64-0.89, SPAEF= 0.63-0.81). The most successful estimations for this season were obtained from coastal areas with low elevations. The weakest estimations were obtained for the summer season (C' = 0.52-0.85, SPAEF= 0.59-0.77). These results show that the ET0 estimation ability of the CFSR reanalysis dataset is satisfactory for the study area. In addition, it has been observed that CFSR tends to overestimate the observation data, especially in the southern and western regions. These findings indicate that the results of the ET0 calculation using the CFSR reanalysis data set are relatively successful for the study area. However, the data should be evaluated with observation data before being used, especially in the summer models.
