Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

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Now showing 1 - 6 of 6
  • Article
    Citation - WoS: 7
    Citation - Scopus: 9
    A Holistic Overview of the Applications of Grace-Observed Terrestrial Water Storage in Hydrology and Climate Science
    (Springer, 2025) Khorrami, Behnam; Gunduz, Orhan
    Terrestrial Water Storage (TWS) represents a vital element of the hydrological cycle, with its fluctuations significantly impacting the climate of the Earth and its ecological balance. Since its launch in 2002, the Gravity Recovery and Climate Experiment (GRACE) satellite mission has revolutionized the ability to observe and analyze large-scale mass changes within Earth's system components. This paper offers a comprehensive and current overview of GRACE satellite gravimetry, highlighting its relevance to hydrological and climate-related studies. It outlines the fundamental measurement principles of the GRACE mission, provides an in-depth explanation of GRACE data products (including spherical harmonic and mascon solutions), examines emerging trends in GRACE-based research, and reviews key applications in hydrology and climate science. Additionally, it addresses the major challenges in utilizing GRACE data and explores promising avenues for future research and applications.
  • Article
    Citation - WoS: 8
    Citation - Scopus: 9
    Comprehensive Comparison of Different Gridded Precipitation Products Over Geographic Regions of Türkiye
    (Spie-soc Photo-optical instrumentation Engineers, 2024) Khorrami, Behnam; Sahin, Onur Gungor; Gunduz, Orhan
    The traditionally used rain gauge stations provide the most reliable data on the spatiotemporal distribution of precipitation; however, they are limited in space and time. As an alternative to field observations, the gridded precipitation products (GPPs) offered by remote sensing missions are widely used. On account of the uncertainties associated with the GPPs, they have to be quality-checked for confidence in application over the region of interest. Although accuracy assessment of precipitation data is a common task, there is a gap in the literature regarding a comprehensive assessment of the currently available GPPs. In this study, 14 GPPs were used to investigate their performance in catching the spatio-temporal characteristics of precipitation over geographic regions of T & uuml;rkiye. According to the results, integrated multi-satellite retrievals for Global Precipitation Measurement (IMERG), multi-source weighted-ensemble precipitation (MSWEP), and Tropical Rainfall Measuring Mission (TRMM) show better performance on monthly and annual scales while on the climatology scale, CHELSA, Climate Hazards Group Infrared Precipitation with Station, ERA5, and ERA5-Land also manifest better performance. The mean monthly correlation over Aegean Region (AEG), Marmara Region (MAR), Central Anatolian Region (CAR), Mediterranean Region (MED), Black Sea Region (BSR), East Anatolian Region (EAR), and South East Anatolian Region (SEA) are 0.77, 0.81, 0.77, 0.80, 0.79, 0.77, and 0.77, respectively. The annual assessment suggests that over the MAR, CAR, MED, and SEA, the IMERG mission performs very well. While TRMM showcases its best performance in the AEG, MED, BSR, and EAR, MSWEP performs well in the BSR and SEA Region. Overall, taking the country-average results into account, it can be stated that among the used GPPs, TRMM, MSWEP, and IMERG yield the best results for T & uuml;rkiye as a whole.
  • Article
    Citation - WoS: 36
    Citation - Scopus: 40
    Statistical Downscaling of Grace Twsa Estimates To a 1-Km Spatial Resolution for a Local-Scale Surveillance of Flooding Potential
    (Elsevier, 2023) Khorrami, Behnam; Pirasteh, Saied; Ali, Shoaib; Şahin, Onur Güngör; Vaheddoost, Babak
    The Gravity Recovery and Climate Experiment (GRACE) paved the way for large-scale monitoring of the hydrological extremes. However, local scale analysis is aslo challenging due to the coarse resolution of the GRACE estimates. The feasibility of the downscaled GRACE data for the flood monitoring in the Kizilirmak Basin (KB) in Turkiye is investigated in this study by integrating the GRACE and hydrological model outputs of a random forest approach. Results suggest that the TWSA, over the Asagi Kizilirmak Basin (AKB), is ascending with an annual rate of + 3.51mm/yr; while the Orta Kizilirmak Basin (OKB), Yukari Kizilirmak Basin (YKB), Delice Basin (DB), Develi Kapali Basin (DKB), and Seyfe Kapali Basin (SKB) showed descending trend respectively as -1.15mm/yr, -1.58mm/yr, -1.14mm/yr, -2.34mm/yr, and -1.31mm/yr. The hydrological status of the basin showed that in 2003, 2005, 2010-2013, and 2015-2016 periods the study area was prone to the inundation. Hence, by validating the Flood Potential Index (FPI) rates acquired from the downscaled GRACE data, it was shown that the best correlation coefficient (0.73) between FPI and streamflow (Q) is associated with the SKB. It is also concluded that the downscaled TWSA associated with the fine-resolution models depicts acceptable accuracy in determination of the flood potential at local scales.
  • Article
    Citation - WoS: 21
    Citation - Scopus: 21
    Remote Sensing-Based Monitoring and Evaluation of the Basin-Wise Dynamics of Terrestrial Water and Groundwater Storage Fluctuations
    (Springer, 2023) Khorrami, Behnam; Gündüz, Orhan
    The recent dynamics of terrestrial water storage (TWS) and groundwater storage (GWS) fluctuations were investigated based on the Gravity Recovery And Climate Experiment (GRACE) observations over 25 basins of Türkiye. Coarse-resolution GRACE estimates were downscaled based on the Random Forest algorithm. The impacts of precipitation (P) and evapotranspiration (ET) on the variations of water storage were also assessed. The findings demonstrated good performance for the RF model in simulating finer resolution estimates of TWS. The results indicated a diminishing trend of TWS and its hydrologic components over all the basins from 2003 to 2020. The Doğu Akdeniz Basin with the annually decreasing TWS and GWS of 1.15cm/yr and 1.10cm/yr was the most critical basin of Türkiye. The least storage loss was observed in the Batı Karadeniz Basin with the annual TWS and GWS loss of 0.38cm/yr and 0.45cm/yr , respectively. Based on the results, Türkiye has lost, on average, an estimated 5.16km3/yr and 4.09km3/yr of its TWS and GWS, respectively, which are equivalent to the total storage loss of 92.88km3 and 73.62km3 of TWS and GWS during the last 18 years. The results also indicated that P and ET interact differently with the variations of TWS and GWS. The net water flux was revealed to be partially correlated with the total water storage fluctuations, suggesting the governing role of other deriving forces particularly the anthropogenic factors in the spatiotemporal variations of Türkiye’s water storage; therefore, a sector-specific analysis of the water storage variations is crucial for the country, particularly by concentrating more on the dynamics of GWS. Graphical Abstract: [Figure not available: see fulltext.]. © 2023, The Author(s), under exclusive licence to Springer Nature Switzerland AG.
  • Article
    Citation - WoS: 40
    Citation - Scopus: 38
    Investigating the Local-Scale Fluctuations of Groundwater Storage by Using Downscaled Grace/Grace-fo Jpl Mascon Product Based on Machine Learning (ml) Algorithm
    (Springer, 2023) Khorrami, Behnam; Ali, Shoaib; Gündüz, Orhan
    Groundwater storage is of grave significance for humanity by sustaining the required water for agricultural irrigation, industry, and domestic use. Notwithstanding the impressive contribution of the state-of-the-art Gravity Recovery and Climate Experiment (GRACE) to detecting the groundwater storage anomaly (GWSA), its feasibility for the characterization of GWSA variation hotspots over small scales is still a major challenge due to its coarse resolution. In this study, a spatial water balance approach is proposed to enhance the spatial depiction of groundwater storage and depletion changes that can detect the hotspots of GWSA variation. In this study, Random Forest Machine Learning (RFML) model was utilized to simulate fine-resolution (10 km) groundwater storage based on the coarse resolution (50 km) of GRACE observations. To this end, parameters including soil moisture, snow water, evapotranspiration, precipitation, surface runoff, surface elevation, and GRACE data were integrated into the RFML model. The results show that with a correlation of above 0.98, the RFML model is very successful in simulating the fine-resolution groundwater storage over the Western Anatolian Basin (WAB), Turkiye. The results indicate an estimated annual depletion rate of 0.14 km(3)/year for the groundwater storage of the WAB, which is equivalent to about 2.57 km(3) of total groundwater depletion from 2003 to 2020. The findings also suggest that the downscaled GWSA is in harmony with the original GWSA in terms of temporal variations. The validation of the results demonstrates that the correlation is increased from 0.56 (for the GRACE-derived GWSA) to 0.60 (for the downscaled GWSA) over the WAB.
  • Article
    Citation - WoS: 44
    Citation - Scopus: 45
    An Enhanced Water Storage Deficit Index (ewsdi) for Drought Detection Using Grace Gravity Estimates
    (Elsevier, 2021) Khorrami, Behnam; Gündüz, Orhan
    Accurate detection and monitoring of drought events are important particularly in arid and semi-arid regions of the world. Gravity Recovery and Climate Experiment (GRACE) gravity estimates have been used widely for this purpose and a number of indices have been developed using the GRACE Terrestrial Water Storage Anomalies (TWSA) values. In the current study, a new approach is proposed to enhance the performance of the GRACE-based Water Storage Deficit Index (WSDI). The proposed Enhanced Water Storage Deficit Index (EWSDI) was developed based on the grid-based standardization of the Water Storage Deficit (WSD) values. The decomposed time series of the TWSA were computed in an attempt to evaluate the performance of the approach based on different components of the TWSA time series. Standardized Precipitation Index (SPI) and modelled Soil Moisture Storage (SMS) were also used to validate the functionality of this new GRACE-derived index. The applicability of the EWSDI index was tested in the semi-arid climatic conditions of Turkey and the results showed that the detrended EWSDI better correlated with SPI-09 and annual SPI with correlation coefficient values of 0.70 and 0.76, respectively. The findings also suggested an approximate enhancement of 13% over the existing WSDI when applied on the detrended TWSA. The findings of this study reveal that the proposed approach is effective in improving the performance of the existing WSDI to detect drought events in terms of monthly and annual correlation coefficients achieved. © 2021 Elsevier B.V.