Mohammad J. Tourian

Mohammad J. Tourian
Universität Stuttgart · Institute of Geodesy

Dr.-Ing.

About

72
Publications
38,708
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1,258
Citations
Introduction
Mohammad J. Tourian currently works at the Institute of Geodesy, Universität Stuttgart. Mohammad does research in Geodesy and Surveying.

Publications

Publications (72)
Article
Full-text available
The proposed Surface Water and Ocean Topography (SWOT) mission aims to improve spaceborne estimates of river discharge through its measurements of water surface elevation, river width and slope. SWOT, however, will not observe baseflow depth, which limits its value in estimating river discharge especially for those rivers with heterogeneous channel...
Article
Limitations of satellite radar altimetry for operational hydrology include its spatial and temporal sampling as well as measurement problems caused by local topography and heterogeneity of the reflecting surface. In this study, we develop an approach that eliminates most of these limitations to produce an approximately 3-day-temporal resolution wat...
Article
GRACE observations of the time-dependent gravity field provide a direct measurement of the monthly state of mass and thus monthly total water storage in a catchment. This for the first time allows for a direct comparison of monthly runoff and water storage. Investigations of global scale Runoff-Storage (R-S) relationships for different climatic con...
Article
Study area Iran. Study focus Iran, once a pioneer of sustainable water management, is currently facing water bankruptcy. Aggressive exhaustion of non-renewable water has led to a suite of environmental and socio-economic problems across the country. Nevertheless, the understanding of Iran’s water loss is still incomplete due to a lack of conclusiv...
Article
Against the backdrop of global change, in terms of both climate and demography, there is a pressing need for monitoring of the global water cycle. The publicly available global database is very limited in its spatial and temporal coverage worldwide. Moreover, the acquisition of in situ data and their delivery to the database have been in decline si...
Article
Full-text available
The Congo River Basin (CRB) is the second largest river system in the world, but its hydroclimatic characteristics remain relatively poorly known. Here, we jointly analyze a large record of in situ and satellite-derived observations, including long-term time series of Surface Water Height (SWH) from radar altimetry (a total of 2,311 virtual station...
Preprint
Full-text available
ECMWF Reanalysis (ERA), one of the most widely used precipitation products evolved over time from ERA-40 to ERA-20CM, ERA-20C, ERA-Interim, and ERA5. Studies evaluating the performance of individual ERA products cannot adequately assess the evolution in the products. We compared the performance of all ERA precipitation products using daily, monthly...
Preprint
Full-text available
ECMWF Reanalysis (ERA), one of the most widely used precipitation products evolved over time from ERA-40 to ERA-20CM, ERA-20C, ERA-Interim, and ERA5. Studies evaluating the performance of individual ERA products cannot adequately assess the evolution in the products. We compared the performance of all ERA precipitation products using daily, monthly...
Preprint
Full-text available
The Congo Basin is of global significance for biodiversity and the water and carbon cycles. However, its freshwater availability remains highly unknown. Here, we leverage a new method to characterize the relationship between drainable water storage and river discharge across the entire basin. We estimate that the Congo Basin currently holds 481 ± 2...
Article
Full-text available
The number of active gauges with open‐data policy for discharge monitoring along rivers has decreased over the last decades. Therefore, spaceborne measurements are investigated as alternatives. Among different techniques for estimating river discharge from space, developing a rating curve between the ground‐based discharge and spaceborne river wate...
Article
More than 600 million people (about 10% of the world’s population) live in coastal areas that are less than 10 m above sea level. Despite the urgent need to monitor coastal waters, in-situ measuring stations including wave buoys around the world do not provide sufficient insight into coastal water level variations, and in particular, they cannot pr...
Conference Paper
Full-text available
This report summarises the main results, conclusions and recommendations of the “HYDROSPACE-GEOGLOWS 2021” Workshop organised by the European Space Agency (ESA), in collaboration with the French Space Agency (CNES) and the GEO Global Water Sustainability Initiative (GEOGloWS) (Fig. 1). This Workshop is a sequel to the ones held in Toulouse (F) in 2...
Preprint
Full-text available
ECMWF Reanalysis (ERA), one of the most widely used precipitation products, has evolved over time from ERA-40 to ERA-20CM, ERA-20C, ERA-Interim, and ERA5. Studies evaluating the performance of individual ERA precipitation products cannot adequately assess the evolution in the products. Therefore, we compared the performance of five successive ERA p...
Article
Global gridded precipitation datasets have been developed using rain gauges, satellite observations, and data assimilation techniques to fulfill the need in regions with a limited contribution of ground observations like Iran. This study presents a comprehensive evaluation of currently available precipitation datasets over Iran at monthly (44 datas...
Article
Full-text available
Northeast Brazil is one of the most populated semiarid regions in the world. The region is highly dependent on reservoirs for human water supply, irrigation, industry, and livestock. The objective of this study was to validate water level time series from the satellites Envisat, SARAL, Sentinel-3A/-3B, Jason-2/-3 in small reservoirs in Northeast Br...
Preprint
Full-text available
Against the backdrop of global change, both in terms of climate and demography, there is a pressing need for monitoring the global water cycle. The publicly available global database is very limited in its spatial and temporal coverage worldwide. Moreover, the acquisition of in situ data and their delivery to the database are in decline since the l...
Preprint
Full-text available
The Congo River Basin (CRB) is the second largest river system in the world, but its hydroclimatic characteristics remain relatively poorly known. Here, we jointly analyze a large record of in situ and satellite-derived observations, including long term time series of Surface Water Height (SWH) from radar altimetry (a total of 2,311 virtual station...
Article
Full-text available
The Zayandeh-Rud River Basin in the central plateau of Iran continues to grapple with water shortages due to a water-intensive development path made possible by a primarily supply-oriented water management approach to battle the water limits to growth. Despite inter-basin water transfers and increasing groundwater supply, recurring water shortages...
Article
Satellite altimetry is increasingly considered as a valuable source of information in many hydrological and hydraulic applications. However, the accuracy of different sensors adopted for monitoring the water level from satellite and the limited temporal resolution that characterizes each sensor (i.e. revisit time most of time varying from 10 to 35...
Article
Lake Urmia, located in the North West of Iran, was once the most extensive permanent hypersaline lake in the world. Unsustainable water management in response to increasing demand together with climatic extremes have given rise to the lake's depletion during the last two decades. The Urmia Lake Restoration Program (ULRP) was established in 2013 and...
Article
Full-text available
The Zayanderud Basin is an important agricultural area in central Iran. In the Basin, irrigation consumes more than 90 percent of the water used, which threatens both the downstream historical city of Isfahan and the Gavkhuni Wetland reserve-the final recipient of the river water. To analyze impacts of land use changes and the occurrence of metrolo...
Article
Full-text available
During the last decades, the endorheic Lake Urmia basin in northwestern Iran has suffered from declining groundwater tables and a very strong recent reduction in the volume of Lake Urmia. For the case of Lake Urmia basin, this study explores the value of different locally and globally available observation data for adjusting a global hydrological m...
Article
An increasing number of studies suggest that climate change causes variation in the terrestrial water cycle. It is known that the precipitation as the source of water storage change on land and ocean is directly influenced by sea surface temperature (SST). At scales larger than, say, 350 km such water storage variation can be monitored by the satel...
Article
The hydrology of the Third Pole, Asia's freshwater tower, has shown considerable sensitivity to the impacts of climate change and human interventions, which affect the headwaters of many rivers that originate therein. For example, the Yangtze River has its basin (YRB) experiencing wetness of terrestrial water storage (TWS), which rainfall seems to...
Article
Full-text available
Decreasing the volume of the Urmia Lake, as the largest inland water body in Iran, is one of the current environmental and water resource management concerns. This study obtains a reliable spaceborne water level (WL)–area–volume relationship for the Urmia Lake using terrestrial, aerial and satellite-based data. The aim of this study is to improve U...
Article
Full-text available
The Bakhtegan catchment, an important agricultural region in southwestern Iran, has suffered groundwater depletion in recent years. As groundwater is considered the main source of fresh water in the catchment, especially for agriculture, monitoring groundwater responses to irrigation is important. Gravity Recovery and Climate Experiment (GRACE) sat...
Article
Full-text available
By combining long-term ground-based data on water withdrawal with climate model projections, this study quantifies the compounding effects of human activities and climate change on surface water availability in Iran over the twenty-first century. Our findings show that increasing water withdrawal in Iran, due to population growth and increased agri...
Article
Although total storage deficit index (TSDI) is a well-known GRACE-based drought index, it is not efficient for the basins with high consumption because water harvesting in these areas affect GRACE signal. To overcome this limitation, the modified total storage deficit index (MTSDI) is introduced in this paper. To develop MTSDI, residuals of the sig...
Article
Full-text available
The Bakhtegan catchment, an important agricultural region in south-western Iran, has suffered groundwater depletion in recent years. As groundwater is considered the main source of fresh water in the catchment, especially for agriculture, monitoring groundwater responses to irrigation is important. Gravity Recovery and Climate Experiment (GRACE) sa...
Article
Thanks to the large number of satellites, the multimission approach is becoming a viable method to integrate measurements and intensify the number of samples in space and time for monitoring the earth system. In this paper, we merged data from different satellite missions, optical sensors, and altimetry, for estimating daily river discharge through...
Article
Full-text available
During the last decades, the endorheic Lake Urmia basin in northwestern Iran has suffered from decreased precipitation, groundwater levels and a very strong reduction in the volume and more recently also in the extent of Lake Urmia. Human water use has exacerbated the desiccating impact of climatic variations. This study quantifies the contribution...
Article
In the Amazon River basin, water stored for months to years in the soils and subsurface provide a persistent resource that regulates local and global climate via teleconnections and provides water to plants in times of little rain. While Gravity Recovery and Climate Experiment (GRACE) satellites have provided the hydrological community with large a...
Article
Full-text available
In this study, a waveform retracking algorithm based on finding the inflection-point of the waveform is proposed. After two-steps pre-processing procedure, we employ this method for 145 cycles of Jason-2 data for two tracks 81 and 16 over the Strait of Hormuz. Moreover, we obtain the corrected SSH by the common empirical methods namely Offset Centr...
Article
Full-text available
Tropospheric correction is one of the most important corrections in satellite altimetry measurements. Tropospheric wet and dry path delays have strong dependence on temperature, pressure and humidity. Tropospheric layer has particularly high variability over coastal regions due to humidity, wind and temperature gradients. Depending on the extent of...
Chapter
Full-text available
Drought monitoring is vital considering the immense costs of this natural hazard. The root cause for all types of drought (meteorological, agricultural, hydrological, and socio-economic) is sustained below average precipitation. Since regional precipitation variability depends on large-scale climatic and oceanic circulation patterns, it is necessar...
Article
Full-text available
Our knowledge of the spatio-temporal variation of river hydrological parameters is surprisingly poor. In situ gauge stations are limited in spatial and temporal coverage, and their number has been decreasing during the past decades. On the other hand, remote sensing techniques have proven their ability to measure different parameters within the Ear...
Chapter
Ocean tides cause notable aliasing errors in the gravity field from single pair space-borne gravimetry missions like GRACE. Several studies into future gravity missions have shown that constellations with two or more GRACE-like tandems lead to a significant reduction of aliasing error from all kinds of high-frequency signal sources. Despite such re...
Article
Full-text available
In order to cope with the steady decline of the number of in situ gauges worldwide, there is a growing need for alternative methods to estimate runoff. We present an Ensemble Kalman Filter based approach that allows us to conclude on runoff for poorly or irregularly gauged basins. The approach focuses on the application of publicly available global...
Conference Paper
Full-text available
Availability of simultaneous in situ river discharge measurements and satellite image acquisitions is the biggest restriction of remote sensing based river discharge estimation methods. In this paper, we propose a width-discharge method for river discharge estimation, that does not need coinciding observations. The method constructs the rating curv...
Conference Paper
Full-text available
Satellite imagery has a great potential to estimate river discharge for gauging rivers. Discharge is estimated from cloud free images by developing a river width-discharge rating curve. As well as spatial resolution of remote sensing images, method used to derive temporal water masks is the main source of error in discharge estimation. In this stud...
Chapter
One of the major concerns of hydrology is to quantify the hydrological cycle of basins e.g. by means of modeling the hydrological interactions. However, current hydrological models are far from perfect. The main challenge of modeling is the poor spatio-temporal coverage of in situ databases, which are declining steadily over the past few decades. A...
Article
Full-text available
Given the continuous decline in global runoff data availability over the past decades, alternative approaches for runoff determination are gaining importance. When aiming for global scale runoff at a sufficient temporal resolution and with homogeneous accuracy, the choice to use spaceborne sensors is only a logical step. In this respect, we take wa...
Conference Paper
GRACE is undoubtedly one of the most important sources to observe mass transport on global scales. However, GRACE has outlived its predicted life time and the satellite system is showing signs of fatigue. As the value of any geophysical or environmental record is proportional to the length of the time series, the geo-scientific communities are seri...
Thesis
How much freshwater do we have on land? How is the freshwater cycle changing with time? Actually, we can not properly answer these questions as our knowledge of the spatial and temporal dynamics of the hydrological cycle is limited. The lack of knowledge is mainly induced by shortage of observational evidence, which motivates the objective of this...
Book
Full-text available
How much freshwater do we have on land? How is the freshwater cycle changing with time? Actually, we can not properly answer these questions as our knowledge of the spatial and temporal dynamics of the hydrological cycle is limited. The lack of knowledge is mainly induced by shortage of observational evidence, which motivates the objective of this...
Article
Users share a lot of personal information with friends, family members, and colleagues via social networks. Surprisingly, some users choose to share their sleeping patterns, perhaps both for awareness as well as a sense of connection to others. Indeed, sharing basic sleep data, whether a person has gone to bed or waking up, informs others about not...
Article
The publicly available global discharge database is limited in spatial and temporal coverage. Although regional exceptions exist, the population of the database has declined over the past several years. As discharge is one of the most important parameters for modeling hydrological interactions, alternative measuring techniques must be sought. In th...
Article
[1] In the event of a termination of the Gravity Recovery and Climate Experiment (GRACE) mission before the launch of GRACE Follow-On (due for launch in 2017), high-low satellite-to-satellite tracking (hl-SST) will be the only dedicated observing system with global coverage available to measure the time-variable gravity field (TVG) on a monthly or...
Article
Monitoring the variation of water storage in a long period is a primary issue for understanding the impact of climate change and human activities on earth water resources. In order to obtain the change in water volume in a lake and reservoir, in addition to water level, water extent must be repeatedly determined in an appropriate time interval. Op...
Article
Lake Urmia, a hypersaline lake in northwestern Iran is under the threat of drying up. The high importance of the lake's watershed for agricultural purposes demands a comprehensive monitoring of the watershed's behaviour. Spaceborne sensors provide a number of novel ways to monitor the hydrological cycle and its interannual changes. The use of GRACE...
Article
Full-text available
The technique of deriving time variable gravity (TVG) field observations from high-low satellite-to-satellite tracking (hl-SST) is beginning to establish itself as a valuable and supplementary source for the determination and description of long wavelength geophysical phenomena. Recent developments in data processing techniques have pushed the limi...
Article
The uncertainty in GRACE gravimetric data emanates from a superposition of errors from different sources, whose separation is difficult. In situ hydrological and hydro-meteorological observations, under certain conditions, facilitate the identification of different uncertainty types, and the quantification of their contribution to the overall error...
Conference Paper
The publicly available global discharge database has been on the decline, lately. In the recent past, satellite altimetry has been investigated as an alternative for monitoring inland water level. In the present study, altimetry footprints in the vicinity of river gauging stations are analyzed for a functional relationship between the water level m...
Article
Full-text available
Stochastic filtering of the monthly fields of GRACE time-variable gravity requires the computation of a signal covariance model, which is usually computed as a power-law from the GRACE data itself. The computation of the power-law involves the averaging of the degree variance models of all the available months of data, and fitting a straight line t...
Article
Gravity measurements within the Gravity Recovery and Climate Experiment (GRACE) provide a direct measure of monthly changes in mass over the Earth’s land masses. As such changes in mass mainly correspond to water storage changes, these measurements allow to close the continental water balance on large spatial scales and on a monthly time scale with...
Article
Full-text available
To close the continental water balance, runoff data is required. However, the number of catchments with available runoff data is low. The main objective of this study is to investigate the feasibility of extracting runoff data using satellite altimetry over all possible continental surface waters. Hence, all possible footprints in all catchments ha...
Article
The correlations of aggregated GRACE signal time series between different catchments (Inter Catchment Correlation) show a specific pattern mainly created by the periodic local climatic conditions. Inter Catchment Correlations of monthly residuals of GRACE signals - monthly values minus mean monthly values - show a sinusoidal dependence on latitude....