111 research outputs found
Der Einfluss der räumlichen Variabilität des Niederschlags auf die Vorhersageunsicherheit hydrologischer Modelle
No full textHydrological models are simplified representations of a part of the hydrological cycle. The fact that natural processes are described with mathematical equations and the corresponding parameters are estimated using observations leads to uncertainties. The uncertainty stems from the parameters, the model structure and measurements of input and output data. Precipitation is one of the most important hydrological model inputs. Precipitation is often significantly variable in space and time within a catchment. The main aim of this dissertation was to investigate and quantify the impact of spatial variability of precipitation on the predictive uncertainty of hydrological model simulations. Given the importance of the role of the precipitation input in hydrological applications, the following research questions were addressed: (a) how does the spatial variability of precipitation influence the hydrological simulation results? (b) will a higher spatial resolution of model input data necessarily lead to a better model performance? (c) what is the impact on the simulated hydrographs of interpolated precipitation at different spatial resolutions through varying raingauge networks? (d) what is the benefit of using conditionally simulated precipitation in hydrological modeling? (e) how does uncertainty in precipitation affect parameter identification of a conceptual model? The modified rainfall-runoff model HBV was applied to investigate the majority of the objectives. Based on the HBV model concept, four different structures namely, fully-lumped, semi-lumped, semi-distributed and distributed were developed. The physically-based spatially-distributed modeling system SHETRAN was also used to investigate how uncertainty in precipitation affects parameter identification of a conceptual model? The upper Neckar catchment, located in south-west Germany, was selected as test catchment. A number of simulation experiments were carried out in line with the objectives and scope of this study. The study aimed to investigate the influence of spatial variability of precipitation in a rainfall-runoff model indicated no significant differences in the model performance when the model was run using averaged precipitation at different spatial scales. However, there was a clear deterioration in the model performance during the summer season. The results also highlight that there can be a significant deterioration in the model performance when the model calibrated using detailed precipitation is run using relatively less detailed input precipitation. The study on the comparison of modelling performance using different representations of spatial variability indicates that for the present study catchment semi-distributed and semi-lumped model structures out-perform the distributed and fully-lumped model structures for the given level of information. The results indicate that using interpolated precipitation on finer resolution does not improve the simulation accuracy in either the calibration or validation periods at the subcatchments’ outlets. The study suggests that there can be a trade-off among the model complexity and available observations. The study related to assess the impacts of raingauge density on the simulation results showed that the number and spatial distribution of raingauges affect the simulation results. It was found that the model performances worsen radically with an excessive reduction of raingauges. However, the performances were not significantly improved by increasing the number of raingauges more than a certain threshold number. The analysis also indicates that models using different raingauge networks might need their parameters recalibrated. Specifically, models calibrated with dense input precipitation information fail when run with sparse information. However, the models calibrated with sparse input precipitation information can perform well when run with dense information. Also the model calibrated with complete set of observed precipitation and being run with incomplete observed precipitation data associated with data estimated at the locations with missing measurements using multiple linear regression technique, performed well. Conditional spatial rainfall simulation indicates significantly more spatial variability in the simulated rainfall than interpolated rainfall. The model performs better for modeling the peak discharges using conditionally simulated rainfall than the model using interpolated rainfall. Thus conditional rainfall simulation is reasonable for flood modeling. The analysis also indicates that inadequate representation of spatial variability of precipitation in modeling is partly responsible for modeling errors and also this leads to the problems in parameter estimation of a conceptual hydrological model. Thus spatial variability must be captured and used as an input to the hydrological model in order to eliminate the errors due to input rainfall data.Hydrologische Modelle sind die vereinfachte Abbildung eines Teils des hydrologischen Kreislaufs. Die Tatsache, dass natürliche Prozesse mit mathematischen Gleichungen beschrieben werden und die entsprechenden Parameter über Beobachtungen angepasst werden, führt zu Unsicherheiten. Unsicherheiten ergeben sich aus der Modelstruktur und den Messungen der Eingangs- und Ausgangsdaten. Der Niederschlag ist eine der wichtigsten hydrologischen Eingangsdaten und ist innerhalb eines Einzugsgebiets räumlich und zeitlich sehr variabel. Das Hauptziel dieser Dissertation war es deshalb, den Einfluss räumlicher Niederschlagsvariabilität auf die Vorhersageunsicherheit hydrologischer Modelle zu untersuchen und zu quantifizieren.
Folgenden Fragestellungen wurden untersucht: a. Wie beeinflusst die räumliche Variabilität des Niederschlags die Ergebnisse hydrologischer Simulation? b. Wird eine höhere räumliche Auflösung der Eingangsdaten eines Modells zwingender Weise zu einer besseren Modelleistung führen? c. Welchen Einfluss hat eine Variation des Messstationen Netzwerks bei der Interpolation des Niederschlags auf verschiedenen räumlichen Skalen auf simulierte Abflussganglinien? d. Welchen Nutzen bietet die Verwendung bedingter Niederschlagssimulation in hydrologischer Modellierung? e. Wie beeinflusst die Unsicherheit der Niederschlagsdaten die Parameteridentifikation eines konzeptionellen Modells?
Die Mehrzahl der Fragestellungen wurde mit einer modifizierten Version des HBV Niederschlag-Abfluss Modells untersucht. Auf dessen Basis wurden vier verschiedene Modellstrukturen entwickelt: das räumlich aggregierte, das halb-aggregierte, das halb-verteilte und das verteilte Modell. Der Hauptunterschied zwischen den Modellstrukturen liegt in der Repräsentierung des Niederschlagsinputs. Für die letzte Fragestellung wurde das physikalisch basierte, räumlich-verteilte Modellsystem SHETRAN verwendet. Als Testgebiet wurde das obere Neckareinzugsgebiet in Süddeutschland gewählt. Die Untersuchung des Einflusses der räumlichen Niederschlagsvariabilität zeigt keine signifikanten Unterschiede der Modellleistung, wenn das Niederschlags-Abfluss-Modell mit gemittelten Niederschlägen auf unterschiedlicher räumlicher Skala betrieben wurde. Es trat jedoch eine klare Störung der Modelleistung während des Sommers auf. Auch kann die Modellleistung stark zurückgehen, wenn ein Modell, das mit sehr detaillierten Niederschlagsdaten kalibriert wurde, mit wenig detailliertem Niederschlags-Input betrieben wird. Der Vergleich der Modellleistung bei Verwendung verschiedener Repräsentierungen der räumlichen Variabilität kommt zu dem Schluss, dass die halb-verteilte und die halb-aggregierte Modellstruktur der aggregierten und der verteilten Struktur bei dem gegebenen Informationsniveau überlegen sind. Es wird deutlich, dass die Verwendung interpolierter Niederschlagsdaten auf einem höher aufgelösten Raster die Genauigkeit der Simulation des Abflusses am Auslass des Untereinzugsgebietes weder für die Kalibrierungsperiode noch für die Validierungsperiode verbessert. Dies deutet auf einen möglichen Ausgleich hin zwischen der Komplexität des Modells und der zur Verfügung stehenden Beobachtungen. Die Untersuchung des Einflusses der Dichte eines Niederschlagsmesstationennetzes auf die Simulationsergebnisse zeigte, dass die Anzahl und Verteilung der Messtationen die Simulationsergebnisse deutlich beeinflusst. Vermindert man die Anzahl an Regenmessstationen im Modell übermäßig, geht die Modellleistung extrem zurück. Umgekehrt jedoch, wenn man mehr Messstellen berücksichtigt, verbessert sich ab einem bestimmten Schwellenwert die Leistung des Modells nicht mehr signifikant. Modelle, die mit unterschiedlichen Messstellennetzen betrieben werden, müssen dementsprechend nachkalibriert werden. Speziell versagen Modelle, die mit einer sehr hohen Informationsdichte kalibriert wurden, wenn Sie mit sehr wenig Information betrieben werden. Umgekehrt können Modelle, die mit wenig Niederschlagsinformation kalibriert wurden, gute Ergebnisse bringen, wenn sie mit einer hohen Dichte an Inputinformation betrieben werden. Modelle, die mit vollständigen Sets beobachteter Niederschlagswerte kalibriert wurden, können gute Simulationsergebnisse liefern, wenn sie mit unvollständigen Sets betrieben werden, deren Datenlücken mit multipler linearer Regression ausgefüllt wurden. Für die Hochwassermodellierung sehr sinnvoll ist der Einsatz bedingter räumlicher Niederschlagssimulation. Damit ergibt sich signifikant mehr räumliche Variabilität als bei Niederschlagsinterpolation und Abflussspitzen können besser abgebildet werden. Die Analyse zeigt außerdem, dass eine inadäquate Abbildung der räumlichen Niederschlagsvariabilität für Modellierungsfehler verantwortlich ist, was zu Problemen der Parameteraschätzung konzeptioneller Modelle führt
Pattern of skin diseases in a peripheral hospital′s skin OPD: A study of 2550 patients
No full textThis study was done amongst 2550 consecutive skin patients in our male OPD. Infective dermatoses was seen in 36.41% and allergic diseases in 29.88% of our patients. New cases of leprosy accounted for 5.64% of our cases, which we consider is a disturbing trend. Occupational dermatoses was seen 15.24% of our cases. Farmers and agricultural labourers comprised the largest segment (37.72%) of our patients
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Predicting the Effects of Climate Change on the Size and Frequency of Floods in the Sacramento-San Joaquin Valley
No full textHow might climate change alter California’s risk of floods in the future? Findings from this project suggest that flooding will become more intense in the San Joaquin and (to a lesser extent) Sacramento watersheds by the end of the century, irrespective of whether the climate becomes wetter or drier. More intense flooding appears to be a consequence of several factors—principally bigger storms, more frequent big storms and more days of precipitation falling as rain instead of snow. Moister winter soils, which may be too saturated to absorb added water, also contribute to flooding in some areas
Physiological and Biochemical Responses to Hypoxia in the Blue Crab, Callinectes Sapidus Rathbun, the Lesser Blue Crab, Callinectes Similis Williams, and the Southern Oyster Drill, Stramonita Haemastoma Linnaeus.
No full textThis study measured the physiological and biochemical changes associated with exposure of the juvenile blue crab, Callinectes sapidus Rathbun and the lesser blue crab. C. similis Williams, to long term (28 d) hypoxia, short term (10 d) transfer from hypoxia to normoxia and a diurnally fluctuating oxygen regime for 28 days. The southern oyster drill, Stramonita haemastoma Linnaeus, was also exposed to 28 days of constant hypoxia to compare the responses of a tolerant species with the two species of Callinectes. The 28 day LC\sb{50} estimates for C. sapidus, C. similis and S. haemastoma were respectively 106, 43 and 11.5 Torr under constant hypoxic exposure for 28 d. Feeding rates for the crabs of both species exposed to 50 and 25 Torr oxygen were significantly lower than for crabs exposed to higher levels of oxygen. Growth and molting rates of crabs exposed to constant hypoxia were always lower than for crabs exposed to normoxia. Feeding rate in S. haemastoma declined linearly with declining oxygen under constant exposure to hypoxia. Oxygen consumption rates of the two crab species under various hypoxic levels were significantly different. Mean oxygen consumption in C. similis exposed to hypoxia was higher than for crabs exposed to normoxia. Rate of adaptation for blue crabs transferred from hypoxia to normoxia was faster than when transferred from normoxia to hypoxia. Detection and avoidance of hypoxic water by the two species of crabs was also observed under laboratory conditions. Both species of crabs were able to detect and avoid hypoxic water and stay at an intermediate oxygen tension. Crabs were found to be more active at higher oxygen tensions. The feeding rate of C. sapidus exposed to diurnally varying oxygen tension was significantly higher than for the crabs exposed to normoxia while the feeding rate of C. similis exposed to diurnally varying oxygen tension was significantly lower than the ones exposed to normoxia. RNA and DNA concentration decreased over time in both species of crabs exposed to diurnal variation in oxygen tension. Concentration of the individual nucleic acids were found to be a reliable measure of hypoxia stress than the RNA:DNA ratio
STATUS OF SAFETY CONDITIONS OF THE SECONDARY SCHOOL IN THE LIGHT OF RASHTRIYA MADHYAMIK SHIKSHA ABHIYAN (RMSA)
No full textAfter independence, various initiatives and strategies have played an important role in providing better education and better learning outcomes for students. Rashtriya Madhyamik Shiksha Abhiyan is a program centrally sponsored by the Ministry of Human Resources Development of India to promote secondary education in public schools throughout India. According to the RMSA guidelines, school safety conditions are an important aspect. The term ‘safety’ is comprehensive and it covers several aspects. The present study aims to investigate the present status of safety conditions in secondary schools among selected districts of West Bengal in the light of RMSA. The findings of the present study clearly show that selected secondary schools of both Nadia and Murshidabad districts have no proper safety conditions according to the guidelines of RMSA and comparatively the safety conditions are better among selected secondary schools of Nadia district than in the selected secondary schools of Murshidabad district
Analysis and mitigation of the adverse effects of voltage sags and swells on wind farms
No full textWind farms have become an important source of sustainable electricity generation as renewable energy is becoming more and more popular around the world. The widespread adoption of wind farms causes some new problems. Wind generators are prone to damage during electricity grid instability and, therefore, some sort of protection is required for continuous operation of wind generators. This thesis focuses on the design of novel protection mechanism for wind generators during electricity grid instability. This will make the adoption of wind farms more feasible
A Study about the Attitude of Grade Eight Students for the Use of Plastic in Gwarko, Balkumari, Lalitpur District
No full textAbstractThe paper sets out a systematic empirical investigation for understanding the use of plastic materials for grade eight students. A survey method was conducted with a five point Likert scale to measure attitude. The paper developed an overall understanding of the knowledge towards behavior under the impact of plastic use. A gap between knowledge and behavior was located under the challenges from knowledge gain, to attitude building, and behavior change. Transferring knowledge to behavior lost some knowledge due to mode and instrument of transfer. Academic knowledge transfer rate was very good but the process was affected by educational barriers and other societal factors
Multi-model (VIC, NoahMP, SAC-SMA, and Catchment) parameters and representative outputs; pre-processing and post-processing data and scripts, for analyses in the Northern Sierra Nevada Basin, the Southern Sierra Nevada Basin, the Upper Colorado Basin, and the Columbia Basin, from 1916 to 2018.
No full textThis package includes all the representative data used in the analyses in the paper
entitled "Understanding the role of asymmetrical warming on streamflow changes in the Western U.S.", submitted by Zhaoxin Ban, Tapash Das, Dan Cayan, Mu Xiao, and Dennis P. Lettenmaier to Water Resources Research.</i
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