Assimilating remotely sensed snow observations into a macroscale hydrology model   总被引：1，自引：0，他引：1  

Konstantinos M. Andreadis  Dennis P. Lettenmaier 《Advances in water resources》2006

Accurate forecasting of snow properties is important for effective water resources management, especially in mountainous areas like the western United States. Current model-based forecasting approaches are limited by model biases and input data uncertainties. Remote sensing offers an opportunity for observation of snow properties, like areal extent and water equivalent, over larger areas. Data assimilation provides a framework for optimally merging information from remotely sensed observations and hydrologic model predictions. An ensemble Kalman filter (EnKF) was used to assimilate remotely sensed snow observations into the variable infiltration capacity (VIC) macroscale hydrologic model over the Snake River basin. The snow cover extent (SCE) product from the moderate resolution imaging spectroradiometer (MODIS) flown on the NASA Terra satellite was used to update VIC snow water equivalent (SWE), for a period of four consecutive winters (1999–2003). A simple snow depletion curve model was used for the necessary SWE–SCE inversion. The results showed that the EnKF is an effective and operationally feasible solution; the filter successfully updated model SCE predictions to better agree with the MODIS observations and ground surface measurements. Comparisons of the VIC SWE estimates following updating with surface SWE observations (from the NRCS SNOTEL network) indicated that the filter performance was a modest improvement over the open-loop (un-updated) simulations. This improvement was more evident for lower to middle elevations, and during snowmelt, while during accumulation the filter and open-loop estimates were very close on average. Subsequently, a preliminary assessment of the potential for assimilating the SWE product from the advanced microwave scanning radiometer (AMSR-E, flown on board the NASA Aqua satellite) was conducted. The results were not encouraging, and appeared to reflect large errors in the AMSR-E SWE product, which were also apparent in comparisons with SNOTEL data.  相似文献   

Seismicity characteristics of a potentially active Quaternary volcano: The Tatun Volcano Group, northern Taiwan     

Konstantinos I. Konstantinou  Cheng-Horng Lin  Wen-Tzong Liang 《Journal of Volcanology and Geothermal Research》2007,160(3-4):300-318

The Tatun Volcano Group (TVG) is located at the northern tip of Taiwan, near the capital Taipei and close to two nuclear power plants. Because of lack of any activity in historical times it has been classified as an extinct volcano, even though more recent studies suggest that TVG might have been active during the last 20 ka. In May 2003 a seismic monitoring project at the TVG area was initiated by deploying eight three-component seismic stations some of them equipped with both short-period and broadband sensors. During the 18 months observation period local seismicity mainly consisted of high frequency earthquakes either occurring as isolated events, or as a continuous sequence in the form of spasmodic bursts. Mixed and low frequency events were also present during the same period, even though they occurred only rarely. Arrival times from events with clear P-/S-wave phases were inverted in order to obtain a minimum 1D velocity model with station corrections. Probabilistic nonlinear earthquake locations were calculated for all these events using the newly derived velocity model. Most high frequency seismicity appeared to be concentrated near the areas of hydrothermal activity, forming tight clusters at depths shallower than 4 km. Relative locations, calculated using the double-difference method and utilising catalogue and cross-correlation differential traveltimes, showed insignificant differences when compared to the nonlinear probabilistic locations. In general, seismicity in the TVG area seems to be primarily driven by circulation of hydrothermal fluids as indicated by the occurrence of spasmodic bursts, mixed/low frequency events and a b-value (1.17 ± 0.1) higher than in any other part of Taiwan. These observations, that are similar to those reported in other dormant Quaternary volcanoes, indicate that a magma chamber may still exist beneath TVG and that a future eruption or period of unrest should not be considered unlikely.  相似文献   

Climatic variability and the anchovy/sardine ratio in Hellenic waters     

I. Konstantinos Stergiou  Alex Lascaratos 《GeoJournal》1997,41(3):245-254

In the present work, the monthly anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) commercial catches, the anchovy/sardine commercial catch ratio as well as different climatic parameters in Hellenic waters (air and sea surface temperature AIRT and SST, sea level pressure SLP, N-S wind component NSW, and wind speed cubed WISC) over the 1964 to 1989 period were analyzed using spectral and cross-spectral analyses. The monthly anchovy and sardine catches as well as the anchovy/sardine catch ratio all exhibited a pronounced seasonal cycle that is related to the behaviour of sardine and anchovy and the nature of the purse seine fishery. Spectral analysis of the monthly sardine catches and anchovy/sardine catch ratio in the Hellenic waters also revealed cycles of 2.7 yr whereas that of anchovy catches revealed a prominent peak at 4.6 yr and secondary ones at 3.6 and 1.9 yr. Cross-spectral analysis resolved significant coherence between the anchovy/sardine ratio and SLP at 2.7 yr and marginally with NSW and WISC at 2.7 and 5.3 yr, respectively. The corresponding phase spectra showed that increased SLP and NSW over the north Aegean Sea proceed and are associated with decreased anchovy/sardine ratio with a lag of about 2.5 months for SLP and 6 months for NSW whereas increased WISC over the north Aegean proceed and are associated with increased anchovy/sardine ratio with a lag of 28 months. Cross-spectral analysis also resolved significant coherence between the anchovy catches and AIRT and SLP at 2.7 yr, NSW at 1.8 yr and WISC at 5.3 yr. The corresponding phase spectra showed that increased SLP, AIRT and NSW over the north Aegean Sea proceed and are associated with decreased anchovy catches with a lag of about 2 months for SLP, 16 months for AIRT and 6 months for NSW whereas increased WISC over the same area proceed and are associated with increased anchovy catches with a lag of 30 months. In contrast, cross-spectral analysis resolved no significant coherence between sardine catches and all five climatic variables. Possible mechanisms underlying such patterns are discussed.  相似文献   

Nutrient relationships of Greek lakes: Water eutrophication monitoring,assessment and forecasting     

Alexis Conides  Theodore Koussouris  L Gritzalis  Konstantinos  Alkistis Parpoura  George Fotis 《GeoJournal》1995,36(4):383-390

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Micro-sized enterprises: vulnerability to flash floods     

Konstantinos Karagiorgos  Micha Heiser  Thomas Thaler  Johannes Hübl  Sven Fuchs 《Natural Hazards》2016,81(2):1091-1106

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Analysis of broad-band regional waveforms of the 1996 September 29 earthquake at Bárdarbunga volcano, central Iceland: investigation of the magma injection hypothesis     

Konstantinos I. Konstantinou  Honn Kao  Cheng-Horng Lin  Wen-Tzong Liang 《Geophysical Journal International》2003,154(1):134-145

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Influence of spatial scales of observation on temporal change in diversity and trophic structure of fine-sand communities from the English Channel and the southern North Sea   总被引：2，自引：0，他引：2  

Ghertsos  Konstantinos; Luczak  Christophe; Dewarumez  Jean-Marie; Dauvin  Jean-Claude 《ICES Journal of Marine Science》2000,57(5):1481-1487

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The 30 October 2020, MW = 7.0, Samos earthquake: aftershock relocation,slip model,Coulomb stress evolution and estimation of shaking     

Lentas  Konstantinos  Gkarlaouni  Charikleia G.  Kalligeris  Nikos  Melis  Nikolaos S. 《Bulletin of Earthquake Engineering》2022,20(2):819-851

Bulletin of Earthquake Engineering - We study the major MW = 7.0, 30 October 2020, Samos earthquake and its aftershocks, by calculating improved locations using differential travel times and...  相似文献   

A tentative model for the explanation of Båth law using the order parameter of seismicity in natural time          下载免费PDF全文

Konstantina A. Papadopoulou  Efthimios S. Skordas  Nicholas V. Sarlis 《地震科学（英文版）》2016,29(6):311-319

Using the order parameter of seismicity defined in natural time, we suggest a simple model for the explanation of Båth law, according to which a mainshock differs in magnitude from its largest aftershock by approximately 1.2 regardless of the mainshock magnitude. In addition, the validity of Båth law is studied in the Global Centroid Moment Tensor catalogue by using two different aftershock definitions. It is found that the mean of this difference, when considering all the pairs mainshock-largest aftershock, does not markedly differ from 1.2 and the corresponding distributions do not depend on the mainshock’s magnitude threshold in a statistically significant manner. Finally, the analysis of the cumulative distribution functions provides evidence in favour of the proposed model.  相似文献   

Statistical Significance of Minimum of the Order Parameter Fluctuations of Seismicity Before Major Earthquakes in Japan     

N. V. Sarlis  E. S. Skordas  S.-R. G. Christopoulos  P. A. Varotsos 《Pure and Applied Geophysics》2016,173(1):165-172

In a previous publication, the seismicity of Japan from 1 January 1984 to 11 March 2011 (the time of the \(M9\) Tohoku earthquake occurrence) has been analyzed in a time domain called natural time \(\chi.\) The order parameter of seismicity in this time domain is the variance of \(\chi\) weighted for normalized energy of each earthquake. It was found that the fluctuations of the order parameter of seismicity exhibit 15 distinct minima—deeper than a certain threshold—1 to around 3 months before the occurrence of large earthquakes that occurred in Japan during 1984–2011. Six (out of 15) of these minima were followed by all the shallow earthquakes of magnitude 7.6 or larger during the whole period studied. Here, we show that the probability to achieve the latter result by chance is of the order of \(10^{-5}\). This conclusion is strengthened by employing also the receiver operating characteristics technique.  相似文献