A comparison of MODIS and NOHRSC snow‐cover products for simulating streamflow using the Snowmelt Runoff Model

Remote sensing is an important source of snow‐cover extent for input into the Snowmelt Runoff Model (SRM) and other snowmelt models. Since February 2000, daily global snow‐cover maps have been produced from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS). The usefulness of this snow‐cover product for streamflow prediction is assessed by comparing SRM simulated streamflow using the MODIS snow‐cover product with streamflow simulated using snow maps from the National Operational Hydrologic Remote Sensing Center (NOHRSC). Simulations were conducted for two tributary watersheds of the Upper Rio Grande basin during the 2001 snowmelt season using representative SRM parameter values. Snow depletion curves developed from MODIS and NOHRSC snow maps were generally comparable in both watersheds: satisfactory streamflow simulations were obtained using both snow‐cover products in larger watershed (volume difference: MODIS, 2·6%; NOHRSC, 14·0%) and less satisfactory streamflow simulations in smaller watershed (volume difference: MODIS, −33·1%; NOHRSC, −18·6%). The snow water equivalent (SWE) on 1 April in the third zone of each basin was computed using the modified depletion curve produced by the SRM and was compared with in situ SWE measured at Snowpack Telemetry sites located in the third zone of each basin. The SRM‐calculated SWEs using both snow products agree with the measured SWEs in both watersheds. Based on these results, the MODIS snow‐cover product appears to be of sufficient quality for streamflow prediction using the SRM in the snowmelt‐dominated basins. Copyright © 2005 John Wiley & Sons, Ltd.     

The causes and petrological significance of cathodoluminescence emissions from alkali feldspars

The cathodoluminescence (CL) of a variety of alkali feldspars from South Greenland has been examined in an attempt to understand the causes of the CL and its petrological significance. Analytical methods have included CL spectroscopy, secondary ion mass spectrometry (SIMS) and electron paramagnetic resonance (EPR) to correlate the presence of certain CL emissions to the presence of certain trace element and point defects. Where possible, blue and red luminescent fractions of the same rock samples have been separated and analysed separately. Blue CL appears to relate to the presence of electron holes on bridging oxygens, particularly on the Al-O-Al bridge, as determined from EPR studies. No correlation with other proposed activators for blue CL such as Eu²⁺, Ga³⁺ or Ti⁴⁺ was observed. Some blue luminescent feldspars also have an emission in the infra-red (IR), invisible during normal visible CL petrography. The red and IR CL emissions correspond to features in EPR spectra attributed to Fe³⁺ and support previous suggestions that Fe³⁺ is related to this emission. However, our studies indicate that the visible red CL relates specifically to Fe³⁺ on the T1 site, whereas the equivalent CL from disordered feldspars lies in the IR. The difference between red and IR CL emissions therefore relates to the state of Fe³⁺ order across the tetrahedral sites. These data allow more meaningful interpretations of CL as a petrographic tool in alkali feldspar-bearing rocks. Received: 5 March 1998 / Accepted: 23 November 1998     

A high-resolution Holocene record on the Southern Brazilian shelf: Paleoenvironmental implications

A high-resolution, multi-proxy record has been used to determine the environmental changes during the Holocene on the southern Brazilian shelf. Present oceanographic conditions reveal wind and freshwater input as the determinants of short-term productivity changes in the study area. Magnetic susceptibility and grain-size variations, together with proxies of productivity (organic carbon, carbon accumulation rate, Ba, Sr, and Ca content, Ba/Al, Ba/Ti, and Al/Ti ratios) were analyzed and compared with proxies of redox condition (V/Ti ratio), terrigenous input (Fe/Ca and Ti/Ca ratios), as well as other Element/Ti ratios, to evaluate the paleoceanographic and paleoclimatic changes over the period.The core covers a time interval of about 7650 years, with sedimentation rates varying from 0.025 to 0.250 cm a⁻¹, which represent time intervals of between 8 and 80 a per sample. There is a clear change in the sedimentation rate at about 2800 B.P.All grain-size and elemental results indicate the occurrence of conspicuous changes between 5200 and 5000 cal. B.P., as well as between 3000 and 2800 cal. B.P. A comparison of the results with the palynological information available from the adjacent continental areas suggests that the sedimentary changes in this last interval may be correlated with the onset of modern climatic conditions in South America, and especially, with the onset of the Plata Plume Water, a water mass that carries cold, less saline waters towards the north. However, minor changes are observed at ca. 1500 B.P. and are correlated with an increase in the atmospheric humidity. Furthermore, a time-series analysis undertaken using several proxies indicated the occurrence of Sub-Milankovitch cycles, which may be compared with those reported worldwide.     

Tidal triggering of reservoir-associated earthquakes

If the effect of a reservoir is to bring a fault zone gradually to failure and trigger an earthquake, then it is reasonable that rapidly fluctuating tidal stresses may influence the time of the induced earthquakes. An examination of earthquakes from eight reservoirs shows that earthquakes at six sites occur at preferred times in the semidiurnal tidal cycle. Tidal-stress orientations and the phase within the semidiurnal tidal cycle were calculated for only the largest earthquakes occurring at each site. This insures the elimination of aftershocks and selects earthquakes which are independent of each other. Sites of a significant earthquake/tide correlation with less than a 3% chance of occurring randomly include Hebgen Lake, Mont., U.S.A.; Kariba, Rhodesia; Kerr Dam, Mont., U.S.A.; Kremasta, Greece; Lake Mead, Nev., U.S.A.; and Monteynard, France. Each data set includes from about ten to twenty earthquakes. In most of the above cases earthquake triggering seems to occur when tidal stress enhances slip, i.e., when tidal stresses are oriented to enhance the tectonic stress.     

Collocation of hydrological and biological attenuation of nitrate in an urban stream

The hydrologic and biogeochemical processes that control nutrient export in urban streams are not well understood. Attenuation can occur by tributary dilution, groundwater discharge, and biological processing both in the water column and the hyporheic zone. A wastewater treatment plant on Pennypack Creek, an urban stream near Philadelphia, PA, provided high nitrate concentrations for analysis of downstream attenuation processes. Longitudinal sampling for an 8‐km reach revealed decreases in nitrate concentration of 2 mg l^?1 at high flow and 4.5 mg l^?1 during low flow. During high flow, δ¹⁵N‐NO₃ increased from 9.5 to 10.5‰ and during low flow increased from 10.1 to 11.1‰. Two reaches were sampled at fine spatial intervals (approximately 200 m) to better identify attenuation processes. Mixing analysis indicated that groundwater discharge and biological processing both control nitrate concentration and isotope signatures. However, fine‐scaled sampling did not reveal spatially discrete zones; instead, these processes were occurring simultaneously. While both processes attenuate nitrate, they have opposite isotope signatures, which may have muted changes in δ¹⁵N‐NO₃. At high flow, a decrease in Cl/NO₃ ratios helped distinguish groundwater discharge occurring along both finely sampled reaches. At low flow, biological processing seemed to be occurring more extensively, but the δ¹⁵N‐NO₃ signature was not consistent with either a single process or a sequential combination of groundwater dilution and biological nitrate attenuation. The collocation of processes makes it more difficult to assess biological processing hot spots and predict how urbanization and subsequent stream restoration influence nitrate attenuation. Copyright © 2016 John Wiley & Sons, Ltd.     

Integrating knowledge to assess coastal vulnerability to sea-level rise: The development of the DIVA tool

This paper describes the development of the DIVA tool, a user-friendly tool for assessing coastal vulnerability from subnational to global levels. The development involved the two major challenges of integrating knowledge in the form of data, scenarios and models from various natural, social and engineering science disciplines and making this integrated knowledge accessible to a broad community of end-users. These challenges were addressed by (i) creating and applying the DIVA method, an iterative, modular method for developing integrating models amongst distributed partners and (ii) making the data, scenarios and integrated model, equipped with a powerful graphical user interface, directly and freely available to end-users.     

Regression model for generating time series of daily precipitation amounts for climate change impact studies

The precipitation amounts on wet days at De Bilt (the Netherlands) are linked to temperature and surface air pressure through advanced regression techniques. Temperature is chosen as a covariate to use the model for generating synthetic time series of daily precipitation in a CO₂ induced warmer climate. The precipitation-temperature dependence can partly be ascribed to the phenomenon that warmer air can contain more moisture. Spline functions are introduced to reproduce the non-monotonous change of the mean daily precipitation amount with temperature. Because the model is non-linear and the variance of the errors depends on the expected response, an iteratively reweighted least-squares technique is needed to estimate the regression coefficients. A representative rainfall sequence for the situation of a systematic temperature rise is obtained by multiplying the precipitation amounts in the observed record with a temperature dependent factor based on a fitted regression model. For a temperature change of 3°C (reasonable guess for a doubled CO₂ climate according to the present-day general circulation models) this results in an increase in the annual average amount of 9% (20% in winter and 4% in summer). An extended model with both temperature and surface air pressure is presented which makes it possible to study the additional effects of a potential systematic change in surface air pressure on precipitation.     

Pressure anomalies in the Indian Ocean area, 1796–1960

Summary Barometric anomalies for stations near the Indian Ocean since 1841 are tabulated and combined for years and half-years. Early records for India yield a further series back to 1796. Regional anomalies for the west Indian Ocean correlate inversely with Nile Flood data, and those for the east Indian Ocean inversely with Java tree-rings. Combined values (including Australia), if reversed, correlate well with such rainfall indicators and at the same time provide good indicators of the half-yearly anomalies of the Southern Oscillation and the yearly anomalies of the Pressure Parameter. The Pressure Parameter is an index linked also with tropical temperature changes and with climatic fluctuations in various parts of the world.

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Zusammenfassung Luftdruckwerte für Orte im Gebiete des Indischen Ozeans seit 1841 wurden zusammengestellt in Tabellen jährlicher und halbjährlicher Anomalien. Frühe Aufzeichnungen in Indien sind erhältlich seit 1796. Regionale Anomalien des Luftdruckes im westlichen Indischen Ozean sind umgekehrt korreliert mit der Nilflut, solche im östlichen Indischen Ozean mit den Jahresringbreiten von Bäumen auf Java. Kombinierte Luftdruckanomalien (Australien eingeschlossen) sind umgekehrt korreliert mit solcherart Indikatoren des Niederschlags und ergeben zur gleichen Zeit gute Anweisungen für die halbjährlichen Anomalien der sogenannten Südlichen Schwankung und der jährlichen Anomalien eines gewissen Luftdruckparameters. Der Luftdruckparameter ist verbunden mit tropischen Temperaturänderungen und klimatischen Schwankungen in verschiedenen Weltteilen.

     

Monitoring changes in shoreline position adjacent to the Hadera power station, Israel

The paper focuses on the shoreline changes following the construction of a power station cooling harbor in Hadera, Israel, and uses a statistical analysis method capable of mitigating the effect of short-term changes on the measurement of long-term changes. The changes in shoreline position detected 25 years after the harbor's construction were compared with forecasts of the Central Lab for Hydraulics of France (LCHF) in 1976, which correctly predicted the effects of the construction on the nearby coast and with studies conducted a few years after the construction. A comparison between later studies and the study described herein shows a spatial effect of the harbor on shoreline position of 750 m north of the northern breakwater. No effect was found south of the harbor. The harbor's temporal effects extend over a few years from the beginning of the construction until the coast reaches a new sedimentary equilibrium. The statistical analysis method employed was found useful for the detection of long-term changes in shoreline position such as those caused by the construction of coastal structures; it will not be suitable for the detection of long-term changes resulting from a rise in sea-level.