Water and nutrient predictions in ungauged basins: set-up and evaluation of a model at the national scale

Abstract

A dynamic water quality model, HYPE, was applied to a large, data-sparse region to study whether reliable information on water quantity and water quality could be obtained for both gauged and ungauged waterbodies. The model (called S-HYPE) was set up for all of Sweden (～450 000 km²), divided into sub-basins with an average area of 28 km². Readily available national databases were used for physiographic data, emissions and agricultural practices, fixed values for representative years were used. Daily precipitation and temperature were used as the dynamic forcing of the model. Model evaluation was based on data from several hundred monitoring sites, of which approximately 90% had not been used in calibration on a daily scale. Results were evaluated using the Nash-Sutcliffe efficiency (NSE), correlation and relative errors: 92% of the spatial variation was explained for specific water discharge, and 88% and 59% for total nitrogen and total phosphorus concentrations, respectively. Day-to-day variations were modelled with satisfactory results for water discharge and the seasonal variation of nitrogen concentrations was also generally well captured. In 20 large, unregulated rivers the median NSE for water discharge was 0.84, and the corresponding number for 76 partly-regulated river basins was 0.52. In small basins, the NSE was typically above 0.6. These major achievements relative to previous similar experiments were ascribed to the step-wise calibration process using representative gauged basins and the use of a modelling concept, whereby coefficients are linked to physiographic variables rather than to specific sites.

Editor D. Koutsoyiannis

Citation Strömqvist, J., Arheimer, B., Dahné, J., Donnelly, C. and Lindström, G., 2012. Water and nutrient predictions in ungauged basins: set-up and evaluation of a model at the national scale. Hydrological Sciences Journal, 57 (2), 229–247.     

Simultaneous measurements of Martian plasma boundaries by Rosetta and Mars Express

We present the first two-spacecraft near-simultaneous observations of the Martian bow shock (BS), magnetic pileup boundary (MPB) and photo-electron boundary (PEB) obtained by the plasma instruments onboard Rosetta and Mars Express during the Rosetta Mars flyby on February 25, 2007. Our observations are compared with shape models for the BS and MPB derived from previous statistical studies. The MPB is found at its expected position but the BS for this event is found significantly closer to the planet than expected for the rather slow and moderately dense solar wind. Cross-calibration of the density measurements on the two spacecraft gives a density profile through the magnetosheath, indicating an increasing solar wind flux during the Rosetta passage which is consistent with the multiple BS crossings at the Rosetta exit.     

A New Machine for Planarity Measurement of CCDs and Mosaics of CCDs

High quality CCD detectors are now being produced with 2048× 4096 square pixels, each 15 m on a side. Evenlarger detector areas are built with several CCDs mounted into amosaic. To be useful in an instrument the light must be in focuson all CCDs, requiring that all CCDs in a mosaic must typicallybe aligned within 30 micron of a flat plane. To achieve thisaccuracy in many cases the measurement and correction of the CCDalignment is necessary. One way allowing a surface measurement,even when the CCD is protected by a window, is to usetriangulation sensor. The principle of a triangulation sensor,its application and its implementation in a measuring machineare presented here.     

Der geopotentielle Fehler eines barometrischen Höhenmessers sowie einige Bemerkungen zur vertikalen Navigation mit Hilfe von Druck- und Dichtemessungen

Zusammenfassung Einleitend werden die verschiedenen bei der barometrischen Höhenmessung auftretenden Fehler erörtert. Sodann werden das Geopotential und die Einheiten 1 geodynamisches Meter und 1 geopotentielles Meter besprochen. Ein Zahlenbeispiel für die Interpretation geopotentieller Einheiten wird angegeben. Der durch die üblichen Höhenmesser-Korrekturverfahren nicht erfaßte geopotentielle Fehler wird diskutiert. Abschließend wird der Zusammenhang zwischen Druckhöhe und Dichtehöhe einer näheren Betrachtung unterzogen, und Druckhöhe sowie Dichtehöhe werden im Hinblick auf ihre Verwendbarkeit für die Zwecke der vertikalen Navigation verglichen.

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Summary The various errors involved in the barometric measurement of altitude are discussed. The concept of the geopotential and its units (geopotential meter and geodynamic meter) are examined and a numerical example is given for the interpretation of geopotential units, followed by a discussion of the geopotential error not included in the usual procedure of altimeter correction. The relationship between pressure altitude and density altitude and their applicability for the purposes of vertical navigation are evaluated.

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Résumé Pour débuter, les auteurs examinent les erreurs pouvant se produire lors des mesures d'altitude au moyen du baromètre. Ils discutent ensuite le géopotentiel et les unités: mètre géodynamique et mètre géopotentiel. Ils donnent un exemple numérique pour l'interprétation des unités géopotentielles. Ils discutent en outre l'erreur géopotentielle qui n'est pas prise en considération dans les méthodes usuelles de correction des altimètres. Pour teminer, ils examinent la relation existant entre l'altitude mesurée par la pression et celle basée sur la densité de l'air. On compare ces deux altitudes à la lumière de leur utilisation pratique en navigation aérienne.

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Barometrischer Höhenmesser mit verschiebbarer sowie stauch- und streckbarer Eichkurve

Zusammenfassung Nach einer Skizzierung der allgemeinen Probleme der barometrischen Höhenmessung wird die Anpassung der Eichkurve eines Höhenmessers an die aktuelle Atmosphäre behandelt.Ein durch Radargerät zu eichender barometrischer Höhenmesser wird vorgeschlagen. Dieser Höhenmesser hat nicht wie die üblichen barometrischen Höhenmesser nur eine Stellschraube mit mb-Durchbruchskala zur senkrechten Verschiebung der Eichkurve, sondern darüber hinaus eine zweite Stellschraube mit Durchbruchskala zur Änderung des Übersetzungsverhältnisses zwischen Membrandose und Zeiger. Hierdurch läßt sich eine Stauchung und Streckung der Eichkurve erzielen, ohne daß Manipulationen an der Membrandose vorgenommen werden müssen.Während konventionelle barometrische Höhenmesser mit einer Stellschraube nur in einer Höhe eine vom meteorologischen Fehler freie Anzeige liefern, zeigt der besprochene Höhenmesser zumindest in zwei Höhen richtig an. Ist der Temperaturgradient der aktuellen Atmosphäre konstant, so ist die Anzeige des Höhenmessers mit zwei Stellschrauben in sämtlichen Höhen frei vom meteorologischen Fehler.

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Summary After a short review of the general problems of barometric altimetry the adjustment of the calibration curve of an altimeter to actual atmospheric conditions is treated.An improved altimeter for aviation is described. In addition to the single adjusting screw for vertical displacement of the calibration curve the new altimeter possesses an additional screw for adjusting the ratio of transmission between membrane and pointer. It provides a possibility to stretch or shrink the calibration curve, without any manipulation of the menbrane.The conventional altimeter is free of meteorological errors only at one level. The improved altimeter indicates correct altitude at least at two levels. If the temperature gradient in the atmosphere, is constant, the improved altimeter is free of meteorological errors at all levels. Setting of the instrument may be done by radar measurement.

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Résumé Après un bref exposé du problème général de la mesure barométrique de l'altitude, on présente le cas de l'adaptation de la courbe d'étalonnage d'un altimètre à l'état instantané de l'atmosphère.On propose un altimètre à étalonnage effectué à l'aide d'un appareil de radar. Cet altimètre a non seulement la vis de réglage usuelle pour le déplacement vertical de la courbe d'étalonnage, mais encore une deuxième vis permettant de faire varier l'amplitude, sans toucher à la boîte de pression.Alors que les altimètres ordinaires livrent une indication exacte à un seul niveau, celui qui est ici décrit la fournit à deux niveaux au moins. Si le gradient vertical de température instantané est constant, les indications sont exactes à tous les niveaux.

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Relations of field line resonances and upstream waves and the winter attenuation of pulsations

Using data on the occurrence frequency of geomagnetic pulsations of different periods from three observatories in Central Europe, conclusions are drawn about the occurrence of field line resonances and pulsations directly driven by upstream waves at L-values below 3. It was found that both types occur during the interval studied (first 6 months of the year 1991), but both the occurrence frequency of the two types and the characteristic period of the field line resonance change significantly as compared to other intervals. During Northern winter, pulsation activity is severely damped in solar maximum years, including the year 1991. The decrease in the activity of the pulsations is more significant at shorter periods.     

Wave Energy from the North Sea: Experiences from the Lysekil Research Site

This paper provides a status update on the development of the Swedish wave energy research area located close to Lysekil on the Swedish West coast. The Lysekil project is run by the Centre for Renewable Electric Energy Conversion at Uppsala University. The project was started in 2004 and currently has permission to run until the end of 2013. During this time period 10 grid-connected wave energy converters, 30 buoys for studies on environmental impact, and a surveillance tower for monitoring the interaction between waves and converters will be installed and studied. To date the research area holds one complete wave energy converter connected to a measuring station on shore via a sea cable, a Wave Rider? buoy for wave measurements, 25 buoys for studies on environmental impact, and a surveillance tower. The wave energy converter is based on a linear synchronous generator which is placed on the sea bed and driven by a heaving point absorber at the ocean surface. The converter is directly driven, i.e. it has no gearbox or other mechanical or hydraulic conversion system. This results in a simple and robust mechanical system, but also in a somewhat more complicated electrical system.     

The capabilities of the EISCAT Svalbard Radar for inter-hemispheric coordinated studies

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