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Digitale Medien

COLUMBIA RIVER FLOW AND DROUGHT SINCE 1750 (2004)

Gedalof, Ze'ev ; Peterson, David L. ; Mantua, Nathan J.

Oxford, UK : Blackwell Publishing Ltd

Journal of the American Water Resources Association 40 (2004), S. 0

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ISSN: 1752-1688

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie

Notizen: : A network of 32 drought sensitive tree-ring chronologies is used to reconstruct mean water year flow on the Columbia River at The Dalles, Oregon, since 1750. The reconstruction explains 30 percent of the variability in mean water year (October to September) flow, with a large portion of unexplained variance caused by underestimates of the most severe low flow events. Residual statistics from the tree-ring reconstruction, as well as an identically specified instrumental reconstruction, exhibit positive trends over time. This finding suggests that the relationship between drought and streamflow has changed over time, supporting results from hydrologic models, which suggest that changes in land cover over the 20th Century have had measurable impacts on runoff production. Low pass filtering the flow record suggests that persistent low flows during the 1840s were probably the most severe of the past 250 years, but that flows during the 1930s were nearly as extreme. The period from 1950 to 1987 is anomalous in the context of this record for having no notable multiyear drought events. A comparison of the flow reconstruction to paleorecords of the Pacific Decadal Oscillation (PDO) and El Nino/Southern Oscillation (ENSO) support a strong 20th Century link between large scale circulation and streamflow, but suggests that this link is very weak prior to 1900.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1752-1688.2004.tb01607.x

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Digitale Medien

Monitoring Air Quality in Mountains: Designing an Effective Network (2000)

Peterson, David L.

Springer

Environmental monitoring and assessment 64 (2000), S. 81-91

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ISSN: 1573-2959

Schlagwort(e): air pollution ; air quality ; monitoring network ; mountainous regions ; multi-scale assessment ; spatial and temporal scales ; tropospheric ozone

Quelle: Springer Online Journal Archives 1860-2000

Thema: Energietechnik

Notizen: Abstract A quantitatively robust yet parsimonious air-quality monitoring network in mountainous regions requires special attention to relevant spatial and temporal scales of measurement and inference. The design of monitoring networks should focus on the objectives required by public agencies, namely: 1) determine if some threshold has been exceeded (e.g., for regulatory purposes), and 2) identify spatial patterns and temporal trends (e.g., to protect natural resources). A short-term, multi-scale assessment to quantify spatial variability in air quality is a valuable asset in designing a network, in conjunction with an evaluation of existing data and simulation-model output. A recent assessment in Washington state (USA) quantified spatial variability in tropospheric ozone distribution ranging from a single watershed to the western third of the state. Spatial and temporal coherence in ozone exposure modified by predictable elevational relationships (∼ 1.3 ppbv ozone per 100 m elevation gain) extends from urban areas to the crest of the Cascade Range. This suggests that a sparse network of permanent analyzers is sufficient at all spatial scales, with the option of periodic intensive measurements to validate network design. It is imperative that agencies cooperate in the design of monitoring networks in mountainous regions to optimize data collection and financial efficiencies.