TY - Generic T1 - Distributed Temperatures in the Snow Zone: Spatial Patterns and Innovative Measurement Techniques T2 - 75th Annual Western Snow Conference Y1 - 2007 A1 - Lundquist, J.D. A1 - Rochford, C. KW - Yosemite National Park, temperature, lapse rate, EOF, spatial temperature patterns AB - Mountains are spatially complex and sparsely sampled. Temperatures are usually interpolated from distant stations assuming a standard atmospheric lapse rate (decrease of 6.5°C per 1000 m elevation gain). However, examination of observed surface temperatures indicates that temperature patterns differ diurnally, synoptically, and seasonally and do not always increase linearly with elevation. Fortunately, new technology has become available to monitor temperature in remote locations, such as the Onset Hobo and the Maxim i-button. Approximately 200 of these self-recording sensors have been deployed in Yosemite National Park, California and Niwot Ridge and Rocky Mountain National Park, Colorado over the past several years. Empirical orthogonal functions (EOFs) are used to identify the dominant spatial temperature patterns within each study area and how they vary in time. Comparison between study sites allows for generalizations of temperature patterns across space (mapping spatial patterns using topography) and time (mapping temporal variations using large-scale weather parameters), which can be utilized in more sparsely sampled areas. Experimentation with such a large number of sensors also illuminates how to best deploy these small instruments to sample topographically-controlled, versus vegetation-controlled, versus radiation-controlled, temperatures. JF - 75th Annual Western Snow Conference T3 - Proceedings of the 75th Annual Western Snow Conference PB - Western Snow Conference CY - Kailua-Kona, HI UR - sites/westernsnowconference.org/PDFs/2007Lundquist.pdf ER - TY - Generic T1 - The Effect of Basin Scale on Diurnal Streamflow Timing T2 - 72nd Annual Western Snow Conference Y1 - 2004 A1 - Lundquist, J.D. A1 - Dettinger, M. KW - Streamflow timing, Tuolumne River, travel time, basin scale, diurnal flow AB - Hourly streamflow timing, as revealed by diurnal fluctuations in discharge in snowfed watersheds, provides a new tool for understanding transport times and processes in river basins. Travel time delays at different basin scales were measured in nested subbasins (6 to 775 km2) of the Tuolumne River in Yosemite National Park throughout the spring 2002 and 2003 melt seasons. The travel time increases with longer percolation times through deeper snowpacks, increases with longer travel times overland and along longer stream channels, and increases with slower in-stream flow velocities. In basins smaller than 30 km2, snow properties that determine the travel times through the snowpack dominate streamflow timing. In particular, daily peak flows shift to earlier in the day as the snowpack thins and mean discharge increases. In basins larger than 150 km2, snowpack heterogeneity and mixing cause the hour of peak flow to be remarkably consistent, with little or no variation due to snowpack properties. Basins with areas in between 30 and 150 km2 exhibit different characteristics in different years, illustrating the transition between small and large-scale basin characteristics. Increasing channel travel times as the snowline retreats to higher elevations are not enough to offset the observed decrease in mean snowpack travel times. JF - 72nd Annual Western Snow Conference T3 - Proceedings of the 72nd Annual Western Snow Conference PB - Western Snow Conference CY - Richmond, B.C. UR - sites/westernsnowconference.org/PDFs/2004Lundquist.pdf ER - TY - Generic T1 - Snow, topography, and the diurnal cycle in streamflow T2 - 70th Annual Western Snow Conference Y1 - 2002 A1 - Lundquist, J.D. A1 - Knowles, N. A1 - Dettinger, M. A1 - Cayan, D. KW - Snowmelt, Satellite, Maximum annual discharge, Seasonal discharge shift AB - Because snowmelt processes are spatially complex, point measurements, particularly in mountainous regions, are often inadequate to resolve basin-scale characteristics. Satellite measurements provide good spatial sampling but are often infrequent in time, particularly during cloudy weather. Fortunately, hourly measurements of river discharge provide another widely available, but as yet underutilized, source of information, providing direct information on basin output at a fine temporal scale. The hour of maximum discharge recorded each day reflects the travel time between peak melt and the time most water reaches the gauge. Traditional theories, based on numerical models of melt-water percolation through a snowpack and localized, small-basin observations, report that the hour of daily maximum flow becomes earlier as the snowpack thins and matures, reflecting shorter travel times for surface melt to reach the base of the snowpack. However, an examination of hourly discharge from 100 basins in the Western United States, ranging in size from 1.3 km2 to 10,813 km2, reveals a more complex situation. The sequences of seasonal evolution of the hour of maximum discharge are unique to each basin, but within a given basin are remarkably consistent between years, regardless of the size of the snowpack. This seems to imply that basin topography strongly influences the timing of peak flow. In most of the basins examined, at the end of the melt season, the hour of maximum discharge shifts to later in the day, reflecting increased travel times as the snowline retreats to higher elevations. JF - 70th Annual Western Snow Conference T3 - Proceedings of the 70th Annual Western Snow Conference PB - Western Snow Conference CY - Granby, Colorado UR - sites/westernsnowconference.org/PDFs/2002Lundquist.pdf ER -