High-Resolution Spatial Modeling of Daily Weather Elements for a Catchment in the Oregon Cascade Mountains, United States

Abstract

High-quality, daily meteorological data at high spatial resolution are essential for a variety of hydrologic and ecological modeling applications that support environmental risk assessments and decision making. This paper describes the development, application, and assessment of methods to construct daily highresolution (ϳ50-m cell size) meteorological grids for the 2003 calendar year in the Upper South Santiam Watershed (USSW), a 500-km 2 mountainous catchment draining the western slope of the Oregon Cascade Mountains. Elevations within the USSW ranged from 194 to 1650 m. Meteorological elements modeled were minimum and maximum temperature; total precipitation, rainfall, and snowfall; and solar radiation and radiation-adjusted maximum temperature. The Parameter-Elevation Regressions on Independent Slopes Model (PRISM) was used to interpolate minimum and maximum temperature and precipitation. The separation of precipitation into rainfall and snowfall components used a temperature-based regression function. Solar radiation was simulated with the Image-Processing Workbench. Radiation-based adjustments to maximum temperature employed equations developed from data in the nearby H. J. Andrews Experimental Forest. The restrictive terrain of the USSW promoted cold-air drainage and temperature inversions by reducing large-scale airflow. Inversions were prominent nearly all year for minimum temperature and were noticeable even for maximum temperature during the autumn and winter. Precipitation generally increased with elevation over the USSW. In 2003, precipitation was nearly always in the form of rain at the lowest elevations but was about 50% snow at the highest elevations. Solar radiation followed a complex pattern related to terrain slope, aspect, and position relative to other terrain features. Clear, sunny days with a large proportion of direct radiation exhibited the greatest contrast in radiation totals, whereas cloudy days with primarily diffuse radiation showed little contrast. Radiation-adjusted maximum temperatures showed similar patterns. The lack of a high-quality observed dataset was a major issue in the interpolation of precipitation and solar radiation. However, observed data available for the USSW were superior to those available for most mountainous regions in the western United States. In this sense, the methods and results presented here can inform others performing similar studies in other mountainous regions.

Physiographically sensitive mapping of climatological temperature and precipitation across the conterminous United States

“…and W e are the cluster, distance, elevation, coastal proximity, topographic facet, vertical layer, topographic position, and effective terrain weights, respectively, and F d and F z are userspecified distance and elevation weighting importance scalars Daly et al, 2007). All weights and importance factors, individually and combined, are normalized to sum to unity.…”

“…The resulting grid represents the local, or relative, elevation variations within a given area ( Figure 5). The selection of the search and averaging parameters (Table II) was again somewhat subjective and pragmatic, and depended largely on station data density (Daly et al, 2007).…”

“…Several additional spatial climate-forcing factors are most important at relatively small scales of less than 1 km, but can have influences at larger scales as well. These factors include slope and aspect (McCutchan and Fox, 1986;Barry, 1992;Bolstad et al, 1998;Lookingbill and Urban, 2003;Daly et al, 2007), riparian zones (Brosofske et al, 1997;Dong et al, 1998;Lookingbill and Urban, 2003), and land use/landcover (Davey and Pielke, 2005). Land use/landcover variations are a major consideration in the spatial representativeness of climate stations at much larger scales.…”

Local atmospheric decoupling in complex topography alters climate change impacts

“…Located on the western or windward slopes of the Cascade Range, the HJA receives orographically enhanced precipitation that typically increases with elevation. The steep, deeply incised slopes and narrow valleys are highly susceptible to cold air drainage and pooling (Daly et al, 2007;Pypker et al, 2007). In situations with a negative radiation balance and low wind speeds, temperatures stratify quickly with cool, dense air draining into local valleys and depressions.…”

Parameterizing sub-surface drainage with geology to improve modeling streamflow responses to climate in data limited environments

“…Here we use a relatively simple approach where point meteorologic measurements of temperature are scaled using a constant environmental lapse rate of temperature with elevation, and precipitation is scaled based on long-term mean patterns derived from PRISM (Daly et al, 1994). Recent studies have shown that air temperature lapse rates with elevation are considerably more complex in this region, reflecting temperature inversions and cold air pooling (Lundquist and Cayan, 2007;Daly et al, 2007). Similarly, there are likely to be substantial errors in interpolating precipitation data for specific storm events.…”