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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, D11124, doi:10.1029/2006JD007561, 2007

Surface temperature patterns in complex terrain: Daily variations and long-term change in the central Sierra Nevada, California

Jessica D. Lundquist

Cooperative Institute for Research in Environmental Sciences–NOAA Earth Systems Laboratory, Boulder, Colorado, USA


Daniel R. Cayan

Scripps Institution of Oceanography, La Jolla, California, USA
U. S. Geological Survey, La Jolla, California, USA


Abstract

A realistic description of how temperatures vary with elevation is crucial for ecosystem studies and for models of basin-scale snowmelt and spring streamflow. This paper explores surface temperature variability using temperature data from an array of 37 sensors, called the Yosemite network, which traverses both slopes of the Sierra Nevada in the vicinity of Yosemite National Park, California. These data indicate that a simple lapse rate is often a poor description of the spatial temperature structure. Rather, the spatial pattern of temperature over the Yosemite network varies considerably with synoptic conditions. Empirical orthogonal functions (EOFs) were used to identify the dominant spatial temperature patterns and how they vary in time. Temporal variations of these surface temperature patterns were correlated with large-scale weather conditions, as described by National Centers for Environmental Prediction-National Center for Atmospheric Research Reanalysis data. Regression equations were used to downscale larger-scale weather parameters, such as Reanalysis winds and pressure, to the surface temperature structure over the Yosemite network. These relationships demonstrate that strong westerly winds are associated with relatively warmer temperatures on the east slope and cooler temperatures on the west slope of the Sierra, and weaker westerly winds are associated with the opposite pattern. Reanalysis data from 1948 to 2005 indicate weakening westerlies over this time period, a trend leading to relatively cooler temperatures on the east slope over decadal timescales. This trend also appears in long-term observations and demonstrates the need to consider topographic effects when examining long-term changes in mountain regions.

Received 25 May 2006; accepted 22 February 2007; published 14 June 2007.

Keywords: Mountain temperature; climate change; Sierra Nevada.

Index Terms: 3305 Atmospheric Processes: Climate change and variability (1616, 1635, 3309, 4215, 4513); 3322 Atmospheric Processes: Land/atmosphere interactions (1218, 1631, 1843); 3394 Atmospheric Processes: Instruments and techniques; 1848 Hydrology: Monitoring networks.

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Citation: Lundquist, J. D., and D. R. Cayan (2007), Surface temperature patterns in complex terrain: Daily variations and long-term change in the central Sierra Nevada, California, J. Geophys. Res., 112, D11124, doi:10.1029/2006JD007561.