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Comparison of the Sensitivity of Surface Downward Longwave Radiation to Changes in Water Vapor at Two High Elevation SitesAmong the potential reasons for enhanced warming rates in many high elevation regions is the nonlinear relationship between surface downward longwave radiation (DLR) and specific humidity (q). In this study we use ground-based observations at two neighboring high elevation sites in Southwestern Colorado that have different local topography and are 1.3 kilometers apart horizontally and 348 meters vertically. We examine the spatial consistency of the sensitivities (partial derivatives) of DLR with respect to changes in q, and the sensitivities are obtained from the Jacobian matrix of a neural network analysis. Although the relationship between DLR and q is the same at both sites, the sensitivities are higher when q is smaller, which occurs more frequently at the higher elevation site. There is a distinct hourly distribution in the sensitivities at both sites especially for high sensitivity cases, although the range is greater at the lower elevation site. The hourly distribution of the sensitivities relates to that of q. Under clear skies during daytime, q is similar between the two sites, however under cloudy skies or at night, it is not. This means that the DLR-q sensitivities are similar at the two sites during daytime but not at night, and care must be exercised when using data from one site to infer the impact of water vapor feedbacks at another site, particularly at night. Our analysis suggests that care should be exercised when using the lapse rate adjustment to infill high frequency data in a complex topographical region, particularly when one of the stations is subject to cold air pooling as found here.
Document ID
20150023365
Document Type
Reprint (Version printed in journal)
Authors
Chen, Yonghua (Columbia Univ. New York, NY, United States)
Naud, Catherine M. (Columbia Univ. New York, NY, United States)
Rangwala, Imtiaz (Colorado Univ. Boulder, CO, United States)
Landry, Christopher C. (Center for Snow and Avalanche Studies Silverton, CO, United States)
Miller, James R. (Rutgers Univ. New Brunswick, NJ, United States)
Date Acquired
December 18, 2015
Publication Date
November 18, 2014
Publication Information
Publication: Environmental Research Letters
Volume: 9
Issue: 11
Subject Category
Meteorology and Climatology
Report/Patent Number
GSFC-E-DAA-TN19060
Funding Number(s)
CONTRACT_GRANT: NSF-1064326
CONTRACT_GRANT: NNX14AB99A
CONTRACT_GRANT: NSF-1064281
Distribution Limits
Public
Copyright
Other
Keywords
elevation
nonlinearity
daytime
night
Colorado