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Lookup NU author(s): Thomas Frost,
Professor Robert Upstill-Goddard
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The relationships between gas transfer velocity, k(600), wind speed, wind direction, rainfall, and relative humidity were examined using measurements of SF, evasion from Coatenhill Reservoir, a small (0.017 km(2)), shallow (1.9 +/- 0.1 m), man-made lake in northeast England characterized by predominantly low to intermediate wind speeds similar to1-10 m s(-1). A graphical method was used to estimate the wind speed at a standard height of 10 m, U-10 from wind speed measurements at 2 m and 3.8 m. Derived values of U-10 normalized to remove thermal stability effects (U-10-n) were significantly correlated with k(600) (R-2 = 0.71, p < 0.001). A detailed analysis of surface roughness lengths estimated with this procedure showed the k(600) versus U-10-n relationship to be sensitive to wind speed modification by the meteorological mast and sensors. With normalization to remove these effects, the correlation between k(600) and U-10-n substantially improved (R-2 = 0.86, p < 0.001). In contrast to previous laboratory findings, relative humidity was not significantly correlated with k(600) and rainfall rate (R-n) was only weakly correlated with k(600), possibly as a consequence of the effects of these variables being largely masked by the time scales of data averaging and SF6 sampling. Similarly, k(600) was not correlated with wind direction (i.e., fetch). An empirical gas exchange model accounted for 88% of the total variance in k(600) (P = 0.01) at Coatenhill, with U-10-n and R-n accounting for 86% and 2%, respectively. Future field investigations of the meteorological controls of k(600) will require careful experimental design to allow for more detailed sampling than hitherto has been possible.
Author(s): Upstill-Goddard RC; Frost T
Publication type: Article
Publication status: Published
Journal: Limnology and Oceanography
ISSN (print): 0024-3590
ISSN (electronic): 1939-5590
Publisher: American Society of Limnology and Oceanography, Inc.
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