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Combining the bulk transfer formulation and surface renewal analysis for estimating the sensible heat flux without involving the parameter k B − 1
Author(s) -
Castellví F.,
Gavilán P.,
GonzálezDugo M. P.
Publication year - 2014
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1002/2013wr014950
Subject(s) - sensible heat , advection , eddy covariance , environmental science , flux (metallurgy) , heat flux , heat transfer , homogeneous , mechanics , meteorology , mathematics , thermodynamics , materials science , physics , ecology , ecosystem , biology , metallurgy
The single‐source bulk transfer formulation (based on the Monin‐Obukhov Similarity Theory, MOST) has been used to estimate the sensible heat flux, H , in the framework of remote sensing over homogeneous surfaces ( H MOST ). The latter involves the canopy parameter, k B − 1, which is difficult to parameterize. Over short and dense grass at a site influenced by regional advection of sensible heat flux, H MOST with k B − 1 = 2 (i.e., the value recommended) correlated strongly with the H measured using the Eddy Covariance, EC, method, H EC . However, it overestimated H EC by 50% under stable conditions for samples showing a local air temperature gradient larger than the measurement error, 0.4 km −1 . Combining MOST and Surface Renewal analysis, three methods of estimating H that avoid k B − 1dependency have been derived. These new expressions explain the variability of H versusu *( T c − T ( z )) , whereu *is the friction velocity,T cis the radiometric surface temperature, andT ( z )is the air temperature at height, z. At two measurement heights, the three methods performed excellently. One of the methods developed required the same readily/commonly available inputs as H MOST due to the fact that the ratio between( T c − T ( z ))and the ramp amplitude was found fairly constant under stable and unstable cases. Over homogeneous canopies, at a site influenced by regional advection of sensible heat flux, the methods proposed are an alternative to the traditional bulk transfer method because they are reliable, exempt of calibration against the EC method, and are comparable or identical in cost of application. It is suggested that the methodology may be useful over bare soil and sparse vegetation.