Combining the bulk transfer formulation and surface renewal analysis for estimating the sensible heat flux without involving the parameter

Abstract

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, kB 21 , which is difficult to parameterize. Over short and dense grass at a site influenced by regional advection of sensible heat flux, H MOST with kB 21 5 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 21 . Combining MOST and Surface Renewal analysis, three methods of estimating H that avoid kB 21 dependency have been derived. These new expressions explain the variability of H versus u à T c 2T ðzÞ À Á , where u à is the friction velocity, T c is the radiometric surface temperature, and T ðzÞ 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 2T ðzÞ À Á 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.

A New Method to Estimate Reference Crop Evapotranspiration from Geostationary Satellite Imagery: Practical Considerations

“…For a number of selected days, we will use ten-minute observations from Cabauw and half-hourly data from the lysimeter in Cordoba and from the RIA sites (see also [18]).…”

Daytime sensible heat flux estimation over heterogeneous surfaces using multitemporal land‐surface temperature observations

“…Appendix shows that the intercept a corrects for differences between the aerodynamic temperature and LST and that the slope may be interpreted as the ratio between the vertical surface velocity scale for heat transfer predicted by MOST and by SR analysis. Equation was first analyzed in the inertial sublayer over a homogeneous canopy [ Castellví et al ., ]. Combining equations and allows expressing the following SR‐flux expression for estimating the sensible heat flux involving LST ( H SR‐LST ): …”

“…Integration of the temperature gradient involves the parameter kB −1 which often has been presumed fairly constant. However, for more than five decades the parameter kB −1 has been a matter of basic research because its behavior and parameterization beyond neutral cases is not well understood [ Kustas et al ., ; Castellví et al ., ].…”

“…Castellví et al . [] proposed to linearly relate (LST − T Z ) and A Z , showing that a linear relationship holds for a wide range of atmospheric stability conditions over dense, short, irrigated grass. Therefore, it was possible to derive SR‐based equations for estimating H over a homogeneous canopy requiring measurements taken at low frequency as input.…”

“…Noteworthy that the SR‐flux approaches that do not require the ramp period as input have performed closely to the Eddy Correlation (EC) method over both homogeneous and heterogeneous canopies [e.g., Castellví et al ., ; Castellví , ; Castellví et al ., ]. It is, therefore, of interest to know if a linear relationship between (LST − T Z ) and A Z applies also for a heterogeneous canopy and if the two coefficients involved (slope and intercept) can be estimated using readily available measurements as input.…”