Predicting Latent and Sensible Heat Fluxes in Stream Temperature Models: Current Challenges and Potential Solutions. Issue 2 (24th February 2021)

• Record Type: Journal Article
• Authors: Moore, R. D.; Leach, J. A.
• Is Part Of: Water resources research. Volume 57:Issue 2(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-02-24
• Subjects: Dalton equation -- energy balance -- evaporation -- Penman combination equation -- stream temperature -- wind function; Hydrology -- Periodicals; 333.91
• DOI: 10.1029/2020WR028712
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: Stream temperature studies typically use either the Penman combination equation (PCE) or empirical wind functions to compute the latent heat flux, which can be an important control on daily maximum water temperature. The sensible heat flux is usually computed from the latent heat flux via the Bowen ratio or a bulk transfer model. Unfortunately, both the PCE and empirical wind functions involve challenges. The PCE is inappropriate for application to subdaily stream evaporation because, as implemented in many stream temperature studies, it does not account for energy associated with warming or cooling of the water column or bed heat fluxes. The PCE thus tends to overestimate evaporation under conditions typical of warm summer days during the diurnal warming phase, which is when evaporation is likely to be an important heat loss mechanism. Empirical wind functions involve substantial uncertainty given the broad range of coefficient values that have been reported in the literature and the lack of above‐stream meteorological data to use in their application. We provide suggestions for improving current practice and also identify research directions to support development of robust approaches to computing the latent and sensible heat fluxes. Key Points: The Penman combination equation is not appropriate for computing subdaily stream evaporation There is considerable uncertainty associated with coefficients in empirical wind functions for computing evaporation and sensible heat flux Suggestions for current practice and longer‐term research are provided