Abstract

The major undetermined problem in evaporation (ET) retrieval using thermal infrared (TIR) remote sensing is the lack of a physically based ground heat flux (G) model and its amalgamation with surface energy balance (SEB) model. Here, we present a novel approach based on coupling a thermal inertia (TI)-based mechanistic G model with an analytical SEB model (Surface Temperature Initiated Closure) (STIC, version STIC1.2). The coupled model is named as STIC-TI and it uses noon-night land surface temperature (TS), surface albedo and vegetation index from MODIS Aqua in conjunction with a clear-sky net radiation model and ancillary meteorological information. The SEB flux estimates from STIC-TI were evaluated with respect to the in-situ fluxes from Eddy Covariance (EC) measurements in diverse agriculture and natural ecosystems of contrasting aridity in the northern hemisphere (e.g., India, United States of America) and southern hemisphere (e.g., Australia). Sensitivity analysis revealed substantial sensitivity of the STIC-TI derived fluxes due to TS uncertainty and partial compensation of sensitivity of G to TS due to the nature of the equations used in the TI-based G model. An evaluation of STIC-TI G estimates with respect to in-situ measurements showed an error range of 12–21 % across six flux tower sites in both the hemispheres. A comparison of STIC-TI G estimates with other G models revealed substantially better performance of the former. While the instantaneous noontime net radiation (RNi) and latent heat flux (LEi) was overestimated (15 % and 25 %), sensible heat flux (Hi) was underestimated with error of 22 %. The errors in Gi were associated with the errors in daytime TS and mismatch of footprint between the model estimates and measurements. Overestimation (underestimation) of LEi (Hi) was associated with the overestimation of net available energy (RNi – Gi) and use of unclosed SEB measurements. Being independent of any leaf-scale conductance parameterization and having a coupled sub-model of G, STIC-TI can make valuable contribution to map and monitor water stress and evaporation in the terrestrial ecosystems using noon-night thermal infrared observations from existing and future EO missions such as INSAT 4th generation and TRISHNA.

Highlights

  • Ground heat flux (G) is an intrinsic component of the surface energy balance (Sauer and Horton, 2005), affecting the net available energy for evaporation (ET) and sensible heat flux

  • The current study addresses the following research questions and objectives: (i) What is the performance of Surface Temperature Initiated Closure (STIC)-thermal inertia (TI) G estimates when compared with contemporary empirical models in ecosystems having low mean fractional vegetation cover (≤0.5) and having larger soil exposure to radiation for example in Savanna?

  • Some divergence of data points within the cluster were noticed 474 which could be associated with different albedo ( R) levels

Read more

Summary

Introduction

Ground heat flux (G) is an intrinsic component of the surface energy balance (Sauer and Horton, 2005), affecting the net available energy for evaporation (ET) (the equivalent water depth of latent heat flux, LE) and sensible heat flux. Land surface temperature (LST or TS) retrieved through thermal infrared (TIR) remote sensing carries imprints of soil water content and is extraordinarily sensitive to evaporative cooling, which makes it a crucial variable for estimating sensible heat flux (H) ET through the SEB models (Kustas and Anderson, 2009; Mallick et al, 2014, 2015a, 2018a; Cammalleri and Vogt, 2015; Anderson et al, 2012). It is the aerodynamic temperature (T0) that is responsible for the sensible heat transfer and the inequality of Ts versus T0 introduces additional uncertainty in ET retrieval through the SEB models.

Methods
Results
Discussion
Conclusion
Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.