Evapotranspiration Modelling and Observation

The HALO Group undertake cutting edge research in both the measurement and modelling of evapotranspiration. These activities range from determining the irrigation water requirements (and use) of agricultural fields to describing the global scale distribution and pattern of latent and sensible heat fluxes. We use a range of modelling and measurement approaches to do this, further details of which are provided in some of the links below:

• Global scale estimation of surface heat fluxes: the HALO Group is involved in a number of international efforts to monitor and measure the exchanges of heat and energy fluxes at regional to global scales. Two of the major activities include work with the  GEWEX Data and Assessments Panels LandFLUX project and the  European Space Agency WACMOS-ET project, both of which Prof McCabe is actively engaged with. The LandFLUX project has a number of recent publications and presentation that further describe these activities. 

Global intercomparison of 12 land surface heat flux estimates​ (external link to Jimenez et al. 2011)

• ​Multi-model estimation of evaporation: considerable research efforts have been focused on understanding the limitations, sensitivities and uncertainties in the estimation of surface heat fluxes across a range of models. These works include  globlaly distributed assessments of surface heat fluxes (model comparison against tower data) and ongoing work related to the issue of appropriate parameterization description and selection. 

We have recently published some research examining the role of input forcing uncertainty in heat flux estimation, using a novel Bayesian Inference Technique to describe model uncertainty and error. See Ershadi et al (2013) “ A Bayesian analysis of sensible heat flux estimation: quantifying uncertainty in meteorological forcing to improve model prediction” in Water Resources Research. 

• Scale issues in remote sensing of evaporation:​ understanding how heat fluxes scale in space (and time) is a considerable challenge - especially when undertaking retreivals via satellite based sensors. With a wide range of possible sensors and systems available from which to derive heat fluxes (see Kalma et al, 2008 for a comprehsive review), determining the consistency and variabilty between them is of much interest. Following earlier work of McCabe et al. (2006) on " Scale influences on the remote estimation of evapotranspiration using multiple satellite sensors", Mr Ali Ershadi has recently published an extensive examination of scale issues in flux retrieval using a time-series of high resolution LandSat data, finding that there are important consequences with both the resolution at which fluxes are retrieved and also the importance of the aggregation/disaggregation technique. Further details on this work can be found in Ershadi et al. (2013) “ Effects of spatial aggregation on the multi-scale estimation of evapotranspiration” in Remote Sensing of Environment.