Development and evaluation of global land surface evaporative flux records

Understanding the spatial and temporal behavior of evaporation at regional and global scales is important for improving our understanding of the water, energy and carbon cycles. In recent years, there have been a number of efforts to develop global products of land surface heat flux, spanning a range of space and time scales and utilising a variety of different forcing and underlying model structures. In the context of the GEWEX-LandFlux and WACMOS-ET projects, the efforts have been guided by a need for independent and observation driven predictions of the heat fluxes, using remotely sensed data where available and supplementing with other forcing when required. The GEWEX based project has provided long-term records of fluxes that will enable an assessment of trends and variability to be examined, while the WACMOS-ET project, operating over a shorter period, has offered insights into the inter-model variability of flux response over many regions. These data sets provide a means to better understand the cycling of water through the Earth system, examining not only the absolute range of flux observed, but also how this changes in space and time. Here we will present some of the key outcomes and findings of these efforts, together with some of the lessons learned in delivering long-term, consistent flux records. Results focusing on examining the multimodel and multi-scale assessment of flux products will be presented, together with an evaluation of product differences and areas where future work is required to improve flux characterization. Issues of product independence, model structure, forcing data and model sensitivity will also be explored.