A portion of generated surface and groundwater resources evaporates from wetlands, water bodies and irrigated areas. At the global scale, a lack of detailed water balance studies and direct observations limits our understanding of the magnitude and spatial and temporal distribution of this ‘secondary’ evaporation.

We assimilated satellite-derived information into the landscape hydrological model W3 at 0.05°, or ca. 5km resolution globally. The assimilated data are all derived from MODIS observations, including surface water extent, surface albedo, vegetation cover, leaf area index, canopy conductance and land surface temperature (LST). The information from these products is imparted on the model in a simple but efficient manner, through a combination of direct insertion of the surface water extent, an evaporation flux adjustment based on LST and parameter nudging for the other observations.

Reference

van Dijk, A. I. J. M., Schellekens, J., Yebra, M., Beck, H. E., Renzullo, L. J., Weerts, A., and Donchyts, G.: Global 5 km resolution estimates of secondary evaporation including irrigation through satellite data assimilation, Hydrol. Earth Syst. Sci., 22, 4959-4980, https://doi.org/10.5194/hess-22-4959-2018, 2018.

Data access

You can find daily 0.05° estimates of ET and its components for the period 2000-2014 via our OpenDAP THREDDS catalogue:  http://dapds00.nci.org.au/thredds/catalog/ub8/global/W3/v2/0_05d/catalog.html

Available ET variables include:

• potential evaporation (E0)
• total ET (ETtot)
• secondary ET (Elat)
• transpiration (Et)
• soil evaporation (Es)
• water evaporation (Er)

Estimates of other radiation, water and energy balance terms as well as gross primary production are also available from the same location.

Notes:

• It is recommended to disregard data for 2000 as spin-up artefacts can occur.
• secondary ET has not been attributed to the evaporation mechanism. A method to do so can be found in the reference paper.