Global Land Evaporation Amsterdam Model
GLEAM (Global Land Evaporation Amsterdam Model) is a set of algorithms that separately estimate the different components of land evaporation (i.e. 'evapotranspiration'). These include transpiration, bare-soil evaporation, interception loss, open-water evaporation and sublimation. Additionally, GLEAM provides surface and root-zone soil moisture, potential evaporation and evaporative stress conditions.
The rationale of the method is to maximize the recovery of information about evaporation contained in current satellite observations of climatic and environmental variables.
The Priestley and Taylor equation used in GLEAM calculates potential evaporation based on observations of surface net radiation and near-surface air temperature. Estimates of potential evaporation for the land fractions of bare soil, tall canopy and short canopy are converted into actual evaporation using a multiplicative evaporative stress factor based on observations of microwave Vegetation Optical Depth (VOD) and estimates of root-zone soil moisture. The latter is calculated using a multi-layer running-water balance. To try to correct for random forcing errors, observations of surface soil moisture are also assimilated into the soil profile. Interception loss is calculated separately in GLEAM using a Gash analytical model. Finally, estimates of actual evaporation for water bodies and regions covered by ice and/or snow are obtained using the Priestley and Taylor equation adapted for ice and super-cooled waters.
The consideration of soil moisture constraints acting on evaporation
The detailed parameterization of tall-canopy interception loss
The extensive use of microwave observations, which is an asset under cloudy conditions
Since its development in 2011, GLEAM has been continuously revised and updated. Recently, a third version of the model (GLEAM v3.0) has been developed, and three datasets produced using this version of the model are currently available under Downloads.
The GLEAM v3.0 includes:
This version is described in detail by Martens et al. (2016, GMDD); a short description is provided below, including a list of the differences from the previous BETA version.
Version 3.0 datasets
Differences between this final GLEAM v3.0 and the previous BETA version are:
The three v3.0 datasets differ only in their forcing and spatio-temporal coverage.
For more detailed information, users are directed to the readme file on the server.
regarding GLEAM datasets
Datasets are freely available and can be downloaded after submitting your email. Use of the data is subject to the following terms and conditions:
Whenever GLEAM datasets are used in a scientific publication, the following references should be cited:
Martens, B., Miralles, D.G., Lievens, H., van der Schalie, R., de Jeu, R.A.M., Fernández-Prieto, D., Beck, H.E., Dorigo, W.A., and Verhoest, N.E.C.: GLEAM v3: satellite-based land evaporation and root-zone soil moisture, Geoscientific Model Development Discussions, doi: 10.5194/gmd-2016-162, 2016.
Miralles, D.G., Holmes, T.R.H., de Jeu, R.A.M., Gash, J.H., Meesters, A.G.C.A., Dolman, A.J.: Global land-surface evaporation estimated from satellite-based observations, Hydrology and Earth System Sciences, 15, 453–469, doi: 10.5194/hess-15-453-2011, 2011.
GLEAM datasets will not be used for commercial purposes.
. . . from the GLEAM front
New ERC grant using GLEAM
The ERC-granted DRY-2-DRY project will investigate drought self-intensification and self-propagation via land–atmospheric feedbacks. The work will take place over the next five years and will contribute to improving our understanding of drought evolution.
GLEAM v3 paper published
A paper describing the novel aspects of GLEAM v3 and the validation of the v3.0 datasets against in situ data has been published online in GMDD. Results show the added skill of the new set of algorithms. Please note that this paper serves as an official reference for the v3.0 datasets. Check user policy.
BAMS State of the Climate in 2015 published
The BAMS State of the Climate Report 2015 has been published. Results based on an analysis of GLEAM data show the impact of the strong 2015 El Niño on the terrestrial water cycle. Evaporation anomalies reflects the overlaying effects of multi-decadal climate trends and internal oscillations.
MSWEP paper online
The Multi-Source Weighted-Ensemble Precipitation (MSWEP) dataset is a new precipitation product selected as forcing for the GLEAM v3.0a dataset. The rationale of MSWEP is to optimally merge precipitation data retrieved from satellite-, gauge- and reanalysis products. The discussion paper describing the full methodology can be found here.
Version 3.0 datasets
Selected publications using GLEAM data
Zhang, Y., Peña-Arancibia, J.L., McVicar, T.R., Chiew, F.H.S., Vaze, J., Liu, C., Lu, X., Zheng, H., Wang., Y., Liu, Y.Y., Miralles, D.G., Pan M.: Multi-decadal trends in global terrestrial evapotranspiration and its components, Scientific Reports, 5, 19124, 2016.