When GLEAM4 datasets are used in a scientific publication, the following references should be cited:

• GLEAM

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

• GLEAM4 datasets

Miralles, D.G., Koppa, A., Baez-Villanueva, O.M., Tronquo, E., Bonte, O., Zhong, F., Beck, H.E., Hulsman, P., Haghdoost, S., Dorigo, W.A. GLEAM4: global evaporation and soil moisture datasets at 0.1° resolution from 1980 to near present, in prep.

• Interception module

Zhong, F., Jiang, S., Dijk, A.I.J.M. van, Ren, L., Schellekens, J., Miralles, D.G. Revisiting large-scale interception patterns constrained by a synthesis of global experimental data, Hydrology and Earth System Sciences, 26, 5647–5667, 2022

• Soil module

Hulsman, P., Keune, J., Koppa, A., Schellekens, J. & Miralles, D. G. Incorporating Plant Access to Groundwater in Existing Global, Satellite‐Based Evaporation Estimates, Water Resources Research, 59, 2023

• Stress module

Koppa, A., Rains, D., Hulsman, P., Poyatos, R., Miralles, D.G. A deep learning-based hybrid model of global terrestrial evaporation, Nature Communications, 13, 1912, 2022

After registration on the website, I didn’t receive the login details. What should I do?
Login details are automatically sent to the email address submitted on the website. If you did not receive login details within one hour after registration, please check your SPAM-folder. If you did not receive any email after that time, you can send your request to info@gleam.eu.
 

I am not able to connect to the server, what am I doing wrong?
Carefully read the login details and make sure that you are using the right credentials. Also make sure that you are defining the right file transfer protocol, being SFTP (Secure File Transfer Protocol). Check your firewall settings to make sure that the access to our server through port 2225 is not blocked.
 

What is terrestrial evaporation, and how does it relate to the latent heat flux and 'evapotranspiration'?
Terrestrial evaporation is the total flux of water from land into the atmosphere (typically expressed in mm) from soil (bare soil evaporation), plant surfaces (interception loss), water surfaces (open-water evaporation), and through plant stomata (transpiration). This flux is often referred to as evapotranspiration. The associated consumption of energy to change the phase of water from liquid to gas during the process, is the latent heat flux (typically expressed in W.m^-2), and can be calculated by accounting for the latent heat of vaporization. More information on the use of the term evapotranspiration.
 

Where can I find more information about GLEAM?
A detailed description of the methodology is provided in different scientific articles listed under Publications.
 

Are the data direct observations? What is their accuracy?
Actual evaporation is not directly measured from space. The articles under Publications contain a subset of the validations, product inter-comparisons and error analyses undergone to date.
 

Are the estimates from GLEAM directly comparable with eddy-covariance latent heat flux measurements?
Due to several issues, both estimates cannot be directly compared, and validation studies should be carefully designed: (1) the footprint of eddy-covariance towers is typically on the order of 1 km, while GLEAM pixels cover an area that is substantially larger (aprox. 10 x 10 km). This results in a representativity error, especially in heterogeneous areas; (2) the energy balance at eddy-covariance sites is generally not closed, and the actual latent heat flux tends to be underestimated; (3) eddy-covariance measurements are unreliable during rain events. Because interception fluxes can be large in nature – and so will GLEAM estimates of this flux – we strongly recommend masking times of rain and interception fluxes when comparing to eddy-covariance measurements. This is common practice in validation studies.
 

Why are there negative values in the evaporation dataset?
Missing data is indicated with a value of “–999” for all variables. Negative values (apart from “–999”) in the evaporation data indicate a negative latent heat flux, and thus a net condensation of water vapor. This typically occurs when the net radiation at the surface is negative.
 

At what spatial and temporal resolution are the data available?
All datasets are available on a 0.1° latitude-longitude regular grid and at daily temporal resolution.
 

Why is there no data available over oceans?
GLEAM is only designed to estimate evaporation over land surfaces.
 

Is the forcing data of GLEAM available on the server?
The forcing of GLEAM is not available from the server. All data used to force GLEAM are freely available from the respective data portals. References for all datasets are provided in the README file on the server and/or in Miralles et al. (in prep.).
 

Are the static parameters of GLEAM available from the server?
The static parameters of GLEAM (e.g. soil properties) are not available from the server. All data used are freely available from the respective data portals. References for all datasets are provided in the README file on the server and/or in Miralles et al. (in prep.).
 

How is the data structured?
The data is provided in netCDF format. A README file is available on the server describing the structure of the data in full detail.
 

What is the difference between the GLEAM4.1a and GLEAM4.1b datasets?
These datasets are produced using the same methodology, but different forcing datasets. They also differ in their temporal coverage. A detailed description is provided under Datasets and in the README file available on the server. 
 

How often are the datasets updated?
Datasets are typically updated and extended once a year, and are generally released around April. All users are notified when new data are available.
 

Are old versions of the dataset still available for download?
When a new version of a dataset is released, the older version becomes obsolete and is removed from the server. However, previous versions are still available upon request.