A harmonized global land evaporation dataset from model-based products covering 1980–2017

Jiao Lu,Giri Kattel,Guojie Wang,Tiexi Chen,Daniel Fiifi Tawia Hagan,Jian Peng,Buda Su,Tong Jiang,Shijie Li

doi:10.5194/essd-13-5879-2021

Abstract

Abstract. Land evaporation (ET) plays a crucial role in the hydrological and energy cycle. However, the widely used model-based products, even though helpful, are still subject to great uncertainties due to imperfect model parameterizations and forcing data. The lack of available observed data has further complicated estimation. Hence, there is an urgency to define the global proxy land ET with lower uncertainties for climate-induced hydrology and energy change. This study has combined three existing model-based products – the fifth-generation ECMWF reanalysis (ERA5), Global Land Data Assimilation System Version 2 (GLDAS2), and the second Modern-Era Retrospective analysis for Research and Applications (MERRA-2) – to obtain a single framework of a long-term (1980–2017) daily ET product at a spatial resolution of 0.25∘. Here, we use the reliability ensemble averaging (REA) method, which minimizes errors using reference data, to combine the three products over regions with high consistencies between the products using the coefficient of variation (CV). The Global Land Evaporation Amsterdam Model Version 3.2a (GLEAM3.2a) and flux tower observation data were selected as the data for reference and evaluation, respectively. The results showed that the merged product performed well over a range of vegetation cover scenarios. The merged product also captured the trend of land evaporation over different areas well, showing the significant decreasing trend in the Amazon Plain in South America and Congo Basin in central Africa and the increasing trend in the east of North America, west of Europe, south of Asia and north of Oceania. In addition to demonstrating a good performance, the REA method also successfully converged the models based on the reliability of the inputs. The resulting REA data can be accessed at https://doi.org/10.5281/zenodo.4595941 (Lu et al., 2021).

Highlights

Land evaporation plays an important role in the exchange of energy, water and carbon in the terrestrial biosphere, hydrosphere and atmosphere
In the high latitudes of the Northern Hemisphere, Global Land Data Assimilation System Version 2 (GLDAS2)– Noah ET is more than 20 % higher than the mean of the three products and ERA5 ET is almost the same as the mean, while MERRA-2 ET is more than 20 % lower than the mean
ERA5 ET is more than 20 % higher than the ensemble mean, while GLDAS2–Noah ET is more than 20 % lower than it

Summary

Introduction

Land evaporation plays an important role in the exchange of energy, water and carbon in the terrestrial biosphere, hydrosphere and atmosphere. It is one of the dominant components of land water and the energy budget, as well as a key driver of drought episodes (Seneviratne, 2012; Sheffield et al, 2012). It is important to quantify the spatial and temporal patterns of land evaporation. The strength of the hydrological cycle determines water availability and affects the climate system in a variety of ways (Mueller et al, 2013).

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Conclusion