ECLand: The ECMWF Land Surface Modelling System

Abstract

The land-surface developments of the European Centre for Medium-range Weather Forecasts (ECMWF) are based on the Carbon-Hydrology Tiled Scheme for Surface Exchanges over Land (CHTESSEL) and form an integral part of the Integrated Forecasting System (IFS), supporting a wide range of global weather, climate and environmental applications. In order to structure, coordinate and focus future developments and benefit from international collaboration in new areas, a flexible system named ECLand, which would facilitate modular extensions to support numerical weather prediction (NWP) and society-relevant operational services, for example, Copernicus, is presented. This paper introduces recent examples of novel ECLand developments on (i) vegetation; (ii) snow; (iii) soil; (iv) open water/lake; (v) river/inundation; and (vi) urban areas. The developments are evaluated separately with long-range, atmosphere-forced surface offline simulations and coupled land-atmosphere-ocean experiments. This illustrates the benchmark criteria for assessing both process fidelity with regards to land surface fluxes and reservoirs of the water-energy-carbon exchange on the one hand, and on the other hand the requirements of ECMWF’s NWP, climate and atmospheric composition monitoring services using an Earth system assimilation and prediction framework.

ERA5-Land: a state-of-the-art global reanalysis dataset for land applications

“…The land surface model used in ERA5-Land, CHTESSEL, also has the option to estimate carbon fluxes and its coupling with plants transpiration through the A-gs formulation (Jacobs et al, 1996;Calvet et al, 1998;Boussetta et al, 2013a). This module is operationally active for the vegetation, and it allows estimates for the carbon fluxes in a modular approach with evaporation being computed through a resistance approach (Jarvis et al, 1976).…”

“…All the components discussed above are currently under research, but they are not the only ones. ECMWF is currently working with a flexible, modular system called ECLand (Boussetta et al, 2021) which allows us to separately develop several modelling aspects of the land surface, such as the increase in the number of soil layers or the introduction of a multi-layer snow scheme, as well as make progress on other longer-term perspectives such as the introduction of a groundwater storage or the reduction of the model time step. All the above ongoing developments will provide the basis for a future new version with improved accuracy for the land states at multi-decadal timescales.…”

“…More recently, multi-model intercomparison studies and datasets focusing on water resources monitoring (Harding et al, 2011;Schellekens et al, 2017) or climate modelling (van den Hurk et al, 2016;Krinner et al, 2018) have gained significant visibility. Offline simulations remain attractive due to their computational affordability and the needs that follow from the rapid evolution of land surface models (Pitman, 2003;Vereecken et al, 2019;Boussetta et al, 2021).…”

Hydrological Impact of the New ECMWF Multi-Layer Snow Scheme

“…The hydrological core of the analyzed data sets was provided by the ECLand landsurface model, formerly known as HTESSEL (The Hydrology-Tiled ECMWF Scheme for Surface Exchange over Land [20,21,36]). ECLand is part of the Integrated Forecasting System (IFS) at ECMWF and used in coupled land-atmosphere simulations for describing the evolution of soil, vegetation and snow conditions over land, at various spatial resolutions, from short-to seasonal-range.…”

“…The snow scheme currently used operationally in the ECLand land-surface model at the European Centre for Medium-Range Weather Forecasts (ECMWF) [20,21] and which is used in the production of the ERA5 [22] and ERA5-Land [23] reanalysis datasets, is a single-layer snow scheme (SLS hereafter) with an additional snow layer on top of the soil [17]. The use of only one layer limits the handling of the temporal evolution of the snow, as changes on multiple time scales (i.e., diurnal to seasonal) cannot be accurately represented.…”