A Revised Hydrology for the ECMWF Model: Verification from Field Site to Terrestrial Water Storage and Impact in the Integrated Forecast System

TLDR

The Tiled ECMWF Scheme for Surface Exchanges over Land (TESSEL) is operational in the Integrated Forecast System, modeling soil, vegetation, and snow evolution across continents at multiple resolutions. H‑TESSEL was introduced to remedy TESSEL’s lack of surface runoff and its use of a globally uniform soil texture. H‑TESSEL incorporates infiltration and runoff algorithms that depend on soil texture and orography variability, and its performance was evaluated in stand‑alone experiments against field observations and in coupled data‑assimilation runs. The revised scheme yields a larger dynamical range of continental land water mass, improves river runoff predictions, and reduces midlatitude errors in soil moisture and 2‑m temperature, with only minor impact on atmospheric fluxes.

Abstract

Abstract The Tiled ECMWF Scheme for Surface Exchanges over Land (TESSEL) is used operationally in the Integrated Forecast System (IFS) for describing the evolution of soil, vegetation, and snow over the continents at diverse spatial resolutions. A revised land surface hydrology (H-TESSEL) is introduced in the ECMWF operational model to address shortcomings of the land surface scheme, specifically the lack of surface runoff and the choice of a global uniform soil texture. New infiltration and runoff schemes are introduced with a dependency on the soil texture and standard deviation of orography. A set of experiments in stand-alone mode is used to assess the improved prediction of soil moisture at the local scale against field site observations. Comparison with basin-scale water balance (BSWB) and Global Runoff Data Centre (GRDC) datasets indicates a consistently larger dynamical range of land water mass over large continental areas and an improved prediction of river runoff, while the effect on atmospheric fluxes is fairly small. Finally, the ECMWF data assimilation and prediction systems are used to verify the effect on surface and near-surface quantities in the atmospheric-coupled mode. A midlatitude error reduction is seen both in soil moisture and in 2-m temperature.