Assimilation of Screen-Level Variables in ECMWF’s Integrated Forecast System: A Study on the Impact on the Forecast Quality and Analyzed Soil Moisture
Open Access
- 1 February 2007
- journal article
- Published by American Meteorological Society in Monthly Weather Review
- Vol. 135 (2), 300-314
- https://doi.org/10.1175/mwr3309.1
Abstract
In many operational numerical weather prediction applications, the soil moisture analysis is based on the modeled first-guess and screen-level variables; that is, 2-m temperature and 2-m relative humidity. A set of two global 61-day analysis/forecast experiments based on the Integrated Forecast System at the European Centre for Medium-Range Weather Forecasts (ECMWF) has been performed for June and July 2002. Analyses and forecasts based on the operational Optimal Interpolation (OI) scheme are compared against results obtained from an open loop system, in which soil moisture evolves freely. It is found that soil moisture assimilation or analysis has a significant impact on the model atmosphere. Temperature forecasts for the Northern Hemisphere up to a level of 700 hPa and up to nine days were significantly improved when the operational analysis was used. A comparison of volumetric soil moisture against in situ observations from the Oklahoma Mesonet reveals, however, that the operational OI system fails to improve both the analysis and the subsequent forecast of soil moisture itself. In addition, the system is not able to correct soil moisture for errors introduced through wrong precipitation in the background forecasts. Biweekly observations from the Illinois Climate Network support these findings. This study confirms the long assumed (but rarely proven) characteristics of analysis schemes using screen-level variables: The observations are efficient in improving the turbulent surface fluxes and consequently the weather forecast on large geographical domains. The quality of the resulting soil moisture profile is often not sufficient for hydrological or agricultural applications.Keywords
This publication has 37 references indexed in Scilit:
- A Proposed Structure for Coupling Tiled Surfaces with the Planetary Boundary LayerJournal of Hydrometeorology, 2004
- Correcting Land Surface Model Predictions for the Impact of Temporally Sparse Rainfall Rate Measurements Using an Ensemble Kalman Filter and Surface Brightness Temperature ObservationsJournal of Hydrometeorology, 2003
- Operational Implementation of the ISBA Land Surface Scheme in the Canadian Regional Weather Forecast Model. Part I: Warm Season ResultsJournal of Hydrometeorology, 2003
- The assimilation of remotely sensed soil brightness temperature imagery into a land surface model using Ensemble Kalman filtering: a case study based on ESTAR measurements during SGP97Advances in Water Resources, 2003
- Using a Soil Hydrology Model to Obtain Regionally Averaged Soil Moisture ValuesJournal of Hydrometeorology, 2000
- Improved Installation Procedures for Deep-Layer Soil Moisture MeasurementsJournal of Atmospheric and Oceanic Technology, 2000
- Sequential Assimilation of Soil Moisture from Atmospheric Low-Level Parameters. Part I: Sensitivity and Calibration StudiesJournal of Applied Meteorology and Climatology, 1993
- Parameterization of Orography-Induced Turbulence in a Mesobeta--Scale ModelMonthly Weather Review, 1989
- A Statistical Exploration of the Relationships of Soil Moisture Characteristics to the Physical Properties of SoilsWater Resources Research, 1984
- Empirical equations for some soil hydraulic propertiesWater Resources Research, 1978