Multi-model assessment of the impact of soil moisture initialization on mid-latitude summer predictability
Land surface initial conditions have been recognized as a potential source of predictability in sub-seasonal to seasonal forecast systems, at least for near-surface air temperature prediction over the mid-latitude continents. Yet, few studies have systematically explored such an influence over a sufficient hindcast period and in a multi-model framework to produce a robust quantitative assessment. Here, a dedicated set of twin experiments has been carried out with boreal summer retrospective forecasts over the 1992–2010 period performed by five different global coupled ocean–atmosphere models. The impact of a realistic versus climatological soil moisture initialization is assessed in two regions with high potential previously identified as hotspots of land–atmosphere coupling, namely the North American Great Plains and South-Eastern Europe. Over the latter region, temperature predictions show a significant improvement, especially over the Balkans. Forecast systems better simulate the warmest summers if they follow pronounced dry initial anomalies. It is hypothesized that models manage to capture a positive feedback between high temperature and low soil moisture content prone to dominate over other processes during the warmest summers in this region. Over the Great Plains, however, improving the soil moisture initialization does not lead to any robust gain of forecast quality for near-surface temperature. It is suggested that models biases prevent the forecast systems from making the most of the improved initial conditions.
KeywordsLand-surface initialization Seasonal forecasting Land–atmosphere coupling Multi-model Ensemble forecast
The authors thank Jeff Knight (Met Office Hadley Centre) for his constructive comments on earlier versions of this manuscript. The research leading to these results received funding from the European Union Seventh Framework Programme (FP7/2007–2013) SPECS project (Grant Agreement Number 308378) and H2020 Framework Programme IMPREX project (Grant Agreement Number 641811). Constantin Ardilouze was also supported by the BSC Centro de Excelencia Severo Ochoa Programme.
- Alessandri A, Catalano F, De Felice M, Van Den Hurk B, Doblas Reyes FJ, Boussetta S, Balsamo G, Miller P (2016) Multi-scale enhancement of climate prediction over land by increasing the model sensitivity to vegetation variability in EC-Earth. Clim Dyn (in press)Google Scholar
- Boussetta S, Balsamo G, Beljaars A et al (2012) Natural land carbon dioxide exchanges in the ECMWF integrated forecasting system: implementation and offline validation. European Centre for Medium-Range Weather Forecasts, Shinfield Park, ReadingGoogle Scholar
- Doblas-Reyes FJ, García-Serrano J, Lienert F et al (2013) Seasonal climate predictability and forecasting: status and prospects. WIREs Clim Change 4:245–268. doi: 10.1002/wcc.217
- Douville H (2009) Relative contribution of soil moisture and snow mass to seasonal climate predictability: a pilot study. Clim Dyn 34:797–818. doi: 10.1007/s00382-008-0508-1
- Hurk BVD, Doblas-Reyes F, Balsamo G et al (2010) Soil moisture effects on seasonal temperature and precipitation forecast scores in Europe. Clim Dyn 38:349–362. doi: 10.1007/s00382-010-0956-2
- Hurk BVD, Kim H, Krinner G et al (2016) The land surface, snow and soil moisture model intercomparison program (LS3MIP): aims, set-up and expected outcome. Geosci Model Dev Discuss 1–41. doi: 10.5194/gmd-2016-72
- Lorenz R, Jaeger EB, Seneviratne SI (2010) Persistence of heat waves and its link to soil moisture memory. Geophys Res Lett 37:L09703. doi: 10.1029/2010GL042764
- Palmer TN, Doblas-Reyes FJ, Hagedorn R et al (2004) Development of a European multimodel ensemble system for seasonal-to-interannual prediction (DEMETER). Bull Amer Meteor Soc 85(6):853–872. doi: 10.1175/BAMS-85-6-853
- Schneider U, Fuchs T, Meyer-Christoffer A, Rudolf B (2008) Global precipitation analysis products of the GPCC. Global Precipitation Climatology Centre (GPCC), DWD, Internet Publication, vol 112. ftp://ftp.dwd.de/pub/data/gpcc/PDF/GPCC_intro_products_2008.pdf. Accessed 25 May 2016