Impact of soil moisture initialization on boreal summer subseasonal forecasts: mid-latitude surface air temperature and heat wave events

Eunkyo Seo, Myong In Lee, Jee Hoon Jeong, Randal D. Koster, Siegfried D. Schubert, Hye Mi Kim, Daehyun Kim, Hyun Suk Kang, Hyun Kyung Kim, Craig MacLachlan, Adam A. Scaife

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

This study uses a global land–atmosphere coupled model, the land–atmosphere component of the Global Seasonal Forecast System version 5, to quantify the degree to which soil moisture initialization could potentially enhance boreal summer surface air temperature forecast skill. Two sets of hindcast experiments are performed by prescribing the observed sea surface temperature as the boundary condition for a 15-year period (1996–2010). In one set of the hindcast experiments (noINIT), the initial soil moisture conditions are randomly taken from a long-term simulation. In the other set (INIT), the initial soil moisture conditions are taken from an observation-driven offline Land Surface Model (LSM) simulation. The soil moisture conditions from the offline LSM simulation are calibrated using the forecast model statistics to minimize the inconsistency between the LSM and the land–atmosphere coupled model in their mean and variability. Results show a higher boreal summer surface air temperature prediction skill in INIT than in noINIT, demonstrating the potential benefit from an accurate soil moisture initialization. The forecast skill enhancement appears especially in the areas in which the evaporative fraction—the ratio of surface latent heat flux to net surface incoming radiation—is sensitive to soil moisture amount. These areas lie in the transitional regime between humid and arid climates. Examination of the extreme 2003 European and 2010 Russian heat wave events reveal that the regionally anomalous soil moisture conditions during the events played an important role in maintaining the stationary circulation anomalies, especially those near the surface.

Original languageEnglish
Pages (from-to)1695-1709
Number of pages15
JournalClimate Dynamics
Volume52
Issue number3-4
DOIs
StatePublished - 15 Feb 2019

Bibliographical note

Funding Information:
Acknowledgements This study was supported by the Korea Meteorological Administration Research and Development Program under KMIPA 2016-6010. DK was also supported by the University of Washington startup fund.

Funding Information:
This study was supported by the Korea Meteorological Administration Research and Development Program under KMIPA 2016-6010. DK was also supported by the University of Washington startup fund.

Publisher Copyright:
© 2018, Springer-Verlag GmbH Germany, part of Springer Nature.

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