Journal
CLIMATE DYNAMICS
Volume 47, Issue 7-8, Pages 2155-2175Publisher
SPRINGER
DOI: 10.1007/s00382-015-2956-8
Keywords
Mid-high latitude intraseasonal temperature variability; Southeastward propagation; Extended-range forecast
Categories
Funding
- China National 973 project [2015CB453200]
- NSFC [41475084]
- NRL [N00173-13-1-G902]
- Jiangsu Shuang-Chuang Team
- Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
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The intraseasonal oscillation (ISO) of air temperature over the mid- and high-latitude Eurasia in boreal winter was investigated by NCEP-NCAR reanalysis data. It is found that the intraseasonal temperature disturbances exhibit maximum variability near the surface in the region of 50A degrees-75A degrees N, 80A degrees aEuro'120A degrees E and they propagate southeastwards at average zonal and meridional phase speeds of 3.2 and 2.5 m s(-1), respectively. The low-level temperature signal is tightly coupled with upper-tropospheric height anomalies, and both propagate southeastward in a similar phase speed. A diagnosis of the temperature budget reveals that the southeastward propagation is primarily attributed to the advection of the temperature anomaly by the mean wind. A wave activity flux analysis indicates that the southeastward propagating wave train is likely a result of Rossby wave energy propagation. The source of the Rossby wave train appears at the high latitude Europe/Atlantic sector, where maximum wave activity flux convergence resides. During its southeastward journey, the ISO perturbation gains energy from the mean flow through both kinetic and potential energy conversions. A physics-based empirical model was constructed to predict the intraseasonal temperature anomaly over southeast China. The major predictability source is the southeastward-propagating ISO signal. The data for 1979aEuro'2003 were used as a training period to construct the empirical model. A 10-yr (2004aEuro'2013) independent forecast shows that the model attains a useful skill of up to 25 days.
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