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, but the KE index inferred from OFES exhibits shorter and less regular fluctuations prior to the 1976–77 North Pacific climate shift ( Qiu et al. 2014 ). Here, we focus on the 1979–2012 period, which corresponds to the availability of the latest reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) (ERA-Interim; Dee et al. 2011 ). The mean seasonal cycle of the KE index was subtracted by regression onto the first two annual harmonics, which accounted for 2.4% of the total
, but the KE index inferred from OFES exhibits shorter and less regular fluctuations prior to the 1976–77 North Pacific climate shift ( Qiu et al. 2014 ). Here, we focus on the 1979–2012 period, which corresponds to the availability of the latest reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) (ERA-Interim; Dee et al. 2011 ). The mean seasonal cycle of the KE index was subtracted by regression onto the first two annual harmonics, which accounted for 2.4% of the total
; in particular, large positive anomalies occur over the northern Europe and Siberian coast. It is suggested that the winds from the north of Greenland to the north of Alaska’s coast could enhance sea-ice cover over the East Siberian Sea through the combined effect of cold air and sea-ice advection. 1 The annual mean SLP anomalies regressed on the maximum Okhotsk sea-ice index in the following winter ( Fig. 4b ) are characterized by a seesaw pattern between the Arctic Ocean and the midlatitudes
; in particular, large positive anomalies occur over the northern Europe and Siberian coast. It is suggested that the winds from the north of Greenland to the north of Alaska’s coast could enhance sea-ice cover over the East Siberian Sea through the combined effect of cold air and sea-ice advection. 1 The annual mean SLP anomalies regressed on the maximum Okhotsk sea-ice index in the following winter ( Fig. 4b ) are characterized by a seesaw pattern between the Arctic Ocean and the midlatitudes
Atlantic eddy-driven jet and the increase in European blocking frequency in response to the GS SST front (see also O’Reilly et al. 2016 ). Fig . 1. (a) Detrended and normalized (to unit standard deviation) JFM GSI ( Joyce et al. 2000 ) for the period 1954–2012. (bottom) The linearly regressed (b) SST (color shading, °C) and (c) column-integrated (1000–50 hPa) northward synoptic eddy heat flux (color shading, 10 7 W m −1 ) overlaid with the Z 250 (m, CI = 2) when the JFM GSI leads by 1 yr ( Kwon and
Atlantic eddy-driven jet and the increase in European blocking frequency in response to the GS SST front (see also O’Reilly et al. 2016 ). Fig . 1. (a) Detrended and normalized (to unit standard deviation) JFM GSI ( Joyce et al. 2000 ) for the period 1954–2012. (bottom) The linearly regressed (b) SST (color shading, °C) and (c) column-integrated (1000–50 hPa) northward synoptic eddy heat flux (color shading, 10 7 W m −1 ) overlaid with the Z 250 (m, CI = 2) when the JFM GSI leads by 1 yr ( Kwon and
1. Introduction During the winter of 2012/13, surface air temperatures (SATs) in the northern midlatitudes were abnormally cool over Europe, the Eurasian continent, and North America, and abnormally cold winters have continued over East Asia and Japan for the last three winters (2010/11, 2011/12, 2012/13). Commonly variations of the large-scale atmospheric circulation are mainly responsible for year-to-year variations of SATs (e.g., He and Wang 2013 ). In this paper, we demonstrate oceanic
1. Introduction During the winter of 2012/13, surface air temperatures (SATs) in the northern midlatitudes were abnormally cool over Europe, the Eurasian continent, and North America, and abnormally cold winters have continued over East Asia and Japan for the last three winters (2010/11, 2011/12, 2012/13). Commonly variations of the large-scale atmospheric circulation are mainly responsible for year-to-year variations of SATs (e.g., He and Wang 2013 ). In this paper, we demonstrate oceanic
and its association to the North Atlantic Oscillation and climate variability of northern Europe . J. Climate , 10 , 1635 – 1647 , doi: 10.1175/1520-0442(1997)010<1635:NASTVA>2.0.CO;2 . Saha , S. , and Coauthors , 2010 : The NCEP Climate Forecast System Reanalysis . Bull. Amer. Meteor. Soc. , 91 , 1015 – 1057 , doi: 10.1175/2010BAMS3001.1 . Sampe , T. , and S.-P. Xie , 2007 : Mapping high sea winds from space: A global climatology . Bull. Amer. Meteor. Soc. , 88 , 1965 – 1978
and its association to the North Atlantic Oscillation and climate variability of northern Europe . J. Climate , 10 , 1635 – 1647 , doi: 10.1175/1520-0442(1997)010<1635:NASTVA>2.0.CO;2 . Saha , S. , and Coauthors , 2010 : The NCEP Climate Forecast System Reanalysis . Bull. Amer. Meteor. Soc. , 91 , 1015 – 1057 , doi: 10.1175/2010BAMS3001.1 . Sampe , T. , and S.-P. Xie , 2007 : Mapping high sea winds from space: A global climatology . Bull. Amer. Meteor. Soc. , 88 , 1965 – 1978
horizontal resolution, T119 spectral truncation (equivalently 100-km grid intervals) with 48 levels for AFES, and 0.5° grid intervals with 54 vertical levels for OIFES ( Taguchi et al. 2012 ). The initial conditions of the atmosphere and ocean are climatology at 0000 UTC 1 January from the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40; Uppala et al. 2005 ) and the World Ocean Atlas 1998 ( WOA98 ; Antonov et al. 1998a , b , c ; Boyer et al. 1998a , b , c
horizontal resolution, T119 spectral truncation (equivalently 100-km grid intervals) with 48 levels for AFES, and 0.5° grid intervals with 54 vertical levels for OIFES ( Taguchi et al. 2012 ). The initial conditions of the atmosphere and ocean are climatology at 0000 UTC 1 January from the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40; Uppala et al. 2005 ) and the World Ocean Atlas 1998 ( WOA98 ; Antonov et al. 1998a , b , c ; Boyer et al. 1998a , b , c
contribution of SST to the THF. Section 5 discusses possible causes of SST variation in the eastern part of the KOC. Section 6 presents a summary and concluding remarks. 2. Data and methods Recently, Yu et al. (2008) developed the objectively analyzed air–sea fluxes (OAFlux) dataset with a relatively high spatial resolution of 1° (latitude) × 1° (longitude). The products of this dataset are a combination of observed satellite-derived data, the 40-yr European Centre for Medium-Range Weather Forecasts
contribution of SST to the THF. Section 5 discusses possible causes of SST variation in the eastern part of the KOC. Section 6 presents a summary and concluding remarks. 2. Data and methods Recently, Yu et al. (2008) developed the objectively analyzed air–sea fluxes (OAFlux) dataset with a relatively high spatial resolution of 1° (latitude) × 1° (longitude). The products of this dataset are a combination of observed satellite-derived data, the 40-yr European Centre for Medium-Range Weather Forecasts
the ERA-Interim global atmospheric reanalysis ( Dee et al. 2011 ) produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), in which resolution of prescribed SST has been improved twice. Our investigation targets the KOE region, or the North Pacific SAFZ, which is not merely a single frontal zone but rather characterized by a pair of SST fronts ( Yasuda 2003 ; Nonaka et al. 2006 ; Seo et al. 2014 ). In the KOE region, part of the Oyashio flows eastward to the north of the KE
the ERA-Interim global atmospheric reanalysis ( Dee et al. 2011 ) produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), in which resolution of prescribed SST has been improved twice. Our investigation targets the KOE region, or the North Pacific SAFZ, which is not merely a single frontal zone but rather characterized by a pair of SST fronts ( Yasuda 2003 ; Nonaka et al. 2006 ; Seo et al. 2014 ). In the KOE region, part of the Oyashio flows eastward to the north of the KE
northeastern Pacific (NEP). Recently, O’Reilly et al. (2016) showed that the SST front associated with the Gulf Stream modulates wintertime European blocking through storm-track enhancement. The SST front regions are also the places where explosive extratropical cyclones, so-called bomb cyclones, frequently develop. Sanders and Gyakum (1980) first suggested the relationship between the geographical distribution of explosive cyclones and SST fronts. Yoshiike and Kawamura (2009) found that explosive
northeastern Pacific (NEP). Recently, O’Reilly et al. (2016) showed that the SST front associated with the Gulf Stream modulates wintertime European blocking through storm-track enhancement. The SST front regions are also the places where explosive extratropical cyclones, so-called bomb cyclones, frequently develop. Sanders and Gyakum (1980) first suggested the relationship between the geographical distribution of explosive cyclones and SST fronts. Yoshiike and Kawamura (2009) found that explosive
AIRS data from the winter months between December 2003 and February 2013 are analyzed. Both the TRMM and AIRS data are provided by the NASA Goddard Earth Sciences Data and Information Services Center. To assess the satellite-derived results, we used reanalysis data from the ERA-Interim (e.g., Dee et al. 2011 ), which are produced by the European Centre for Medium-Range Weather Forecasts and are available since 1979 onward at a 0.75° resolution. The atmospheric variables of the ERA-Interim data
AIRS data from the winter months between December 2003 and February 2013 are analyzed. Both the TRMM and AIRS data are provided by the NASA Goddard Earth Sciences Data and Information Services Center. To assess the satellite-derived results, we used reanalysis data from the ERA-Interim (e.g., Dee et al. 2011 ), which are produced by the European Centre for Medium-Range Weather Forecasts and are available since 1979 onward at a 0.75° resolution. The atmospheric variables of the ERA-Interim data
