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; Minobe et al. 2008 ; Tokinaga et al. 2009 ). The local imprints of ocean currents, including surface wind, precipitation, and cloud formation, are well represented in satellite data from over a short period of just a few years. Two mechanisms, the vertical mixing mechanism and the pressure adjustment mechanism, have been proposed to explain the processes behind the ocean forcing on the overlying boundary layer at frontal scales. The vertical mixing mechanism attributes the correspondence of the SST
; Minobe et al. 2008 ; Tokinaga et al. 2009 ). The local imprints of ocean currents, including surface wind, precipitation, and cloud formation, are well represented in satellite data from over a short period of just a few years. Two mechanisms, the vertical mixing mechanism and the pressure adjustment mechanism, have been proposed to explain the processes behind the ocean forcing on the overlying boundary layer at frontal scales. The vertical mixing mechanism attributes the correspondence of the SST
regression model cannot perfectly extract the impacts of individual large-scale forcing, since 1) it takes some time for clouds to respond to the forcing, and 2) the clouds and boundary layer properties are advected spatially by the large-scale horizontal airflow. Nevertheless, the derived local dependence is useful for quantifying their local control on LCF. The regression slope thus derived for each variable is shown in Table B1 . We have calculated confidence intervals following the supporting
regression model cannot perfectly extract the impacts of individual large-scale forcing, since 1) it takes some time for clouds to respond to the forcing, and 2) the clouds and boundary layer properties are advected spatially by the large-scale horizontal airflow. Nevertheless, the derived local dependence is useful for quantifying their local control on LCF. The regression slope thus derived for each variable is shown in Table B1 . We have calculated confidence intervals following the supporting
frontal regions, on the other hand, can lead to an equatorward shift of the entire low-level atmospheric circulation system, including the surface westerlies, jet streams, and subtropical high pressure belt ( Sampe et al. 2010 ). By comparing atmosphere-only model simulations forced by prescribed SSTs, Taguchi et al. (2009) showed a reduced storm-track activity in response to a weakened SST gradient forcing due to the decreased meridional gradient of turbulent heat fluxes and moisture fluxes across
frontal regions, on the other hand, can lead to an equatorward shift of the entire low-level atmospheric circulation system, including the surface westerlies, jet streams, and subtropical high pressure belt ( Sampe et al. 2010 ). By comparing atmosphere-only model simulations forced by prescribed SSTs, Taguchi et al. (2009) showed a reduced storm-track activity in response to a weakened SST gradient forcing due to the decreased meridional gradient of turbulent heat fluxes and moisture fluxes across
( Lau 1997 ; Alexander et al. 2002 ) and internal atmospheric variability ( Frankignoul 1985 ; Kushnir et al. 2002 ). In fact, Robinson (2000) reported difficulties in atmospheric general circulation model (AGCM) experiments to yield systematic atmospheric responses to prescribed midlatitude SST anomalies. It has been suggested recently (e.g., Taguchi et al. 2012 ), however, that persistent SST anomalies in the North Pacific subarctic frontal zone (SAFZ) can force basin-scale atmospheric
( Lau 1997 ; Alexander et al. 2002 ) and internal atmospheric variability ( Frankignoul 1985 ; Kushnir et al. 2002 ). In fact, Robinson (2000) reported difficulties in atmospheric general circulation model (AGCM) experiments to yield systematic atmospheric responses to prescribed midlatitude SST anomalies. It has been suggested recently (e.g., Taguchi et al. 2012 ), however, that persistent SST anomalies in the North Pacific subarctic frontal zone (SAFZ) can force basin-scale atmospheric
1. Introduction Satellite-borne observations of the atmospheric response to fronts of sea surface temperature (SST) have revolutionized the understanding of midlatitude air–sea interaction ( Xie 2004 ; Small et al. 2008 ). While the traditional, large-scale view holds that the ocean primarily responds to forcing by the atmosphere, the ocean mesoscale shows a ubiquitous imprint of SST fronts on the atmospheric boundary layer ( Chelton and Xie 2010 ; Xie 2004 ). For scales shorter than about
1. Introduction Satellite-borne observations of the atmospheric response to fronts of sea surface temperature (SST) have revolutionized the understanding of midlatitude air–sea interaction ( Xie 2004 ; Small et al. 2008 ). While the traditional, large-scale view holds that the ocean primarily responds to forcing by the atmosphere, the ocean mesoscale shows a ubiquitous imprint of SST fronts on the atmospheric boundary layer ( Chelton and Xie 2010 ; Xie 2004 ). For scales shorter than about
1. Introduction Owing to greater persistence of SST anomalies than atmospheric anomalies, a robust atmospheric response to oceanic forcing, if any, could contribute to improvement in seasonal forecast skill. Influence of extratropical SST anomalies on the large-scale atmospheric circulation has long been believed to be insignificant, in the presence of a prevailing remote influence from the tropics ( Lau 1997 ; Alexander et al. 2002 ) and large intrinsic atmospheric variability ( Frankignoul
1. Introduction Owing to greater persistence of SST anomalies than atmospheric anomalies, a robust atmospheric response to oceanic forcing, if any, could contribute to improvement in seasonal forecast skill. Influence of extratropical SST anomalies on the large-scale atmospheric circulation has long been believed to be insignificant, in the presence of a prevailing remote influence from the tropics ( Lau 1997 ; Alexander et al. 2002 ) and large intrinsic atmospheric variability ( Frankignoul
). The formation of the SLP trough also acts to force frictional wind convergence near the surface and associated updraft at the MABL top. At the same time, static stability is also reduced within the overlying MABL, where the “vertical mixing effect” ( Wallace et al. 1989 ; Hayes et al. 1989 ), thus enhanced, translates a larger amount of westerly momentum down from the free troposphere to modify the ageostrophic wind field. Experiments by Koseki and Watanabe (2010) with an atmospheric general
). The formation of the SLP trough also acts to force frictional wind convergence near the surface and associated updraft at the MABL top. At the same time, static stability is also reduced within the overlying MABL, where the “vertical mixing effect” ( Wallace et al. 1989 ; Hayes et al. 1989 ), thus enhanced, translates a larger amount of westerly momentum down from the free troposphere to modify the ageostrophic wind field. Experiments by Koseki and Watanabe (2010) with an atmospheric general
midtroposphere at 0000 UTC 1 September 2004, when the typhoon center is located at 20.4°N, 146.4°E, between Guam and the Ogasawara Islands ( Fig. 2a ). A spiral feature around the typhoon can be identified, even in a 15-km-resolution simulation. We take the spatial average for diabatic heating rate as in Fig. 2a and provide it at only the typhoon central grid cell and eight surrounding grid cells of the LBM as the forcing. In this example, the diabatic heating rate rises to 900 K day −1 in the wall-cloud
midtroposphere at 0000 UTC 1 September 2004, when the typhoon center is located at 20.4°N, 146.4°E, between Guam and the Ogasawara Islands ( Fig. 2a ). A spiral feature around the typhoon can be identified, even in a 15-km-resolution simulation. We take the spatial average for diabatic heating rate as in Fig. 2a and provide it at only the typhoon central grid cell and eight surrounding grid cells of the LBM as the forcing. In this example, the diabatic heating rate rises to 900 K day −1 in the wall-cloud
1. Introduction Large-scale extratropical ocean–atmosphere interaction has long been recognized as dominated by atmospheric forcing of the ocean ( Davis 1976 ; Frankignoul and Hasselmann 1977 ; Frankignoul 1985 ). However, ocean–atmosphere coupling varies considerably across the midlatitude ocean basins, with oceanic processes likely to be more important to sea surface temperature (SST) variability in the vicinity of the western boundary currents (WBCs) and their associated SST fronts ( Qiu
1. Introduction Large-scale extratropical ocean–atmosphere interaction has long been recognized as dominated by atmospheric forcing of the ocean ( Davis 1976 ; Frankignoul and Hasselmann 1977 ; Frankignoul 1985 ). However, ocean–atmosphere coupling varies considerably across the midlatitude ocean basins, with oceanic processes likely to be more important to sea surface temperature (SST) variability in the vicinity of the western boundary currents (WBCs) and their associated SST fronts ( Qiu
Magnusdottir 2014 ; O’Reilly et al. 2016 ). The diabatic forcing associated with an SST anomaly initiates a baroclinic adjustment in the atmosphere near the forcing region ( Hoskins and Karoly 1981 ; Li and Conil 2003 ; Ferreira and Frankignoul 2005 ), which is linear about the sign and size of the SST anomaly ( Deser et al. 2007 ). However, the overall large-scale response has an equivalent barotropic structure with no strong resemblance to the prescribed SST anomaly pattern ( Ferreira and Frankignoul
Magnusdottir 2014 ; O’Reilly et al. 2016 ). The diabatic forcing associated with an SST anomaly initiates a baroclinic adjustment in the atmosphere near the forcing region ( Hoskins and Karoly 1981 ; Li and Conil 2003 ; Ferreira and Frankignoul 2005 ), which is linear about the sign and size of the SST anomaly ( Deser et al. 2007 ). However, the overall large-scale response has an equivalent barotropic structure with no strong resemblance to the prescribed SST anomaly pattern ( Ferreira and Frankignoul
