Ocean-atmosphere interaction over sea surface temperature front along Kuroshio Extension and North Pacific subtropical front.

在日本以东的北太平洋西部，海温（SST）显示一个横过黑潮延伸区（KE）的陡峭锋。KE附近的海温梯度为5℃/200 km，因此该地区海温变化非常大。在本研究中，我们于2005年7月（2006年1月）作为Scripps海洋研究所（东京大学海洋研究所）Roger Revelle研究船（R/V Hakuho-maru）的研究巡航，在锋面进行了全球定位系统（GPS）无线电探空大气探测。在初夏，虽然覆盖KE区域的低层大气表现出天气扰动，但由于海洋的大惯性，海温锋在巡航期间的几周内几乎是相同的。对大气探测和高度计测量结果的分析表明，大气边界层垂直结构在锋面上发生了改变。在暖/湿（冷/干）气团覆盖KE区域的情况下，观察到从积云到低层云，偶尔到雾（从具有固体云甲板的层状云到具有较低云底的破碎层状云散射）的云系在温暖到寒冷的海温中转移。在深冬，由于温暖的海洋和凉爽/干燥的大气，近地表总是不稳定的。因此，主要逆温形成于混合均匀层的顶部。混合层顶（MLT）的时间变化与地面热通量有很好的相关性，主要对应于观测到的云底。滞后相关性在通量比MLT提前5 ~ 12 h时达到最大。在天气风暴通过后，地面热通量偶尔超过800W m^<-2>，从而在MLT形成层积云。这些观测结果表明，尽管上覆大气表现出天气干扰，但沿KE锋面海温的空间变化对海洋大气边界层有一定的修正作用。

Over the western North Pacific east of the Japan, sea surface temperature (SST) shows a steep front across the Kuroshio Extension (KE). The SST gradient near the KE is 5℃/200 km through seasons, therefore changes in SST are very large in that region. In the present study, we conducted global positioning system (GPS) radio sonde atmospheric soundings across the front in July 2005 (January 2006) as a research cruise of research vessel (R/V) Roger Revelle, Scripps Institute of Oceanography (R/V Hakuho-maru, Ocean Research Institute, University of Tokyo).In early summer, whilst the lower atmosphere overlying the KE region exhibits synoptic disturbances, SST front is nearly the same for several weeks during the cruise due the large inertia of the ocean. Analyses of the atmospheric soundings and ceilometer measurement show that the vertical structure of atmospheric boundary layer is modified across the front. In case of warm/moist (cold/dry) air mass overlying the KE region, a cloud regime shift from cumulus to low-level stratus, occasionally to fog (from stratus with solid cloud deck to broken stratus scattering with lower cloud base) is observed across warm-to-cold SST.In deep winter, the near surface is always unstable because of warm ocean and cool/dry atmosphere. Hence, the main inversion is formed at the top of well-mixed layer. Temporal variation of the mixed layer top (MLT), which is mostly corresponding to the observed cloud base, is well correlated with surface heat flux. The lag correlation becomes the maximum when the flux leads by 5-12 hours the MLT. After a passage of synoptic storm, the surface heat flux occasionally exceeded 800W m^<-2> and thereby the stratus and stratocumulus were formed at the MLT.These observational findings indicate that the marine atmospheric boundary layer is modified by the spatial changes in SST along the KE front even though the overlying atmosphere displays its synoptic distrubances.