Study on SST front disappearance in the subtropical North Pacific using microwave SSTs
Study on SST front disappearance in the subtropical North Pacific using microwave SSTs
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DOI：
10.1007/s10872-012-0106-z
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发表时间：
2012-04
影响因子：
2.3
通讯作者：
C. Qiu;H. Kawamura
中科院分区：
文献类型：
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作者：
C. Qiu;H. Kawamura
利用对地观测系统先进微波扫描辐射计，以1天/12.5公里的时空分辨率对7年的副热带海温锋减弱过程进行了研究。4月海温锋强，具有高梯度幅度（GM）和Jensen-Shannon散度（JSD）带；8月，海温趋于均匀（28 ~ 30℃），伴有较小的GMs（<0.8℃/100 km）和jsd（<0.75）。由于海温锋面特征在GM/JSD快照和周-月平均图像中变得不可见，我们称这种现象为“海温锋面消失（SFD）”。SFD发生在8月，但8月的高海温（bbb30°C）比7月少，说明SFD是低海温增加和高海温减少的结果。与5月和8月相比，6月和7月的GM分布有较大的标准差。我们还利用原位温度/盐度剖面研究了STF的垂向剖面。结果表明，SFD的影响扩展到50 m深度。综合热通量高和混合层深度浅的区域对应于6 - 8月平均气温从0.9°C/100 km下降到0.6°C/100 km的区域。定量分析证实，SFD机制可能是由于5 - 7月高综合热通量形成的浅层混合层所致。7 - 8月，海温锋面南北的海温加热/冷却可能加速SFD。
We investigated the processes relating to the weakening of the SST front in the subtropical front (STF) zone using the Advanced Microwave Scanning Radiometer for the Earth Observing System SSTs for 7 years with temporal/spatial resolutions of 1 day/12.5 km. In April, the SST front is strong with a high gradient magnitude (GM) and Jensen–Shannon divergence (JSD) band; in August, SSTs become uniform (28–30 °C), together with small GMs (<0.8 °C/100 km) and JSDs (<0.75). Since the SST front features become invisible in GM/JSD snapshots and weekly–monthly averaged images, we call this phenomenon ‘SST front disappearance (SFD)’. The SFD occurs in August, but the number of high SSTs (>30 °C) in August is smaller than that in July, which indicates that the SFD results from not only the increase in lower SSTs but also the decrease in higher SSTs. In June and July, the GM distributions have quite large standard deviations compared to those in May and August. We also investigated the vertical profile of STF using in situ temperature/salinity profiles. It was revealed that the SFD influence extends to 50 m depth. The area of high integrated heat flux and shallow mixed layer depth were found to correspond to the area where the GM decreases from 0.9 to 0.6 °C/100 km during June–August. Quantitative analyses confirmed that the SFD mechanism may be attributable to the establishment of the shallow mixed layer by the high integrated heat flux from May to July. From July to August, the SST heating/cooling in the north/south of the SST front may accelerate the SFD.