ABSTRACT Cyclone Nilofar was the third-strongest cyclone in the Arabian Sea. It was a category 4 cyclone that arrived in last week of October 2014. It lingered in the Arabian Sea for 10 days and caused a significant phytoplankton bloom that was detected by satellite observation. In this study, the authors investigated the ocean biological and physical responses to cyclone Nilofar using chlorophyll a (chl a) concentration, sea surface temperature (SST), sea surface height anomaly (SSHA), sea surface wind measurements derived from different satellites, and in situ data. The maximum chl a concentration (>3.34 mg m−3) increased about 28 times in the Arabian Sea after the passage of the cyclone in comparison with the chl a concentration (0.12–0.92 mg m−3) before the passage of cyclone. Using the relationship of wind stress curl and upwelling, the authors found that during the cyclone the speed of upwelling increased more than 18 times compared with the speed in the period before the cyclone. Moreover, the mixed layer deepened by about 40 m. These findings reveal that the enhancement of chl a concentration was triggered by strong vertical mixing and upwelling. Along the track of the cyclone, the maximum sea surface cooling (4°–5°C) took place in the Arabian Sea along segments A–B and D–F where the translation speed of the cyclone was only 0.9–1.3 m s−1, and the mixed-layer depth was about 10 m in the pre-cyclone period. However, the drop in SST along segment C–D was only 1°–2°C, whereas in the pre-cyclone period the translation speed of the cyclone was 3.1–4.4 m s−1, and the mixed-layer depth was about 25 m in. So, the extent of the SST drop was probably due to the translation speed of the cyclone and the depth of the mixed layer. In addition, the region with the largest decline in SSHA can indicate the location of maximum cooling.

中文翻译：

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上层海洋对气旋尼洛法尔响应的卫星证据

摘要 气旋尼洛法尔是阿拉伯海第三强气旋。这是 4 级气旋，于 2014 年 10 月的最后一周抵达。它在阿拉伯海逗留了 10 天，并导致卫星观测发现显着的浮游植物大量繁殖。在这项研究中，作者使用叶绿素 a (chl a) 浓度、海面温度 (SST)、海面高度异常 (SSHA)、来自不同卫星的海面风测量数据以及现场数据。与气旋通过前的 chl a 浓度（0.12–0.92 mg m−3）相比，气旋通过后阿拉伯海的最大 chl a 浓度（>3.34 mg m−3）增加了约 28 倍。利用风应力旋度与上升流的关系，作者发现，在气旋期间，上升流的速度比气旋前的速度增加了 18 倍以上。此外，混合层加深了约40 m。这些发现表明，强烈的垂直混合和上升流触发了 chl a 浓度的增加。沿着气旋的轨迹，最大的海面冷却（4°–5°C）发生在阿拉伯海沿 A–B 和 D–F 段，其中气旋的平移速度仅为 0.9–1.3 ms-1 , 气旋前期混合层深度约为 10 m。然而，沿 C-D 段的海温下降仅 1°-2°C，而在气旋前期，气旋的平移速度为 3.1-4.4 ms-1，混合层深度约为 25米。所以，SST 下降的程度可能是由于旋风的平移速度和混合层的深度。此外，SSHA 下降幅度最大的区域可以指示最大冷却的位置。