Variability of the Equatorial Indian Ocean (EIO) winds play crucial roles in driving the upper EIO dynamics and modifying the ocean–atmosphere interactions in the Indian Ocean (IO). This study, using a satellite-sensed high-resolution (0.25° × 0.25°) monthly winds, has revealed many salient features of the seasonal and inter-annual variability of winds at various dynamically significant regions of the EIO. Though annual mean wind pattern of the EIO shows westerlies east of 60°E, the different local areas in this ocean exhibit significant seasonal wind variations. Migrations and fluctuations of southerlies and westerlies primarily determine the EIO wind variability. In the western (eastern) EIO, SW and NE monsoon winds are stronger (weaker) and of longer (shorter) duration. Near to the equator (1°S–1°N), in the central EIO, weaker winds occur during SW and NE monsoons, whereas stronger winds during transition periods. Near the equator, meridional winds show a significant annual period, especially in the western EIO. But zonal winds exhibit semi-annual period east of 55°E with a peak in the central ocean associated with the active westerlies during spring and fall, and annual period west of 55°E in the western EIO due to monsoon reversals. Westerlies are stronger during the fall compared to spring. Zonal wind variability in the central EIO is the essential deciding factor for the zonal wind variability occurring in the whole EIO. Both Zonal Sea Level Pressure Gradient (ZSLPG) and Momentum Advection (MA) fields determine the dynamics of zonal winds in the EIO. Zonal winds are weak in the western EIO because of the semi-annual harmonics of both ZSLPG and MA, though with substantial amplitude, exhibiting opposite accelerations there. But stronger zonal winds occur in the central EIO (60°E–80°E) because of the same accelerations set by the relatively weaker ZSLPG and MA fields. The zonal winds show substantial inter-annual variability compared to the meridional winds. The inter-annual variability of zonal winds shows the predominance of two modes, with EOF1 50% and EOF2 20% of the total variance. Zonal wind pattern of EOF1 resembles the monsoon transition seasons, while that of EOF2 describes the SW monsoon. In the EIO, Indian Ocean Dipole (IOD) influences the patterns of winds and SST anomalies better than that of El Niño–Southern Oscillation (ENSO). Spatiotemporal variability of the EIO winds during ENSO and IOD indicates the prevalence of stronger zonal wind anomalies in the eastern and central EIO and weaker anomalies in the western EIO. Although spatial patterns of wind anomalies are similar during El Niño and Positive IOD (PIOD) periods, the monthly variations, spatial extensions, and intensities of anomalies are much different while comparing. Prospectus for understanding the EIO winds variations can help to understand the changes occurring in the wind-driven surface and subsurface zonal currents.

中文翻译：

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关于赤道印度洋海面风的季节和年际变化

赤道印度洋 (EIO) 风的变化在驱动 EIO 上层动力学和改变印度洋 (IO) 的海洋-大气相互作用方面起着至关重要的作用。这项研究使用卫星传感的高分辨率（0.25° × 0.25°）月风，揭示了 EIO 各个动态重要区域风的季节性和年际变化的许多显着特征。尽管 EIO 的年平均风向显示 60°E 以东偏西风，但该海域的不同局部区域表现出显着的季节性风变化。南风和西风的迁移和波动主要决定了 EIO 风的变率。在西部（东部）EIO、SW 和 NE 季风较强（较弱）且持续时间较长（较短）。靠近赤道 (1°S–1°N)，在 EIO 中部，SW 和 NE 季风期间出现较弱的风，而在过渡时期出现较强的风。在赤道附近，经向风呈现出显着的年度周期，尤其是在 EIO 西部。但纬向风在 55°E 以东呈现半年周期，在春季和秋季与活跃的西风相关的中央海洋出现高峰，在 EIO 西部，由于季风逆转，每年周期在 55°E 以西。与春季相比，秋季西风更强。中央 EIO 的纬向风变率是整个 EIO 中发生的纬向风变率的重要决定因素。纬向海平面压力梯度 (ZSLPG) 和动量平流 (MA) 场都决定了 EIO 中纬向风的动态。由于 ZSLPG 和 MA 的半年谐波，EIO 西部的纬向风很弱，虽然幅度很大，在那里表现出相反的加速度。但是，由于相对较弱的 ZSLPG 和 MA 场设置的加速度相同，因此在 EIO 中部（60°E-80°E）出现更强的纬向风。与经向风相比，纬向风显示出明显的年际变化。纬向风的年际变化显示两种模式占优势，EOF1 占总方差的 50%，EOF2 占总方差的 20%。EOF1 的纬向风型类似于季风过渡季节，而 EOF2 的纬向风型描述了西南季风。在 EIO 中，印度洋偶极子 (IOD) 比厄尔尼诺-南方涛动 (ENSO) 更好地影响风和海温异常模式。ENSO和IOD期间EIO风的时空变化表明东部和中部EIO的纬向风异常普遍存在，而西部EIO的异常较弱。尽管厄尔尼诺和正IOD（PIOD）期间风异常的空间格局相似，但在比较时，异常的月变化、空间扩展和强度有很大不同。了解 EIO 风变化的说明书有助于了解风驱动的地表和地下纬向流中发生的变化。