Sil Sourav, Gangopadhyay Avijit, Gawarkiewicz Glen, Pramanik Saikat
School of Earth, Ocean and Climate Sciences, Indian Institute of Technology, Bhubaneswar, India.
School for Marine Science and Technology, University of Massachusetts Dartmouth, Dartmouth, MA, 02747, USA.
Sci Rep. 2021 Nov 11;11(1):22052. doi: 10.1038/s41598-021-01607-6.
In recent years, the seasonal patterns of Tropical Cyclones (TC) in the Bay of Bengal have been shifting. While tropical depressions have been common in March-May (spring), they typically have been relatively weaker than the TCs during October-December. Here we show that the spatial pattern of recent warming trends during the last two decades in the southwestern Bay has allowed for stronger springtime pre-monsoon cyclones such as Amphan (May 2020, Super Cyclone) and Fani (April-May 2019, Extremely Severe Cyclone). The tracks of the pre-monsoon cyclones shifted westward, concurrent with an increasing rate of warming. This shift allowed both Fani and Amphan tracks to cross the northeastward warm Western Boundary Current (WBC) and associated warm anti-cyclonic eddies, while the weaker Viyaru (April 2013, Cyclonic Storm) did not interact with the WBC. A quantitative model linking the available along-track heat potential to cyclone's intensity is developed to understand the impact of the WBC on cyclone intensification. The influence of the warming WBC and associated anti-cyclonic eddies will likely result in much stronger springtime TCs becoming relatively common in the future.
近年来，孟加拉湾热带气旋（TC）的季节性模式一直在发生变化。虽然热带低压在3月至5月（春季）较为常见，但它们通常比10月至12月期间的热带气旋相对较弱。我们在此表明，过去二十年中孟加拉湾西南部近期变暖趋势的空间格局使得春季季风前的气旋，如安攀（2020年5月，超级气旋）和法尼（2019年4月至5月，特强气旋风暴）更为强劲。季风前气旋的路径向西移动，同时变暖速率增加。这一移动使得法尼和安攀的路径穿过东北方向温暖的西边界流（WBC）及相关的暖性反气旋涡旋，而较弱的维亚鲁（2013年4月，气旋风暴）则未与西边界流相互作用。我们建立了一个将沿路径可用热势与气旋强度联系起来的定量模型，以了解西边界流对气旋增强的影响。变暖的西边界流及相关反气旋涡旋的影响可能会导致未来春季更强的热带气旋变得相对常见。
