Evaluation of Leftward Biased Cold Wakes Induced by Tropical Cyclones in the North Hemisphere

Abstract

AbstractThe cold wake features are one of the most significant characteristics left behind by tropical cyclones (TCs) over the warm ocean. In the past several decades, the cold wakes have been widely conceived to be rightward biased (in the Northern Hemisphere). This basic cognition is examined in this study based on satellite sea surface temperature (SST) data with the high‐resolution of ∼0.09° between 2002 and 2021. Statistical results reveal that roughly one third (∼30.58%) of TC cold wakes are actually leftward biased in real world. On average, the maximum cooling of leftward cold wakes is approximately −0.7°C, appearing at ∼60 km to the left of the storm track. The proportion of leftward cases decreases steadily with increasing TC intensity, while shows little relation with the translation speed. The leftward biased phenomena are found to be independent from meso‐scale oceanic features and mainly attributed to inhomogeneous large‐scale background oceanic environment. The generally deeper (shallower) pre‐storm mixed layer and weaker (stronger) stratification found in the right (left) of track can effectively suppress rightward (enhance leftward) surface cooling and synchronously deform the normal spatial patterns of cold wakes. These effects cooperate with leftward‐biased surface enthalpy flux resulted from asymmetric pre‐storm SST, and eventually contributes to the left‐shifted feature. A series of three‐dimensional simulations using the three‐dimensional Price‐Weller‐Pinkel (3DPWP) model consolidate these physical explanations. Further observations suggest that distributions of cold wakes could significantly affect the asymmetric precipitation of TCs, confirming the importance of leftward cases to the TCs structure.