Modulating Effects of Mesoscale Oceanic Eddies on Sea Surface Temperature Response to Tropical Cyclones Over the Western North Pacific

Abstract

The impact of mesoscale oceanic eddies on the temporal and spatial characteristics of sea surface temperature (SST) response to tropical cyclones is investigated in this study based on composite analysis of cyclone‐eddy interactions over the western North Pacific. The occurrence times of maximum cooling, recovery time, and spatial patterns of SST response are specially evaluated. The influence of cold‐core eddies (CCEs) renders the mean occurrence time of maximum SST cooling to become about half a day longer than that in eddy‐free condition, while warm‐core eddies (WCEs) have little effect on this facet. The recovery time of SST cooling also takes longer in presence of CCEs, being overall more pronounced for stronger or slower tropical cyclones. The effect of WCEs on the recovery time is again not significant. The modulation of maximum SST decrease by WCEs for category 2–5 storms is found to be remarkable in the subtropical region but not evident in the tropical region, while the role of CCEs is remarkable in both regions. The CCEs are observed to change the spatial characteristics of SST response, with enhanced SST decrease initially at the right side of storm track. During the recovery period the strengthened SST cooling by CCEs propagates leftward gradually, with a feature similar as both the westward‐propagating eddies and the recovery of cold wake. These results underscore the importance of resolving mesoscale oceanic eddies in coupled numerical models to improve the prediction of storm‐induced SST response.

Imprints of Tropical Cyclones on Structural Characteristics of Mesoscale Oceanic Eddies Over the Western North Pacific

“…The decrease in SST anomaly is more effective in CCEs than in WCEs, as consistently shown in previous studies (Z. Ma et al 2018). After about 20 days, the SST in WCEs has basically recovered to their pre-storm state.…”

“…The TC translation speed is calculated by dividing the distance between TC centers at 0 and + 6 h by the time interval of 6 h. Similarly, the eddy propagation speed is obtained by dividing the distance between eddy centers on 0 and + 1 day to the time interval of 1 day. Following Ma et al (2017Ma et al ( , 2018, the TC-eddy interaction is defined to occur as their central distance is equal to or smaller than the eddy radius. When an eddy is judged to be affected by a TC, it is tracked until the end of its lifetime.…”

A Definition of Rapid Weakening for Tropical Cyclones Over the Western North Pacific

“…The background SST of non‐RW cases becomes increasingly lower than that of non‐RW cases 24 hr after the RW onset (Figure S6), further amplifying their intensity difference. Generally, the sea surface cooling induced by TCs reaches its maximum 1–2 days after the TC passage (Ma et al, , ). Figures e and f compare the SST decrease 1 day after TC passage.…”

Potential Predictability of the Tropical Cyclone Frequency Over the Western North Pacific With 50‐km AGCM Ensemble Experiments

“…Therefore, efforts should be made towards improvements of AGCM cloud parameterizations (Baba, 2019, 2020). Furthermore, previous studies indicate that air‐sea coupling may be critical to improve seasonal or longer time‐scale TCF forecasts through the consideration of the impact of active entrainment of subsurface water on SST and extreme TC activity predictions (Ma et al., 2018; Ogata et al., 2015, 2016; Vincent et al., 2012), which is not taken into account in the current study with the use of an AGCM. Thus, as a next step, we plan to further investigate this topic using coupled GCMs.…”