Observed three‐dimensional structure of ocean cooling induced by Pacific tropical cyclones

Abstract

Sea surface cooling along tropical cyclone (TC) tracks has been well observed, but a complete understanding of the full three‐dimensional structure of upper ocean TC‐induced cooling is still needed. In this study, observed ocean temperature profiles derived from Argo floats and TC statistics from 1996 to 2012 are used to determine the three‐dimensional structure of TC‐induced cooling over the northwest Pacific. The average TC‐induced sea surface temperature change derived from Argo reaches −1.4°C, which agrees well with satellite‐derived estimates. The Argo profiles further reveal that this cooling can extend to a depth of ~30 m and can persist for about 20 days. The time scale of cooling recovery is somewhat longer in subsurface layers between a depth of ~10–15 m. Over the ocean domain where the mixed layer is shallower (deeper), the cooling is stronger (weaker), shallower (deeper), and more (less) persistent. The effect of initial MLD on the cooling derived from Argo observations may be only half of the idealized piecewise continuous model of tropical cyclone. These findings have implications for the total upper ocean heat content change induced by northwest Pacific TCs.

The responses of cyclonic and anticyclonic eddies to typhoon forcing: The vertical temperature‐salinity structure changes associated with the horizontal convergence/divergence

“…In recent years, two‐dimensional composite analyses are employed to ocean thermal structure response to typhoon forcing. By ignoring the eddies, the max average of SST change in cooling area within 3 days was about −1.4°C [ Wang et al ., ]. But the max average of SST change (including both cooling and warming) within the same period dropped to a relatively smaller value of −0.8°C (from −0.5°C to −1.1°C depending on the wind forcing strength) [ Cheng et al ., ].…”

“…The longer the period is the smaller the cooling tends to be. The max average of SST change in cooling area within 10 days dropped to −1.0°C [ Wang et al ., ], whereas the max average of SST change within 4–20 days dropped to −0.2°C [ Cheng et al ., ]. The present investigation used average within 10 days after typhoon passing, the cooling values should be reasonably smaller.…”

“…Since we focus on the eddy more than typhoon, we use eddy‐center coordinate [ Zhang et al ., ; Wang et al ., ] other than typhoon‐center coordinate [ Wang et al ., ] for composite analysis in this study. As a reference, the climatological composition of temperature, salinity, and density profiles of CEs, AEs, and background (BG) before typhoon forcing are shown in Figure .…”

“…In previous studies [e.g., Sun et al, 2012;Wu and Chen, 2012;Zhang et al, 2013;Cheng et al, 2015;Foltz et al, 2015;Mei et al, 2015;Wang et al, 2016], the region under the influence of typhoon is simply chosen according to the distance from typhoon center. In this study, the typhoon forcing region is chosen based on the typhoon work to the ocean current, so that both the distance from typhoon center and the typhoon forcing time are considered.…”

Tropical Cyclone Cold Wake Size and Its Applications to Power Dissipation and Ocean Heat Uptake Estimates

“…Key parameters to identify the ROI are (1) a threshold value of SSTA (−0.7 °C) to mask the SSTA field where only SSTAs below this threshold are accounted, which is used to identify the ROIs, and (2) a tolerance distance with a radius of 6° from the TC center to exclude those ROIs far away from the TC center. The first criterion is chosen following Wang et al (), who showed that the cold wake region is hardly distinctive from the background in regions where SSTAs are warmer than −0.5 ~−0.8 °C. A larger tolerance distance (11°) reduces the mean of ROI size slightly (<5%; see Table S2).…”