Inner-core sea surface cooling induced by a moving tropical cyclone

2021 ◽  
Author(s):  
Zhumin Lu ◽  
Guihua Wang ◽  
Xiaodong Shang
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Mixing Time ◽  
Sea Surface ◽  
Shear Instability ◽  
Surface Cooling ◽  
Horizontal Advection ◽  
Sea Surface Cooling ◽  
Slow Moving ◽  
Wind Driven Currents

AbstractAs a key to modulate the negative feedback to tropical cyclone (TC) intensity, the TC-induced inner-core sea surface cooling (SSCIC) is poorly understood. Using a linear two-layer theory and OGCM experiments, this study illustrates that the pattern of the inner-core mixing can be well interpreted by the wind-driven currents in the mixed layer (ML). This interpretation is based on: 1) the mixing is triggered by the ML bulk shear instability; 2) the lag of upwelling makes the inner-core bulk shear equivalent to the inner-core wind-driven currents. Overall, the patterns of the inner-core bulk shear and mixing resemble the crescent body of a sickle. As an accumulative result of mixing, the SSCIC is clearly weaker than the maximum cold wake because of the weaker mixing ahead of the inner core and nearly zero mixing in a part of the inner core. The SSCIC induced by a rectilinear-track TC is mainly dominated by the inner-core mixing. Only for a slow-moving case, upwelling and horizontal advection can make minor contributions to the SSCIC by incorporating them with mixing. The SSCIC strength is inversely proportional to the moving speed, suggesting the mixing time rather than the mixing strength dominates the SSCIC. Despite inability in treating the mixing strength, this study elucidates the fundamental dynamical mechanisms of SSCIC, especially emphasizes the different roles of mixing, upwelling and horizontal advection for fast- and slow-moving TCs, and thus provides a good start point to understand SSCIC.

scholarly journals The Effect of Atmosphere–Ocean Coupling on the Structure and Intensity of Tropical Cyclone Bejisa in the Southwest Indian Ocean

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 688
Author(s):  
Soline Bielli ◽  
Christelle Barthe ◽  
Olivier Bousquet ◽  
Pierre Tulet ◽  
Joris Pianezze
Keyword(s):  
Tropical Cyclone ◽  
Mixed Layer ◽  
Heat Fluxes ◽  
Sea Surface ◽  
Ocean Mixed Layer ◽  
Surface Cooling ◽  
Southwest Indian Ocean ◽  
Left Hand ◽  
Sea Surface Cooling ◽  
The Impact

A set of numerical simulations is relied upon to evaluate the impact of air-sea interactions on the behaviour of tropical cyclone (TC) Bejisa (2014), using various configurations of the coupled ocean-atmosphere numerical system Meso-NH-NEMO. Uncoupled (SST constant) as well as 1D (use of a 1D ocean mixed layer) and 3D (full 3D ocean) coupled experiments are conducted to evaluate the impact of the oceanic response and dynamic processes, with emphasis on the simulated structure and intensity of TC Bejisa. Although the three experiments are shown to properly capture the track of the tropical cyclone, the intensity and the spatial distribution of the sea surface cooling show strong differences from one coupled experiment to another. In the 1D experiment, sea surface cooling (∼1 ∘C) is reduced by a factor 2 with respect to observations and appears restricted to the depth of the ocean mixed layer. Cooling is maximized along the right-hand side of the TC track, in apparent disagreement with satellite-derived sea surface temperature observations. In the 3D experiment, surface cooling of up to 2.5 ∘C is simulated along the left hand side of the TC track, which shows more consistency with observations both in terms of intensity and spatial structure. In-depth cooling is also shown to extend to a much deeper depth, with a secondary maximum of nearly 1.5 ∘C simulated near 250 m. With respect to the uncoupled experiment, heat fluxes are reduced from about 20% in both 1D and 3D coupling configurations. The tropical cyclone intensity in terms of occurrence of 10-m TC wind is globally reduced in both cases by about 10%. 3D-coupling tends to asymmetrize winds aloft with little impact on intensity but rather a modification of the secondary circulation, resulting in a slight change in structure.

scholarly journals Extreme Sea-Surface Cooling Induced by Eddy Heat Advection During Tropical Cyclone in the North Western Pacific Ocean

2021 ◽  
Vol 8 ◽  
Author(s):  
Chunhua Qiu ◽  
Hong Liang ◽  
Xiujun Sun ◽  
Huabin Mao ◽  
Dongxiao Wang ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Heat Balance ◽  
General Circulation ◽  
Vertical Mixing ◽  
Sea Surface ◽  
Surface Cooling ◽  
Coupled Models ◽  
Heat Advection ◽  
Sea Surface Cooling ◽  
Wave Glider

A tropical cyclone (TC) usually induces strong sea-surface cooling due to vertical mixing. In turn, surface cooling influences the intensities and tracks of TCs. Therefore, the relationship between sea-surface temperature (SST) and TC is one of the important components of air-sea interaction. Sea-surface cooling associated with three TCs (Bailu, Lingling, and Mitag) was investigated based on wave-glider observations, satellite altimetry, and Massachusetts Institute of Technology General Circulation Model (MITgcm) numerical experiments from August 3rd to October 10th, 2019. Surface cooling varied among the three TCs. TC Lingling had the nearest distance to the wave-glider position, the slowest translation speed, and the strongest intensity of three TCs, but extreme cooling (1.4) occurred during TC Bailu. Although MITgcm underestimated the extreme cooling, the SST trend driven by the net heat flux, advection, and vertical mixing within the mixed layer was greater during TC Bailu than during other TCs. Advection was the largest of the three heat balance terms during TC Bailu, while it was quite small during the other two TCs. Interestingly, the extreme cooling occurred at the position of preexisting warm eddy. Based on heat balance analysis, we found that the eddy-induced heat advection transport reached −0.4/day, contributing 60% of the heat balance; this was attributed to extreme cooling via eddy disturbance. We suggest TC Bailu leads to the decrease in SST and increase in the area of the cold eddy, and then, the cooled-enlarged eddy is advected to the neighbored position of wave glider, which observes the extreme cooling. These findings provide the utilization of wave gliders and help improve air-sea coupled models during TCs.

scholarly journals Estimating Typhoon-Induced Sea Surface Cooling Based upon Satellite Observations

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3060
Author(s):  
Dan Song ◽  
Lulu Xiang ◽  
Linghui Guo ◽  
Bo Li
Keyword(s):  
Satellite Observations ◽  
Sea Surface ◽  
Maximum Response ◽  
Reference Temperature ◽  
Northwestern Pacific ◽  
Surface Cooling ◽  
Wind Force ◽  
Sea Surface Cooling ◽  
Slow Moving ◽  
Grid Based

Typhoons frequently occur in the summer in the northwestern Pacific Ocean, and the responses of the upper ocean to typhoons have drawn extensive attention for decades. In the present work, a modified grid-based maximum response (GMR) method was proposed to estimate the sea surface cooling (SSC) caused by typhoons. The current algorithm (CA) is different from the original GMR method mainly in two aspects: (1) it uses a 5 day average rather than a 2 day average of the sea surface temperature (SST) before the typhoon as the reference temperature; (2) it modifies the fixed radius of 400 km to the level-7 Beaufort scale wind-force (~17.1 m/s) radius to determine the area where the SSC should be calculated. Then the MW-IR OISST data derived from satellite observations were used to compare the SSC estimated by different algorithms in four typhoon cases, Megi, LionRock, Trami and KongRey. The results show that, in all cases, maximum response methods have approached similar results, while the others seemed to have underestimated the SSC in degrees. In the slow-moving LionRock case, grid-based methods were found to have better performance, while in the successive typhoon cases, Trami and KongRey, CA showed an improved result in representing the pre-existing sea surface status before the typhoon KongRey by using the pentad mean SST as the reference temperature. In addition, the use of level-7 wind-force coverage made the results much livelier. In a word, the algorithm proposed here is valid in general. It has advantages in estimating the SSC caused by both slow-moving typhoons and successive typhoons, and should be further applied to related research.

Satellite observations of sea surface cooling by hurricanes

1986 ◽  
Vol 91 (C4) ◽  
pp. 5031 ◽  
Author(s):  
Lothar Stramma ◽  
Peter Cornillon ◽  
James F. Price
Keyword(s):  
Satellite Observations ◽  
Sea Surface ◽  
Surface Cooling ◽  
Sea Surface Cooling
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