17:15 〜 19:15
[AOS12-P08] Observation-based estimation of salinity impact on TC-induced sea surface temperature cooling
キーワード：熱帯低気圧、海面水温低下、塩分、Argo
When a tropical cyclone (TC) moves over the ocean, a decrease in sea surface temperature (SST) along its track is often observed by satellites. The SST cooling induced by a TC plays a crucial role in shaping the seasonal SST cycle in TC-prone regions. Furthermore, it influences TC-ocean interactions and affects the development of subsequent TCs in these regions. It is well known that the primary cause of SST cooling is vertical mixing in the upper ocean, driven by TC-induced winds, which brings cooler water from deeper layers to the surface. In general, the intensity of TC-induced vertical mixing in the upper ocean is governed by two factors: the magnitude of the input energy driving the mixing and the ocean’s resistance to mixing, which is determined by the vertical gradient of seawater density (i.e., stratification).
This study quantitatively evaluates the impact of salinity stratification on SST changes during TC passage using observational data products. First, the energy imparted to the upper ocean by the TC is quantified based on changes in upper ocean potential energy before and after TC passage. Next, we estimate the SST decrease by assuming a hypothetical water column with only temperature stratification (i.e., without salinity stratification) and subjecting it to the estimated energy input from the TC. By comparing the computed SST decrease with the actual SST decrease, we quantify the influence of salinity stratification on SST cooling during TC passage. Using gridded Argo temperature and salinity products, we found that salinity stratification modulates SST cooling by up to approximately 50% in major TC-prone ocean regions worldwide.
This study quantitatively evaluates the impact of salinity stratification on SST changes during TC passage using observational data products. First, the energy imparted to the upper ocean by the TC is quantified based on changes in upper ocean potential energy before and after TC passage. Next, we estimate the SST decrease by assuming a hypothetical water column with only temperature stratification (i.e., without salinity stratification) and subjecting it to the estimated energy input from the TC. By comparing the computed SST decrease with the actual SST decrease, we quantify the influence of salinity stratification on SST cooling during TC passage. Using gridded Argo temperature and salinity products, we found that salinity stratification modulates SST cooling by up to approximately 50% in major TC-prone ocean regions worldwide.