Importance of vertical mixing and barrier layer variation on seasonal mixed layer heat balance in the Bay of Bengal

Abstract

Time series measurements from the Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) moorings at 15° N, 90° E; 12° N, 90° E; 8° N, 90° E; 4° N, 90° E; 1.5° N, 90° E; 0° N, 90° 30E are used to investigate the seasonal mixed-layer heat balance and the importance of barrier layer thickness (BLT) and vertical mixing ( −ℎ ) in the Bay of Bengal (BoB). It is found that the BLT, −ℎ and mixed-layer heat balance all have a strong seasonality in the central BoB. Sea surface temperature (SST), salinity and wind are important for the observed strongest seasonal cycle of BLT in the central BoB, and wind is more important than the SST in the southern BoB. The heat storage rate (HSR) is primarily driven by latent heat flux and shortwave radiation ( ). 35Seasonal variations and the magnitudes of longwave radiation ( ), sensible heat flux ( ), and horizontal mixedlayer heat advection are much weaker compared to those of . −ℎ follows a pronounced seasonal cycle in the central BoB and is significantly positively correlated with the seasonal cycle of BLT at each mooring location.The seasonal variability of the stability favors the −ℎ during winter and summer monsoon and suppress −ℎ during monsoon transition periods. We found that −ℎ plays the secondary role in the seasonal mixed-layer heat balance in 40 the BoB. It is evident from the analysis that −ℎ associated with temperature inversion (∆ ) warms the mixed layer during winter and cools the mixed layer during summer. The warming tendency during winter is strong in the central BoB and weakens towards the equator, indicating a cooling tendency around the year. Our analysis further indicates the weakening of −ℎ during monsoon transition periods favors the existence of warmer SST in the BoB, associated with thermal and salinity stratification in the central BoB. 50 55Ocean Sci. Discuss., https://doi

Tropical cyclone-induced cold wakes in the northeast Indian Ocean

“…, they are mostly moderately fast moving). 48 The complete analysis for all cyclones is presented in Tables S1–S3 †…”

“…Therefore, other factors could also influence the cold wakes produced by TCs. When analysing the EPV values of each cyclone, it is found that higher EPV 48 ). The complete analysis for all cyclones is presented in Tables S1, S2 and S3.…”

“…The SST drop is largely inuenced by the translational speed and EPV, and the cyclones have an average translational speed of 4.86 m s À1 , a MLD (as analysed from 1994 to 2020) of 14.6 m and an EPV of 1.94 Â 10 À4 m s À1 (i.e., they are mostly moderately fast moving). 48 The complete analysis for all cyclones is presented in Tables S1-S3. † Table S3 † lists the translational speed, EPV, wind stress and different uxes during each cyclone period.…”