Impact of tropical cyclones on the ocean heat budget in the Bay of Bengal during 1999: 1. Model configuration and evaluation

Abstract

[1] The impacts of two consecutive, strong tropical cyclones (TCs) -04B (10/15-10/19) and 05B (10/25-11/3) in 1999 (hereafter, TC1 and TC2) -on the upper ocean temperature and surface height of the Bay of Bengal (BoB) are examined using the Hybrid Coordinate Ocean Model (HYCOM). The HYCOM control run is driven by the Cross-Calibrated MultiPlatform (CCMP) satellite winds, European Center for Medium-Range Weather Forecasts Re-analysis Interim (ERAI) surface reanalysis data, and Tropical Rainfall Measuring Mission precipitation. In order to investigate ocean response to high wind conditions, which are not well resolved by the CCMP or ERAI products, a modified Rankine vortex is adopted to reconstruct the TC winds in an experimental run. Wind stress is determined from wind speed when considering the level-off and decline of drag coefficient at wind speed of 34 m/s and greater. The experimental run reproduces the strong SST reduction ($À3 C) near the Orissa seashore along and on the right of the TC tracks. TC2 (category 5) cools the BoB SST less than TC1 (category 4) likely due to the initial SST depression by TC1. TC2 has higher winds and lingers over the ocean longer than TC1, and hence the onshore Ekman transport and mass convergence induced by TC2 wind is more prominent. The HYCOM mixed layer temperatures and depths to the south of the BoB generally agree with the observations very well. The simulations, however, have weaker vertical temperature gradient in the thermocline layer, suggesting that HYCOM produces a more diffusive thermocline than the observations.

Effects of the diurnal cycle in solar radiation on the tropical Indian Ocean mixed layer variability during wintertime Madden-Julian Oscillations

“…The diffusion/mixing parameters of the model are identical to those used in Wang et al . []. The nonlocal KPP [ Large et al ., ] mixing scheme is used.…”

The Role of Temperature Inversions in the Generation of Seasonal and Interannual SST Variability in the Far Northern Bay of Bengal

“…Temperature inversions can have a significant impact on the heat budget of the surface mixed layer, because the mixed layer can be warmed by vertical heat advection, entrainment, or vertical diffusion at its base (Han et al 2001;de Boyer Montégut et al 2007;Wang et al 2012;Girishkumar et al 2013;Akhil et al 2014). On the other hand, some studies based on numerical experiments (Howden and Murtugudde 2001;de Boyer Montégut et al 2007) and observations (Shenoi et al 2002(Shenoi et al , 2005 claimed that the mixed layer heat budget in the Bay of Bengal was mostly dominated by surface heat flux forcing.…”

“…Rao et al (2002) suggested that the thick barrier layer prohibited thermocline movement from affecting SST variability along the coast of the bay, but they did not specify what process controlled SST variability. Wang et al (2012) and Girishkumar et al (2013) found nonnegligible influence of temperature inversions on SST. The former was based on numerical experiments with an ocean general circulation model (OGCM) and focused on short-term variability related to the passages of two cyclones; the latter used 11-month records from a moored buoy deployed at the interior of the bay.…”

Influence of atmospheric intraseasonal oscillations on seasonal and interannual variability in the upper Indian Ocean

“…To assess the effect of this internal variability on the modeled seasonal and interannual signals, an additional HYCOM experiment is performed (HYCOM_InternalEXP; Table 1). HYCOM_InternalEXP is a finer resolution model run, with 0.25° × 0.25° grid spacing and 30 layers [ Wang et al , 2012], and it is forced by ERA‐Interim monthly climatology [ Dee et al , 2011] and run forward in time for 59 years. The results from years 16–40 are analyzed.…”