Simulation of marine boundary layer characteristics over theIndian Ocean during INDOEX-IFP’99

The characteristic features of the marine boundary layer (MBL) over the Indian Ocean during the north-east monsoon and the factors influencing it have been investigated. The Indian Ocean Experiment (INDOEX) Intensive Field Phase-1999 (IFP’99) has provided the atmospheric sounding data for this study. This is for the first time that such high-resolution upper air data are obtained over the Indian Ocean. Different synoptic scenarios corresponding to convectively active and convectively suppressed situations over the Indian Ocean are considered to study the variability in MBL characteristics using one-dimensional (1-D) multi-level PBL model with a TKE-e closure scheme. The NCMRWF-GCM was also used to simulate surface layer parameters such as sensible heat and latent heat fluxes, the marine boundary layer height, etc. The simulations also include the vertical profiles of potential temperature, specific humidity and zonal and meridional wind components. It is noticed that, in general, the non-local closure and the scheme due to turbulent kinetic energy (TKE) can simulate vertical profiles closer to the observations. The 1-D PBL model simulates the temporal evolution of TKE, marine boundary layer height (MBLH) and sensible and latent heat fluxes. The model also generates the vertical profiles of potential temperature, specific humidity, and zonal and meridional wind. These simulated values are comparable with the observations available from INDOEX experiment. The 1-D model could not simulate the dynamical features associated with advection and winds satisfactorily. However, the convective regimes are well simulated.