Influence of the Planetary Boundary Layer Physics on Medium-range Prediction of Monsoon over India

Abstract

Abstract-The present study emphasizes the importance of proper representation of boundary layer physics in a general circulation model. The Turbulent Kinetic Energy (TKE) closure scheme incorporates important processes of the Planetary Boundary Layer (PBL) compared to a simplistic first-order closure model. Hence the model which has the TKE closure scheme is capable of simulating important weather systems associated with summer monsoon, such as monsoon depressions and lows that form over the Indian subcontinent quite well compared to the first-order closure model. The present study indicates better performance of the global model with the TKE scheme in the prediction of the monsoon circulation, including the tracks of the depressions over the Indian subcontinent. Medium-range weather prediction has also improved with the use of the TKE closure. However further studies are necessary to improve the forecast, with emphasis on boundary layer processes.

Variation of coastal atmospheric boundary layer characteristics with convective activity along the west coast of India during the Arabian Sea Monsoon Experiment (ARMEX) 2002

“…Therefore, the present study was undertaken using NLC-HP. A detailed description of the scheme (NLC-HP) is also given by Basu et al (1999Basu et al ( , 2002 and Sam (2005).…”

“…The latent heat of water vapour that is set free in the moist south-west current over land leads to the enhancement of convective currents and cloud growth (Basu et al 1999), which, to a great extent, depends on the characteristics of the planetary boundary layer (PBL). Therefore, it is very important for one to understand the processes that characterize the PBL in the development and sustenance of semipermanent features such as heat low, off-shore trough, monsoon low-level jet (MLLJ), and other low-level processes that bring in copious amount of rainfall during the SWM.…”

Evaluation of several different planetary boundary layer schemes within a single model, a unified model and a multimodel superensemble

“…In this, several terms in the RHS are parametrized (Stull, 1988). The last term ɛ (dissipation term) is also prognostically determined using where a 1 = 1.44, a 2 = 1.92 and a 3 = 0.77 (Basu et al, 1999) and…”

“…where a 1 = 1.44, a 2 = 1.92 and a 3 = 0.77 (Basu et al, 1999) and w θ = −K h ( ∂θ ∂z − γ cg ) The counter gradient term γ cg is taken as 0.7 × 10 −3 • K m −1 . The counter gradient term (which is against the local gradient) deals with the non-local effects.…”

Evaluation of ABL parametrization schemes in the COSMO, a regional non-hydrostatic atmospheric model over an inhomogeneous environment

“…With the development of highresolution atmospheric models used for the NWP, requirements for accurate ABL parametrization schemes have dramatically increased, making them a key element in the weather and climate predictions, as well as in several other environmental applications, such as pollutant dispersion and biometeorology (Yamartino and Wiegand 1986;Nielsen-Gammon et al 2010;Hu et al 2010). Despite a considerable progress in the prediction of synoptic weather conditions through atmospheric models, the errors and uncertainties associated with the ABL parametrization schemes in the NWP model simulations remain one of the primary sources of inaccuracies, especially for the tropics where small-scale cumulus convection dominate (Basu et al 1998(Basu et al , 1999Lee and Hong 2005;Pleim 2007a, b;Shah et al 2010). One of the major challenges of modelling the ABL processes through parametrization is the prediction of the temporal variation of vertical and horizontal structures in response to the influence of the major processes acting in the atmosphere and at the Earth's surface.…”