Dynamical simulation of Indian summer monsoon circulation, rainfall and its interannual variability using a high resolution atmospheric general circulation model

Abstract

This paper discusses the simulations of Indian summer monsoon (ISM) using a high-resolution National Center for Environmental Prediction (NCEP) T170/L42 model for a 20-year period (1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004) with observed Sea Surface Temperature (SSTs) as boundary conditions and using five initial conditions in the first week of May. Good agreement is found between the observed and simulated climatologies. Interannual variability (IAV) of the ISM rainfall as simulated in individual ensemble members and as provided by ensemble average shows that the two series are found to agree well; however, the simulation of the actual observed year-to-year variability is poor. The model simulations do not show much skill in the simulation of drought and excess monsoon seasons. One aspect which has emerged from the study is that where dynamical seasonal prediction has specific base for the large areal and temporal averages, the technique is not to be stretched for application on short areal scale such as that of a cluster of a few grid point. Monsoon onset over Kerala (MOK) coast of India and advance from Kerala coast to northwest India is discussed based on ensemble average and individual ensemble member basis. It is suggested that the model is capable of realistically simulating these processes, particularly if ensemble average is used, as the intermember spread in the ensemble members is large. In short, the high-resolution model appears to provide better climatology and its magnitude of IAV, which compares favourably with observations, although year-to-year matching of the observed and simulated seasonal/monthly rainfall totals for India as a whole is not good.

Assessment of the Weather Research and Forecasting (WRF) model for simulation of extreme rainfall events in the upper Ganga Basin

“…Global models have been employed in several studies to understand the large-scale circulation pattern and for quantitative analysis of the monsoon rainfall, but due to their coarse resolution, they are unable to represent the local to regional characteristics of monsoon rainfall. Regional models, however, can explicitly simulate the interactions between the large-scale weather phenomenon and regional topography, making the climate simulations reliable (Gadgil and Sajani, 1998;Ratna et al, 2011;Srinivas et al, 2013). Furthermore, regional models have a better representation of convection, thus offsetting one of the major sources of errors and uncertainties in the global models.…”

Simulation of the Indian summer monsoon regional climate using advanced research WRF model

“…Lau et al, 2009;Chen et al, 2010). However, the GCMs as a result of coarse resolution cannot represent the regional characteristics of monsoons (Gadgil and Sajini, 1998;Krishnamurti et al, 2000;Kang et al, 2002;Gadgil et al, 2005;Krishna Kumar et al, 2005;Wang et al, 2005;Satyaban et al, 2010). The 1196 C. V. SRINIVAS et al features of orography, low pressure trough across India and the off-shore trough on the west coast associated with the monsoon need to be represented precisely to capture the regional circulation patterns and the rainfall.…”

Assessment of two versions of regional climate model in simulating the Indian Summer Monsoon over South Asia CORDEX domain

“…ISMR exhibits significant temporal and spatial variability (Mooley and Parthasarathy 1984;Thapliyal and Kulshrestha 1991;Kripalani and Kulkarni 2001;Sahai et al 2003;Naidu et al 2015). Several scientists have investigated the inter-annual and intra-seasonal variations of monsoon rainfall and the associated phenomena over the last several years using observed data (Webster et al 1998;Gadgil et al 2003) and conducting modeling studies (Ratna et al 2011;Satyanarayana and Kar 2016;Pattnayak et al 2016a). The key features of Indian summer monsoon include the sudden onset and gradual withdrawal, which signify the beginning and end of the rainy season respectively.…”