Dynamic and thermodynamic characteristics of the Asian summer monsoon during the onset phase over the Indian Peninsula (Kerala coast) and its variability are examined with reanalysis data sets. For this study, daily averaged (0000 and 1200 UTC) reanalysis data sets of National Centre for Environmental Prediction-National Centre for Atmospheric Research for the period 1948-99 are used.Based on 52 years of onset dates of the Indian summer monsoon, we categorized pre-onset, onset and post-onset periods (each averaged 5 days) to investigate the mean circulation characteristics and the large-scale energetics of the Asian summer monsoon. It is found that the strength of the low-level Somali jet and upper tropospheric tropical easterly jet increase rapidly during the time of evolution of the summer monsoon over India. Over the Bay of Bengal and the Arabian Sea, predominant changes are noticed in the large-scale balances of kinetic energy, heat and moisture from the pre-onset to the post-onset periods. Prior to the onset of the summer monsoon over India, a zone of flux convergence of heat and moisture is noticed over the eastern sector of the Bay of Bengal and this intensifies in the onset and postonset periods. During onset of the monsoon over India, the horizontal flux convergence of heat and moisture, as well as diabatic heating, are enhanced over the Arabian Sea. These subsequently increase with the evolution and advancement of the monsoon over India.Further, the dynamics of the evolution processes (15 days before and 30 days after the onset date of the monsoon over Kerala for each annual cycle) are studied over various sectors, such as the Arabian Sea, Bay of Bengal and Indian Peninsula region. The study reveals that the low-level kinetic energy, vertically integrated generation of kinetic energy and net tropospheric moisture over Arabian Sea can be used as potential predictors for the prediction of the possible onset date of the summer monsoon over the Indian Peninsula.
In this article, the interannual variability of certain dynamic and thermodynamic characteristics of various sectors in the Asian summer monsoon domain was examined during the onset phase over the south Indian peninsula (Kerala Coast). Daily average (0000 and 1200 UTC) reanalysis data sets of the National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) for the period 1948-1999 were used. Based on 52 years onset date of the Indian summer monsoon, we categorized the pre-onset, onset, and post-onset periods (each an average of 5 days) to investigate the interannual variability of significant budget terms over the Arabian Sea, Bay of Bengal, and the Indian peninsula. A higher difference was noticed in low-level kinetic energy (850 hPa) and the vertically integrated generation of kinetic energy over the Arabian Sea from the pre-onset, onset, and post-onset periods. Also, significant changes were noticed in the net tropospheric moisture and diabatic heating over the Arabian Sea and Indian peninsula from the pre-onset to the post-onset period. It appears that attaining the magnitude of 40 m 2 s -2 and then a sharp rise in kinetic energy at 850 hPa is an appropriate time to declare the onset of the summer monsoon over India. In addition to a sufficient level of net tropospheric moisture (40 mm), a minimum strength of low-level flow is needed to trigger convective activity over the Arabian Sea and the Bay of Bengal. An attempt was also made to develop a location-specific prediction of onset dates of the summer monsoon over India based on energetics and basic meteorological parameters using multivariate
This is the peer reviewed version of the following article: Tiwari, P. R., Kar, S. C., Mohanty, U. C., Dey, S., Sinha, P., Raju, P. V. S. and Shekhar, M. S., ???On the dynamical downscaling and bias correction of seasonal-scale winter precipitation predictions over North India???, quarterly Journal of the Royal Meteorological Society, Vol. 142 (699):2398-2410, June 2016, which has been published in final form at DOI: https://doi.org/10.1002/qj.2832. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. ?? 2016 Royal Meteorological SocietyThis study presents the results of high-resolution (30 km) climate simulations over North India using an optimized configuration of the Regional Climate Model (RegCM), driven by a global spectral model (T80 model with horizontal resolution of ???1.4???) for a period of 28 years (1982???2009). The main aim of this work is to analyze the capabilities of the RegCM to simulate the wintertime precipitation over North India in the recent past.The RegCM validation revealed a good improvement in reproducing the precipitation compared to results obtained from the T80 model. This improvement comes due to better representation of vertical pressure velocity, moisture transport, convective heating rate and temperature gradient at two different latitudinal zones. Moreover, orography in the high-resolution RegCM improves the precipitation simulation in the region where sharp orography gradient plays an important role in wintertime precipitation processes. Two bias correction (BC) methods namely mean bias-remove (MBR) and quantile mapping (QM) have been applied on the T80 driven RegCM model simulations. It was found that the QM method is more skillful than the MBR in simulating the wintertime precipitation over North India. A comparison of model-simulated and bias corrected precipitation with observed precipitation at 17 station locations has also been carried out. Overall, the results suggest that when the BC is applied on dynamically downscaled model, it has better skill in simulating the precipitation over North India and this model is a useful tool for further regional downscaling studies
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