Study of Active and Break Spell Phenomena of Indian Summer Monsoon Using WRF Downscaled Data

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Prathipati, Vinay Kumar
Vijaya Kumari, K.
Chennu, Venkateswara Naidu
Dasari, Hari Prasad

KAUST Department
Physical Science and Engineering (PSE) Division

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This study evaluates the performance of a dynamically downscaled Weather Research and Forecasting (WRF) model by capturing the characteristics of the interseasonal variability in terms of active and break spells of the Indian summer monsoon during the period 1980–2014. We identify the active and break days based on the standard criteria of previous studies. Further, the composite means in the rainfall and different rainfall events, along with the thermal and dynamical features associated with active and break spells, are analyzed and discussed. Our results clearly show that the WRF model reproduces the observed features of monsoon circulation in active spells such as the wider and intensified lower tropospheric winds, the presence of mid-tropospheric cyclonic circulation, and the dominance of strong upper-level tropical easterlies along with the high influx of moisture towards the Indian subcontinent. Even in the break spells, the WRF model effectively simulates the observed features of the ERA, such as weaker monsoon winds at both low and upper levels and decreased strength of northwesterly winds of Shamal, the presence of a strong thermal inversion over the northwestern part of the Arabian Sea, and a significant increase in the African easterly jet. Moreover, our rainfall analysis during active and break spells reveals that the WRF model accurately reproduces the observed characteristics of the regional-scale precipitation. The results also reveal that the spatial distributions of moderate, heavy, and very heavy rainfall events over the monsoon core region are well captured by the WRF model, with only slight intensity variations compared to the observed distributions.

Prathipati, V. K., Viswanadhapalli, Y., Chennu, V. N., & Dasari, H. P. (2021). Study of Active and Break Spell Phenomena of Indian Summer Monsoon Using WRF Downscaled Data. Pure and Applied Geophysics. doi:10.1007/s00024-021-02837-5

The author, P. Vinay Kumar, wishes to thank the DST, Government of India, for providing research fellowships [DST/INSPIRE Fellowship/IF160113] and for providing the computational facility under the FIST programme at the Department of Meteorology and Oceanography, Andhra University, Visakhapatnam. The authors acknowledge the India Meteorological Department for providing the high-resolution gridded rainfall (0.25° × 0.25°) and ECMWF Copernicus Climate Change Service for providing the ERA5 data. This work is part of the PhD work of P. Vinay Kumar.

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Pure and Applied Geophysics


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