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Observed features of monsoon low-level jet and its relationship with rainfall activity over a high-altitude site in Western Ghats, India

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Abstract

In the present work, monsoon low-level jet (MLLJ) characteristics and its relationship with rainfall activity have been studied using three years (2016–2018) of radiosonde observations taken from a high altitude site (Mahabaleshwar, 1348 m AMSL) in Western Ghats, India. Initial analysis of zonal and meridional winds showed an apparent monthly variation with respect to altitude with robust features in zonal winds compared to meridional winds. Analyzed zonal wind and vertical shear in zonal wind during south west monsoon showed clear intra seasonal variation with respect to altitude especially below 5 km. Derived MLLJ characteristics, such as core speed, core height, and westerly wind depth, also exhibited apparent intra-seasonal variation where core height was comparatively invariant. Strong zonal wind and vertical shear in the zonal wind including higher core speed and westerly wind depth was noticed during July and August compared to June and September. Further, MLLJ association with rainfall activity has been analyzed. An increase in core speed and westerly wind depth was noted during the active period of monsoon compared to the break period. Later, the evolution of MLLJ characteristics before, during, and after heavy and high rainfall has been analyzed which showed strengthening of zonal wind, vertical shear in zonal wind, core speed, and westerly wind depth before and during the rainfall events categorized. Abundant moisture transport from the Arabian Sea to the Indian land mass prior to the event was noticed in the analysis of zonal water vapor flux. Intensification of few MLLJ characteristics mostly brings copious moisture, possibly leading to heavy or high rainfall over the study region.

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Data availability

Radiosonde and impact disdrometer data is available upon reasonable request to the corresponding author. Zonal wind, meridional wind, and specific humidity data are available at https://www.ecmwf.int/en/forecasts/datasets/reanalysis-datasets/era-interim.

Code availability

All the calculations and plots have been done using MATLAB and Origin software.

Change history

  • 21 August 2022

    The article title was mentioned twice and the other occurrence was removed.

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Acknowledgements

The authors are thankful to the team members of HACPL of IITM. The authors thank the Director, IITM for his full support. Indian Institute of Tropical Meteorology (IITM) and HACPL are fully funded by the Ministry of Earth Sciences (MoES), Government of India. All the data sources are duly acknowledged.

Funding

This research is carried out at IITM Pune. No additional funding support was received.

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Contributions

Leena P. P.: Data analysis, plotting, and manuscript preparation, Sanket B. R.: Data analysis and written initial draft as a part of his MTech thesis, V. Anil Kumar: Manuscript editing and reviewing, collecting radiosonde and impact disdrometer data, Resmi. E. A.: Manuscript editing and reviewing, plotting, G. Kishore Kumar and G. Pandithurai: Manuscript editing and reviewing, Rohit Patil: collecting radiosonde and impact disdrometer data.

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Correspondence to Leena P. P..

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P., L.P., Sanket, B.R., Kumar, V.A. et al. Observed features of monsoon low-level jet and its relationship with rainfall activity over a high-altitude site in Western Ghats, India. Theor Appl Climatol 150, 551–565 (2022). https://doi.org/10.1007/s00704-022-04167-5

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  • DOI: https://doi.org/10.1007/s00704-022-04167-5