Abstract
The monsoon low-level jet (MLLJ) originates at Mascarene high and after traveling thousands of kilometers enters India from the western boundary causing deep convection, cloudiness, and rainfall. Although its core lies at 850 hPa, it has a large vertical extent; therefore, different meteorological parameters at different levels have a large influence on the Indian summer monsoon rainfall. This study aims to examine the upper-air climatology of 9 stations on the west coast and central Peninsular India and to find out the effects of various parameters at different standard pressure levels on the Indian summer monsoon rainfall variability. We used the 34-yr (1971–2004) actual upper-air radiosonde/radio wind and standard synoptic surface observations data from these 9 stations and reported some new aspects of the MLLJ. The NCEP/NCAR and ECMWF reanalysis wind data have also been used to holistically study the features of MLLJ over sea and land areas. This study, as opposed to some recent studies, confirms the splitting of MLLJ into two branches, which can be seen on a few days during the monsoon season. Further analyses show that the change in geopotential height between 800 and 900 hPa has a strong bearing on the strength of MLLJ. The change in the upper-air pressure gradient force over the Indian landmass can cause a change in the wind speed of MLLJ during the monsoon season.
References
ADGM(R) and IMD, 2015: Forecasting Circular No. 5/2015 (3.7). Available online at https://cn.bing.com/search?q=www.imdsikkim.gov.in%2FFCT.pdf&form=IPRV10. Accessed on 1 February 2023.
Aneesh, S., and S. Sijikumar, 2016: Changes in the South Asian monsoon low level jet during recent decades and its role in the monsoon water cycle. J. Atmos. Solar-Terr. Phys., 138–139, 47–53, doi: https://doi.org/10.1016/j.jastp.2015.12.009.
Asnani, G. C., 1993: Tropical Meteorology. G. C. Asnani, c/o Indian Institute of Tropical Meteorology, Pashan, 321–322.
Attri, S. D., and A. Tyagi, 2010: Climate Profile of India Met Monograph No. Environmental Meteorology-01/2010. India Meteorological Department, New Delhi, Available online at https://www.researchgate.net/publication/291772903_Climate_profile_of_India. Accessed on 1 February 2023.
Bonner, W. D., 1968: Climatology of the low level jet. Mon. Wea. Rev., 96, 833–850, doi: https://doi.org/10.1175/1520-0493(1968)096<0833:COTLLJ>2.0.CO;2.
Bretherton, C. S., M. Widmann, V. P. Dymnikov, et al., 1999: The effective number of spatial degrees of freedom of a time-varying field. J. Climate, 12, 1990–2009, doi: https://doi.org/10.1175/1520-0442(1999)012<1990:TENOSD>2.0.CO;2.
Chakraborty, A., R. S. Nanjundiah, and J. Srinivasan, 2009: Impact of African orography and the Indian summer monsoon on the low-level Somali jet. Int. J. Climatol., 29, 983–992, doi: https://doi.org/10.1002/joc.1720.
Findlater, J., 1969: A major low-level air current near the Indian Ocean during the northern summer. Quart. J. Roy Meteor. Soc., 95, 362–380, doi: https://doi.org/10.1002/qj.49709540409.
Findlater, J., 1971: Mean Monthly Airflow at Low Levels Over the Western Indian Ocean. Stationery Office Books, London, 53 pp.
Grossman, R. L., and D. R. Durran, 1984: Interaction of low-level flow with the western Ghat mountains and offshore convection in the summer monsoon. Mon. Wea. Rev., 112, 652–672, doi: https://doi.org/10.1175/1520-0493(1984)112<0652:IOLLFW>2.0.CO;2.
Hersbach, H., B. Bell, P. Berrisford, et al., 2018: ERA5 Hourly Data on Pressure Levels from 1979 to Present. Available online at https://confluence.ecmwf.int/pages/viewpage.action?pageId=129134800. Accessed on 16 January 2023.
Hersbach, H., B. Bell, P. Berrisford, et al., 2020: The ERA5 global reanalysis. Quart. J. Roy Meteor. Soc., 146, 1999–2049, doi: https://doi.org/10.1002/qj.3803.
num.php?explnum_id=3855. Accessed on 16 January 2023.
Joseph, P. V., and P. L. Raman, 1966: Existence of low level westerly jet stream over Peninsular India during July. MAUSAM, 17, 407–410, doi: https://doi.org/10.54302/mausam.v17i3.5731.
Joseph, P. V., and S. Sijikumar, 2004: Intraseasonal variability of the low-level jet stream of the Asian summer monsoon. J. Climate, 17, 1449–1458, doi: https://doi.org/10.1175/1520-0442(2004)017<1449:IVOTLJ>2.0.CO;2.
Joseph, P. V., and A. Simon, 2005: Weakening trend of the southwest monsoon current through Peninsular India from 1950 to the present. Curr. Sci., 89, 687–694.
Kalapureddy, M. C. R., D. N. Rao, A. R. Jain, et al., 2007: Wind profiler observations of a monsoon low-level jet over a tropical Indian station. Ann. Geophys., 25, 2125–2137, doi: https://doi.org/10.5194/angeo-25-2125-2007.
Krishnamurti, T. N., J. Molinari, and H. L. Pan, 1976: Numerical simulation of the Somali jet. J. Atmos. Sci., 33, 2350–2362, doi: https://doi.org/10.1175/1520-0469(1976)033<2350:NSOTSJ>2.0.CO;2.
Krishnan, R., T. P. Sabin, D. C. Ayantika, et al., 2013: Will the South Asian monsoon overturning circulation stabilize any further. Climate Dyn., 40, 187–211, doi: https://doi.org/10.1007/s000382-012-1317-0.
Kumar, M. R. R., S. S. C. Shenoi, and P. Schluessel, 1999: On the role of the cross equatorial flow on summer monsoon rainfall over India using NCEP/NCAR Reanalysis Data. Meteor. Atmos. Phys., 70, 201–213, doi: https://doi.org/10.1007/s007030050034.
Kumar, V., D. K. U. R. Bhagat, M. S. Kumar, et al., 2007: Impact of low level jet on heavy rainfall events over Mumbai. MAUSAM, 58, 229–240, doi: https://doi.org/10.54302/mausam.v58i2.1221.
Raman, M. R., M. V. Ratnam, M. Rajeevan, et al., 2011: Intriguing aspects of the monsoon low-level jet over Peninsular India revealed by high-resolution GPS radiosonde observations. J. Atmos. Sci., 68, 1413–1423, doi: https://doi.org/10.1175/2011JAS3611.1.
Roxy, M. K., S. Ghosh, A. Pathak, et al., 2017: A threefold rise in widespread extreme rain events over central India. Nat. Commun., 8, 708, doi: https://doi.org/10.1038/s41467-017-00744-9.
Sarker, R. P., 1966: A dynamical model of orographic rainfall. Mon. Wea. Rev., 94, 555–572, doi: https://doi.org/10.1175/1520-0493(1966)094<0555:ADMOOR>2.3.CO;2.
Sijikumar, S., L. John, and K. Manjusha, 2013: Sensitivity study on the role of Western Ghats in simulating the Asian summer monsoon characteristics. Meteor. Atmos. Phys., 120, 53–60, doi: https://doi.org/10.1007/s00703-013-0238-8.
Stensrud, D. J., 1996: Importance of low-level jets to climate: A review. J. Climate, 9, 1698–1711, doi: https://doi.org/10.1175/1520-0442(1996)009<1698:IOLLJT>2.0.CO;2.
Subrahmanyam, M. V., and B. Pushpanjali, 2018: Low level jet variations during summer monsoon onset and rainfall variations. Indian J. Geo Mar. Sci., 47, 1154–1159.
Viswanadhapalli, Y., H. P. Dasari, S. Dwivedi, et al., 2020: Variability of monsoon low-level jet and associated rainfall over India. Int. J. Climatol., 40, 1067–1089, doi: https://doi.org/10.1002/joc.6256.
Xavier, A., A. Kottayil, K. Mohanakumar, et al., 2018: The role of monsoon low-level jet in modulating heavy rainfall events. Int. J. Climatol., 38, e569–e576, doi: https://doi.org/10.1002/joc.5390.
Acknowledgments
The author is thankful to the Director-General of India Meteorological Department and Deputy Director-General of Regional Meteorological Centre, New Delhi for their kind support and encouragement. We thank the Nation Data Centre, Pune for providing the necessary data and the NOAA/OAR/ESRL and ECMWF for providing the reanalysis and associated data.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Thapliyal, R. The Monsoon Low-Level Jet: Climatology and Impact on Monsoon Rainfall over the West Coast and Central Peninsular India. J Meteorol Res 37, 112–125 (2023). https://doi.org/10.1007/s13351-023-2099-5
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s13351-023-2099-5