Subtropical jet regulates Arabian winter precipitation: a viable mechanism

Taraphdar, S., Gopalakrishnan, D., Liu, C., Pauluis, O., Xue, L., Ajayamohan, R. S., Leung, L. R., Hagos, S., Grabowski, W., Chen, S., Rasmussen, R. and Tessendorf, S. (2025) Subtropical jet regulates Arabian winter precipitation: a viable mechanism. Journal of the Atmospheric Sciences. ISSN 1520-0469 doi: 10.1175/JAS-D-23-0213.1 (In Press)

Abstract/Summary

The present study explores the mechanism governing wintertime (Nov – Apr) precipitation over the Arabian Peninsula (AP) using a 17-year-long (2002 – 2018) high-resolution WRF simulation. The composite analysis of strong precipitation events suggests that the equatorward extension of upper-level jet together with the embedded upper-level trough creates a positive (cyclonic) middle-level vorticity and subsequently generates an anomalous lower-level convergence through Ekman pumping. This leads to the development of an anomalous surface low, which is further enhanced in presence of the existing Red Sea trough over the AP. This surface low weakens the persistent anticyclone over the AP, shifting it further eastward to the Arabian Sea. The eastward shift in the lower-level anticyclone contributes to the transport of warm moist air from the Arabian Sea and the Red Sea towards the AP. This warm moist air converges with the cold and dry air advected by the mid-latitude jet and creates a moisture convergence zone, leading to the initiation of convection. We test the proposed mechanism through numerical experiments with modified upperlevel wind and demonstrate that a strong, southward intrusion of jet can indeed lead to precipitation over the AP. The above mechanism also explains the interannual variability of precipitation over the AP. During wet years, we notice approximately 3 ms−1 stronger jet core magnitude and about a 2° equatorward shift of the jet compared to dry years. While the equatorward extension of the jet explains about 21% of the interannual variability, the jet magnitude explains around 7% of the variability during wet years.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/121783
Identification Number/DOI	10.1175/JAS-D-23-0213.1
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	American Meteorological Society
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