South Asian subtropical low-level jet: Influence on regional hydrology and aerosol optical depth

Abstract

A 38-year high-resolution wind climatology shows a consistent occurrence of hitherto unreported South Asian subtropical low-level jets (SASLLJs) over the 31°-35°N and 60°-62°E latitude-longitude region, occurring throughout the year are the northerly LLJs (NLLJs) and southerly LLJs (SLLJs). The NLLJ is persistent mostly during the monsoon season. The NLLJ is frequent, unlike the SLLJ. The synoptic heat low in South Asia (62°-66°E and 27°-32°N) and the anticyclone over Turkmenistan (40°-50°N and 50°- 60°E) are critical in inducing the NLLJ. Regional topography permits direct mid-latitude air intrusion into the subtropical region. Importantly, we find that the NLLJ results in enhancing the transportation of dust to the Indian subcontinent and the northern part of the Arabian Sea due to wind blows. Long-term NLLJ intensity displays waning trend because of the weakening of pressure gradients between the heat low in South Asia and over Turkmenistan.