The Role of Indian monsoon low pressure systems in up-and-over moisture transport to the southwestern Tibetan Plateau modulated by ENSO events
Abstract
As an integral part of the South Asian summer monsoon system, monsoon low pressure systems (LPSs) bring large amounts of precipitation to agrarian north-central India during their passage across the subcontinent. They also play an important role in supplying moisture from north-central India to the southwestern Tibetan Plateau (SWTP) via up-and-over transport, in which convectively-lifted moisture over the Indian subcontinent is swept over the SWTP by southwesterly winds in the middle troposphere. In this study, we explore the impacts of ENSO events on the up-and-over moisture transport based on ERA-Interim reanalysis as well as the latest GFDL AM4.0 model. The results show that the up-and-over moisture transport is weaker during El Niño events. Consequently, dry anomalies of precipitation are noted over both north-central India and the SWTP. Further investigation demonstrates that, though the number of LPSs differ slightly during different phases of ENSO, the tracks of LPSs are shifted poleward in El Niño years. The development of LPSs is then suppressed due to the presence of the Himalayas (friction and vortex squashing), which makes the up-and-over moisture transport less efficient. In addition, the mid-tropospheric circulation during El Niño events is less favorable for the advection of moisture into the SWTP. Our findings indicate that LPSs are influential in extending the northern boundary of the South Asian monsoon system across the Himalayas into the interior of the SWTP. The strength of this connection depends on both LPS characteristics and the configuration of the background environment.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGC31A..07D
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSES;
- 3373 Tropical dynamics;
- ATMOSPHERIC PROCESSES;
- 1630 Impacts of global change;
- GLOBAL CHANGE