South Asian Summer Monsoon variability in Isentropic coordinates
Abstract
The atmospheric circulation and thermodynamic structure during the South Asian Summer Monsoon season is analyzed in isentropic coordinates. This technique, originally developed to analyze the global mean meridional circulation, makes it possible to identify the thermodynamic properties of different air mass, which can be used to systematically analyze the complex atmospheric flows. The method uses the mass transport in terms of the equivalent potential temperature of the air parcels in isentropic coordinates to understand the thermodynamic evolution of air parcels as they move through the atmosphere. we demonstrated here how the properties of various air masses, such as the inflow of warm moist air in the boundary layer, upper tropospheric outflow, and mid-latitudes dry air intrusion over the monsoon region are identified using the joint distribution of the mass transport as a function of dry and moist entropy. The vertical mass flux in terms of the equivalent potential temperature of the ascending and descending air mass over the Indian subcontinent, allow us to infer further the thermodynamic transformation occurring during the monsoon. Finally the mass transport and isentropic thickness for different moist ventilation range of tropical atmosphere are used to represent the characteristics of airmass in the isentropic framework for better understanding the thermodynamic evolution of air parcels as they evolve as part of the large-scale monsoon system in a warm moist environment. Diagnosis based on the isentropic thickness reveals that the regional monsoon circulation and precipitation features are better explained by this method in the Asian monsoon regions. We extended our analysis in diagnosing the active break phases of Asian summer monsoon, which will be highlighted in this work. The study uses, data from AMIP-type simulations carried out with prescribed Sea Surface Temperature and sea ice for a 25 year period (1981-2005) from the GFDL High-resolution atmospheric model (HiRAM) with an average grid spacing of 25km over the globe.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.A13F0339T
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 3371 Tropical convection;
- ATMOSPHERIC PROCESSESDE: 3373 Tropical dynamics;
- ATMOSPHERIC PROCESSESDE: 3374 Tropical meteorology;
- ATMOSPHERIC PROCESSES