Onset and withdrawal of the large-scale South Asian monsoon: A dynamical definition using change point detection
Abstract
This study introduces a robust, objective definition for onset and withdrawal of the South Asian summer monsoon (SASM), based on the large-scale atmospheric moisture budget. The change point index (CHP) allows precise characterization of the different stages and timescales of the large-scale SASM and is also highly correlated with the commonly used local operational index, the monsoon onset over Kerala. The onset and withdrawal dates defined by CHP, which capture the expected seasonal transitions in rainfall and winds, correspond with regime changes in the large-scale SASM water vapor budget between negative and positive net precipitation. Analysis of climatological composites reveals that the seasonal transitions in SASM sector mean precipitation and circulation bear close resemblance to those of the zonal mean Hadley circulation. Computing the CHP index at grid points within the SASM domain yields a robust definition of local onset and withdrawal dates, which are well correlated with the large-scale index on interannual timescales, providing insight into the regional variability associated with the large-scale SASM.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.A22D..06W
- 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