Regional and Local Impacts of the ENSO and IOD Events of 2015 and 2016 on the Indian Summer Monsoon—A Bhutan Case Study

The Indian Summer Monsoon (ISM) plays a vital role in the livelihoods and economy of those living on subcontinent, including small, mountainous country Bhutan. ISM fluctuates over varying temporal scales its variability is related to many internal external factors El Niño Southern Oscillation (ENSO) Ocean Dipole (IOD). In 2015, Super occurred tropical Pacific alongside positive IOD was followed 2016 by simultaneous La Niña negative IOD. These events had worldwide repercussions. However, it unclear how affected during this time, both at regional scale whole area local First, an evaluation data products comparing ERA5 reanalysis, TRMM GPM satellite, GPCC precipitation against weather station measurements from Bhutan, indicated that reanalysis suitable investigate change these two years. datasets showed there disruption period, with late onset monsoon shifted flow July 2015 August 2016, withdrawal 2016. resulted neither surplus nor deficit across years but instead large spatial-temporal variability. It possible attribute some changes ENSO events, expected impact are not recognizable. likely 2015/16 driven combination IOD, boundary conditions, Decadal Oscillation, Atlantic Multi-decadal more. At scale, intricate topography orographic processes ongoing within Bhutan further amplified or dampened already altered ISM.