Intraseasonal-to-interannual variability of the Indian Monsoon: the present climate and future projections of climate change

Abstract:

The Asia Monsoon is among Earth’s most intriguing and spectacular phenomena. The Indian Monsoon System (IMS) is a regional manifestation this continental-scale phenomenon with complex characteristics and predictive challenges. India exhibits one of the largest rates of population growth that relies on IMS cycle for water supply. Thus, understanding the temporal variability of the IMS is essential to realistically predict the impacts of climate change on Asia’s water resources and food security. Here we investigate intraseasonal-to-interannual variability of the IMS in the climate of the 20^th century using the Climate Forecast System Reanalysis (CFSR) and examine future scenarios of climate change using the high spatial resolution models of the Coupled Model Intercomparison Project Phase 5 (CMIP5) project. IMS is characterized with a large-scale index continuous in time and obtained by performing combined EOF analysis (CEOF) of variables that characterize the monsoon cycle: precipitation, low level circulation at 10 m, specific humidity and temperature at 2m. CFSR is used to derive the index (1979-2013). Projections of the CEOF onto the tropical rainfall measuring mission (TRMM) indicate that the first CEOF captures the large-scale features of the South and East Asia Monsoon. The second CEOF is associated with the IMS and its time coefficient is used as large-scale index for the IMS (LIMS). LIMS realistically defines IMS onset and withdrawal, and its amplitude associates with total seasonal precipitation. Moreover, the spectral analysis of the ISMI shows peaks on intraseasonal timescales that are related to IMS’s active and break phases. Moreover, we demonstrate that LIMS identifies the interannual variability of IMS and can be used to investigate floods and droughts that have occurred over India. Similar approach is used to investigate the skill of the CMIP5 models in realistically simulating active and break phases of the IMS in the ‘historic’ run (1951-2005). We select the models that best represent the intraseasonal variability of IMS and examine projected changes in the amplitude and persistence of the break and active periods in the high-emission representative concentration pathway 8.5 (RCP8.5) (2006-2100). This research has been supported by the National Science Foundation (NSF- 1116105).