On the impacts of ENSO and Indian Ocean dipole events on sub-regional Indian summer monsoon rainfall

Abstract

The relative impacts of the ENSO and Indian Ocean dipole (IOD) events on Indian summer (June-September) monsoon rainfall at sub-regional scales have been examined in this study. GISST datasets from 1958 to 1998, along with Willmott and Matsuura gridded rainfall data, all India summer monsoon rainfall data, and homogeneous and sub-regional Indian rainfall datasets were used. The spatial distribution of partial correlations between the IOD and summer rainfall over India indicates a significant impact on rainfall along the monsoon trough regions, parts of the southwest coastal regions of India, and also over Pakistan, Afghanistan, and Iran. ENSO events have a wider impact, although opposite in nature over the monsoon trough region to that of IOD events. The ENSO (IOD) index is negatively (positively) correlated (significant at the 95% confidence level from a two-tailed Student t-test) with summer monsoon rainfall over seven (four) of the eight homogeneous rainfall zones of India. During summer, ENSO events also cause drought over northern Sri Lanka, whereas the IOD events cause surplus rainfall in its south. On monthly scales, the ENSO and IOD events have significant impacts on many parts of India. In general, the magnitude of ENSO-related correlations is greater than those related to the IOD. The monthly-stratified IOD variability during each of the months from July to September has a significant impact on Indian summer monsoon rainfall variability over different parts of India, confirming that strong IOD events indeed affect the Indian summer monsoon.

Seasonal streamflow forecasting in the upper Indus Basin of Pakistan: an assessment of methods

“…The commonly used SOI (Southern Oscillation Index) has been linked with winter Hindu Kush Himalayan region precipitation (Afzal et al, 2013), Indian Summer Monsoon precipitation (Ashok et al, 2004;Ashok and Saji, 2007), central southwest Asian winter precipitation (Syed et al, 2006), Pakistan weather station temperature (del Río et al, 2013) and north-west India winter precipitation (Kar and Rana, 2014). Stronger links have been reported between ENSO, western disturbances and interannual winter precipitation variability in recent decades (Yadav et al, 2009a, b).…”

Assessment of methods for seasonal streamflow forecasting in the Upper Indus Basin of Pakistan

“…Himalayan region precipitation (Afzal et al, 2013); Indian Summer Monsoon Precipitation (Ashok et al, 2004;Ashok and Saji, 2007); central southwest Asian winter precipitation (Syed et al, 2006); Pakistan station temperature (del Río et al, 2013); and northwest India winter precipitation (Kar and Rana, 2014). Stronger links have been reported between ENSO, western disturbances and interannual winter precipitation variability for recent decades (Yadav et al, 2009a;Yadav et al, 2009b).…”

Interannual variability of temperature in the UTLS region over Ganges–Brahmaputra–Meghna river basin based on COSMIC GNSS RO data

“…The atmospheric conditions over the basin are largely controlled by the monsoon circulation during the summer, which is often modulated by global and regional large-scale climate variabilities such as ENSO and Indian Ocean Dipole (IOD) (e.g., Chowdhury, 2003;Ashok and Saji, 2007). The impact of global warming, increasing population, and rapid industrial and agricultural activities, and land-use changes across the basin may have contributed significantly to the recent tropospheric warming (Gautam et al, 2009;Lau et al, 2009).…”