Why Is ENSO Influencing Northwest India Winter Precipitation in Recent Decades?

Abstract

This study examines decadal changes of the El Niñ o-Southern Oscillation (ENSO) influence on the interannual variability of northwest India winter precipitation (NWIWP). The analysis is based on correlations and regressions performed using India Meteorological Department (IMD) records based on station data and reanalysis fields from 1950 to 2008. The authors find that the interannual variability of NWIWP is influenced by the ENSO phenomenon in the recent decades. This conclusion is supported by a consistency across the different observational datasets employed in this study and confirmed by numerical modeling. A physical mechanism for such an influence is proposed, by which western disturbances (WDs) are intensified over northwest India because of a baroclinic response due to Sverdrup balance related to large-scale sinking motion over the western Pacific during the warm phase of ENSO. This response causes an upper-level cyclonic circulation anomaly north of India and a low-level anticyclonic anomaly over southern and central India. The cyclonic circulation anomaly intensifies the WDs passing over northwest India.

Multi-annual variations in winter westerly disturbance activity affecting the Himalaya

“…Lang and Barros (2004) found the PE to significantly influence geopotential height in the WWD track affecting CH. The AO, PE and ENSO have previously been linked to modifications of the wintertime westerly jet as well as precipitation totals over the KH (Syed et al 2006;Yadav et al 2010). Yadav et al (2010) found a statistically significant correlation between the Niño 3.4 index and northwest India precipitation for the period 1968-2008, with an increasingly strong correlation for the period .…”

“…The AO, PE and ENSO have previously been linked to modifications of the wintertime westerly jet as well as precipitation totals over the KH (Syed et al 2006;Yadav et al 2010). Yadav et al (2010) found a statistically significant correlation between the Niño 3.4 index and northwest India precipitation for the period 1968-2008, with an increasingly strong correlation for the period . In this work, we also consider the SH, which is a predominant thermal high positioned over northern continental Asia.…”

“…The MEI warm-phase has been linked to precipitation increases in the western Himalaya during winter (Yadav et al 2010). Figure 13d shows an increase in U200 over southern Asia.…”

“…Atmospheric modes such as the Arctic Oscillation (AO), Siberian High (SH), Polar/Eurasian Pattern (PE) and the El Niño-Southern Oscillation (ENSO) play an important role in the interannual climatic variability of the KH by modulating the strength or position of the Asian jet (Barlow et al 2005;Syed et al 2006;Yadav et al 2010). The position of mid-and upper-tropospheric troughs in the zonal westerlies influences the strength and vertical extent of WWD (Ridley et al 2013).…”

Characteristic features of winter precipitation and its variability over northwest India

“…In the earlier studies by Yadav et al (2007Yadav et al ( , 2009aYadav et al ( , 2009bYadav et al ( , 2010 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 …”