Regional teleconnections of ENSO, IOD events, and rainfall trends in Central India

Abstract

The study investigates teleconnections of ENSO (El Niño Southern Oscillation), IOD (Indian Ocean Dipole) events to rainfall trends. Spatiotemporal rainfall analysis for 50 years (1971–2020) is carried out. Trend analysis for 50 (1971–2020) and 30 (1991–2020) years using four Mann-Kendall (MK) tests, based on MK statistics (Z value), is carried out for six districts of Nagpur division of central India. Theil-Sen's slope estimator is used to compute trend magnitudes. Out of four tests, the Yue and Wang Modified MK test provides the most significant result in Z values. Trend analysis of 50 years shows that June had no trend, July and September had an increasing trend, while August had a decreasing trend in some districts. The impact of ENSO (El Niño and La Niña) and IOD (positive and negative IOD) events on ISMR (Indian Summer Monsoon Rainfall) has been investigated using spatiotemporal variation, rainfall deficiency, and correlation analysis. The response of vegetation to ENSO and IOD events was used for validation purposes. Results indicate that El Niño events are associated with drier conditions in Low NDVI (Normalized Difference Vegetation Index) areas, whereas positive IOD events are associated with wetter conditions (High NDVI area) in Nagpur division. La Niña and negative events show both drier and wetter conditions (Low and high NDVI). The IOD events show a significant correlation with ISMR compared to ENSO events in the study area.