Northeast monsoon over India: variability and prediction

Abstract

South peninsular India experiences a large portion of the annual rainfall during the northeast monsoon season (October to December). In this study, the facets of diurnal, intra-seasonal and inter-annual variability of the northeast monsoon rainfall (the NEMR) over India have been examined. The analysis of satellite derived hourly rainfall reveals that there are distinct features of diurnal variation over the land and oceans during the season. Over the land, rainfall peaks during the late afternoon/evening, while over the oceans an early morning peak is observed. The harmonic analysis of hourly data reveals that the amplitude and variance are the largest over south peninsular India. The NEMR also exhibits significant intra-seasonal variability on a 20-40 day time scale. Analysis also shows significant northward propagation of the maximum cloud zone from south of equator to the south peninsula during the season. The NEMR exhibits large inter-annual variability with the co-efficient of variation (CV) of 25%. The positive phases of ENSO and the Indian Ocean Dipole (IOD) are conducive for normal to above normal rainfall activity during the northeast monsoon. There are multi-decadal variations in the statistical relationship between ENSO and the NEMR. During the period 2001-2010 the statistical relationship between ENSO and the NEMR has significantly weakened. The analysis of seasonal rainfall hindcasts for the period 1960-2005 produced by the state-of-the-art coupled climate models, ENSEMBLES, reveals that the coupled models have very poor skill in predicting the inter-annual variability of the NEMR. This is mainly due to the inability of the ENSEMBLES models to simulate the positive relationship between ENSO and the NEMR correctly.

Precipitation Seasonality over the Indian Subcontinent: An Evaluation of Gauge, Reanalyses, and Satellite Retrievals

“…Far less effort has focused on pre-and postmonsoon precipitation in spite of its importance to water resources, agriculture, and livelihoods in the northwestern/Himalayan and southern peninsular regions of the subcontinent (Immerzeel et al 2009;Bookhagen and Burbank 2010). The magnitude and mechanistic explanation of precipitation and its variability during these seasons and/or regions remains unclear and poorly investigated (Kripalani and Kumar 2004;Sen Roy 2006;Rajeevan et al 2012;Kar and Rana 2013).…”

Characterizing pentad rainfall variations during the North‐East Indian monsoon season over the southeastern peninsular India

“…The positive vorticity during the wet conditions shifted northwards from the seasonal climatology and the center of positive anomaly located over the southeastern peninsular India (see Figures (a) and (d)). The northward movement of cyclonic circulation during the State‐1 was consistent with the northward propagation of rainfall episodes during the NEIMR period (Rajeevan et al, ). These physical processes could result in the wet NEIMR condition observed over the southeastern peninsular India.…”

“…As Charlotte et al () highlighted, it was not simple to correlate the identified prominent variations in seasonal NEIMR to intra‐seasonal NEIMR. Therefore, extensive research is required to understand the intra‐seasonal nature of NEIMR (Charlotte et al, ; Rajeevan et al, ).…”

Thermodynamical and cloud microphysical response during the transition from southwest to northeast monsoon

“…The SW and NE monsoon were studied separately by many researchers viz. Pai (2004), Rajeevan et al (2012), Balachandran et al (2006) etc. The excess or deficit SW monsoon rainfall is negatively correlated with NE monsoon rainfall (Dhar and Rakhecha, 1983;Selvaraj and Aditya, 2011).…”