Why does June rainfall over India have different variability and contribution to the seasonal rainfall compared to other months during the recent period?

The present study observed a decreasing trend in rainfall over the Indian landmass during June month, while rainfall from July to September has an increasing trend in the recent decades. The contribution of June (September) rainfall to the seasonal total has also significantly decreased (increased) during the period. The study advances that the decreasing June rainfall trend results from reduced circulation, moisture advection, and convergence over India during June. The reduced convection trend over India has co-occurred with increased rainfall over the northwest Pacific and the equatorial Indian Ocean. Many of the seasonal strong (or weak) monsoon years during the study period exhibit opposite anomalies in June. Over the recent decades, the onset of the El Niño-Southern Oscillation (ENSO) has been delayed, shifting the ENSO-Monsoon teleconnection towards July-September. Additionally, the influence of North Tropical Atlantic (NTA) sea surface temperature (SST) anomalies on ISMR is also stronger towards the end of the monsoon season. Pre-monsoon SST anomalies in the Indian Ocean (IO) have shown a warming trend, leading to increased moisture advection and convection in the equatorial and northern Indian Ocean. These processes initiate early rainfall activity over the Indian land region towards the latter parts of May, creating an onset situation following a dry period during June, during which the influence of large-scale forcing is minimal. This leads to a decreased trend and lower rainfall in June compared to the rest of the season. Thus, June rainfall variability primarily depends on the pre-monsoon warming in the equatorial IO and the associated early propagation of monsoon onset, while rainfall in the other months is influenced by spring season NTA SST and concurrent ENSO anomalies during recent years.