Temporal Change in the Diurnal Cycle of Rainfall over India in last four decades

Hourly rainfall data recorded at 109 Self Recording Rain gauge Stations (SRRG) for the period 1969-2014 are analyzed to study the diurnal cycle of rainfall in India. Temporal change in the phase of diurnal cycle of rainfall is emphasized in this study. Different aspects of hourly rainfall such as, amount, frequency and intensity have been examined. Temporal change in the diurnal cycle of rainfall showed that there is a shift in the phase of the diurnal cycle of rainfall in the recent times in most of the stations. For the north central India (CI), the phase of diurnal cycle of rainfall shifts to a later time of the day and for south CI, the phase of the diurnal cycle of rainfall shifts to an earlier time of the day. Stations in south India do not show shift in the phase of diurnal cycle of rainfall. Coastal and orographic regions showed phase shift of more than 9 hours in the recent times. Both frequency and intensity contribute to this shift. However, the change in the number of heavy rainfall events in the recent times can be attributed to the change of phase of diurnal cycle of rainfall in most of the stations.