Precipitation diurnal cycle over the maritime continent modulated by ENSO

This study examines the modulation by ENSO of the diurnal cycle of precipitation in boreal winter for the period 1998-2016 over the maritime continent (MC), using the Tropical Rainfall Measuring Mission data and the weather research and forecasting (WRF) model. The diurnal cycles are composited for the ENSO warm (El Nino) and cold (La Nina) phases. It is found that there are statistically significant differences in the diurnal cycle amplitude between El Nino and La Nina, with a non-uniform spatial pattern over the MC. The amplitude of precipitation diurnal cycle is larger over the western MC but smaller over the eastern MC during El Nino, and vice versa for La Nina. A diagnosis of the moisture budget shows that the difference in the diurnal cycle amplitude is primarily attributed to the vertically integrated convergence of the interannual background moisture by diurnal winds. A further analysis indicates that the ENSO-related background moisture plays a key role in causing the difference in diurnal wind activity between El Nino and La Nina, which leads to the difference in the precipitation diurnal cycle.