Department of Agricultural Meteorology, College of Agriculture, Vellanikkara Kerala Agricultural University, Thrissur-680656, Kerala, India
This study was conducted to analyse the diurnal variation or hourly variation in seasonal rainfall in Vellanikkara, Thrissur, collected from the meteorological observatory located at KAU, Vellanikkara from 2016 to 2020. The hourly rainfall data of normal years (2017 and 2020) were compared with drought year (2016) and flood years (2018 and 2019). The highest south west monsoon rainfall (SWM) was observed from 2 am to 8 am in all years except 2019, where it was observed from 8 pm to 2 am. The lowest SWM rainfall was observed from 8 am to 2 pm in 2016, 2017 and 2019 and from 2 pm to 8 pm in 2018 and 2020. The highest north east monsoon rainfall (NEM) was observed from 2 am to 8 am in 2016, from 2 pm to 8 pm in 2018 and 2019, and from 8 pm to 2 am in 2017 and 2020. The least NEM rainfall was obtained from 8 am to 2 pm during all years. The light hourly winter rainfall was recorded in 2016 and 2018 from 8.00 pm to 2.00 am and no winter rainfall was received in 2017, 2019 and 2020. The highest summer rainfall was observed from 8 pm to 2 am and the least rainfall was observed from 8 am to 2 pm in all years. The rainfall data during each time period was correlated with rice yield from 2016 to 2020 at Vellanikkara. It was found that the rainfall during emergence to active tillering (8 pm to 2 am and 2 am to 8 am) and physiological maturity (2 pm to 8 pm and 8 pm to 2 am) had a significant negative correlation. The night rainfall was found to be a key factor affecting rice yield.
Hourly variability, Seasonal rainfall, Southwest monsoon, Northeast monsoon, Rice yield, Climate impact
