Influence of El Nino Southern Oscillation (ENSO) on Evapotranspiration and Rice Planting Period

Increased intensity, frequency, and fluctuations of El Niño-Southern Oscillation (ENSO) can affect evapotranspiration and contribute to the timing of rice planting. We used the Penman-Monteith method to estimate evapotranspiration values under the influence of ENSO phases from 1991 to 2022. We also calculated the value of reference evapotranspiration (ETo), actual evapotranspiration (ETa), and crop evapotranspiration (ETc) in the critical phase of rice plants to calculate the value of crop water sufficiency index (Is) and potential yield reduction (RYL) to estimate the onset of rice planting period. The findings reveal that the ETo, ETa, and ETc values in the El Niño phase are 0.77% greater, 1.12% lower, and 0.69% lower, and La Niña is 2.84% lower, 10.98% greater, 7.98% greater compared to the neutral phase, sequentially. Furthermore, the El Niño phase causes the rice planting season to be one dekad later than the neutral phase, and the La Niña phase causes the rice planting season to be two dekads earlier than the neutral phase. In addition, the more robust La Niña phase can cause a more extended rice planting season due to abundant water availability. Further research can be carried out by including rice production results on ENSO impacts.