Differential response of rice evapotranspiration to varying patterns of warming

Abstract

Rice is a staple food crop that provides more calories to the global population than any other crop. Rice production is also a major consumer of fresh-water resources. Hence, changes in rice evapotranspiration (ETc) due to projected warming patterns is becoming necessary in any management of water resources and food security assessments. Here, air temperature (Ta) measurements from 1003 meteorological stations covering the period from 1967 to 2016 in China, Japan and the Philippines are first used to assess warming trends. Energy fluxes were then assembled so as to evaluate the responses of rice ETc to various warming trends. A modified Priestley-Taylor formulation was used to interpret ETc under differing warming scenarios. Results showed that the average values of daily mean Ta from 1997–2016 increased by 4.6% relative to the period from 1967–1996, where 85% of all stations marked an increase of 0.5–1.5 °C. Greater increment in average daily minima in Ta (5.1%) was noted in the past 20 years compared to the average daily maximum in Ta (3.7%), showing asymmetric warming. The changed growth duration linearly decreased as ambient seasonal mean Ta increased, and higher temperature sensitivity of altered growth duration occurred at greater warming level. Overall, the proposed modified Priestley-Taylor model can be used for estimating ETc of rice for both half-hourly and daily scales provided the growth duration is a priori known. Changes in seasonal ETc of rice under varying types of warming patterns are largely explained by both ambient seasonal mean Ta and changes in growth duration.