Concurrent Precipitation Extremes Modulate the Response of Rice Transplanting Date to Preseason Temperature Extremes in China.

Understanding how crop phenology responds to climate change is critical for enabling agricultural adaptation measures. Pre‐season temperature alone leads to well‐understood changes in crop phenology. Nevertheless, the modulation effect of concurrent precipitation extremes on the response to temperature extremes has been largely under‐addressed. Here, we investigate the response of rice transplanting dates to pre‐season temperature extremes and reveal the modulation effects of concurrent precipitation extremes by using station‐observed rice transplanting dates from 1981 to 2018 across mainland China. We also evaluate the performance of a remotely sensed phenology product, ChinaCropPhen1km, in reproducing the above temperature responses and modulation effects. Our results showed that transplanting dates tended to advance in response to an extremely hot pre‐season, while concurrent extreme drought offset the advance by up to 2.6 days. Transplanting dates tended to be delayed in response to an extremely cold pre‐season, while concurrent extreme precipitation exacerbated the delay by up to 1 day. Responses to temperature extremes and modulation effects were divergent across different regions. Under extremely hot conditions, transplanting dates advanced further in hotter and wetter regions, while under extremely cold pre‐seasons, transplanting dates delayed less in colder and drier regions. Transplanting dates from the ChinaCropPhen1km product underestimated the responses to temperature extremes by up to 4.7 days and detected the opposite modulation effect compared to those obtained from observations. Our results highlight that the need to improve our understanding and modeling of modulation effects of precipitation extremes on temperature–phenology relationship, which benefits the field of agriculture risk analysis and climate change adaptation. Plain Language Summary: Frequent climate extremes are projected with ongoing climate change. This paper reveals the effect of concurrent precipitation extremes in modulating rice transplanting date response to pre‐season temperature extremes in China and assesses remotely sensed transplanting dates from the ChinaCropPhen1km product in reproducing the above temperature responses and modulation effects. Results show that concurrent precipitation extremes substantially influence the temperature–transplanting date relationship. Two kinds of modulation effects are detected: (a) concurrent extreme precipitation tends to exacerbate the extremely cold‐induced delay by up to 1 day, and (b) concurrent extreme drought conditions tend to offset the extremely hot‐induced advance by up to 2.6 days. From a spatial perspective, responses to temperature extremes and modulation effects are divergent across regions. Additionally, remotely sensed transplanting dates from the ChinaCropPhen1km product underestimate the temperature responses and detect the opposite modulation effects compared to observations. This study highlights the critical role of concurrent precipitation extremes in modulating temperature impact on crop phenology, which requires more understanding and modeling in future analysis. Key Points: Concurrent extreme drought offset the extreme hot induced‐advance, and extreme precipitation exacerbate the extreme cold induced‐delayResponses to temperature extremes and modulation effects of precipitation extremes are divergent across regionsRemotely sensed transplanting dates from ChinaCropPhen1km underestimate the responses to temperature extremes and modulation effects [ABSTRACT FROM AUTHOR]