Biophysical effects of paddy rice expansion on land surface temperature in Northeastern Asia

Authors: LIU, WENQI - Chinese Academy Of Sciences; DONG, JINWEI - Chinese Academy Of Sciences; DU, GUOMING - Northeast Agricultural University; ZHANG, GELI - China Agricultural University; HAO, ZHIXIN - Chinese Academy Of Sciences; YOU, NANSHAN - Chinese Academy Of Sciences; ZHAO, GUOSONG - China University Of Geosciences; Flynn, Kyle; YANG, TONG - China Agricultural University; ZHOU, YUTING - Oklahoma State University

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2022
Publication Date: 1/18/2022
Citation: Liu, W., Dong, J., Du, G., Zhang, G., Hao, Z., You, N., Zhao, G., Flynn, K.C., Yang, T., Zhou, Y. 2022. Biophysical effects of paddy rice expansion on land surface temperature in Northeastern Asia. Agricultural and Forest Meteorology. 315. Article 108820. https://doi.org/10.1016/j.agrformet.2022.108820.
DOI: https://doi.org/10.1016/j.agrformet.2022.108820

Interpretive Summary: Global cropland displacement and expansion plays a significant role in climate change processes. The pending extensive rice expansion in monsoon-heavy northeastern Asia, especially in the northeast China, affects local and regional climates by altering biophysical characteristics. Influences on biophysical characteristics include diurnal and seasonal albedo, evapotranspiration (ET), and land surface temperature (LST) changes. Here we selected northeast China as the study area, and used statistical measures to examine biophysical effects of paddy rice expansion at different temporal scales (diurnal and seasonal), based on satellite-derived biophysical proxies and a high-resolution crop map. We found that the daily mean LST of rice paddies was lower than that of corn and soybean fields during the growing season (May to September), as a result of daytime cooling and nighttime warming leading to a narrower diurnal LST range. The cooling effects were more significant in the early season (May and June) than in the late season (July to September) of growing. This study showed the cooling effects of rice expansion and its seasonal variation. Furthermore, it explained the climate feedbacks of rice expansion through the biophysical mechanism with albedo and ET, which contributes to improved model biophysical feedbacks of land use change.

Technical Abstract: Global cropland displacement and expansion plays a significant role in climate change processes. The pending extensive rice expansion in monsoon-heavy northeastern Asia, especially in the northeast China, affects local and regional climate by altering both biogeochemical (e.g., CO2, CH4) and biophysical processes (e.g., evapotranspiration and albedo). While the biogeochemical effects of rice expansion have attracted plenty of attention, its biophysical effects have not been well documented, especially influences on diurnal and seasonal albedo, evapotranspiration (ET), and land surface temperature (LST). Here we selected northeast China as the study area, and used a pair-wise comparison approach to examine biophysical effects of paddy rice expansion at different temporal scales (diurnal and seasonal), based on satellite-derived biophysical proxies and a high-resolution crop map. We found that the daily mean LST of rice paddies was 0.5°C lower than that of corn and soybean fields during the growing season (May to September), as a result of daytime cooling (-1.8 and -2.0°C) and nighttime warming (0.8 and 1.1°C), which subsequently led to a narrower diurnal LST range (-2.6 and -3.0°C). The cooling effects were more significant in the early season (May and June) than in the late season (July to September). Due to seasonal dynamics of surface biophysical characteristics, the albedo of paddy rice was lower in the early season and higher in the late season comparing with the upland crops, while the differences among ET were opposite. The relatively greater energy dissipation caused by the increased ET than energy absorption caused by the decreased albedo resulted in the net cooling effect during the early season. This study showed the cooling effects of rice expansion and its seasonal variation. Furthermore, it explained the climate feedbacks of rice expansion through the biophysical mechanism with albedo and ET, which contributes to improved model biophysical feedbacks of land use change.