Chinese Journal of Agrometeorology ›› 2025, Vol. 46 ›› Issue (3): 326-338.doi: 10.3969/j.issn.1000-6362.2025.03.005

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Spatiotemporal Variation Characteristics of Reference Crop Evapotranspiration in Shaanxi Province Based on the Calibration of Ångström-Prescott Model Parameters

ZHANG Ya-jun, LI Pei, ZHANG Meng, YANG Fan   

  1. 1.College of Land and Resources, Hebei Agricultural University, Baoding 071001, China; 2.School of Water and Environment, Chang’an University, Xi’an 710054; 3.College of Resources and Environmental Science, Hebei Agricultural University, Baoding 071001; 4.Key Laboratory for Farmland Eco-Environment of HeBei Province, Baoding 071001; 5.Shaanxi Union Research Center of University and Enterprise for River and Lake Ecosystems Protection and Restoration, Xi’an 710065; 6.Power China Northwest Engineering Corporation Limited, Xi’an 710065
  • Received:2024-04-01 Online:2025-03-20 Published:2025-03-19

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Abstract:

 In this study, the two parameters (a and b) in the Ångström-Prescott (A-P) model for estimating solar radiation (Rs) were calibrated and validated at the seasonal and annual scales using the observations of Rs and sunshine hours from the three meteorological stations (Yan’an, Xi’an and Ankang) in Shaanxi province. Furthermore, the Penman-Monteith method was applied to calculate the reference crop evapotranspiration (ET0) using the daily meteorological data from 92 stations in Shaanxi province from 1971 to 2021. The spatiotemporal variation characteristics of ET0 were analyzed by linear regression analysis and Hurst index after Anusplin interpolation in Shaanxi province as a whole and in its three regions (northern Shaanxi, central Shaanxi, and southern Shaanxi). The results showed that: (1) the recommended values by FAO for the two parameters were not suitable for Shaanxi province. The ranges of calibrated parameters a and b at the three stations were 0.14−0.19 and 0.53−0.58 respectively. Annual scale with simpler calibration process was the relatively optimal choice. (2) Compared with the calibrated parameters at the annual scale, the ET0 values estimated using FAO recommended values were overestimated by 8.6% in Shaanxi province overall. Specifically, the overestimations were 9.3%, 4.8% and 11.8% in northern Shaanxi, central Shaanxi, and southern Shaanxi, respectively. Regarding individual seasons, the overestimations were 7.5%, 9.5%, 8.1%, and 2.9% in spring, summer, autumn and winter, respectively. (3) From 1971 to 2021, the ET0 values in Shaanxi province ranged from 764.54mm to 986.06mm, with higher value in central Shaanxi, followed by southern and northern Shaanxi. The temporal and future trends of ET0 in the province and its three regions were not significant. The ET0 in the spring, summer, autumn and winter seasons contributed to approximately 30.8%, 40.5%, 18.1% and 10.6% of the annual ET0, respectively. In northern and southern Shaanxi, the seasonal ET0 trends were not significant, whereas in central Shaanxi, the ET0 showed significant increasing and decreasing trends in the spring and summer seasons, respectively. The future trends of seasonal ET0 in the Shaanxi province and its three regions were not significant.

Key words: Reference crop evapotranspiration, Parameter calibration, Penman-Monteith method, Anusplin, Spatial-temporal variations