Upscaling instantaneous ET obtained using UAV multispectral and thermal data into daily ET with and without UAV flights

Abstract

Accurate estimation of daily actual evapotranspiration (ETₐ ₐcₜ) is important for many aspects of research and field management. ETₐ ₐcₜ can be calculated from the reference crop ET (ETₒ) and actual crop coefficient (Kc ₐcₜ) which are influenced by the actual crop growth conditions and soil water conditions. In this study, a new framework was developed to estimate the daily actual Kc ₐcₜ using multispectral and thermal data obtained from unmanned aerial vehicles (UAVs). With UAVs flights, the daily ETc ₐcₜ was calculated by the Surface Energy Balance Algorithm for Land model (SEBAL). Without UAVs flights, daily ETc ₐcₜ was corrected by crop coefficient under full water condition (Kc fᵤₗₗ wₐₜₑᵣ) and water stress coefficient (Kₛ), based on remote sensing data, SEBAL model, and soil water balance equation. This framework was tested on winter wheat grown under six irrigation treatments from no irrigation (I0) up to five irrigations (I5) for four seasons from 2019 to 2023. The six irrigation treatments created a wide range of soil moisture and crop growing conditions. The results showed that the best timing to estimate daily ETc ₐcₜ was using the remote sensing data obtained at 11:00 local time with an R² of 0.88 and an RMSE of 0.53 mm/day. The daily ET c ₐcₜ estimated by the new framework on days without UAV flights was consistent with the ET c ₐcₜ calculated using soil water balance equation, with R² value varying from 0.74 to 0.80 under the different irrigation treatments. The results from this study demonstrated that the new framework based on UAV remote sensing data could estimate the daily ET c ₐcₜ in real time and could be further used to estimate daily ET c ₐcₜ on days without UAV flights.

Plant phenotyping relevance

UAVマルチスペクトル・熱画像とSEBAL等を統合し、作物の実蒸発散量・水ストレス状態を推定する枠組みを開発・検証しており、測定手法が中心である。

Code and data availability

公開状態または取得可能な本文経路を確認できませんでした。

No evidence-backed public reproduction asset is currently recorded.