Reconstruction of Daily Evapotranspiration on Cloudy Sky Conditions from Field and Modis Data

• Main Authors: Jiang, Yazhen, Jiang, Xiaoguang, Tang, Ronglin, Li, Zhao-Liang, Zhang, Xiaoping, Di, Suchuang, Lu, Yajing, Xue, Wanlai
• Format: Conference Proceeding
• Language: English
• Subjects: Atmospheric modeling; Clouds; Cloudy sky condition; Estimation; Evapotranspiration; MODIS; Potential evapotranspiration ratio; Remote sensing; Soil moisture; Temperature measurement
• ISSN: 2153-7003
• DOI: 10.1109/IGARSS.2019.8898184

Evapotranspiration (ET) is widely considered as one of the key parameters in a variety of practical applications. However, because of the contamination of cloud cover, the retrieval of daily ET from optical remote sensing data under cloudy sky conditions is full of challenge. In this paper, we reconstructed daily ET on cloudy days using the relationship between the potential evapotranspiration ratio (R PET ) and the available water fraction (F AW ). The field data from 8 Ameriflux sites were chosen to explore this relationship and applied for gap-filling of daily ET at these sites at first. Then MODIS data and meteorological data from Yucheng site in China were used to estimate daily ETs on clear days, and daily ETs on cloudy days at this site were reconstructed using the explored relationship between the R PET and the F AW , as an application of this reconstruction method. The results from 8 flux sites showed that daily ET reconstructions had good agreement with ET measurements, with the root mean square error (RMSE) less than 31.25 W/m 2 . Based on MODIS and filed data from the Yucheng site, the reconstructed daily ETs under cloudy sky conditions were also consistent with measured daily ETs, with a bias of 2.62 W/m 2 and an RMSE of 35.21W/m 2 .