Synergistic use of spectral information from Landsat and Sentinel-2 data
for modeling near real-time crop water status across California
vineyards
Abstract
Landsat-based monitoring of seasonal and near real-time
evapotranspiration (ET) in California vineyards is currently challenged
by its low temporal revisit period and missing data under cloudy
conditions. Gap-filling approaches, such as data fusion with
high-temporal resolution images (e.g., MODIS) and interpolation of
actual to potential ET ratio (ET/ETo) between image acquisition dates
are now commonly used to overcome this challenge. However, these methods
may not fully capture non-linear changes in crop condition due to
scheduled irrigation, and other management decisions affecting ET during
days when satellite images are unavailable and can lead to biased ET
estimates. In this study, we combined Landsat-8 and Sentinel-2 data to
develop a Shuttleworth-Wallace (SW) based near real-time ET modeling
framework for mapping daily ET across three California Vineyard sites.
In addition, we utilized daily Leaf area index (LAI) products derived
from the Harmonized Landsat and Sentinel-2 (HLS) surface reflectance and
MODIS LAI data products to constrain key resistance parameters in the SW
model and tested the model across nine flux towers covering three
vineyard sites in California. Results suggest that compared to the
linear interpolation-based ET/ETo approach, this framework can help
reduce biases and root mean squared error of estimated daily ET by over
10%. Results point to a potential utility of the combined Landsat-8 and
Sentinel-2 based approach to monitor near real-time ET and complement
ongoing thermal remote sensing-based ET modeling approaches to better
characterize near real-time crop water status in California vineyards.