Abstract
Drought is one of the extreme climatic events that has a severe impact on crop production and food supply. Our main goal is to test the suitability of remote sensing-based indices to detect drought impacts on crop production from a global to regional scale. Moderate resolution imaging spectroradiometer (MODIS) based imagery, spanning from 2001 to 2017 was used for this task. This includes the normalized difference vegetation index (NDVI), land surface temperature (LST), and the evaporative stress index (ESI), which is based on the ratio of actual to potential evapotranspiration. These indices were used as indicators of drought-induced vegetation conditions for three main crops: maize, wheat, and soybean. The start and end of the growing season, as observed at 500 m resolution, were used to exclude the time steps that are outside of the growing season. Based on the three indicators, monthly standardized anomalies were estimated, which were used for both analyses of spatiotemporal patterns of drought and the relationship with yield anomalies. Anomalies in the ESI had higher correlations with maize and wheat yield anomalies than other indices, indicating that prolonged periods of low ESI during the growing season are highly correlated with reduced crop yields. All indices could identify past drought events, such as the drought in the USA in 2012, Eastern Africa in 2016–2017, and South Africa in 2015–2016. The results of this study highlight the potential of the use of moderate resolution remote sensing-based indicators combined with phenometrics for drought-induced crop impact monitoring. For several regions, droughts identified using the ESI and LST were more intense than the NDVI-based results. We showed that these indices are relevant for agricultural drought monitoring at both global and regional scales. They can be integrated into drought early warning systems, process-based crop models, as well as can be used for risk assessment and included in advanced decision-support frameworks.
Highlights
Drought is one of the most severe natural hazards and can impose a massive impact on water supply, crop, and forage production, and can lead to broad socio-economic and environmental impacts [1,2]
Droughts identified using the evaporative stress index (ESI) and land surface temperature (LST) were more intense than the normalized difference vegetation index (NDVI)-based results
Anomalies in the ESI had higher correlations with maize yield than the NDVI and LST in arid and semi-arid regions, indicating that prolonged periods of a low ESI during the growing season are highly correlated with reduced yields for maize (Figure 2a,b)
Summary
Drought is one of the most severe natural hazards and can impose a massive impact on water supply, crop, and forage production, and can lead to broad socio-economic and environmental impacts [1,2]. An increase in both drought frequency and severity over the last decades has had adverse impacts on agriculture, for example for East Asia, the Mediterranean region, and Southern. Drought is a result of climate-related factors such as rainfall, moisture deficiency, temperature and high evapotranspiration, it can be impacted by human induced changes of hydrological processes and the environment [12]
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