Ambiguous Agricultural Drought: Characterising Soil Moisture and Vegetation Droughts in Europe from Earth Observation

Abstract

Long-lasting precipitation deficits or heat waves can induce agricultural droughts, which are generally defined as soil moisture deficits that are severe enough to negatively impact vegetation. However, during short soil moisture drought events, the vegetation is not always negatively affected and sometimes even thrives. Due to this duality in agricultural drought impacts, the term “agricultural drought” is ambiguous. Using the ESA’s remotely sensed CCI surface soil moisture estimates and MODIS NDVI vegetation greenness data, we show that, in major European droughts over the past two decades, asynchronies and discrepancies occurred between the surface soil moisture and vegetation droughts. A clear delay is visible between the onset of soil moisture drought and vegetation drought, with correlations generally peaking at the end of the growing season. At lower latitudes, correlations peaked earlier in the season, likely due to an earlier onset of water limited conditions. In certain cases, the vegetation showed a positive anomaly, even during soil moisture drought events. As a result, using the term agricultural drought instead of soil moisture or vegetation drought, could lead to the misclassification of drought events and false drought alarms. We argue that soil moisture and vegetation drought should be considered separately.

Impact of the North Sea–Caspian pattern on meteorological drought and vegetation response over diverging environmental systems in western Eurasia

“…Xu et al, 2014), increasing solar irradiation (Teuling, 2013), and increasing CO 2 fertilization (Lian et al, 2021), which may lead the vegetation to be less affected by the declining water availability. According to previous studies, the vegetation responses to drought conditions are divergent for different climate environments, and the similarity and differences in water and vegetation variability need to be further explored (Denissen et al, 2020;Peled et al, 2010;van van Hateren et al, 2021). To explore the long-term interactions among climate, regional hydrology and vegetation cover, which is related to the water-limited and energy-limited environment, the Budyko framework is applied (Abera et al, 2019;Li et al, 2013;D.…”

Agricultural Drought Detection with MODIS Based Vegetation Health Indices in Southeast Germany

“…Furthermore, during the 2018 agricultural drought in the Netherlands, negative soil moisture anomalies occurred 2-3 weeks before the first VI reduction, using near-infrared reflectance of terrestrial vegetation and VOD as VI [30]. When comparing NDVI and Climate Change Initiative soil moisture data, an offset between soil moisture drought and vegetation drought in Europe was also found [31].…”

Capturing hydrological variability : Spatio-temporal aspects of the Rhine basin

“…Similar findings of increased evapotranspiration and vegetation productivity during drought in (pre-)Alpine regions were reported in Chapter 4 and by Jolly et al (2005) and Mastrotheodoros et al (2020). The complex and climatedependent relation between soil moisture and vegetation provides an argument to consider vegetation and soil moisture separately in analyses of agricultural drought (van Hateren et al, 2021). Hydrological drought dynamics also differ from meteorological drought.…”