Assessing the suitability of remote sensing estimates of soil moisture and land evaporation in Switzerland for a better preparedness for projected drying trends

Climate projections indicate an increasing risk of dry and hot episodes in Central Europe, including in Switzerland. However, models display a large spread in projections of changes in summer drying, highlighting the importance of related observations to evaluate climate models and constrain projections. Land hydrological variables play an essential role for these projections. This is particularly the case for soil moisture and land evaporation, which are directly affecting the development of droughts and heatwaves in both present and future.
The recent 2020 spring as well as 2015 and 2018 summer droughts in Switzerland have highlighted the importance of monitoring and assessing changes of soil moisture and land evaporation, which are strongly related to drought impacts on agriculture, forestry, and ecosystems.
The only Switzerland-wide soil moisture monitoring programme currently in place is the SwissSMEX (Swiss Soil Moisture Experiment) measurement network. It was initiated in 2008 and comprises 19 soil moisture measurement profiles at 17 different sites (grassland, forest and arable land). Since 2017, seven grassland SwissSMEX sites are complemented with land evaporation measurements from mini-lysimeters.
Here we analyze long-term satellite-based drought parameters, namely ASCAT Soil Water Index (SWI) derived from an H SAF test data set and LSA SAF Meteosat land evaporation products. We compare the satellite-based datasets with the SwissSMEX in-situ measurements of soil moisture and lysimeter land evaporation. The comparison of in-situ soil moisture and land evaporation data with the satellite parameters shows strong agreement in terms of anomalies. SWI indicates high correlations of 0.6 to 0.8 with in-situ measurements. The Meteosat land evaporation products strongly agree with measurements, with correlations of 0.7 and 0.9 for potential and actual land evaporation, respectively (Burgstall et al.).
These analyses provide useful insights in order to provide near-real time monitoring, enhance process understanding and for a better preparedness for future droughts.

References:
Burgstall, A. et al., Climatological drought monitoring in Switzerland using EUMETSAT SAF satellite products, Remote Sensing, in preparation.