ABSTRACT
Droughts rank first among all natural hazards in terms of induced societal consequences. Among the drought types that are commonly recognized, agricultural drought has the most direct, immediate, and critical impact, because it affects sensitive issues such as water management and food security. Drought monitoring involves the continuous assessment of the natural indicators of drought attributes, and remote sensing can play an important role in drought-monitoring strategies due to its observational advantages, mainly global coverage and frequency. The detection of the state of the vegetation and the soil water content that satellites launched recently allow represent considerable progress in research, assessment, and agricultural drought monitoring.
In this work, two approaches have been used to assess the feasibility of using satellite soil moisture data for agricultural drought monitoring over the Iberian Peninsula at different spatial scales. On the one hand, the Soil Water Deficit Index (SWDI), which uses the soil moisture and ocean salinity-surface soil moisture (SMOS SSM) and soil water parameters, has been used over an agricultural area in the Duero basin (Spain). On the other hand, the Soil Moisture Agricultural Drought Index (SMADI), which also uses SMOS SSM, together with land surface temperature and the Normalized Difference Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS), has been applied in the same agricultural area as well as in diverse rainfed areas along the Iberian Peninsula.
The results of this work clearly show that the use of soil moisture and other satellite data products can be a suitable option for agricultural drought monitoring. The cases studied in the Iberian Peninsula show the reliability of the different approaches used to properly assess and monitor the agricultural drought at different scales and under different bioclimatic conditions. Current soil moisture satellites such as SMOS and Soil Moisture Active Passive (SMAP) are providing a unique opportunity to incorporate remote-sensing tools into agricultural drought monitoring, and, in the next few years, these missions, together with new Earth observation instruments such as those from the Sentinel missions, could address key challenges with regard to drought’s early warning and monitoring. These new advances and methodologies will be especially relevant for near-future agriculture and for facing critical issues such as food security and water scarcity management.
