Using daily vegetation and precipitation products to study drought events in the Horn of Africa

Recent studies indicate an increase in the frequency, severity, and duration of drought events in the Horn of Africa. This research aims to assess the capability of high-frequency Earth observations in detecting drought events in Ethiopia, Somalia, Kenya and Djibouti. By utilizing daily vegetation and precipitation products, we explore the benefits of high frequency data to monitor meteorological and agricultural drought. A vegetation product derived from geostationary satellites with an increased capacity to minimize the effect of clouds is compared with global and regional precipitation daily datasets to analyze the relationship between vegetation and precipitation indices. Our findings demonstrate that certain daily precipitation products offer greater accuracy and a higher probability of detecting rainfall events. Particularly, we found that TAMSAT and CHIRPS products are not well-suited for analyses at daily temporal resolution. Additionally, we investigate the impact of different accumulation periods for the Standard Precipitation Index (SPI) ( McKee et al., 1993 ), finding that longer accumulation windows (e.g., SPI-180) provide greater robustness to wet–dry fluctuations but introduce a trade-off between precision and timeliness in detecting drought events. Through a detailed analysis of four drought events in the area, we assess their effects across different soil types, revealing that cropland and forest soils exhibited greater resilience to water stress compared to other soil types. In contrast, shrubs and bare soil types were particularly affected, contributing to severe humanitarian consequences, such as a drought event in Somalia that resulted in an estimated 250,000 fatalities. This study underscores the significance of using daily temporal resolution to identify drought events that are not visible on a monthly scale, including the alternation of short-term wet–dry spells. • High-frequency data from geostationary enables drought monitoring in the Horn of Africa. • Daily precipitation products enhance accuracy in detecting sub-monthly rainfall events. • Longer SPI accumulation windows improve drought detection but reduce timeliness. • Vegetation status correlates well with 90-day SPI accumulation for drought monitoring. • Vegetation types showed different resilience to the 2009–2010 drought event.