Drought Analysis Using Complementary Relationship Between Evapotranspiration and Atmospheric Evaporative Demand

Drought is a critical natural disaster which can cause significant environmental and socioeconomic impacts such as agricultural loss and water shortages. Under climate change, increasing aridity and rising land surface temperatures have intensified drought frequency and severity. Therefore, effective drought monitoring is essential for early warning systems which can reduce the vulnerability of ecosystem and society from impacts of prolonged water shortages. Detection of drought is conducted using various meteorological/hydrological factors, which includes remote-sensing based methods. Drought reflects the relation between water supply and demand. While traditional studies focused on precipitation as a main variable, recent researchers have emphasized evapotranspiration as a key driver of drought dynamics. Complementary Relationship (CR) between evapotranspiration (ET) and atmospheric evaporative demand can show the relation of supply and demand efficiently. While CR-based drought indices have shown improved performance to land-atmosphere connection, critical challenges remain. These challenges are primarily associated with the assumptions of the Bouchet hypothesis and the limited availability of long-term ET data. In this study, ET was calculated using a CR-based approach driven by meteorological data and satellite-based datasets to provide better spatial continuity and long-term consistency. The approach enables the representation of seasonal variability, and its performance was evaluated through comparison with conventional drought indices. This study suggests a CR-based drought monitoring method that offers a robust and data-efficient framework, particularly in regions with limited ground observations.

Keywords: Drought, Evapotranspiration, Climate Change, Complementary Relationship, Atmospheric Evaporative Demand

Acknowledgment

This research was supported by the BK21 FOUR (Fostering Outstanding Universities for Research) funded by the Ministry of Education (MOE, Korea) and National Research Foundation of Korea (NRF). This work is financially supported by Korea Ministry of Land, Infrastructure and Transport (MOLIT) as 「Innovative Talent Education Program for Smart City」. This work was supported by Korea Environment Industry & Technology Institute (KEITI) through Water Management Program for Drought Project, funded by Korea Ministry of Climate, Energy and Environment (MCEE)(RS-2023-00230286). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (RS-2024-00416443). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (RS-2022-NR070339).