This study investigates the role of atmospheric moisture transport deficits in the development and intensification of droughts. The authors use Lagrangian techniques to estimate moisture contributions from oceanic and terrestrial sources to precipitation and apply copula theory to estimate the conditional probability of drought occurrence given a moisture deficit from these sources. Key findings include: 1. **Moisture Transport Deficit**: The conditional probability of drought occurrence given a moisture deficit from either oceanic or terrestrial sources is significantly higher than 5%, with probabilities over 10% in most land areas. In regions with active atmospheric moisture transport mechanisms, this probability exceeds 15%, and in hotspot regions like central-east North America, south-east South America, and east Europe, it can be over 20%. 2. **Regional Impact**: The contribution of dominant moisture sources to precipitation can improve drought predictability. For example, in central-east North America, droughts are strongly influenced by moisture deficits from the Caribbean/Mexican source, while in south-east South America, the Amazon source plays a crucial role. 3. **Statistical Methods**: The study employs copula theory to estimate conditional probabilities and Lagrangian techniques to track moisture transport. The results show that moisture transport deficits are more predictable than precipitation, making them a valuable metric for drought prediction. 4. **Future Implications**: Understanding the relationship between moisture source contribution deficits and drought occurrence can help improve drought predictability and management. Climate change, through shifts in circulation patterns and land-ocean temperature contrasts, may alter these relationships, affecting drought severity and likelihood. 5. **Conclusion**: The study highlights the significant role of moisture transport deficits in drought genesis, particularly in regions where drought is caused by oceanic or terrestrial moisture deficits. This knowledge can enhance drought predictability and inform strategies for mitigating the impacts of droughts.This study investigates the role of atmospheric moisture transport deficits in the development and intensification of droughts. The authors use Lagrangian techniques to estimate moisture contributions from oceanic and terrestrial sources to precipitation and apply copula theory to estimate the conditional probability of drought occurrence given a moisture deficit from these sources. Key findings include: 1. **Moisture Transport Deficit**: The conditional probability of drought occurrence given a moisture deficit from either oceanic or terrestrial sources is significantly higher than 5%, with probabilities over 10% in most land areas. In regions with active atmospheric moisture transport mechanisms, this probability exceeds 15%, and in hotspot regions like central-east North America, south-east South America, and east Europe, it can be over 20%. 2. **Regional Impact**: The contribution of dominant moisture sources to precipitation can improve drought predictability. For example, in central-east North America, droughts are strongly influenced by moisture deficits from the Caribbean/Mexican source, while in south-east South America, the Amazon source plays a crucial role. 3. **Statistical Methods**: The study employs copula theory to estimate conditional probabilities and Lagrangian techniques to track moisture transport. The results show that moisture transport deficits are more predictable than precipitation, making them a valuable metric for drought prediction. 4. **Future Implications**: Understanding the relationship between moisture source contribution deficits and drought occurrence can help improve drought predictability and management. Climate change, through shifts in circulation patterns and land-ocean temperature contrasts, may alter these relationships, affecting drought severity and likelihood. 5. **Conclusion**: The study highlights the significant role of moisture transport deficits in drought genesis, particularly in regions where drought is caused by oceanic or terrestrial moisture deficits. This knowledge can enhance drought predictability and inform strategies for mitigating the impacts of droughts.