Iran’s Lake Urmia (LU), once the second-largest permanent saltwater lake on Earth, desiccated by 18 88% in 1972-2014. Drought has played a key role in such area shrinkage of LU by reducing its inflow by 44% during 1996-2003. This dryness reflects regional precipitation deficit naturally controlled by large-scale atmospheric circulations (ACPs) like the North Atlantic Oscillation (NAO). Hence, identifying those influential ACPs for meteorological drought dynamics throughout the LU Basin crucially helps develop effective adaptation and mitigation strategies to prevent further shrivelling. Using the Standardized Precipitation Index (SPI), this study evaluated the spatio-temporal variability in wetness and dryness characteristics (in terms of intensity, frequency, and duration) across the LU Basin during 1981-2015. The SPI values were calculated in 12 (annual) and 3 (seasonal) time steps (SPI-12 and -3, respectively). The relationships between such SPI values and well-known large-scale ACPs were also investigated. Based on SPI-12 values, annual dryness was mostly severe, seen in 1997-2001, with higher intensity and frequency in the south part of the LU Basin. Such dryness variability was mainly associated with the annual East Atlantic/West Russia (EA/WR) pattern. On the seasonal scale, springtime (March-May) SPI-3 values showed the highest drying trends, and most frequent drought events, mainly at the extreme level, lasting for 1-2 consecutive years, all particularly in response to variations in the Scandinavian (SCA) pattern. Such findings lay the foundation for sustainable water resources management throughout the LU Basin, acting towards achieving the 2030 United Nations Agenda for Sustainable Development on local, regional, and global scales.

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