Temporal and Spatial Changes of Extreme Climate Events in Mongolia During 1961–2023

ABSTRACT Mongolia has experienced increasingly extreme climate events in recent years. Most previous studies have used data from meteorological stations with uneven spatial coverage and inconsistent time series, resulting in an insufficient understanding of regional variations in extreme climate events. In particular, the characteristics of extreme climate events in the two relatively warm years of 2022 and 2023 need to be investigated. Analysis using the ERA5‐Land reanalysis data revealed that the hottest day (TXx), coldest night (TNn), coldest day (TXn), extreme warm days (TX90p), summer days (SU25) and the warm spell duration indicator (WSDI) presented increasing trends, whereas the extreme cold nights (TN10p), frost days (FD0) and the cold spell duration indicator (CSDI) presented decreasing trends during 1961 to 2023 in Mongolia. Moreover, the increasing rates of the TXx, TNn, TX90p and WSDI in the permafrost regions (0.042°C/year, 0.049°C/year, 0.244%/year and 0.349 days/year, respectively) were greater than those in the seasonally frozen ground regions (0.031°C/year, 0.044°C/year, 0.223%/year and 0.312 days/year, respectively), indicating that the extreme temperature indices in the permafrost regions were more sensitive to extreme warm events. All extreme precipitation indices showed decreasing trends, with higher values in northern Mongolia, except for consecutive dry days (CDD). In 2022 and 2023, the mean annual air temperature (MAAT), TXx, TX90p, SU25 and WSDI accounted for more than 50% of the TOP_10, and CDD accounted for more than 20%, reflecting more extreme warm events and droughts. Compared with neighbouring regions, Mongolia experienced faster increases in extreme warm events and droughts. The Asian Polar Vortex Intensity Index (AAI), Atlantic Multidecadal Oscillation Index (AMO) and MAAT have the greatest impact on extreme temperature indices, and the annual total precipitation (ATP) has the greatest impact on extreme precipitation indices. These findings help study the hydrological, ecological and social impacts of extreme climate events.