Changes in abrupt alternations between wet and dry over the Great Lakes Region of Central Asia during the period 1976-2015

Under climate warming, the frequency of dry-wet abrupt alternation (DWAA) events was largely increased at the global scale. In this study, we identified DWAA events, including dry-wet (D-W) alternation events and wet-dry (W-D) alternation events, based on the Standardized Precipitation Evapotranspiration Index (SPEI) for the Great Lakes Region of Central Asia (GLRCA), and analyzed temporal and spatial variation of DWAA during the period 1976-2015. Over the entire study period, GLRCA experienced an overall wetting trend, and a heavy dry trend was mainly distributed in the southwest. Although both D-W alternation events and W-D alternation events showed a slight decrease at the regional scale, there were two clearly opposite trends between 1976 and 1995 and 1996-2015, with a decrease in 1976-1995 and an increase in 1996-2015. Spatially, the variation in the number of D-W alternation events and W-D alternation events exhibited a large heterogeneity. A significant increase in the frequency of D-W alternation events and W-D alternation events was observed in the southwest of arid climate zone, which may be attributed to the increased frequency of dry months and wet months in the region. This study in DWAA events is of importance to the implementation of water resources management, disaster prevention and mitigation policies in the GLRCA under the challenge of future climate change.

Automated summary

This study identifies and analyzes DWAA events based on the SPEI index in GLRCA, revealing an increasing frequency of such events globally. GLRCA shows an overall wetting trend but with heavy drought in the southwest. While both D-W alternation events and W-D alternation events exhibit slight decreases at the regional scale, they demonstrate contrasting trends in different periods. Spatially, there is significant heterogeneity in the variation of these events, with a significant increase observed in the southwest of the arid climate zone.