Spatial And Temporal Characteristics Of Drought In The Lancang-mekong River Basin And Relationship With Atmospheric Circulation

Drought is one of the natural disasters that have the greatest impact on the world and has a serious impact on the natural environment and social development.As an important cross-border international river in Asia,the Lancang-Mekong River has shown a trend of frequent droughts since the 20 th century.Under the global climate change,understanding the spatial and temporal characteristics of meteorological drought in the Lancang-Mekong River Basin and its correlation with atmospheric circulation is beneficial to comprehensively understand the occurrence and development process of drought,and is of great significance to the management of water resources and drought resistance in the Lancang-Mekong River Basin.and obtains the following main conclusions.(1)After the 1990 s,the Lancang-Mekong River Basin had a significant alternation of wet and dry.On the interannual scale,the frequency of mild drought,moderate drought,and severe drought were 18%,59%,and 5%.The drought intensity in the rainy season showed a decreasing trend from the upstream to the downstream of the basin.The drought intensity in the dry season increased from the upstream to the downstream of the basin.(2)During the rainy season,the humidification trend of the upper Lancang River and the upper Mekong River is significant.The middle and lower reaches of the Lancang River and the middle and lower reaches of the Mekong River show a trend of aridification.During the dry season,the Lancang River Basin and the middle and lower reaches of the Mekong River tend to be arid,and the upper Mekong River is humid.On the interannual scale,the middle and lower reaches of the Lancang River and the middle and lower reaches of the Mekong River show a trend of aridification.(3)The Lancang-Mekong River Basin had the strongest correlation with the simultaneous occurrence of ENSO.The 7-month PDO time lag was significantly negatively correlated with the drought in the lower reaches of the Lancang River and the Mekong River.The NAO time lags of 1 month and 4 months were significantly positively correlated with the drought in the middle and lower reaches of the Lancang River and the upper and middle reaches of the Mekong River.The drought in the upper Lancang River has a significant positive correlation with the AO time lag of 6months.(4)The variability of rainfall characteristics in the Lancang-Mekong River Basin is influenced by multiple factors,among which atmospheric circulation is an important factor leading to the occurrence of drought in the Lancang-Mekong River Basin.Atmospheric circulation causes temporal and spatial variability of precipitation in the Lancang-Mekong basin through dynamic and thermal effects,resulting in regional drought events.