Spring and summer precipitation changes from 1880 to 2011 and the future projections from CMIP5 models in the Yangtze River Basin, China

摘要

Precipitation changes in spring (MAM) and summer (JJA) over the Yangtze River Basin during 1880-2011 were analyzed based on observation datasets from 21 gauge stations. The projected changes in precipitation were evaluated using nine Coupled Model Intercomparison Project Phase 5 (CMIP5) datasets. The results suggest that interannual and interdecadal changes in spring and summer precipitation occurred during 1880-2011. The Dry-Dry events of seasonal evolution generally occurred over the past 132 years. Empirical mode decomposition (EMD) was applied to detect the oscillation periods, in which quasi - 3a, 5a, 15a, and 40a periods of spring and quasi - 3a, 5a, 11a, 22a, and 40a periods of summer were identified. S-EOF analysis was employed to identify the major modes of seasonal precipitation evolution from spring to summer. The abnormal location of the western Pacific subtropical high (WPSH) and insufficient water vapor was found to be associated with the 2011 spring drought, and their sudden change is also responsible for the flood in June. A Taylor diagram showed an improved capability to simulate monthly precipitation using the nine CMIP5 datasets. The projected precipitation changes show that the significant positive linear trends of spring precipitation will occur at representative concentration pathways (RCP)2.6 and RCP8.5, whereas summer precipitation will mainly undergo interannual change. For the projected spatial pattern of precipitation anomaly, spring precipitation will increase in the northern basin but decrease in the south under RCP2.6 and RCP8.5 in the 2020s and 2040s. Under RCP4.5, positive anomalies can be found in the middle and lower basins. In contrast to those in the spring pattern, the negative anomalies of summer precipitation are concentrated in the middle and lower basins under each RCP.