Yangtze runoff, precipitation, and the East Asian monsoon in a 2800 years climate control simulation

摘要

Variability of the Yangtze catchment hydrology is closely linked with the Tibetan Plateau snow cover and the large scale atmospheric circulation in East Asia. These connections are analyzed in a control simulation (2800 years) of the atmosphere-ocean general circulation model (ECHAM5/MPI0M) coupled to vegetation and ocean biogeochemistry modules, (i) Up to decades in time scale, runoff, soil wetness, and temperature show long term memory (LTM) with an intradecadal scaling of the power spectrum with the exponent 0 = 0.6, while precipitation, snow depth, and snow melt reveal no memory, (ii) Multi-decadal variability of runoff, soil wetness, and temperature shows weak LTM similar to snow depth and melt on the Tibetan Plateau, (iii) On the annual time scale, the atmospheric circulation impact of Hadley cell and ENSO on precipitation, temperature and snow melt are weak but significant; on decadal time scales the subtropical monsoon modulates the catchment hydrology. Temperature is anticorrelated with precipitation and soil wetness in the Yangtze catchment. Singular spectrum analysis highlights the 3-4 year ENSO mode in the monsoon indices, precipitation, and snow depth, explaining their high correlations. Projecting snow depth on ENSO shows long term variations explaining conflicting results obtained from correlations in short data sets.