Climate change scenarios for Tibetan Plateau summer precipitation based on canonical correlation analysis.

ABSTRACT Precipitation in the Tibetan Plateau ( TP) reaches its peak in summer. The seasonal projection skill of a statistical downscaling model ( SDM) for summer precipitation in the TP was compared with that of direct model output. The SDM, which is based on canonical correlation analysis ( CCA), significantly increased the projection skill. The CCA reveals the flow patterns behind the seasonal projection skill of summer precipitation in the TP between 1961 and 2012 and quantifies its relative contributions. East Asia 500 hPa geopotential height ( ZG500), tropical Indian Ocean sea surface temperature ( SST) and east Asia 850 hPa meridional water vapour flux ( MWVF850), obtained from the Max Planck Institute Earth System Model, low-resolution ( MPI- ESM- LR) simulations for phase 5 of the Coupled Model Intercomparison Project under the representative concentration pathway ( RCP) 2.6, RCP4.5 and RCP8.5 scenarios are considered as potential predictors. The SDMs are established in 1961-2005, validated in 2006-2012 and applied in 2013-2100. The ensemble canonical correlation ( ECC) is also applied to improve projection skill. The following results are obtained: (1) The SDM projection skill for each predictor is higher than that of the MPI-ESM-LR climate model, and ECC performs even better. (2) Spatial correlation patterns of different predictors with influence on the TP are well recognized by CCA. The high relevance of ZG500 can be explained by the thermal adaptation theory, that of SST exhibits a canonical Indian Ocean Dipole mode, and MWVF850 shows a simple water vapour link. (3) The amount of summer precipitation in the TP will slightly decrease under RCP2.6 by −3.4 mm decade⁻¹, whereas RCP4.5 and RCP8.5 reveal an increase by 2.4 and 18.4 mm decade⁻¹, respectively. [ABSTRACT FROM AUTHOR]