Baseline predictability of daily east Asian summer monsoon circulation indices |
| |
| Authors: | Shucong Ai Quanliang Chen Jianping Li Ruiqiang Ding Quanjia Zhong |
| |
| Institution: | 1.College of Atmospheric Science,Chengdu University of Information Technology, and Plateau Atmospheric and Environment Laboratory of Sichuan Province,Chengdu,China;2.State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing,China;3.College of Global Change and Earth System Sciences (GCESS),Beijing Normal University,Beijing,China;4.College of Earth Science,University of Chinese Academy of Sciences,Beijing,China |
| |
| Abstract: | The nonlinear local Lyapunov exponent (NLLE) method is adopted to quantitatively determine the predictability limit of East Asian summer monsoon (EASM) intensity indices on a synoptic timescale. The predictability limit of EASM indices varies widely according to the definitions of indices. EASM indices defined by zonal shear have a limit of around 7 days, which is higher than the predictability limit of EASM indices defined by sea level pressure (SLP) difference and meridional wind shear (about 5 days). The initial error of EASM indices defined by SLP difference and meridional wind shear shows a faster growth than indices defined by zonal wind shear. Furthermore, the indices defined by zonal wind shear appear to fluctuate at lower frequencies, whereas the indices defined by SLP difference and meridional wind shear generally fluctuate at higher frequencies. This result may explain why the daily variability of the EASM indices defined by zonal wind shear tends be more predictable than those defined by SLP difference and meridional wind shear. Analysis of the temporal correlation coefficient (TCC) skill for EASM indices obtained from observations and from NCEP’s Global Ensemble Forecasting System (GEFS) historical weather forecast dataset shows that GEFS has a higher forecast skill for the EASM indices defined by zonal wind shear than for indices defined by SLP difference and meridional wind shear. The predictability limit estimated by the NLLE method is shorter than that in GEFS. In addition, the June-September average TCC skill for different daily EASM indices shows significant interannual variations from 1985 to 2015 in GEFS. However, the TCC for different types of EASM indices does not show coherent interannual fluctuations. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
