1.Chengdu University of Information Technology;2.Key Laboratory of Physical Oceanography MOE China,Ocean University of China;3.State Key Laboratory of Earth Surface Processes and Resource Ecology
The sea-level pressure (SLP) in the East Asia-Northwest Pacific region directly reflects the circulation characteristics of the lower atmosphere, and its dynamical characteristics have significant effects on the atmospheric circulation situation, the evolution of the pressure system and the development of weather and climate systems. Therefore, an in-depth analysis of the spatial and temporal evolution characteristics of the sea level pressure field in the East Asia-Northwest Pacific region is of great significance to improve the weather and climate forecasting in China. In order to investigate the dynamical characteristics of the daily sea-level pressure field from the perspective of nonlinear dynamics, a new method is used to quantitatively estimate two instantaneous indicators of the sea-level pressure attractor: the instantaneous dimension and the instantaneous stability. The instantaneous dimension characterizes the dispersion of the attractor orbit in local space, and the instantaneous stability characterizes the stability of the orbit in local time, which together characterize the instantaneous (daily) dynamical properties of the sea-level baroclinic attractor. In this paper, different spatial and temporal characteristics of the sea-level pressure field in the East Asia-Northwest Pacific region are screened by the correspondence between the indicator values of different sizes and the daily sea-level pressure circulation field. The main conclusions are: (1) When both indicators of sea-level pressure attractor are low, the spatial characteristics of the corresponding circulation field are as follows: the pressure structure is single, usually with several strong high and low-pressure centers facing each other at east-west direction, while the time characteristics show that the circulation mode can be stable for about 10 days. (2) On the contrary, when both indicators are high, the spatial characteristics of the circulation field are as follows: multiple weak pressure centers exist at the same time, with a chaotic spatial structure. As for the temporal characteristics, the circulation field is extremely unstable, and the duration is only about 1 day. (3) The two indicator anomalies in the East Asia-Northwest Pacific region have a consistent interdecadal trend, both showing a clear downward trend from the 1970s to 1990s, a rapid rising trend in the late 1990s and fluctuating changes after 2000.