Non-linear cyclic regimes of short-term climate variability

• Main Author: Sih, Perry
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/14429

The Circular Non-linear Principal Component Analysis (CNLPCA), a variation of the non-linear version of the traditional Principal Component Analysis (PCA), is introduced. It is then applied to monthly-averaged geopotential heights of the NASA Goddard Institute for Space Studies SI2000 Global Circulation Model (GCM). It is shown that height variability in the model troposphere and stratosphere is essentially linear, even with different aerosol forcings. The daily-averaged model output show weak non-linearity. When CNLPCA is applied to observed geopotential height data, cyclic behaviour appears. The preferred states of the climate system can be seen. This cyclic behaviour can be tracked by recording the phase angle, a unique feature of the CNLPCA. By doing so, the preferred direction, as well as the frequency, of the cyclic behaviour can be found.