As indicated by rainfall histograms at Tainan (Figure 1(c)) and Keelung (Figure 1(d)), the alternation of
the two rainfall regimes is a result of the alternation in the northeast winter and the southwest summer
monsoons with an apparent enhancing effect by the orography (outlined in Section 1). Of course it may
not be completely legitimate to define two rainfall regions over all of Taiwan based on only two stations.
The following questions are raised: (i) What is the geographic coverage of these two rainfall regimes, and
(ii) how does the transition of two rainfall regimes behave following the alternation of the two monsoons?
These questions will be answered by the following analyses: (i) the EOF analysis of rainfall, and (ii) the
seasonal march of rainfall around the coastal zones of Taiwan. The EOF analysis provides a concise view
of the major seasonal variation modes in Taiwan rainfall, while the second approach illustrates the
transition between these seasonal variation modes. Results are reported in the following sections.