ABSTRACT
The “tropics” are defined by the limits of the sun’s vertical rays: the Tropics of Cancer and Capricorn,
23.43732° north and south latitudes. The area between these two latitudes is normally hot and wet. Beyond this general similarity, however, lie infinite variations in climate, soil, and topography, which
have powerful effects on living beings in their struggle to survive. The Seasian tropics can be divided into a grid consisting of nine parts (Figure 2.1). Three climatic
zones lie parallel to the equator: the northern tropics, the equatorial zone, and the southern tropics. The tropics experience significant dry seasons. In the Köppen system the differentiating feature is at
least one month with less than 6 centimeters of rain. The boundary between the northern tropics and the ever-wet equatorial zone begins at approximately 5° north latitude at the north tip of Sumatra, the border between peninsular Malaysia and south Thailand, and north of Mindanao in the Philippines. The southern boundary of the equatorial zone runs from Central Java Province east across the middle of the Java Sea. The equatorial belt is thus approximately 1,100 kilometers wide.
