Rainfall Characteristics of Tropical Rainforest at Pasoh Forest Reserve, Negeri Sembilan, Peninsular Malaysia

Abstract

We investigated the rainfall at the Pasoh Forest Reserve (Pasoh FR), Peninsular Malaysia. Pasoh FR is located in the Southwest rainfall regime, in which the average annual rainfall (1,500–2,000 mm) is less than that in other regions of Peninsular Malaysia. Monthly rainfall in 1996 and 1997 ranged from 2.2 to 206.7 mm with a mean of 115.6 mm. The rainfall in 1997 was much smaller due to the El Niño Southern-Oscillation (ENSO) event. The longest period of dry days was 49 days. Dry periods as well as fluctuation in rainfall are major factors affecting the growth of vegetation. A distinct diurnal cycle in rainfall, in which 52% of the rainfall occurred between 13:00 and 19:00 h, was apparent. The frequency of the amount of rainfall in each event was an inverse J-shaped type distribution. The amount of rainfall in one event ranged from 1.2 and 93.1 mm with a mean of 11.4 mm and a median of 5.6 mm. The rainfall was characterized by a short duration (range:1.0-22.0 h, mean: 3.8 h) and high intensity. The maximum hourly rainfall intensity during a rain event ranged from 0.6 to 63.8 mm h^-1 with a mean of 7.8 mm h^-1 and a median of 3.8 mm h^-1.