Philippine agroclimatic classification based on seasonal duration and rainfall onset and recession

Date

1991

Abstract

This study aimed to: (1) determine the changes in climate based on rainfall distribution; (2) compare the agroclimatic classes based on mean and 80% dependable rainfall; (3) compare the agroclimatic classes based on the monthly and decadal data; (4) develop agroclimatic classifications which show the national picture of seasonal durations; and (5) determine the onset and recession of the rainy season in the different regions of the Philippines. Decadal, monthly and annual summaries of 1901-88 rainfall records in 39 weather stations all over the country were computed. Based on the computations, the following were compared: (1) annual rainfall and dates of onset and recession of rainy seasons of the periods 1901-40 and 1949-88; (2) seasonal durations determined from mean and dependable rainfall; and (3) seasonal durations determined from monthly and decadal data. The onset and recession of rainy seasons were analyzed using the forward and backward rainfall accumulation method Of the 39 stations, only 13 showed significant changes in annual rainfall, dates of onset and recession of rainy season. The current years? (1949-88) annual rainfall in seven stations was found lower than the earlier data (1901-40). Also, the current years? date of rainfall onset in five stations was delayed and the date of rainfall recession in five stations was advanced. The comparison of the seasonal durations showed that monthly mean rainfall classes have longer wet seasons and shorter dry seasons compared with monthly dependable rainfall classes. Comparison of seasonal durations also showed that decadal mean rainfall gives longer dry and wet seasons than the monthly data. The use of decadal dependable rainfall resulted in longer dry seasons and shorter wet seasons compared with monthly data. The wet season maps indicate long wet seasons along the east coast and short wet seasons along the west coast. Conversely, the dry season maps indicate long dry periods along the west coast and shorter dry season when crossing the west to east direction. The length of the wet and dry seasons varies depending on the classification parameter. Early onset of rains occurs in the coasts directly exposed to the major air streams while late onset occurs in areas shielded by mountain ranges. Rainfall recession proceeds from a west to east direction. Rainfall recession is more variable than the onset. Dates of rainfall onset and recession were found to be most variable in the leeward side of mountains and least variable in the windward side.

Document Type

Master Thesis

Language

English

LC Subject

Climatic classification, Meteorology, Agricultural, Crops and climate

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 995 1991 A38 B65

This document is currently not available here.

Share

COinS