There are four climate types in the Philippines according to the Modified Corona system of classification. This system of climate classification was devised by Fr. J. Corona in 1920 (Lantican 2001).
Climate, the most important environmental factor affecting plant growth and development (Went and The Editors of Life, 1963), is the average long-term weather of a place, determined over a period of at least 30 years (Miller, 2001). In contrast, weather is the short-term atmospheric condition of a place. It may occur and change within minutes, days or months.
The climatic factors or weather elements include rainfall, light, temperature, relative humidity, air and wind. Any variation in one of these climatic factors can have significant effects on the others and modify the various physiological processes in plants including photosynthesis, respiration and transpiration.
Poincelot (1980) clarified that climatic data are obtained with the use of instruments that are 2 or more meters above the ground. To distinguish, the term microclimate is used to refer to the climate below this level which is subject to influences of the surface profile while macroclimate refers to the atmospheric climate. The microclimate is affected by slope, wind, presence of adjacent vegetation, soil characteristics, buildings, pavements, and other surface conditions, both natural and artificial.
According to Eagleman (1985), however, climate is more than just average weather and that a realistic description ought to include the extremes as well as the average weather. Fluctuations can occur which are difficult, if not impossible, to predict.
For example, the eruption of Tambora in Indonesia in 1815 injected tons of volcanic dust into the stratosphere. This resulted to the occurrence of killing frosts every month in 1816, the “year without a summer.” Crop failures resulted to food riots in parts of Europe.
Another volcanic eruption, that of Mount Pinatubo in the Philippines in 1991, resulted to slight cooling of the earth which masked the signs of global warming for about 3 years. The devastating effects of drought and typhoons on farm crops throughout the world are testaments to climate’s unpredictability.
There are many climate types worldwide, depending on the system of climate classification used. These systems are based on various criteria such as monthly and annual temperature and precipitation (rainfall) in combination with vegetation boundaries (Koeppen classification); temperature and aridity (Eagleman classification); and human comfort, determined through such factors as the comfort index which is based on temperature and humidity (Terjung classification).
Koeppen’s 12 climate types are: tropical rain forest, tropical monsoon, tropical savanna (all three with temperature above 18 C in coldest month), semiarid or steppe, arid or desert, humid subtropical, summer-dry subtropical, winter-dry subtropical, cold humid tropic, winter–dry cold climate, tundra climate, and frost climate (Eagleman 1985).
In the Philippines, two systems of climate classification have been adopted. These are the Modified system devised by Fr. J. Corona in 1920; and the Modified Thornwaite classification based on the ratios of dry months to wet months that F. Hernandez used in 1954 (Lantican 2001).
According to the modified Corona classification, the four climate types in the Philippines are the Types I, II, III, and IV. A dry month is one with less than 50 mm of rainfall but also considers dry a month having more than 100 mm of rainfall that comes after three or more very dry months.
These Philippine climate types are described below. The country has a tropical climate with a relatively high temperature and humidity having abundant rainfall. This climate type is largely similar to those of countries in Central America (kidlat.pagasa.dost.gov.ph, accessed January 28, 2011). The regions having the specific climate types are obtained from Lantican (2001), citing Kintanar (1984).
Type I. Two pronounced seasons, dry from November to April, and wet during the rest of the year. Maximum rain period is from June to September.
Regions with Type I climate: Ilocos Region, western part of Mountain Province, western part of Nueva Ecija, Central Luzon, Metro Manila, Cavite, Laguna, Batangas, Tarlac, Pampanga, Bulacan, Bataan, Zambales, Occidental Mindoro, southern parts of Antique and Iloilo, northwestern part of Palawan, and the southern parts of Negros Oriental and Negros Occidental).
Type II. No dry season with a very pronounced maximum rain period from December to February. There is not a single dry month. Minimum monthly rainfall occurs during the period from March to May.
Regions with Type II climate: northern part of Kalinga Apayao, northwestern part of Cagayan, western part of Quezon Province, Polillo Island, Bicol Region, northeastern Samar, southern Leyte, Surigao del Norte, Surigao del Sur, Agusan del Sur, Agusan del Norte, and Misamis Occidental.
Type III. No very pronounced maximum rain period, with a short dry season lasting only from one to three months, either during the period from December to February or from March to May. This climate type resembles type I since it has a short dry season.
Regions with Type III climate: northeastern part of Ilocos Norte, Kalinga-Apayao, Cagayan, Mountain Province, western part of Isabela, eastern part of Nueva Viscaya, Bulacan, eastern parts of Laguna and Batangas, Oriental Mindoro, Romblon, Marinduque, Aklan, Capiz, northern parts of Antique and Iloilo, Negros Occidental, Siquijor, Zamboanga del Sur, Basilan, Lanao del Sur, Bukidnon, Misamis Oriental, western part of Agusan del Sur, Lanao del Sur, Bukidnon, Misamis Oriental, western part of Agusan del Sur, and eastern Maguindanao.
Type IV. Rainfall is more or less evenly distributed throughout the year. This climate type resembles the second type more closely since it has no dry season.
Regions with Type IV climate: northern Kalinga-Apayao, eastern Cagayan, Isabela, Quezon Province, western part of Bicol Region, western Samar, southeastern Masbate, northern Leyte, northern part of Cebu, Bohol, Zamboanga del Sur, northern-eastern part of Zamboanga del Norte, Lanao del Norte, Sultan Kudarat, South Cotabato, Davao del Sur, Davao del Norte, Davao Oriental, eastern parts of Agusan del Norte, and Agusan del Sur.
Concepcion (2004) provides the average annual rainfall and typhoon frequencies in the following regions in the Philippines:
CAR: 2500-3600 mm annual rainfall, 2-2.5 times typhoon per year; Region I: 2000-2750 mm, 1.7-2.5 times; Region II: 1700-3000 mm, 1.7-2.5 times; Region III: 1800-3800 mm, 1.7 times; Region IV: 1550-3500 mm, 1.5 times; Region V: 1450-3750 mm, 1.5 times; Region VI: 2250-3350 mm, once per year; Region VII: 1350-1800, once per year; Region VIII: 2850-3250 mm, 1.7 times; Region IX/ARMM: 1750-2450 mm, once in 12 years; Region X/CARAGA: 2150-3650 mm, once in 12 years to once per year; Region XI/CARAGA: 800-4500, once in 12 years to once per year; Region XII/ARMM: 1700-2250, once in 12 years.
However, variation can occur even over short distances within regions having certain climate types based on any system of classification. For example, climate rapidly changes with elevation in mountains, even in tropical regions. Tall mountains have rings of various climates where coffee and rice can be grown from about 0.5 to 1 km; sugar from 1 to 2 km; and corn (maize) as well as beans at elevation of up to 3 km. The snowline is found above 4 km. (Eagleman 1985).
CONCEPCION RN. 2004. Gateway to land and water information: Philippine national report. Retrieved Jan. 23, 2011 from http://www.apipnm.org/swlwpnr/reports/y_ta/z_ph/ph.htm.
EAGLEMAN JR. 1985. Meteorology: The Atmosphere in Action. Belmont, CA: Wadsworth Publishing Company. 394 p.kidlat.pagasa.dost.gov.ph. n.d. Climate of the Philippines. Retrieved January 28, 2011 from http://kidlat.pagasa.dost.gov.ph/cab/climate.htm.
LANTICAN RM. 2001. The Science and Practice of Crop Production. College, Los Banos, Laguna, Phils.: SEAMEO SEARCA and UPLB. 330 p.
MILLER GT Jr. 2001. Environmental Science: Working With The Earth. 8th ed. Pacific Grove, CA, USA: Brooks/Cole. p. 135-167.
POINCELOT RP. 1980. Horticulture: Principles and Practical Applications. Englewood Cliffs, NJ: Prentice-Hall, Inc. 652 p.
WENT FW, THE EDITORS OF LIFE. 1963. The Plants. NY: Time Incorporated. p. 139-158.
(Ben G. Bareja, January 2011)