Seasonal reversal of the ENSO rainfall signal in the Philippines

Abstract

Seasonal rainfall in the Philippines is known to be modulated by the El Niño Southern Oscillation (ENSO) phenomenon, with ENSO warm (cold) events frequently contributing to drought (excessive rainfall) in many areas. Here, using rainfall data from 40 observing stations across the Philippines, it is shown that the seasonal rainfall response to ENSO reverses sign between boreal summer (July–September) and fall (October–December) for both El Niño and La Niña. Above‐median, boreal summer rainfall is observed at several stations in the north‐central Philippines during El Niño before anomalously dry conditions become manifest the subsequent fall. Conversely, during La Niña below‐median summer rainfall occurs at several stations before the onset of anomalously wet conditions in fall. The results are shown to be not simply a consequence of ENSO transitions during boreal spring, but are associated with changes in the large scale monsoon system during the life cycle of ENSO events.

Tropical cyclone influence on the long-term variability of Philippine summer monsoon onset

“…5a. 1Earlier studies have shown the strong influence of the ENSO on Philippine summer monsoon rainfall, which increases during the summer of El Niño developing years (Lyon et al 2006;Kubota and Wang 2009) and decreases during the summer of the following El Niño decaying year (Xie et al 2009). The correlation between Philippine summer monsoon rainfall and the ENSO also shows interdecadal variability (Chowdary et al 2012).…”

“…Rainfall tends to increase during the summer (June-August) of the El Niño developing year (Lyon et al 2006;Kubota and Wang 2009). However, rainfall decreases because of the eastward shift of the tropical cyclone (TC) track in autumn (September-November; Saunders et al 2000;Lyon et al 2006;Lyon and Camargo 2008;Kubota and Wang 2009). The summer monsoon activity of the subsequent El Niño decaying year becomes weak, a phenomenon which is associated with the ENSO influence on sea surface temperature (SST) anomalies in the Indian Ocean (IO; Xie et al 2009).…”

Assessment of Satellite Precipitation Products in the Philippine Archipelago

“…The western part of the country is significantly influenced by convective rains from the warm moist air of the southwest during the Boreal summer while the eastern part gets orographically induced precipitation from lowlevel easterlies originating from the Pacific on winter season (Akasaka, 2007). In addition, rainfall is also influenced by El Niño and La Niña occurrences (Ropelewski and Halpert, 1996, Lyon et al 2006, Hilario et al 2009). In-situ rainfall observations can be significantly influenced by its surrounding environment.…”

The December 2012 Mayo River debris flow triggered by Super Typhoon Bopha in Mindanao, Philippines: lessons learned and questions raised

“…The year before Bopha, from 16 to 17 December 2011 the city of Cagayan de Oro on the Mindanao coast 180 km north of New Bataan received 180 mm of rain from Tropical Storm Washi. Most fell during only 6 h, causing floods that killed 1268 people (Ramos, 2012;Manila Observatory, 2012). A tropical depression made landfall on Mindanao 2 months before Washi, making 2011 only the fifth year since 1945 when Mindanao experienced two tropical cyclones.…”