The Effect of Tropical Cyclones on Southwest Monsoon Rainfall in the Philippines

Abstract

Intense southwest monsoon (SWM) rainfall events causing massive landslides and flash floods along the western sections of the Philippines were studied. These rainfall events, are not directly coming from the tropical cyclones (TCs) for they are situated far north to northeast of Luzon Island. The heavy rainfall is hypothesized as caused by the interaction of strong westerlies with the mountain ranges along the west coast of Luzon that produces strong vertical motion and consequently generates heavy rainfall. Four of heavy SWM rainfall cases were examined to determine how the presence and position of tropical cyclones in the Philippine vicinity a¤ect these SWM rainfall events; three cases with TC of varying positions within the Philippine area of responsibility (PAR) and the fourth case without TC. Using a spatial Fourier decomposition approach, the total streamfunction is decomposed into two flow regimes: monsoon basic flow (Waves 0-1) and tropical cyclone perturbation flow (Waves 2-23) over a domain of (20 E-140 W, 5 S-35 N). The purpose of this flow decomposition is to determine the latter's e¤ect on or contribution to the monsoon activity. The analysis utilized the NCEP Final (FNL) data with 1 long. Â 1 lat. resolution. Results show that the tropical cyclones over the Pacific Ocean located northeast of Luzon generate strong southwesterly winds over the west coast of Luzon. These in addition to the southwesterlies from the basic flow strengthened the southwest winds that interact with the high Cordillera Mountain ranges Corresponding author: Esperanza O. Cayanan, Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), Science Garden, Agham Road, Diliman, Quezon City 1100, Philippines. E-mail: eocayanan@gmail.com 6 2011, Meteorological Society of Japan along the west coast of Luzon. When the tropical cyclone is located north or north-northwest of Luzon, it generates northwesterlies which converge with the southwesterlies from the basic flow. This results to enhancement of rising motion over western Luzon. The much stronger westerlies are then forced to rise above the mountains resulting to strong vertical motion that brings about heavy rainfall.

Aerosol meteorology of the Maritime Continent for the 2012 7SEAS southwest monsoon intensive study – Part 1: regional-scale phenomena

“…This monsoon enhancement has been noted to stretch from east of the Philippines to as far west as Sumatra. Such TC-induced monsoonal enhancements have been noted by Philippine forecasters to bring heavy rainfall to Luzon (e.g., Cayanan et al, 2011;Cruz et al, 2013). Reid et al (2012Reid et al ( , 2015 and Wang et al (2013) noted that such enhancements tend to draw out smoke from the MC into the SCS, where it is then sometimes annihilated by convection associated with the enhancement.…”

Potential impact of sea surface temperature on rainfall over the western Philippines

“…3.6.1 with the Advanced Research WRF dynamical core (Skamarock et al 2008) to examine the impact of SST on precipitation. The initial and lateral boundary conditions used were from the ERAInterim reanalysis data (Berrisford et al 2009) of the European Centre for Medium-Range Weather Forecasts, and SST data were from the Optimum Interpolation Sea Surface Temperature (OISST) ver. 2 (Reynolds et al 2002).…”

Long-range aerosol transport and impacts on size-resolved aerosol composition in Metro Manila, Philippines

“…1c). Typhoon influences on atmospheric aerosol, caused by varying factors such as wind speed and precipitation, have been studied in China (Yan et al, 2016;Liu et al, 2018), Korea (Kim et al, 2007), Malaysia (Juneng et al, 2011), the South China Sea (Reid et al, 2015(Reid et al, , 2016b, and Taiwan (Fang et al, 2009;Chang et al, 2011;Lu et al, 2017). The influences of typhoons on biomass burning emissions and transport in the MC have also been examined (Reid et al, 2012;Wang et al, 2013).…”