Gerry Bagtasa (2019). Enhancement of Summer Monsoon Rainfall by Tropical Cyclones in Northwestern Philippines. J. Meteor. Soc. Japan, 97, https://doi.org/10.2151/jmsj.2019-052
Lagrosas, Nofel, Gerry Bagtasa, Naohiro Manago, and Hiroaki Kuze (2019). Influence of Ambient Relative Humidity on Seasonal Trends of the Scattering Enhancement Factor for Aerosols in Chiba, Japan. Aerosol and Air Quality Research vol. 19(8), pp.1856-1871. DOI: 10.4209/aaqr.2018.07.0267
Abstract. In this study, we used ground instruments, namely, a visibility meter, an integrating nephelometer, an aethalometer, a lidar, and a weather monitor, to measure the scattering enhancement factor, f(RH), which quantifies the effect of ambient relative humidity (RH) on aerosol light-scattering, and to generate a model of its annual variation in the city of Chiba, Japan. First, the f(RH) values were calculated with chemical analysis data. Second, visibility-meter and aethalometer data were used to model the monthly trends of f(RH) at 550 nm. The f(RH) values were higher during summer than during the other three seasons, which can be attributed to the general pattern of the regional climatology as well as the loading of different particle types into the lower troposphere. Third, the f(RH) values at 532 nm were obtained from lidar and aethalometer measurements. Low and constant f(RH) values were observed during November, whereas higher and increasing f(RH) values were observed during May. Also, dust events during March 2015 showed decreasing f(RH) with
Gerry Bagtasa, Mylene G. Cayetano, and Chung-Shin Yuan (2018). Seasonal variation and chemical characterization of PM2.5 in northwestern Philippines. Atmos. Chem. Phys., 18, 4965-4980. https://doi.org/10.5194/acp-18-4965-2018
Abstract. The seasonal and chemical characteristics of fine particulate matter (PM2.5) were investigated in Burgos, Ilocos Norte, located at the northwestern edge of the Philippines. Each 24h sample of fine aerosol was collected for four seasons. Fine particulate in the region shows strong seasonal variation in both concentration and composition. Highest mass concentration was seen during the boreal spring season with a mean mass concentration of 21.6±6.6µg m−3, and lowest was in fall with a mean concentration of 8.4±2.3µg m−3. Three-day wind back trajectory analysis of air mass reveals the influence of the northwestern Pacific monsoon regimes on PM2.5 concentration. During southwest monsoon, sea salt was the dominant component of fine aerosols carried by moist air from the South China Sea. During northeast monsoon, on the other hand, both wind and receptor model analysis showed that higher particulate concentration was due to the long-range transport (LRT) of anthropogenic emissions from northern East Asia. Overall, sea salt and soil comprise 33% of total PM2.5 concentration, while local biomass burning makes up 33%. LRT of industrial emission, solid waste burning and secondary sulfate from East Asia have a mean contribution of 34% to the total fine particulate for the whole sampling period.
Gerry Bagtasa (2017). Contribution of Tropical Cyclones to Rainfall in the Philippines. Journal of Climate. Vol 30. pp. 3621-3633. http://dx.doi.org/10.1175/JCLI-D-16-0150.1
Tropical cyclone (TC)-induced rainfall (TC rain) in the Philippines was investigated using a combination of ground and satellite observations to produce a blended 64-yr precipitation dataset. A total of 1673 TCs were examined using best track data from the Japan Meteorological Agency. Rainfall from 100 (~1110 km) of the TC center was considered as TC-induced rainfall. TC rain contribution is highest in the northern Philippines, particularly along the western coast of Luzon (up to 54%), and lowest in the southern islands of Mindanao (6%). The high TC rain contribution is attributed to the enhancement of the Asian southwest monsoon by TCs located to the northeast of the Philippines. An unsupervised clustering method, k-means clustering, was used to divide the archipelago into four climate subtypes according to monthly rainfall variation. Interannual variability of rainfall from climate clusters with high TC rain contribution generally follows the variability of TC rain. On the other hand, the variability of low TC rain clusters is mainly influenced by El Niño–Southern Oscillation (ENSO). All clusters show increasing trends of 16.9%–19.3% decade−1 in TC rain percentage contribution since 2000. This study hypothesizes that this increasing trend is due to changes in the characteristics of TC steering mechanisms and thermodynamic properties east of the Philippines in the past one and a half decades.
Rhonalyn L. Vergara, Ernest P. Macalalad, Gerry Bagtasa, Edgar A. Vallar, Maria Cecilia D. Galvez, and Raquel V. Francisco (2017). Correlation of Aerosol Optical Properties with Surface Meteorological Parameters Over Manila. Adv. Sci. Lett. 23, 1448–1451
Aerosol optical properties such as aerosol optical depth (AOD) at 500 nm together with wavelength exponent (α) and Ångstrom turbidity coefficient (β) obtained from a sunphotometer over Manila were used to analyze their response to the changes in temperature, relative humidity (RH) and zonal wind. Data retrieved for a one year period of measurements (August 2009–July 2010) were used to describe the variations of the aerosol optical properties. Temperature showed weak correlations with the aerosol optical properties. Surface RH confirmed evidence for its influence on aerosols size distribution and dominant aerosol type. Zonal wind demonstrated influences on the prevailing aerosol present at a certain area and caused alteration the amount of its loading.
BA Racoma, CP David, IA Crisologo and G Bagtasa (2016). The Change in Rainfall from Tropical Cyclones due to Orographic Effect of the Sierra Madre Mountain Range in Luzon, Philippines. Phil. Journal of Science. in press.
This paper discusses the Sierra Madre Mountain Range of the Philippines and its associated influence on the intensity and distribution of rainfall during tropical cyclones. Based on Weather and Research Forecasting model simulations, a shift in rainfall was observed in different portions of the country, due to the reduction of the topography of the mountain. Besides increasing the rainfall along the mountain range, a shift in precipitation was observed during Tropical Storm Ondoy, Typhoon Labuyo, and Tropical Storm Mario. It was also observed that the presence of the Sierra Madre Mountain Range slows down the movement of a tropical cyclones, and as such allowing more time for precipitation to form over the country. Wind profiles also suggest that the windward and leeward sides of mountain ranges during Tropical Cyclones changes depending on the storm path. It has been suggested that in predicting the distribution of rainfall, the direction of movement of a tropical cyclone as well as its adjacent areas be taken into great consideration. While the study shows high amounts of variation in the characteristics of different tropical cyclones with respect of the Sierra Madre Mountain Range, the results of this study can provide insights to pre-disaster operations before tropical cyclones approaches land. The decrease in tropical cyclones speed introduced by the Sierra Madre Mountain Range can be used to identify the possible areas that can experience prolonged rains due to the mountain range. Disaster management authorities can also prepare in advance by identifying which locations can experience orographic enhanced precipitation. However, due to the lack of available data and resources, further studies are recommended due to the study presenting limited cases.
Lagmay AMF, Bagtasa G, Crisologo IA, Racoma BAB and David CPC (2015) Volcanoes magnify Metro Manila’s southwest monsoon rains and lethal floods. Front. Earth Sci. 2:36. doi: 10.3389/feart.2014.00036
Many volcanoes worldwide are located near populated cities that experience monsoon seasons, characterized by shifting winds each year. Because of the severity of flood impact to large populations, it is worthy of investigation in the Philippines and elsewhere to better understand the phenomenon for possible hazard mitigating solutions, if any. During the monsoon season, the change in flow direction of winds brings moist warm air to cross the mountains and volcanoes in western Philippines and cause lift into the atmosphere, which normally leads to heavy rains and floods. Heavy southwest monsoon rains from 18–21 August 2013 flooded Metro Manila (population of 12 million) and its suburbs paralyzing the nation's capital for an entire week. Called the 2013 Habagat event, it was a repeat of the 2012 Habagat or extreme southwest monsoon weather from 6–9 August, which delivered record rains in the mega city. In both the 2012 and 2013 Habagat events, cyclones, the usual suspects for the delivery of heavy rains, were passing northeast of the Philippine archipelago, respectively, and enhanced the southwest monsoon. Analysis of Doppler data, rainfall measurements, and Weather Research and Forecasting (WRF) model simulations show that two large stratovolcanoes, Natib and Mariveles, across from Manila Bay and approximately 70 km west of Metro Manila, played a substantial role in delivering extreme rains and consequent floods to Metro Manila. The study highlights how volcanoes, with their shape and height create an orographic effect and dispersive tail of rain clouds which constitutes a significant flood hazard to large communities like Metro Manila..
- Lidar (atmospheric lidar) analysis of TCCON Burgos
- PM2.5 transport from East Asia and South East Asia haze transport observation and modeling
- aerosol – cloud – climate interaction modeling using WRF-Chem
- Tropical cyclone climatology in the Philippines
- Influence of weather on ambient pollutant concentration
- Mesoscale weather modeling in the Philippines
- PM concentration around power plants in Luzon
- Personal pollutant exposure from Metro Manila traffic.
- “Tempospatial Distribution and Transboundary Transport of Atmospheric Fine Particles across Bashi Channel, Taiwan Strait, and South China Sea” funded by DOST under the Meco-Teco program.
- “Creating cost-effective sensors for IR applications: High Resolution Simulation and Verification of Local CO 2 Flux in the Philippines” funded by the OVPAA Emerging Inter-Disciplinary Research (EIDR) program.
- Inter-decadal and interannual variability of Tropical cyclone wind energy exposure in the Philippines.
- Climatic changes in Metro Manila