Aerosol Impacts on Precipitation during the Monsoon Season in the Philippines

Introduction
The Republic of the Philippines (RP) possesses a complex topography and extensive regional urban air pollution that may influence precipitation variability. Precipitation variability induces localized extremes in rainfall intensity creating pronounced floods and droughts. Cloud and precipitation formation depend upon the availability and physical properties of particulates suspended within the atmosphere and the distribution of water in the troposphere. The primary goal is to examine the impact of local and regional pollutants on the distribution of water in the atmospheric column and precipitation variability within the archipelago. Second, it seeks to identify if specific satellite signatures of monsoonal precipitation can be identified with satellite retrievals of hydrologic related cloud optical properties. Additionally, identify any significant trends which exist within observed precipitation extremes of the past decade. This dissertation investigates how aerosols impact the spatial and temporal distribution of tropospheric water and hydraulic cloud optical properties during the monsoon season.

Experiments and Conclusion
The data obtained in this study is taken from the decade 2001 to 2010 (during the Western North Pacific Summer Monsoon (WNPSM)). Monthly averaged Level-3 MODIS Terra global data retrievals and TRMM V7 3B-43 precipitation data during June through December are employed. 10 MODIS hydrologic cloud retrievals and aerosol properties are examined. Baseline comparisons between the decadal rainfall patterns during the monsoon season and the 50 year climatology are presented.
Results revealed seasonal differences in regions exist between precipitation, hydrologic cloud optical properties, and aerosols loading from the satellite retrievals in the last decade where a dominant southeasterly (northwesterly) latitudinal gradient exist during JAS (OND) is apparent within most assessed variables. Decadal rainfall on average has decreased by 54% in comparison to the baseline. Principal Component Analysis on 9 of the 11 variables conducted indicated, most variability is accounted between precipitation (48% - 66%), aerosol optical depth (AOD), and angstrom exponents (AE). Highest AOD (0.2 – 0.4) loading is associated with urban/industrial aerosols during JAS in the advent of higher rainfall events with smaller particles where AEs exceed 1.Furthermore, extreme decadal rainfall occurs along the western and eastern coasts of the RP which are influenced by marine and urban/industrial aerosols.