Aside from rain, wind, humidity and barometric pressure, raindrop size distribution could also be a factor in predicting weather. Dr. Wei-Yu Chang, Assistant Professor of the Chinese Cultural University, Taiwan, discussed this weather parameter last May 03, 2018 at the SESAM Seminar Room.

In his presentation entitled “Improving the Radar-Based Quantitative Precipitation Estimation (QPE) by Utilizing the Raindrop Size Distribution Data Observed by Disdrometer”, he established a mathematical formula in computing raindrop size distribution.

He uses the laser optical PARticle SIze VELocity (PARSIVEL) disdrometer, which can detect raindrop numbers and particle size, fall velocity and raindrop size distribution. Dr. Chang said the equipment also measures the rainfall of the different parts of a typhoon, within the eye, eyewall and its rainbands.

Based on his study, as drop size increases and velocity, the raindrop becomes flat. “With high concentration of small drop, the higher rainfall rate, while low concentration of big drop, the lower rainfall rate”, Dr. Chang added. 

Dr. Chang said raindrop size distribution data would really help meteorologists in QPE. The information in turn will help engineers in planning, weather prediction and even agriculture. Further, Dr. Chang stressed that flood forecasters can use the integrated rainfall parameters and QPE since rain kinetic energy can be measured in his formula.

The lecture was in line with project of the University of the Philippines Los Baños (UPLB), in partnership with Philippine Atmospheric, Geophysical, and Astronomic Services Administration (PAGASA) entitled “Heavy Rainfall Monitoring and Forecasting in Mountainous Areas and Early Warning for Landslides” of the research program “Improvement of Forecast Capability on Weather, Marine Meteorology and Short Range Climate”. Led by SESAM Dean, Dr. Decibel F. Eslava, the project collaborates with the National Taiwan University, Makiling Center for Mountain Ecosystems-College of Forestry and Natural Resources (MCME-CFNR) and National Institute of Geological Sciences (NIGS), University of the Philippines, Diliman.

This project is funded by the Department of Science and Technology-Philippine Council for Industry, Energy, and Emerging Technology Research and Development (DOSTPCIEERD), under the Manila Economic and Cultural Office-Taipei Economic and Cultural Office’s call for Volcanoes, Oceans, Typhoons and Earthquake (VOTE) collaborative researches. This research project mainly focused on the Mount Makiling Forest Reserve (MMFR) and it aims to produce an early warning system for landslides based on rainfall intensity (I) – duration (D) thresholds.