ON THE ASSIMILATION OF GNSS PWV MEASUREMENTS IN HEAVY TO TORRENTIAL RAIN EVENTS IN DAVAO CITY, PHILIPPINES

A standalone Global Navigation Satellite System (GNSS) receiver was utilized in this study to get a measure of the atmospheric water vapor in Davao City, Philippines. It aims to monitor the variability of GNSS precipitable water vapor (PWV) especially during heavy to torrential rain. The results of the study showed a positive correlation between GNSS-PWV and precipitation especially in these severe (heavy to torrential) rain events which implies that the assimilation of atmospheric water vapor measurements can improve forecasts of such events

1999 Philippine Talent Search for Young Scientists (PTSYS) award

Dr. Edgar Vallar of the Chemistry Department, placed second in the 1999 Philippine Talent Search for Young Scientists (PTSYS) Award among 16 qualified candidates from all over the country. Vallar presented his research titled Generation of 589 nm Laser Radiation by Sum-Frequency of the 1319 nm Output of a Single Nd:YAG Laser (II) to a NAST panel in March, 1999

1999 Philippine talent search for young scientists

Dr. Edgar Vallar of the Physics Department and Dr. Elaine Tolentino of the Chemistry Department received their awards for winning the second and third prizes, respectively, in the 1999 Philippine Talent Search for Young Scientists sponsored by the National Academy of Science and Technology (NAST)

Altitude profile of the effective radius of atmospheric boundary layer aerosols retrieved from simultaneous two-wavelength lidar measurement

The altitude profile of the effective radius, reff, of atmospheric boundary layer aerosols was retrieved from simultaneous two-wavelength lidar measurement near Manila Bay. The effective radius was retrieved using a simple method that makes use of the angstrom coefficient, δ, obtained from the extinction coefficients at the two wavelengths. The altitude profiles of the extinction coefficients at 532-nm and 1064-nm lidar wavelengths were obtained using Fernald\u27s inversion algorithm combined with Klett\u27s boundary value algorithm, used to obtain the aerosol extinction coefficient at the reference height. Assuming a lognormal size distribution, with a geometric standard deviation of 1.54, for atmospheric boundary layer aerosols, and a constant refractive index of 1.45 - 0i, the angstrom coefficient is determined at different mode radius, rg, using Mie Scattering Theory. A curve fitting analysis using the method-of-least-squares is done on the theoretical value of δ to obtain a sixth-order polynomial equation flint gives the dependence of δ with rg. The altitude profile of reff is retrieved by using the measured value of δ into the equation. This method was applied to actual lidar experiments and the effective radius of the atmospheric boundary layer aerosols was observed to vary between 0.26 μm to 0.29 μm within the layer

Simultaneous two-wavelength lidar measurement of cloud and boundary layer aerosol extinction coefficients

Simultaneous two wavelength LIDAR measurements of clouds and boundary layer aerosols were performed near Manila Bay, Philippines. The two-wavelength LIDAR system employs the simultaneous outputs at 1064-nm (420 mJ), and 532-nm (175 mJ) of a Q-Switched, 20-Hz Nd:YAG laser, and a 203.20-mm diameter Schmidt Cassegrain telescope set for 1-mrad field-of-view. The vertically-pointing, biaxial Mie LIDAR facility became operational early last year and is in the STRC building (14.339°N, 120.595°E) of De La Salle University (DLSU), Taft Avenue, Manila. LIDAR measurements were obtained in 1-minute intervals from 0812-0830 hours (local time) on December 20, 1999 and 0650-0930 hours (local time) on March 23, 2000. Extinction coefficients for these boundary layer aerosols and clouds were computed using Klett\u27s modified inversion algorithm. The extinction coefficients for the clouds observed on December 20 were 20 - 100 km-1 (1064 nm) and 5 - 40 km-1 (532 nm). Boundary layer aerosols found on the same day had extinctions of 10 km-1 for both wavelengths and reached up to 300 m above the site. The March 23 data show mostly boundary, layer aerosols from 200 - 600 m above the LIDAR having extinction values of 6 - 8 km-1 for both wavelengths

Retrieval of boundary layer and cloud base heights in Manila from a two-wavelength lidar measurement

The boundary layer and cloud heights were determined from two wavelength lidar measurement in Manila. Normalized concentration gradient (NCG) method was implemented in the boundary layer height retrieval and from the slope of the range squared corrected signal (RSCS), the cloud base heights were retrieved. During the time of the measurement from 1500 to 2200 HR local time, the boundary layer height was found to be stable at around 370 m, which is considered as period of stable stratification. The cloud heights from the slope method during the measurement period was 800 m up to 1.2 km and the other layer starting from 1.6 km to 1.8 km. The calculated cloud heights matched the clouds that can be determined visually from the range-squared corrected signal THI plot

Investigating the effect of urbanization on weather using the weather research and forecasting (WRF) model: A case of Metro Manila, Philippines

The effect of urbanization of Metro Manila, particularly on the amount of sensible heat flux, rainfall and temperature of selected urban and rural areas, was investigated using the Weather Research and Forecasting Version 3.4.1 (WRFV3.4.1) model. National Center for Environmental Prediction-Final (NCEP-FNL) grib1 data from 2000 to 2010 were used as inputs into the model for meteorological data. The Mann–Kendall trend test (M–K test) was utilized to verify the significance of the trends while Sen’s slope estimator was used to quantify the measured trends. Results showed that, on average, the sensible heat flux of Metro Manila is about 1.5 × 108 Jm−2 higher than in selected areas outside Metro Manila. The occurrence of an urban heat island (UHI) effect was detected in Metro Manila by comparing the difference in the minimum and maximum temperatures. For the selected urban and rural areas, the minimum and maximum temperature differences (relative to Metro Manila) are around 0.4 to 2.4°C and 0.83 to 2.3°C, respectively. Metro Manila recorded higher 11-year average values of rainfall during the summer season (8% to 64%), rainy season (15% to 305%), and transition season (8% to 232%) when compared with selected areas from 25 to 100 km from Manila. These results show that the sensible heat flux, temperature and rainfall in Metro Manila is affected by Metro Manila’s urbanization. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Multi-wavelength backscatter measurement of clouds and aerosols using a white lidar system

With the recent technology of the high-peak power femtosecond laser, white light continuum in atmospheric gas can be generated. In 1998, Rairoux et. al. had demonstrated the application of this novel light source for atmospheric remote sensing[l]. The broad spectrum of the white light, can be used for multi-wavelength lidar studies. The multi-wavelength lidar measurements have the capability of obtaining the wavelength dependence of the backscatter coefficients of aerosols, which can be used to evaluate the particle size, and determine its size distribution [Z]. In this paper, application of white light lidar system for the multi- wavelength backscatter measurements of clouds and aerosols will be presented. The white light continuum was generated by a focused 0.8TWll00fs laser pulse in a 9-m long gas cell filled with atmospheric krypton rare gas which generated a broad spectrum of the white light, from 300 nm to 950 nm (Fig.1). We transmitted the white light to the atmosphere (Fig.2) and measured the backscattered light simultaneously with 4 channels of photomultipliers, which had different spectral filters. We observed the temporal evolution of the backscattered coefficient (Fig.3) and analyzed the particle size distribution

Real-Time Chlorophyll-a Pigment Monitoring of <i>Chlamydomonas reinhardtii</i> in a Controlled Environment Using Pulsed LED Fluorescence LiDAR System

The real-time chlorophyll-a pigment monitoring of C. reinhardtii is studied using our developed LED fluorescence light detection and ranging (LiDAR) system. It features a portable set-up that uses a pulsed LED module with an excitation wavelength of 385 nm. We were able to monitor the different growth phases of C. reinhardtii with specific cultivation parameters. The developed fluorescence LiDAR system showed the linear correlation of its chlorophyll-a signal with the optical density and EEM fluorescence measurements at 680 nm emission wavelength. Water quality and weather parameters were also measured, which explains the variation in the growth dynamics of C. reinhardtii during the sampling period. The results from the monitoring demonstrated a different technique that can be used in estimating algal biomass in the environment

On the variability of precipitable water vapor and its probabilistic modeling of precipitation occurrence in Davao City

This study utilized the data files from the local radiosonde station in Davao City to monitor the atmospheric water vapor content in the area. Results of the study showed that the PWV derived from the local radiosonde station was able to provide annual, seasonal and monthly variations of the atmospheric water vapor content in Davao City. A probabilistic modeling of precipitation occurrence utilizing the PWV values was also explored in this study. REEP and logical regression analyses were performed on the three-year (2013-2015) PWV and rainfall data to determine the critical PWV value that would predict a positive or negative probability of rain occurrence. The calculation of odd ratio also showed that the odds of raining increase exponentially as PWV accumulate. © 2017 American Scientific Publishers. All rights reserved