Determination of athmospheric turbidity parameters and aerosol size distribution using a feedback-controlled sun-tracking sunphotometer

Atmospheric turbidity parameters and aerosol size distribution over Manila were obtained using a feedback-controlled sun-tracking sunphotometer from 24 April 2006 26 September 2006. A total of 38 experiment days were conducted. A combination of mathematical and feedback system algorithms was used. The tracking system was incorporated by a data acquisition system that used a PCI-6023E DAQ card. The Sunphotometer Data Acquisition and Processing System (SunDAPS) was developed using LabVIEW 6.1 to acquire and analyze data, and control the sun-tracker automatically using a desktop computer. Calibration procedure was performed in La Salle College-Antipolo in 30 April 2006 using the Langley method. The procedure yielded high correlation coefficients (R \u3e 0.900). A look-up table (LUT) of wavelength exponents was generated from the extinction coefficient from different aerosol types (urban, continental average, continental clean or rural, maritime polluted and maritime clean), which was used to determine the log-normal size distribution of each data set. Size distribution of aerosol using the Junge model was also determined from the wavelength exponent. The daily variation of aerosol optical depth (AOD) for each wavelength, wavelength exponent (a) and Angstrom turbidity coefficient (b), were derived from the direct beam measurements. The values of AOD range from 0.159 (675 nm) to 0.800 (368 nm) while b and a varied from 0.113 to 0.325 and 0.04 to 1.185, respectively. The average value of b per weekday showed that weekdays (with Monday the greatest) exhibit relatively high values of beta than weekends (Saturday being the least). The monthly variation of b showed that the month of May contained the least amount of aerosols. The prevailing value of AOD is around 0.300 to 0.500 while b was predominantly valued from 0.150 to 0.250, with both distributions having the same shape. On the other hand, a reveal the slight dominance of continental aerosols (58%) over the maritime aerosols (42%). However, during the month of September maritime aerosols (79%) were more dominant than continental aerosols (21%). AOD and b gathered from 24 April 2006 to 8 September 2006 show high positive linear correlation (R = 0.818). When plotted against the AOD at 500 nm and b, as lie on the region of low to moderate AODs and bs. The average PM2.5 mass concentration determined in two locations (DLSU-Manila and LSC-Antipolo) were found to be 8.54 µg/m3 and 15.3 µg/m3. The results in LSC-Antipolo were within the range of values obtained in Good Shepherd Spiritual Center, Antipolo by the Manila Observatory (PM2.5 = 18.2 µg/m3). A positive correlation (R = 0.121) of PM2.5 mass concentration with a and negative correlation (R = -0.821) with b was also determined. Moreover, the b in Antipolo was significantly lesser than in Manila. Also the diurnal variation of AOD (500 nm) showed a low standard deviation (SD = 0.019) while the slope of the best-fit line was almost horizontal (slope = 0.006)

Multi-year Precipitable Water Vapor Observations in East Manila, Philippines using Radiosonde and Global Navigation Satellite System

Precipitable water vapor (PWV) is a parameter that used to describe the water vapor content in the atmosphere has the potential to become a precipitation. Thus, it is important to measure PWV and investigate its trends and variability for potential forecasting precipitation. This study presents the variation of PWV at Tanay Upper Station (14°34’52.8”N, 121°22’08.9”E) from radiosonde operated by the Philippine Atmospheric, Geophysical and Astronomical Services Administration and at PIMO station (14°38’08.5”N, 121°04’39.4”E) using Global Navigation Satellite System (GNSS) operated by NASAJet Propulsion Laboratory under the International GNSS Service (IGS) network from 2015-2017. Moreover, there is no significant difference (p-values < 0.05) among PWV radiosonde, GNSS-PWV and rainfall as a function of year of observation. Monthly mean variation conforms to the Coronas climate classification, Climate Type I, in terms of the amount of precipitation. It is shown that PWV is high during wet months and least during dry months (November to April). Further, monthly mean variation is moderate correlated with surface temperature from radiosonde (R = +0.589). Evaporation rate depends on the surface temperature, which contributes in forming water vapor. The results showed that PWV from radiosonde gave reasonable values to be considered during wet and dry season as well as the seasonal variation of rainfall

Development of a low-cost sunphotometer tracking and data acquisition system

A low-cost sun tracking and data acquisition system for the SPO 2 and SP10 1 sun photometers were developed. The sun-tracking system has a 1-degree pointing error and was based on a mathematical algorithm that depends on the position of the observer and the time of observation. A virtual instrument software called The Sun photometer Data Acquisition System (SunDAPS) was developed using LabVIEW6.1TM. It was used to acquire analog signals from the sun photometers and control the tracking system through the NI PCI-6023 ETM DAQ card

Two-Dimensional Mapping of Ionospheric Total Electron Content over the Philippines Using Kriging Interpolation

Monitoring of ionospheric total electron content (TEC) was made possible with the help of satellite data, albeit in one dimension. However, ionospheric TEC maps can be produced from a collection of one-dimensional satellite data over a geographic area. Multiple mapping methods have been recognized; however, this study tried to test one of those methods: kriging interpolation. An algorithm was developed and used to reconstruct GIMs. The optimum number of stations and the semivariogram model were evaluated using GIM maps modeling 12 days of March 2015, accounting for different ionospheric conditions. This includes days of high scintillation and an ionospheric storm due to the St. Patrick’s Day geomagnetic storm of 2015. It was found that 12 stations and the linear semivariogram model had the least mean error in 5 days and had the least standard deviation in 7 days, making it the optimum parameter set. This optimum set was then used to map and analyze the ionosphere using actual satellite data from the Philippine Active Geodetic Network (PAGeNet). From this, it was observed that there is a north–south gradient in VTEC in the region during the day. The VTEC in the north reaches more than 100 TECU, and, in the south, generally around 60–90 TECU depending on the ionospheric condition. VTEC was at a minimum during the night when the VTEC level decreases to around 10 TECU

Atmospheric turbidity measurements using a 355NM-532NM lidar and a sunphotometer in Manila, Philippines

Real-time measurements of atmospheric turbidity were conducted in Manila, Philippines using the De La Salle University (DLSU) 355nm-532nm Mie LIDAR and Middleton SP02 4-channel sunphotometer. The DLSU Mie LIDAR system and the Middleton SP02 Sunphotometer are currently housed in the Science & Technology Research Center of DLSU, Manila, Philippines. DLSU is located in the center of Manila and is approximately 900 meters from Manila Bay. The DLSU LIDAR mainly consists of a 20-Hz, Q-Switched Nd:YAG laser and 20-cm diameter, 800-mm focal length Newtonian telescope. The SP02 Sunphotometer is a 1.25-kg commercial 4-channel Sunphotometer with center wavelengths at 368nm, 500nm, 675nm and 862nm (10-nm bandwidth). The sunphotometer was attached to a homemade tracker mount that tracks the sun and gets data automatically throughout the day. DLSU LIDAR researchers built LabView-based VI\u27s for both the LIDAR and the sunphotometer enabling automatic data acquisition and processing. A detailed description of both systems can be found in www.dlsu-lidar.tk. The optical depth was determined from the data of each instrument. The Ångström turbidity law was then utilized to obtain the atmospheric turbidity. Typical values of turbidity vary from 0.0 to 0.5. For clean, clear, turbid and very turbid atmospheres, the turbidity values are 0.0, 0.1, 0.2 and 0.4, respectively. Experiments were conducted last 2010 January 08, 12 and 22. The average turbidity up to 400 meters horizontal range from the LIDAR site was determined. The LIDAR derived turbidity values were 0.184, 0.23, and 0.0295, respectively for the three dates. The corresponding sunphotometer values are 0.191, 0.235, and 0.0280, respectively. The January 08 and 12 values show a turbid atmosphere while the January 22 value indicates a relatively clear atmospheric condition

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

Matlab-based VHF and UHF amplitude scintillation characterization using the new low-latitude ionospheric tomography network (LITN)

The new LITN network was established in 2006 to study equatorial anomaly dynamics (Hsiao et al., 2009). It has ten Ionospheric Tomography Stations (ITS) placed along the 120°E longitude with stations in Japan, Taiwan, Philippines and Indonesia. These stations independently receive mutually coherent signals at VHF (150 MHz) and UHF (400 MHz) bands, which come from NNSS-like satellites and FORMOSAT-3/COSMIC satellites. Local ionospheric irregularities, that cause rapid fluctuations in radio signals or scintillation, can be studied using the total electron content (TEC) values acquired from the ITS receiver. In this study, a MATLAB-based application was developed to process these data for automatic identification and characterization of amplitude scintillation where six criteria are set to characterize an event as scintillation including the S4 index, elevation angle, transmitting satellite, confirmation from other data recording and ground stations, and location difference of the recordings. LITN data was obtained from August 2008 to February 2011. Scintillation varied with operating frequency, local time, geographical location, solar activity and magnetic activity. Strong scintillation occurred more in VHF than in UHF. Moreover, nighttime scintillations occurred predominantly around local midnight (2000∼0200 LT), while most of the daytime scintillation occurred at 0800∼1000 LT. Scintillation mostly occurred between 15°-25° of geomagnetic latitude and almost none below 10° and above 30° geomagnetic latitude. Generally, the scintillation occurred under quiet magnetic condition and the occurrence increases as the solar activity increases

A climatological study of typhoons over the Philippine Area of Responsibility from 1989–2018

The Philippines is in the Western North Pacific region, where it is a recipient of several weather disturbances such as tropical cyclones. This study aims to determine trends and periodicities of typhoons (TY) within the Philippine Area of Responsibility (PAR), and the rainfall they brought in a 30-year period (1989–2018) for future forecast and disaster risk mitigation efforts of these TY. These TYs are raised when TC’s sustained winds are 118 kph and above. Frequency analysis of TY is done to determine the trends and periodicities in terms of the yearly total occurrence, number of TY that made landfall, distribution of TY classification, and their seasonal variation. The results showed that with PAR the yearly total occurrence of TY seems to have an approximately 12-year periodicity where maximum occurrence was observed around the years 1994, 2004, and 2014 while minimum occurrence was observed in years 1989, 1999, and 2010. Also, track data shows that only 32 % of these TY made a landfall within PAR. Out of the three regions in the Philippines, Luzon Island is the region where most of the severe typhoons made landfall at 80 %. Moreover, TYs occurred mostly during September to November where the transition period between the northeast monsoon and south west monsoon usually occurs. Also, rainfall during which these TYs have occurred were obtained from five synoptic stations across the Philippines. It showed from 1989 to 1998, the total yearly rainfall brought by these TYs ranged from 804 mm to 1 912 mm. But from 1999 to 2018, these TYs brought more rain where their total yearly rainfall ranged from 2 844 mm to 4 941 mm