Edgar A. Vallar

Use of polarimetric lidar for the study of oriented ice plates in clouds

A polarization lidar operating at 532 nm was converted into an automatic, polarimetric lidar capable of measuring the entire Stokes vector of backscattered light and its derived quantities. Among these quantities, circular and linear depolarizations were studied as tools for investigating the presence of anisotropic scattering media. Isotropic scatterers show a simple relationship between linear and circular depolarization, a relation that we confirm theoretically and experimentally. Deviations from this relation, which are possible in the presence of anisotropic scatterers such as horizontally oriented ice plates when they are observed with a slant lidar, were studied both numerically and experimentally.

Diurnal Characteristics of Angstrom Turbidity Parameters Over Manila, Philippines

The diurnal variation of the aerosol optical depth (AOD) at 500nm wavelength and the Angstrom turbidity coefficients (α and β) were derived from direct beam measurements. Results of the measurements showed that the AOD, α, and β variations at different time intervals were mainly influenced by human activities and industrial operations as the day progressed. Hourly variability of AOD (in terms of percent departure from the daily mean) showed that it increases from morning and then reaches its maximum diversion from the mean (25%) at noontime (around 11 AM local time) and then slowly decreases in the afternoon. The wavelength exponent showed an almost similar pattern of diurnal variability as AOD. Its variation ranges at about 6 % above and below the average value of α. However β has a different pattern as compared to AOD and α. It consistently departs above the mean at around 20% in the morning and close to 30% below the mean in the afternoon. Daily values of AOD range from 0.545 to 2.174 with values frequently in the range of 0.5 to 1.5. Daily α was frequently around 1.75 but its values ranged from 0.502 to 3.236. This denoted that fine particles were dominating over coarse particles.

Primary education in Vietnam and pupil online engagement

This paper focuses on exploring the disparities in social awareness and use of the Internet between urban and rural school children in the North of Vietnam. Design/methodology/approach: A total of 525 pupils, aged 9 to 11 years old, randomly selected from 7 urban and rural schools, who are Internet users, participated in the study and consented to responding to a questionnaire adapted from an equivalent European Union (EU) study. A comparative statistical analysis of the responses was then carried out, using IBM SPSS v21, which consisted of a descriptive analysis, an identification of personal self-development opportunities, as well as issues related to pupils’ digital prowess and knowledge of Internet use, and Internet safety, including parental engagement in their offspring’s online activities. Findings: The study highlights the fact that children from both the urban and rural regions of the North of Vietnam mostly access to the Internet from home, but with more children in the urbanized areas accessing it at school than their rural counterparts. Although children from the rural areas scored lower on all the Internet indicators, such as digital access and online personal experience and awareness, there was no disparity in awareness of Internet risks between the two sub-samples. It is noteworthy that there was no statistically significant gender difference towards online activities that support self-development. In relation to safe Internet usage, children are likely to seek advice from their parents, rather than through teachers or friends. However, they are not yet provided with an effective safety net while exposing themselves to the digital world. Originality/value: Although the Vietnamese national curriculum on the Computer Science subject does not explicitly cover the use of the Internet and its related aspects, the majority of children who took part in this study claimed to have used the Internet in their learning activities. This emphasises the urgent need for the MoE and educators in the country to not only improve ICT facilities in schools, but also to revise the Computer Science curriculum in order to (a) provide a supportive environment for learning development and (b) collectively advocate the dynamics of Internet use in order to ensure safe access and use by the children.

Air pollution in Bangalore, India: an eight-year trend analysis.

Bangalore is one of Indias fastest growing metropolises and, although benefiting economically due to its fast development, has a rapidly deteriorating environment. This paper provides a critical analysis of the air pollution trend in the city over the period 2006-2013 at six specific locations where measurements have been consistently recorded. It also discusses the potential health implications pertaining to exceeding levels of pollutants where these are applicable. In order to attain informed decisions on the protection of the health of populations from elevated levels of air pollution, an understanding of spatial-temporal variance of air pollutant patterns is necessary. The study highlights the fact that Bangalore and other similar developing cities do not have an adequate number of fixed monitoring stations that could provide a complete coverage of the air pollution levels for the entire city. It is suggested that this can be overcome by using geospatial interpolation techniques that provide a complete coverage of the levels of pollutants, as well as assist in mapping health characteristics of the population, in order to reach evidence-based decisions and target effective interventions.

Data quality issues in the GIS modelling of air pollution and cardiovascular mortality in Bangalore

Cardiovascular disease (CVD) is the worlds number one cause of mortality. Research in recent years has begun to illustrate a significant association between CVD and air pollution. As most of these studies employed traditional statistics, cross-sectional or meta-analysis methods, a study undertaken by the authors was designed to investigate how a geographical information system (GIS) could be used to develop a more efficient spatio-temporal method of analysis than the currently existing methods mainly based on statistical inference. Using Bangalore, India, as a case study, demographic, environmental and CVD mortality data was sought from the city. However, critical deficiencies in the quality of the environmental data and mortality records were identified and quantified. This paper discusses the shortcomings in the quality of mortality data, together with the development of a framework based on WHO guidelines to improve the defects, henceforth considerably improving data quality.

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, r eff , 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 Fernalds inversion algorithm combined with Kletts 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, r g . 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 that gives the dependence of δ with r g . The altitude profile of r eff is retrieved by using the measured value of 6 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 rnJ) 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 facilily 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 Kletts 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 am). 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 in above the LIDAR having extinction values of 6 —8 km-1 for both wavelengths.