Seminar Schedule in Google Calendar
Tue 21st April 2015
PhD Candidate, UBC Department of Statistics
Air Quality Model Evaluation through the Analysis and Modelling of Ozone Features
Legislative actions regarding ozone pollution use air quality models (AQMs) such as Community Multiscale Air Quality (CMAQ) model for scientific guidance, hence the evaluation of AQM such as CMAQ is an important subject. Traditional point-to-point comparisons between AQM outputs and ozone observations can be uninformative or even misleading since the AQM modelled ozone process and physical observations are governed by different stochastic spatial processes. I propose an alternative model evaluation approach that is based on the comparison of spatial-temporal ozone features, where I compare the dominant space-time structures between AQM and observation. To successfully implement feature-based AQM evaluation, I further developed statistical framework of analyzing and modelling space-time ozone fields using ozone features. Rather than working directly with raw data, I analyze the spatial-temporal variability of ozone fields by extracting data features using Principal Component Analysis (PCA). These features are then modelled as Gaussian Processes (GPs) driven by various atmospheric conditions and chemical precursor pollution. My method is implemented on CMAQ outputs during several ozone episodes in Lower Fraser Valley, BC. I found that the feature-based ozone model is an efficient way of modelling and forecasting a complex space-time ozone field. The framework of ozone feature analysis is then applied to evaluate CMAQ outputs against the observations. Here, I found that CMAQ persistently over-estimates the observed spatial ozone pollution. Through the modelling of ``feature differences'', I identified their associations with CMAQ inputs on ozone precursor emissions, and the CMAQ-observation differences are focused on regions where the pollution process transitions from NOx-sensitive to VOC-sensitive. Through the comparison of dynamic ozone features, I found that CMAQ's over-prediction is also connect to the model producing higher than observed ozone plume in daytime. However, CMAQ model did capture the observed space-time pattern of diurnal ozone advection. Lastly, individual modelling of CMAQ and observed ozone features revealed that even under the same atmospheric conditions, CMAQ tends to significantly over-estimate the ozone pollution during the early morning. In the end, I demonstrated that the feature-based AQM evaluation methods developed in this research are able to provide ``big picture'' process-level understandings of AQM deficiency.
Tue 14th April 2015
Professor Gang (JunYi) Shi (Visiting Associate Professor from Beijing Normal University)
The Moving Holiday Model’s Design and Application - Taking the Chinese Spring Festival for Example
Seasonal adjustment is a very important step for economic data
preprocessing. Holiday adjustment is an inevitable step for the popular
seasonal adjustment methods which include X-12-ARIMA and TRAMO/SEATS.
Because different countries have different kinds of holidays, the
popular seasonal adjustment methods must be modified when they are used
in different countries. For China, the Spring Festival is a very
important and comparatively long holiday, and it occurs in January in
some years and in February in other years. On the base of the X-12-ARIMA
method, taking the Chinese Spring Festival for example, this paper
designs different kinds of moving holiday models with considering the
effects of holiday’s influence as well as spans on economic data. By
selecting different economic indicators and by using software Demetra
and EViews, this paper tests the performance of these different models.
In the end, the best adjustment models are derived based on the criteria
of outlier percentage reduction.
Tue 7th April 2015
Poster Session for STAT 450 & STAT 550
STAT 450 students have been working collaboratively with STAT 550 students on real case studies brought by UBC researchers from other disciplines. STAT 550 students created GitHub repositories to host R-codes, related papers, reports, and discussions. These repositories also enable a fluent and effective communication between both classes, and with TAs and instructor. Supervised by graduate students, STAT 450 students performed the statistical analysis and summarized the results in a poster and report. Students of both classes will present their work in this poster session. An abstract of each case is below.
NEW this year: We will have two eStations to show examples of the GitHub repositories and two shiny applications created by graduate students to explore and illustrate data from their cases. Please, join us in this exciting event!
Poster 1: Assessing the Impact of Population Control Programs on Fertility Rates in Africa
Researcher: Richard Togman, PhD. Candidate, Department of Political Science
STAT450: Kelly Bao, Simon Tai, Gwendolyn Tian
STAT550: Creagh Briefcliffe, Derek Chiu, Xiaoting Ding, Ho Yin Ho
Countries with high population densities are at greater risk of economic instability. To drive economic prosperity, many developing countries have tried to reduce the overall fertility rates. Using survey data from the United Nations database on developing African countries, we have examined the hypothesis that strength of population control programs has minimal impact on declining fertility rate.If true, then the government should reallocate resources to areas where their impact is actually significant.
Poster 2: Factors of Language Diversity in Sikkim, India
Researcher: Mark Turin, PhD, First Nations Languages Program and Anthropology
STAT450: Ho-Hin Leung, Raymond Ye, Jeffrey Yiu
STAT550: Jeff Bone, Gal Av-Gay, Tanja Hoegg, Elena Shchurenkova
The Indian state of Sikkim is a linguistically diverse province and is home to three endangered indigenous languages, Bhutia, Limbu and Lepcha. As the education system and the needs of Sikkim’s youth change, these indigenous languages are in jeopardy. This project aims to establish characteristics and attributes that affect the number and nature of languages spoken by high school students in Sikkim.
Poster 3: The effect of mycorrhizal networks in signal transfer between Douglas fir trees
Researcher: Monika Gorzelak
STAT450: Heather Baek, Robele Baker, Na Nguyen
STAT550: Bo Chang, Alexi Rodriguez-Arelis, Basia Rogula, Yichen Zhao
Mycorrhizas networks that link trees in a forest are formed when soil fungi interact symbiotically with trees. It has been shown that trees will send stress chemicals to neighbors through these networks in response to defoliation by insects. We are interested in the study whether trees will preferentially send stress signals to genetic relatives compared to genetic strangers under difference combinations of Mycorrhizas networks status and herbivory treatments.
eStation 1: GitHub repository of case study: Analyzing Electric Vehicle Usage Pattern
Researcher: Paul Lusina, Research Associate, Dept. of Electrical & Computer Engineering
STAT550: Henry Chen and Ken Lau
As fossil fuel emission is becoming scarcer each year, the UBC fleet management (FM) team is promoting the use of electric vehicles (EV) for operational purposes at UBC. This project investigates the usage pattern of electrical vehicle charging infrastructures used by the UBC fleet in relation to factors such as arrival time, occupancy, and charging duration. A queuing model is constructed to study the capacity of the infrastructure.
eStation 2: Shiny applications
STAT550 students created shiny apps to explore and illustrate the data related to cases 1 and 2 described above.