Skip to main content
Thesis defences

PhD Oral Exam - Ali Gholizadeh Touchaei, Building Engineering

Characterizing the Effect of Increasing Albedo on Urban Meteorology and Air Quality in Cold Climates, a case study for Montreal


Date & time
Monday, March 30, 2015
10 a.m. – 1 p.m.
Cost

This event is free

Organization

School of Graduate Studies

Contact

Sharon Carey
514-848-2424 ext. 3802

Where

Computer Science, Engineering and Visual Arts Integrated Complex
1515 St. Catherine W.
Room EV-11.119

Wheel chair accessible

Yes

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

The higher temperature of urban areas compare to their surroundings and rural areas is called urban heat island (UHI). Several undesirable consequences of UHI in summertime are reported including a noticeable increase in cooling energy demand of buildings, in premature deaths of urban dwellers, and in concentration of air pollutants. Subsequently, mitigation strategies are proposed to confront the related issues. Three main mitigation strategies are:

  1. increasing urban greenery,
  2. increasing the reflectivity (i.e. albedo) of urban surfaces, and
  3. reducing the anthropogenic heat emission.

Increasing the urban albedo is more of an interest because of its low cost. Therefore, the albedo enhancement technique is selected for current study to advance the current state of knowledge. In particular, I am interested in characterizing the effect of implementing reflective roofs, walls, and roads on air temperature and air quality of Canadian cities. Canadian cities are located on high latitudes that the seasonal variation of the extraterrestrial solar radiation is greater than mid- latitude and low-latitude. Hence, the possible penalty of the albedo enhancement is potentially less than cities in moderate and tropical climates. Additionally, the snow cover of roofs and pavements hides their actual color. Accurate assessment of a mitigation strategy is a sophisticated process and it considers interaction between land and atmosphere.

Mesoscale model, urban canopy model (UCM), building energy model (BEM), and chemical transport model (CHEM) are coupled, to accurately investigate the effect of an increase in the urban albedo. The Weather Research and Forecasting (WRF) model is selected to solve the conservation equations for the atmosphere. WRF is a comprehensive model ensemble comprising different parameterizations for microphysics, cumulus, land, planetary boundary layer, and radiation. Additionally, WRF has different options for UCM that can be used and the multi-layer UCM has the capability of coupling to the BEM to account for the heat emission from buildings to the canopy and energy consumption of HVAC systems. Furthermore, a unique ability of WRF for online coupling of meteorological model to chemical transport models, which has been widely used and accepted by the scientific community, highly qualified the model for urban climate and air quality simulations.

To select appropriate models sensitivity of near surface air temperature and near surface wind velocity to a choice of parameterization is evaluated without adding the complexity of heat emission from buildings and chemical reactions in the domain. Thereafter, a set of parameterizations with an acceptable deviation from the measured air temperature and the measured wind velocity is selected for further analysis. Montreal and Toronto, as the two most populated Canadian cities, are selected for initial evaluation of UCM and an increase in the urban albedo. The multi-layer urban canopy model has shown a better performance in predicting the UHI and the air temperature. The albedo enhancement of roofs (0.2 to 0.8) decreased the air temperature in Toronto and Montreal by maximum 1 °C, in a summer day. At this stage, the effect of considering the actual urban morphology of Montreal in prediction of UHI and energy consumption of HVAC systems is investigated using BEM coupled to the multi-layer UCM. A change of 0.7 °C in UHI intensity and 6.3 kWh/100m2 in energy consumption is estimated. Afterward, seasonal performance of the increase in albedo of roofs, walls, and road by 0.45, 0.4, and 0.25, respectively, results in the average decrease of 0.25 °C during summer and negligible effect during winter. The net energy saving in summertime is about 18 Wh/100m2, while, the winter penalty is about 2 Wh/100m2. Considering the effect of air pollution the maximum air temperature decrease in summertime is about 1 °C as well as 0.1 ppbv and 2 μg/m3 reduction in near surface 1-hour ozone and 24-hour PM2.5, respectively.

Back to top

© Concordia University