Something to look at!

Hi, This is the graph showing the assembled 12-CO2 Picarro measurements from the 9th to the 26th of October.

Enjoy!

- Jan-Erik

Transportation Study in Montreal

This is from a report (following a transportation conference) by Chapleau and Morency (from the Civil Engineering Department (Transportation) at Ecole Polytechnique de Montreal): "Generic in nature but specific to the methodological procedures undertaken in the Greater Montreal Area (GMA), the CATI (Computer-Assisted Telephone Interview) household survey is conducted about every five years over a 5% sample. Typically, it represents about 160,000 people belonging to 65,000 households declaring some 400,000 individual trip records for an average weekday. Individual trips are geo-referenced for the residence, trip origin and destination, modal junction points (kiss-and-ride and park-and-ride locations), and are described for their household and personal characteristics (age, gender, car license, car ownership, income) in addition to the trip attributes (purpose, mode, departure time, train-subway-bus routes taken if traveling by transit, bridges and highway taken if traveling by car)."

They have a lot of GIS analysis done on transportation ranging from buses, cars to subway trains. A nice map they made was the percentage of motorized trips in Montreal am rush hour:

We could contact them for the data if we find it is useful!

-Angela.

Mount-Royal Flasks

This morning at 7am (it was still dark outside), Pogo and myself took our first flask measurment! I placed a stick with a Yellow Flag in the ground and I tied an Orange tape across a branch in the air at the spot where i took the measurments. It is directly facing you when you reach the top of the stairs.

-Atleast it is warm today, Angela.

Principles of Urban Meteorology (re atmospheric CO2)

(by Andrew)

The generalization of fundamental meteorological principles over urban environments is more problematic than to other land surfaces. This is for three reasons. First, the heterogeneity of roughness elements within the complex 3-D geometry of the urban “canopy” creates spatial variability in turbulence patterns. Second, the multiple sources and sinks of momentum, heat, moisture, and emissions creates spatial variability in fluxes and concentrations. Third, the impact of human activities to continually re-shape and alter, in new and distinct ways, the urban environment itself limits the long-term validity of any findings. In short, there is considerable uncertainty concerning the dynamics of the unique microclimates found within previously understudied and increasingly complex urban areas.

Both across cities and between cities, significant spatial and temporal variability in CO2 concentrations and fluxes can be expected as a consequence of the distribution of anthropogenic sources (mobile and fixed), processes of urban vegetation (including irrigation, and patterns of atmospheric convection and advection. Previous studies have shown that there is a marked and distinct diurnal cycle in the concentration of CO₂ with a morning peak attributable to anthropogenic (largely traffic), biogenic (nocturnal respiration), and meteorological (atmospheric stability) factors. In contrast, a mid-afternoon minimum can be attributed to vegetative photosynthesis and strong convective turbulence; concentrations then begin to rise again during the evening “rush-hour” traffic-flow.

....

The main roughness elements in urban environments are trees and buildings. Other than being large, trees and buildings share few characteristics of meteorological significance. Aerodynamically, buildings are true “bluff” bodies because of their impermeability, inflexibility, and sharp edges. When exposed to airflow they create strong positive and negative pressure differences over their surface, leading to flow separation and vortex shedding. Trees are also good generators of mechanical turbulence but buildings have to be judged as more effective roughness elements. The effects of smaller roughness elements, such as cars or paved surfaces, are minimum in comparison.

Three spatial scales are commonly utilized for studying urban environments:

-       the micro-scale (10¹–10²m) involves spatial differences in response to individual roughness elements (variability in building/canyon dimensions, trees) and proximity to localized emissions sources (e.g. roads, vegetation);

-       the local-scale (10²–10⁴ m) represents the integrated response of an array of roughness elements with spatial variability reflecting the unique characteristics of different neighborhoods/land-uses;

-       and the meso-scale (10⁴–10⁵ m) considers the city in its entirely, and differentiated from its surroundings, areas of forest, agriculture, etc.

The urban canopy layer (UCL) is defined as being from the ground to the mean height of the roughness elements, usually just below roof –level, where micro-scale effects of the site characteristics are dominated. The UCL is most clearly delineated in areas of high building density; it may be discontinuous or absent in less densely developed suburban areas.

The layer extending from the top of the UCL, to a height where urban surface influences are no longer perceptible, is defined the urban boundary layer (UBL). It includes the roughness sub-layer immediately affected by the individual roughness elements, the turbulent surface layer (local-scale), and the outer mixed layer (meso-scale).

....

Of those studies employing atmospheric-based measurement methods to study CO2 concentrations in urban environments to date, virtually all, with a few exceptions, have focused on the micro-scale, considering processes and patterns within the UCL. Inadequate attention has as yet focused on how micro-scale results can be extrapolated to larger scales and on how to accurately study the local-scale using atmospheric-based measurement methods. 

In regards to the latter, current debates focus on determining the height (or “depth”) of the roughness sub-layer, in which the perturbations caused by individual roughness elements are “blended” together due to atmospheric turbulence. It is as this height that instruments are to be placed in order to study at the local-scale that is spatially representative of a distinct urban neighbourhood/land-use. To be sure, placing instruments are greater heights than this leads to increased risk of incurring errors due to advection from dissimilar upwind surfaces and storage changes below the measurement level due to vertical flux divergence.

It is known that the height of the roughness sub-layer is a function of both the length/height of roughness elements (z_H) and their horizontal spacing. More recent research suggests that the latter factor may in fact be the primary determinant. It has been estimated that, as a general “rule-of-thumb”, instruments must be mounted at a height at least twice the mean height of the roughness elements (approximately 20-90m) to ensure that they are above the influence of individual roughness elements and, therefore, that the measurements represent an integrated response at the local-scale.

....

References

Grimmond, C.S.B., et al. (2006) Progress in measuring and observing the urban atmosphere.

Theoretical and Applied Climatology 84, 3-22.

Grimmond, C.S.B., et al. (2002) Local-scale fluxes of carbon dioxide in urban environments:

methodological challenges and results from Chicago. Environmental Pollution 116,

243-254.

Kanada, Manabu. (2007) Progress in Urban Meteorology: A Review. Journal of the

Meteorological Society of Japan 85B, 363-383.

Koerner, B. and J. Klopatek. (2002) Anthropogenic and natural CO2 emission sources in an

arid urban environment. Environmental Pollution 116, 45-51.

Nemitz, E., K. J. Hargreaves, A. G. McDonald, J. R. Dorsey, and D. Fowler (2002) Micrometerological Measurements of the Urban Heat Budget and CO₂ Emissions on a City Scale. Environ. Sci. Technology 36, 3139-3146.

Oke, T.R., et al. (1988) The urban energy balance. Progress in Physical Geography 12, 471-

483.

Oke, T.R., et al. (1989) The Micrometeorology of the Urban Forest. Philosophical

Transactions of the Royal Society of London 324, 335-349.

Wentz, Elizabeth A., et al. (2002) Spatial Patterns and Determinants of Winter Atmospheric

Carbon Dioxide Concentrations in an Urban Environment. Annals of the Association of American Geographers 99(1), 15-28.

Random Picture and Maps

I posted some pictures and maps I have that may be usefull for our website!
- Angela.

Montreal Land Use Map: map showing land use in montreal from the City of Montreal website.

Drivers to Work: Here is a map showing the percentage of drivers for each bourough from The City of Montreal website (Source is Stats Canada though).

Studay Area: This is a Satelite image from Google maps.

Site Area: Map from google maps.

3D Site Area: From Google Earth.

Mc Tavish and Burnside Wind Speed and Direction (Oct 21-22)

I looked at wind speeds and directions from thursday 21st to friday 22nd. The attached graphs show you what I have found out. First of all, I realised that the Burnside data (for whatever reason) is shifted by 4 hours. So the wind data are recorded with a time tb = tt + 4. To correct for this difference I simply subtracted 4 hours in the time columns for burnside. That is why the burnside data actually starts at t = -4. Note that the datasets end at 8pm local time on the 22nd October (that means at t = 44h, 4 hours before midnight).
If we correct for this shift the two data records correlate quite well. However, this is only based on qualitative estimation. As you can see from the Windrose plots, during relatively large time intervals Burnside and McTavish have more or less the same wind direction.
However, I tried some regression analysis and the correlation coefficients for the wind direction is always very low. That mean we don't have a quantitative proof yet to confirm our hypothesis. Maybe we can ask one of the profs to find out how we can use statistics to proof our finding quantitatively.

- Jan-erik

Weekend CO2 Events

Over the weekend I witnessed a few potential sources of CO2. A building was on fire Friday afternoon and Saturday day and night University street was closed for construction on the sewers.

Friday, on René-Lévesque Blvd. near the intersection with de Lorimier Ave. at 2 p.m. fire crews were on the scene of a two-alarm blaze.

Saturday, morning till night, university street right next to our machine was emmitting this huge cloud of white smoke. I asked the workers what they were doing and they said repairing the sewers. (See pictures posted below, taken at 10pm Saturday night).

Next week I think it would be cool to see if we can detect these events with the use of piccaro and wind speed and directions!

- Angela