The EPiCC Vancouver Experiment : How do urban vegetation - - PowerPoint PPT Presentation

The EPiCC Vancouver Experiment : How do urban vegetation characteristics and garden irrigation control the local scale energy balance?

Andreas Christen (1), B. Crawford(1), N. Goodwin(2,5), R. Tooke(2), N. Coops(2), C.S.B. Grimmond(3), T. R. Oke(1), and J. A. Voogt(4)

(1) University of British Columbia, Department of Geography, Atmospheric Science Program,. (2) University of British Columbia, Department of Forest Resource Management, Vancouver, Canada (3) King’s College London, Department of Geography, London, UK (4) University of Western Ontario, Department of Geography, London, Canada (5) Department of Natural Resources, Queensland Government, Brisbane, Australia.

Motivation for this study

Environmental Prediction in Canadian Cities (EPiCC) network: Include an urban canopy parameterization (UCP) in Canada’s weather forecasting system. Contribute to models that will support water conservation and support sustainable design in Canadian cities.

See also: Voogt et al., paper J.1.4 (same conference, Tuesday, 9:15, Room 124A)

Va08o Va08s Cc97 Sa91u Va92s Cc95 Ma01u Me03h Me03m Me03l Ba02u1 Ba96 Me93 Va92i Ba02u3 Mo05 Lo01 Ba02u2 Tu90u Ba02s1 Oa03r To98 Ch92 Ch95 Mi95 Ac93 Ac94 Sg94 Va83 Bm01

Urban Canopy Parameterizations (UCPs)

Plan area fractions

Urban energy balance field studies:

Va08o Va08s Cc97 Sa91u Va92s Cc95 Ma01u Me03h Me03m Me03l Ba02u1 Ba96 Me93 Va92i Ba02u3 Mo05 Lo01 Ba02u2 Tu90u Ba02s1 Oa03r To98 Ch92 Ch95 Mi95 Ac93 Ac94 Sg94 Va83 Bm01

Urban Canopy Parameterizations (UCPs)

Plan area fractions

Traditional SVAT schemes work well here Urban energy balance field studies:

Va08o Va08s Cc97 Sa91u Va92s Cc95 Ma01u Me03h Me03m Me03l Ba02u1 Ba96 Me93 Va92i Ba02u3 Mo05 Lo01 Ba02u2 Tu90u Ba02s1 Oa03r To98 Ch92 Ch95 Mi95 Ac93 Ac94 Sg94 Va83 Bm01

Urban Canopy Parameterizations (UCPs)

Plan area fractions

Traditional SVAT schemes work well here Urban energy balance field studies: UCPs have been tested here, and work well

Va08o Va08s Cc97 Sa91u Va92s Cc95 Ma01u Me03h Me03m Me03l Ba02u1 Ba96 Me93 Va92i Ba02u3 Mo05 Lo01 Ba02u2 Tu90u Ba02s1 Oa03r To98 Ch92 Ch95 Mi95 Ac93 Ac94 Sg94 Va83 Bm01

Urban Canopy Parameterizations (UCPs)

Plan area fractions

UCPs combined with SVATs do not work so well here, or have not been tested. Traditional SVAT schemes work well here Urban energy balance field studies: UCPs have been tested here, and work well

The Vancouver Validation Experiment

Simultaneously operated energy balance and hydrology sites in two contrasting neighborhoods in the City of Vancouver, BC, Canada and at a rural reference site to address the questions:

The Vancouver Validation Experiment

What is the role of anthropogenic water release associated with irrigation / sprinkling of urban green-space in the urban energy balance? Simultaneously operated energy balance and hydrology sites in two contrasting neighborhoods in the City of Vancouver, BC, Canada and at a rural reference site to address the questions:

The Vancouver Validation Experiment

What is the role of anthropogenic water release associated with irrigation / sprinkling of urban green-space in the urban energy balance? Are the wet-dry contrasts of adjacent urban surfaces (that result from irrigation and paving) boosting evaporation in a non-linear fashion? Simultaneously operated energy balance and hydrology sites in two contrasting neighborhoods in the City of Vancouver, BC, Canada and at a rural reference site to address the questions:

Building and population density 9 Bldg. / ha 30 Inh. / ha 19 Bldg. / ha 60 Inh. / ha Irrigation 61 % automatic 34 % manual 5 % none 1 % automatic 79 % manual 20 % none Vegetation λv = 56% High amount of tall trees

• n streets and private lots

λv = 44% Street trees, but very few trees on private lots. Vancouver-Sunset

Study Sites

Vancouver-Oakridge

Vancouver, BC, Canada

Eddy covariance Fluxes of sensible heat, latent heat (evapotranspiration) Net all-wave radiation

Soil hydrology observations

8 sites

CR10 X Logger Surface Wetness Soil moisture -5cm Soil Temperature -5cm

Rural reference site ‘Westham Island’ with non-irrigated, non-managed grassland

QE / Q* Summer 2008

Ensemble Energy Balance

Ensemble diurnal course, Aug. 11 to 17, 2008

Urban-rural differences

Ensemble diurnal course, Aug. 11 to 17, 2008

The ‘tiling’ approach for urban surfaces

QE = λvQEv + (1 − λv)QEi

Summation of QE based on fraction

The ‘tiling’ approach for urban surfaces

QE = λvQEv + (1 − λv)QEi

Summation of QE based on fraction

1 2 3 4 5 0.2 0.4 0.6 0.8 1

QE (MJ d-1 m-2)

Measured Oakridge Measured Sunset Rural

Vegetation fraction λv

P r e d i c t e d b y s u m m i n g f r a c t i

• n

s

Average daily totals for Aug. 11 to 17, 2008

QEi = 0

Is a summation of fractions adequate?

β = QH / QE is greatly

• verestimated when

summing the urban and rural fractions. Hourly data from Aug 13, 14, 17, and 18 2008 (days with irrigation permitted)

βcalc = 1 λv + βrural − 1

375 750 1,125 1,500 1,875 2,250 2,625 3,000 Mon Tue Wed Thu Fri Sat Sun

1,777 2,807 2,405 2,760 1,340 1,413 1,438

Lawn sprinkling not permitted Lawn sprinkling permitted

Water consumption (l day-1 home-1) Week August 11 to 17, 2008

Daily average water consumption per home

375 750 1,125 1,500 1,875 2,250 2,625 3,000 Mon Tue Wed Thu Fri Sat Sun

380 1,410 1,008 1,363 1,397 1,397 1,340 1,397 1,397 1,413 1,438

Household use Lawn sprinkling fraction

Water consumption (l day-1 home-1) Week August 11 to 17, 2008

Partitioning water consumption

I 1.16 mm d-1

The water balance for Vancouver Oakridge

p

E F Δr ΔS 1.57 mm d-1 0.12 mm d-1 < 0.01 mm d-1

• 0.52 mm d-1

0.00 mm d-1

p + F + I = E + ∆r + ∆S

Residual term Measured by EC Measured by rain gauge Estimated via CO2 flux Measured by TDR Measured by water meters

Aug 11 to 17, 2008

Key points

Vegetation fraction significantly controls the partitioning of turbulent fluxes in the urban energy balance.

Acknowledgments: Canadian Foundation for Climate and Atmospheric Sciences (CFCAS), NSERC, BC hydro, the City of Vancouver, all home owners who agreed to install meters and sensors on their lawns, technical contributions by Jonathan Bau, Kate Liss, Rick Ketler, Zoran Nesic and Chad Siemens.

Key points

Vegetation fraction significantly controls the partitioning of turbulent fluxes in the urban energy balance. However, a simple summation (‘tiling’) of a ‘rural’ vegetated (SVAT) and a dry ‘urban’ impervious fraction (UCP) is was shown to be insufficient to model the summertime energy balance of the study area.

Acknowledgments: Canadian Foundation for Climate and Atmospheric Sciences (CFCAS), NSERC, BC hydro, the City of Vancouver, all home owners who agreed to install meters and sensors on their lawns, technical contributions by Jonathan Bau, Kate Liss, Rick Ketler, Zoran Nesic and Chad Siemens.

Key points

Vegetation fraction significantly controls the partitioning of turbulent fluxes in the urban energy balance. However, a simple summation (‘tiling’) of a ‘rural’ vegetated (SVAT) and a dry ‘urban’ impervious fraction (UCP) is was shown to be insufficient to model the summertime energy balance of the study area. Lawn irrigation was the most important water input during the analyzed week. Hence any appropriate modeling of the urban energy balance must take anthropogenic water input through lawn irrigation (and potentially advective effects) into account.

Acknowledgments: Canadian Foundation for Climate and Atmospheric Sciences (CFCAS), NSERC, BC hydro, the City of Vancouver, all home owners who agreed to install meters and sensors on their lawns, technical contributions by Jonathan Bau, Kate Liss, Rick Ketler, Zoran Nesic and Chad Siemens.