Inclusion of the TEB urban canopy model in GEM and MC2 for atmospheric modeling at

city scale

Aude Lemonsu

Remerciements :

Stéphane Bélair, Jocelyn Mailhot, Richard Hogue, Michel Jean

Gianpaolo Balsamo, Najat Benbouta, Bernard Bilodeau, Mario Benjamin, Frédéric Chagnon, Stéphane Chamberland, Michel Desgagné, Jean-Philippe Gauthier, Bruno Harvey, Vivian Lee, Alexandre Leroux, Gilles Morneau, Radenko Pavlovic, Pierre Pellerin, Sarah Roberts, Lubos Spacek, Linying Tong, Serge Trudel, Michel Valin, James Voogt, Yufei Zhu

Overview

1.Town Energy Balance (TEB)

2.Inclusion of TEB in GEM and MC2

3.Evaluation of the urban modeling system

4.Next …

Urban canopy model for parameterization of water and energy exchanges between canopy and atmosphere

Model specifically designed for built-up covers

3D but idealized geometry- Mean urban canyon- Isotropy of street orientations- No crossing streets

Specific processes inside canopy- Radiation trapping + shadow effect- Heat storage- Urban microclimate inside the street

Independent treatment of urban facets- Independent surface energy balance- Water and snow on roofs and roads

Town Energy Balance (TEB)

QH TrafficQE Traffic

QH IndustryQE Industry

Masson V, 2000: A physically-based scheme for the urban energy balance in atmospheric models. Bound.-Layer Meteor., 94, 357-397

(Masson 2000)

How to include cities in GEM & MC2?

Current versions of GEM and MC2 do not include specific parameterization for built-up covers

GEM and MC2 use a 1-km global LULC classification which includes 1 “URBAN” cover type (defined from the Digital Chart of the World, Danko 1992)

Cities can be represented by sand + large z0m

Urban covers must be taken into account as an independent type associated with its own surface scheme

Higher accurate urban LULC classifications are required to document spatial variability and diversity of urban landscapes

Danko D M, 1992: The digital chart of the world. GeoInfo Systems, 2, 29-36

Initial version of the Physics describes the surface like a mosaic of 4 different types of covers:

(1)Soils and vegetation(2)Glaciers(3)Water(4)Continental ice

+ (5)Aggregation

Each type is associated with a specific surface scheme

The fluxes are aggregated according to the fractions of each type

The inclusion of TEB in the Physics requires an additional type corresponding to built-up covers

New type in the surface mosaic

Sea ice

SoilVegetation Glaciers

Water

Urban

Urban cover characterization (1)

New 60-m land-use land-cover classification including 12 urban classes(Lemonsu et al. 2007)

High buildingsMid-high buildingsLow buildingsVery low buildingsSparse buildingsIndustrial areasRoads and parking lotsRoad mixDense residentialMid-density residentialLow-density residentialMix of nature and built

Montreal 60m LULC

classification

Lemonsu A, Leroux A, Bélair S, Trudel S, and Mailhot J, 2007: A general methodology of urban cover classification for atmospheric modelling, JAMC, in revision

Urban cover characterization (1)

New 60-m land-use land-cover classification including 12 urban classes

Each urban class is an arrangement of built-up covers and vegetation

The vegetated part can be decomposed in three different types: (1) trees, (2) grass, and (3) bare soil

A look-up table defines a set of parameters for each urban class:- fractions of built-up and natural covers - fractions of trees, grass and bare soil- building fraction- building height- roughness length for momentum- canyon aspect ratio- ratio wall/plane built surfaces- albedo and emissivity of roofs, roads, and walls- thermal properties of roofs, roads, and walls

Urban cover characterization (2)

The urban LULC classification is only produced for limited urban areas. It has to be coupled with the 1-km global LULC database

The new geophysical fields include:

VF (vegf) - fractions of the 26 classes of water, natural soils and vegetation

- normalized

UF (urbf) - fractions of the 12 urban classes- not normalized - including fractions of vegetated covers

Ground truthing

UF09

UF10

UF07

VF26

1-km LULC global classification Urban LULC classification

UF09

UF10

UF07

VF26

1-km LULC global classification

VF26

1-km LULC global classification+

Urban LULC classification

UF09

UF10

UF07

VF26

1-km LULC global classification

1-km LULC global classification+

Urban LULC classification

Urban cover characterization (2)

The urban LULC classification is only produced for limited urban areas. It has to be coupled with the 1-km global LULC database

The new geophysical fields include:

VF (vegf) - fractions of the 26 classes of water, natural soils and vegetation

- normalized

UF (urbf) - fractions of the 12 urban classes- not normalized - including fractions of vegetated covers

38 new cover fractions (6F, covf) are computed in the new routine calccovf.ftn called in inisurf1.ftn

The urban mask (UR, urban) is computed as the sum of the built-up fractions of the 12 urban classes

Inclusion of TEB in the RPN physics package is done by avoiding modifying the original version of the TEB’s code as much as possible

TEB is “plugged” to the Physics using two interface routines:- Initialization: initown.ftn90 called in inisurf1.ftn- Physics: town.ftn90 called in surface.ftn

These interface routines allow the transfer of the variables from the physics’ buses to the TEB’s code and inversely

A new key is included in the namelist &gement of gem_settings.nml

P_pbl_schmurb_s = ‘TEB’ (or ‘NIL’)

TEB’s code is already part of Physics v4.4 and is compatible with GEM v3.2.2 and MC2 v4.9.8

Inclusion of TEB in the Physics (1)

TEB’s input parameters (geometric parameters + material properties) are defined using the look-up table associated with the urban LULC classification

TEB’s prognostic variables:

Troof, Troad, Twall Roof, road and wall temperatures

Tcanyon, Qcanyon Canyon air temperature and humidityWSroof, WSroad Roof and road water reservoir

Tibld Internal building temperature Tiroad Deep road temperatureSnow variables for roofs and roads

- Initialized using other analyses (e.g. TT, TS, HU, …), if not available in the forcings

- Read in the analysis field if available (e.g. Cascade run)

Inclusion of TEB in the Physics (2)

Evaluation of the urban modeling system

Joint Urban 2003 (Allwine et al. 2004) is an atmospheric dispersion study held in Oklahoma City in July 2003

Gulf of Mexico

Urban PWIDS network

Evaluation of the urban modeling system

Joint Urban 2003 (Allwine et al. 2004) is an atmospheric dispersion study held in Oklahoma City in July 2003

CBD

ANL

PNNL

Soundings, sodars and radarsupwind and downwind the CBD

GEM-LAM 2.5km, 200x200 GEM-LAM 1km, 200x200

GEM-LAM 250m (IOP6), 200x400 GEM-LAM 250m (IOP9)

Boundary and initial condition of 2.5km GEM-LAM provided by GEM-regional model

2.5km GEM-LAM’s configuration = quasi-operational version

Mixing length calculated using:- Lenderink and Holtslag (2004) formulation for 2.5km and 1km GEM-LAM- Formulation derived from Blackadar and based on the grid size for 250m GEM-LAM

Vertical grid:- 58 levels (first level at 40 m above canopy level) for 2.5km GEM-LAM- More detailed inside the atmospheric boundary layer for 1km and 250m GEM-LAM

Numerical set-up (1)

Lenderink, G. and Holtslag A.A.M., 2004: An updated lengthscale formulation for turbulent mixing in clear and cloudy boundary layers. QJRMS, 130, 3405-3427

Surface schemes:- ISBA for vegetation and natural soils- TEB for built-up covers

Sensitivity tests: - Urban simulation: with TEB- No Urban simulation: city replaced by vegetation

Numerical integrations- IOP6: daytime period on July 16 2003- IOP9: nighttime period on July 26-27 2003

Numerical set-up (2)

ModelStarting date Integration

TimestepIOP6 IOP9 IOP6 IOP9

GEM-regional 2003071600 2003072600 39hr 36hr 450s

2.5km GEM-LAM 2003071606 2003072606 33hr 30hr 60s

1km GEM-LAM 2003071609 2003072612 24hr 24hr 30s

250m GEM-LAM 2003071612 2003072615 21hr 21hr 10s

IOP6July 161800 LST

Norman radiosounding (South of OKC)

IOP9July 270600 LST

IOP6

IOP9

MESONET operation network

12 rural

Stations

(MESONET)

13 urban

Stations

(PWIDS)

Canopy level UHIPositive at nightNegative at day

IOP6 IOP9

IOP6 IOP9

IOP6 IOP9

2100-2200 LST 0100-0400 LST

PNNL upwindANL downwind

Urban effects at night

Near-neutral layer observed at night in the first 300 m ABL warmer downwind than upwind the CBD

ObsModel

Urban effects at night

Vertical and horizontal structure of the UHI

Δθ = θ(Urban) – θ(No Urban)

21 22 23 00 01 02 03 04 05 06

Δθ (oC)

Δθ (oC)

50m acl - 0600 LST

Vertical extension of the UHI in the first 200 m Decrease of the vertical extension during the night

θ(50m)

21 22 23 00 01 02 03 04 05 06 21 22 23 00 01 02 03 04 05 06

Urban effects at night

Potential temperature anomaly

Large-scale horizontal temperature gradient induced by the nocturnal Low Level Jet Effect reinforced by the UHI near the surface

Δθa = θ(City) – θ(Upwind)

Urban No Urban

Δθa (oC)

θ(50m)

21 22 23 00 01 02 03 04 05 06 21 22 23 00 01 02 03 04 05 06

Urban effects at night

Potential temperature anomaly

Large-scale horizontal temperature gradient induced by the nocturnal Low Level Jet Effect reinforced by the UHI near the surface

Δθa = θ(City) – θ(Upwind)

Δθa (oC)

θ(50m)

No UrbanUrban

CRTI Project:

Weekly GEM-LAM simulations using the prototype configuration for the cities of Montreal and Vancouver

Collaborative research network on Environmental Prediction in Canadian Cities (EPiCC) funded by the CFCAS:

Canadian optimized version of TEB-ISBA taking into account the specifics of Canadian cities- Building materials- Vegetation- Snow and cold winter conditions

Modeling studies of the urban boundary layer over Montreal

Next…

TEB offline evaluation for MUSE 2005

MUSE 2005 documents the evolution of surface characteristics and energy budgets in a dense urban area during the winter-spring transition (17 March - 14 April 2005)

Lemonsu A, Bélair S, Mailhot J, Benjamin M, Chagnon F,Morneau G, Harvey B, Voogt J, Jean M, 2007: Overview and first results of the Montreal Urban Snow Experiment (MUSE) 2005, JAMC, in revision

TEB offline evaluation for MUSE 2005Air canyon temperature

Radiative surface temperatures (Walls)

Net all-wave radiation

Sensible heat flux

Latent heat flux

Residue

ObsModel