scale issues atmospheric modelling urban scale
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© Copyright Météo-France 1
Scale issues for atmospheric
modelling at urban scale
Valéry MASSON
Centre National de
Recherches Météorologiques
15 November 2017
ECMWF Workshop
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Cities & Climate
1st december 2015
IPCC synthesis report (2014):
In urban areas climate change is projected to increase risks for people, assets,
economies and ecosystems, including risks from heat stress, storms and extreme
precipitation, inland and coastal flooding, landslides, air pollution, drought, water
scarcity, sea level rise and storm surges (very high confidence)
)
.
• 2.7% of land areas
• 55% of world population
• 80% of GDP
(gross domestic product)
• 70% of Green-House Gases
emissions
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Cities & Climate
1st december 2015
World Weather Research Programme has 4 objectives, 2 related to urban:
1. High Impact Weather and its socioeconomic effect in the context of global change
Urban floods,
Heat & Pollution
in megacities, …
2.Urbanization:
Research & services for megacities
and large urban complexes
Several actions at international scale
Source: https://public.wmo.int
Source: Baklanov, WMO, (2015)
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Cities & Climate
1st december 2015
World Weather Research Programme has 4 objectives, 2 related to urban:
1. High Impact Weather and its socioeconomic effect in the context of global change
Urban floods,
Heat & Pollution
in megacities, …
2.Urbanizarion:
Research & services for megacities
and large urban complexes
scientific issues: […]
high-resolution modelling,
Grey zone, […]
Several actions at international scale
Source: https://public.wmo.int
Source: Baklanov, WMO, (2015)
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Scale issues for modelling at urban scale
1) Mesoscale-impacts on thunderstorms
2) Local-scale impacts: the Urban Heat Island
3) Modelling
4) Description of the cities for models: the « LCZ »
5) Which scale for adaptation strategies ?
ECMWF Workshop
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Scale issues for modelling at urban scale
1) Mesoscale-impacts on thunderstorms
2) Local-scale impacts: the Urban Heat Island
3) Modelling
4) Description of the cities for models: the « LCZ »
5) Which scale for adaptation strategies ?
ECMWF Workshop
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Meso-scale Impacts on Thunderstorms
1st december 2015
Source: Bornstein and Leroy (1985)
2 mains urban effects
Analysis of 2 summers
of convection above NYC
& enhancement
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Meso-scale Impacts on Thunderstorms: splitting
1st december 2015
The splitting effect is mainly due to the increased roughness.
Such effects are mostly studied in USA and China
This may be because megacities are prominent obstacles in flat regions
Source: Niyogi et al, 2006
1st december 2015
Observed radar reflectivity (dBz) from OKC radar
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1st december 2015
Meso-scale Impacts on Thunderstorms: enhancement
Source: WMO website
1st december 2015
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Meso-scale Impacts on Thunderstorms: enhancement
Cas study of 26 August 2011 of flash flood on Tokyo (TOMACS campaign)
Canadian model
GEM at 250m
with
urban scheme
without
urban scheme
Source: Bélair et al,
2015
1st december 2015
Radar
observations
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Meso-scale Impacts on Thunderstorms: enhancement
1st december 2015
Cas study of 26 August 2011 of flash flood on Tokyo (TOMACS campaign)
Source: Bélair et al,
2015
1st december 2015
Canadian model
GEM at 250m
with
urban scheme
Radar
observations
GEM at 2.5km GEM at 1km
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Scale issues for modelling at urban scale
1) Mesoscale-impacts on thunderstorms
2) Local-scale impacts: the Urban Heat Island
3) Modelling
4) Description of the cities for models: the « LCZ »
5) Which scale for adaptation strategies ?
ECMWF Workshop
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1st december 2015 © Copyright Météo-France
Urban Heat Island (UHI)
One summer night in Toulouse (using measurements from 20 met stations)
14°C
20°C17°C
Source: J. Hidalgo
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Modification of the Surface Energy Balance
Source: Nunez & Oke, 1976
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Modification of the Surface Energy Balance
1st december 2015
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1st december 2015 © Copyright Météo-France
Modification of the Surface Energy Balance
Surface Energy Balance, Singapore
Source: Roth et al, 20152015
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Scale issues for modelling at urban scale
1) Mesoscale-impacts on thunderstorms
2) Local-scale impacts: the Urban Heat Island
3) Modelling
4) Description of the cities for models: the « LCZ »
5) Which scale for adaptation strategies ?
ECMWF Workshop
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1st december 2015 © Copyright Météo-France
The old modelling way: rocks !
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The Urban Canopy Models (UCM)
1st december 2015
Oke et al (2017), Krayenoff (2017)
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The Urban Canopy Models (UCM)
1st december 2015
Oke et al (2017), Krayenoff (2017)
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Key physical processes of urban climate
3D surface (street canyon)
Radiative exchanges between walls & roads
Heat Fluxes, Water & Snow, Friction
Allows simulation of :
• Impact on Boundary Layer
• Street micro-climate
• Urban Heat Island
Coupled in many meteorological models
The Town Energy Balance (TEB) model
Modelling the Surface Energy Balance: TEB
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• Energy consumption of buildings
1) Building Energy Module
Wintertime building’s
energy consumption
in Toulouse, France
(Bueno et al 2012, Pigeon et al 2014, Schoetter et al 2017)
Modelling the Surface Energy Balance: TEB
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• Energy consumption of buildings
2) Surface Boundary Layer scheme
3) Three types of Urban vegetation
• Gardens, Street trees, green roofs
1) Building Energy Module
Modelling the Surface Energy Balance: TEB
Validation on Basel
(BUBBLE experiment)
Hamdi and Masson 2008
Lemonsu et al 2012, De Munck et al 2013,
Redon et al 2017
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CO2 fluxes in cities
Simulated Buildings + vegetation CO2 fluxes
4) Exemple of applications
(Goret et al 2018 in prep.)
(TEB)
wintertime, 2005
Modelling the Surface Energy Balance: TEB
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Modelling the Surface Energy Balance: TEB
1st december 2015
UHI simulation in Toulouse (France)
MesoNH model, 250m of resolution
average UHI on 2004 summer
Cloudy days Sunny days
Source: R. Schoetter
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Scale issues for modelling at urban scale
1) Mesoscale-impacts on thunderstorms
2) Local-scale impacts: the Urban Heat Island
3) Modelling
4) Description of the cities for models: the « LCZ »
5) Which scale for adaptation strategies ?
ECMWF Workshop
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Description of cities: the « Local Climate Zones »
Tombouctou,Mali
From: Steward and Oke (2012)
A typology :-recognized by the Urban Climate community
-10 urban classes
-Link with atmospheric models being developed
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World Urban Database initiative
Tombouctou,Mali
A methodology to map cities:-Using satellite images
-100m of resolution
-Produces LCZ maps by local experts
-Approx. 100 cities
www.wudapt.org
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From Buildings data, e.g. Open Street Map
Determination of model urban parameters from building’s databases
1st december 2015
Urban parameters from OSM
Source: Samsonov et al (2015)
LCZ from French Building’s Database
Source: Hidalgo et al (2017)
Moscow
Paris
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Architecture varies from one location to another
At world scale )
Architecture
for mid-rise
buildings
Seattle Copenhagen
Andalousia
Tombouctou,Mali
Quito, EquadorShanghai
Scale issues in
building’s description
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Architecture
for houses
Seattle
Copenhagen
Andalousia
Tombouctou,Mali
Quito, Equador
Shanghai
At world scale )
Architecture varies from one location to another
Scale issues in
building’s description
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Scale issues for modelling at urban scale
1) Mesoscale-impacts on thunderstorms
2) Local-scale impacts: the Urban Heat Island
3) Modelling
4) Description of the cities for models: the « LCZ »
5) Which scale for adaptation strategies ?
ECMWF Workshop
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What scale urban planners wish
• In order to do the link with urban planners and stake holders
– The pertinent spatial scale is …
City of Nantes
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What scale urban planners wish
• In order to do the link with urban planners and stake holders
– The pertinent spatial scale is … the urban block !!!
City of Nantes
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Adaptation of cities to climate change
In 2100, air-conditioning will probably be necessary
Air-conditioning
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1st december 2015
Adaptation of cities to climate change
In 2100, air-conditioning will probably be necessary
With projected air-conditioning(by 2030)
Without cooling
Source : de Munck et al 2013
+2°C
Temp
érature n
octu
rne (°C
)
33
32
31
30
29
28
27
26
25
Air conditioning increases heat outsideNeeds even more cooling !Impacts people without access to air-conditioning
Air-conditioning
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1st december 2015
Adaptation of cities to climate change
In 2100, air-conditioning will probably be necessary
But one can reduce its use !
Air-conditioning Heat waveEmergency practices
Buildings renovation
Urban Vegetation,
water ressources
Urban planning
• Levers that combine mitigation and adaptation
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1st december 2015
Adaptation of cities to climate change
In 2100, air-conditioning will probably be necessary
But one can reduce its use !
Air-conditioning Heat waveEmergency practices
Buildings renovation
Urban Vegetation,
water ressources
Urban planning
• Levers that combine mitigation and adaptation
Comportements et usages
• Evolution of behaviours : very efficient
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1st december 2015
Urban vegetation
Green roofs contribute to building insulation
Ground vegetation and trees are efficient to cool the air
Variation de température
Variation of temperature caused by an increase of 50%
of ground vegetation in available spaces (car parks, sidewalks, places,...)
Source : de Munck 2015
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Grand Paris (Groupe Descartes)
2008
~ 4°C
2030
~ 2°C
Scenario: Local vegetable farming around the city Short supply chains & food governance Cooling of 2 to 3°C
Source : Yves Lion et coll. 2009
The countryside can cool the city
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1st december 2015
Urban Climate Modelling … only starting
Kusaka et al 2012
August Tmin
2000s
August Tmin
2070s
1 month 3km-resolution simulation in
present and future climate in Japan
Need of downscalling methods
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1st december 2015
Urban Climate Modelling … only starting
Kusaka et al 2012
August Tmin
2000s
August Tmin
2070s
1 month 3km-resolution simulation in
present and future climate in Japan
Hamdi et al, 2014
Climate
simulation
at 4km
Downscalling
at 1km
Brussels
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Conclusions
1) Urban scale is meteorologically is at least in the greyzone
2) Specific processes and impacts
3) The city actors want very fine scale …
… even for weather forecast !
ECMWF Workshop
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Urban Weather Forecast
• Weather Forecast during the PAN-American games (Toronto 2015)
Simulations at 250m of resolution
Source: Leroyer et al 2015
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Urban Weather Forecast
•Forecast during the PAN-American games (Toronto 2015)
Source: Leroyer et al 2015
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ECMWF Workshop
Thank
You