session3 meier fred scherer

8/8/2019 Session3 Meier Fred Scherer

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F. Meier & D. Scherer

Technische Universitt Berlin, Institute of Ecology, Chair of Climatology,Rothenburgstr. 12, D-12165 Berlin ([email protected]

)

Trees in the concrete jungle: spatial and temporal

patterns of tree crown temperature in an urbanenvironment

Cracks in the concrete jungleThe 5th international urban ecology congress October 22-24, Berlin


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Outline

Introduction: trees and urban climate

Objectives and research questions

Study site and experimental setup: Berlin Steglitz

Results: spatial and temporal pattern of leaf temperature

Conclusion

References

Spatial and temporal patterns of tree crown temperature in an urban environment


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Trees produce distinct meteorological and climate effects at all scales inurban environments (e.g. Brahe 1976, Heisler 1986, Oke 1989)

Reduction of air temperature, surface temperature and building energyuse, but cooling effect may differ from site to site (e.g. Grimmond et al. 1996,Spronken-Smith & Oke 1998, Akbari et al. 2001, Shashua-Bar et al. 2010)

Modification of solar and thermal radiation concerning the human energy

balance (e.g. Matzarakis & Streiling 2004, Meyer et al. 2009)

Modification of wind field in street canyons e.g. dispersion processes ofpollutants (Gromke & Ruck 2007)

Micro-scale advection (e.g. oasis or clothesline effect) due to spatialheterogeneity influences latent heat flux from urban vegetation (Oke 1987,Hagishima et al. 2007)

Introduction: trees and urban climate



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Objectives and research questions

Assessment of spatial and temporal variability of leaf temperatures forsingle tree crowns by means of Time-Sequential Thermography (TST)

Provide basic data on leaf temperature in an urban environment(diurnal cycle & long-term) in order to validate numerical models or leaftemperature estimations based on meteorological variables

Are there differences between individual urban trees in our study areaand if so, how big are these differences during a diurnal cycle?

What influence has the location within the city?

How does the temperature of leaf depend on atmospheric and plantvariables?



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Study site and experimental setup

Air temperature

Relative humidity

Wind speedWind direction

TIR camera system records one image per minute

ETST = Tleaf4 * * + (1- ) * Eroof ( = leaf emissivity 0.98)

Eroof (W/m2)

ETST (W/m2)

High-rise

building

120m



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Period 1th to 22th July 2010 Tree mask includes 59 trees



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693131213Trees

TiliaQuercusPopulusFagusConiferAcer

Air temperature

Relative humidity

Wind speed

Wind directionGlobal radiation


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Results: Weather July 2010



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Results: daytime spatial pattern


11th July 2010 11:30 12:00 CET

59 tree crowns (median value )

T=Tsurface/leaf - Tair


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Results: daytime spatial pattern

Mean T day pattern 11:30 12:00 CET

Populus

Treessurrounded bysealed surfaces


Clump ofpark trees


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Results: night time spatial pattern


11th July 2010 23:30 24:00 CET

59 tree crowns (median value )

T=Tsurface/leaf - Tair


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Results: night time spatial pattern

Park trees over grass


Mean T night pattern 23:30 24:00 CET


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Results: temporal pattern

Temporal variability of leaf temperature average diurnal cycle1th to 22th July 2010 (30 min averages)

~ 1.0 K

~ 3.0 K



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Results: temporal pattern


T = Tcrown - Tair

Temporal variability of T average diurnal cycle1th to 22th July 2010 (30 min averages)

39 cm235 cm239 cm233 cm2-98 cm2Leaf size

TiliaQuercusPopulusFagusConiferAcer


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Results: atmospheric conditions air temperature


Acer

Populus

Conifer

Fagus

Quercus

Tilia


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Results: atmospheric conditions - vapour pressure


Acer

Populus

Conifer

Fagus

Quercus

Tilia


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Conclusion

Leaf temperature varies more than 3 K at day and up to 1 K at nightin the study area

Trees over sealed surfaces showed higher temperatures than thoseover grass and non-sealed surfaces, which is in accordance to further

studies (Leuzinger et al., 2010; Kjelgren and Montague, 1998).

Populus trees showed the lowest daytime temperature as a result ofits canopy architecture (small fluttering leaves) or higher transpirationrates? However, Populus showed the highest temperature during thenight!

Acer trees showed the highest daytime temperature probably as aresult of its big leaves? However, Acer showed the lowest temperature

during the night!Trees cope with very high air temperatures and vapour pressure

deficits!



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ReferencesAkbari, H., M. Pomerantz, H. Taha, 2001: Cool surfaces and shade trees to reduce energy use and improve air quality in urban

areas. Solar Energy, 70, 295-310.

Brahe, P., 1976: Klimatische Auswirkungen von Gehlzen auf umbauten Stadtpltzen. Das Gartenamt, 23, 61-70.

Grimmond, C.S.B., C. Souch, M.D. Hubble, 1996: Influence of tree cover on summertime surface energy balance fluxes, SanGabriel Valley, Los Angeles. Climate Research, 6, 45-57.

Gromke, C., B. Ruck, 2007: Influence of trees on the dispersion of pollutants in an urban street canyon experimentalinvestigation of the flow and concentration field. Atmospheric Environment, Vol. 41, 3387 - 3302.

Hagishima, A., K. Narita, J. Tanimoto, 2007: Field Experiment on transpiration from isolated urban plants. HydrologicalProcesses, 21, 1217-1222.

Heisler, G.M. 1986: Effects of individual trees on the solar radiation climate of small buildings. Urban Ecology, 9, 337-359.

Kjelgren, R., T. Montague, 1998: Urban tree transpiration over turf and asphalt surfaces. Atmospheric Environment, 32, 35-41.

Leuzinger, S., R. Vogt, C. Krner, 2010: Tree surface temperature in an urban environment. Agricultural and Forest

Meteorology, 150, 56-62.Matzarakis, A., S. Streiling, 2004: Stadtklimatische Eigenschaften von Bumen. Falluntersuchung in Freiburg im Breisgau.

Gefahrstoffe-Reinhaltung der Luft, 64, 307-310.

Mayer, H., S. Kuppe, J. Holst, F. Imbery, A. Matzarakis, 2009: Human thermal comfort below the canopy of street trees on atypical Central European summer day. In: Mayer, H., A. Matzarakis (Eds.): 5th Japanese-German Meeting on UrbanClimatology. Berichte des Meteorologischen Instituts der Albert-Ludwigs-Universitt Freiburg, Nr. 18, 211-219.

Oke, T.R., 1987: Boundary Layer Climates. Second Edition, Routledge.Oke, T.R., 1989: The micrometeorology of the urban forest. Philosophical Transactions of the Royal Society of London. Series

B, Biological Sciences, 324, 335-349.

Spronken-Smith, R.A., T.R. Oke, 1998: The thermal regime of urban parks in two cities with different summer climates.International Journal of Remote Sensing, 19, 2085-2104.

Shashua-Bar, L., O. Potchter, A. Bitan, D. Boltansky, Y. Yaakov, 2010: Microclimate modelling of street tree species effects

within the varied urban morphology in the Mediterranean city of Tel Aviv, Israel. International Journal of Climatology, 30, 44-57.



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Thanks for your attention!

Acknowledgement

Marco Otto, Britta Jnicke, Albert Polze (Chair of Climatology, TU Berlin) andMoritz von der Lippe (Chair of Ecosystem Science / Plant Ecology, TU Berlin)


session3 meier fred scherer

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