ICUC10 Numerical characterization of the Urban Heat Island in Sao - - PowerPoint PPT Presentation

ICUC10

Numerical characterization of the Urban Heat Island in Sao Paulo – Brazil – during summer

Flávia Noronha Dutra Ribeiro School of Arts, Sciences and Humanities University of Sao Paulo - Brazil

UHI in Sao Paulo

• 21 million inhabitants
• 8000 km2 of area
• 50 km from the coast
• Escarpment at South,

mountain chain at North, massif at West

• Frequent cold fronts and sea breeze propagations that impact air

quality conditions

• Sea breeze decreases UHI effects and may affect air quality

conditions (Ribeiro et al. 2018)

• There is a correlation between increased temperatures and annual

mortality rates associated with respiratory and cardiovascular diseases (Ribeiro Sobral, 2005)

UHI in Sao Paulo Observational Studies

• Ferreira et al. 2011: monthly an hourly averages 2004

– Rural stations only South and Southeast from the urban area – Maximum values during the afternoon

• Project MCITY: 3 micrometeorological towers (Oliveira et al.

2018)

Ferreira M.J., Oliveira A.P., Soares J., Codato G., Bárbaro E.W. and Escobedo J.F., 2011: Radiation balance at the surface in the City of São Paulo,

• Brazil. Diurnal and seasonal variations.

Theoretical and applied climatology. (DOI: 10.1007/s00704-011-0480-2).

UHI in Sao Paulo Observational Studies

• Silva et al. 2017: statistical analysis of surface station data from

2002 to 2011

– Rural station South from the urban area – UHI diurnal pattern in agreement with Ferreira et al. 2011 – Substantial spatial variability – Sea breeze influence

Silva, F. B., Longo, K. M., & de Andrade, F. M. (2017). Spatial and Temporal Variability Patterns of the Urban Heat Island in São Paulo. Environments, 4(2), 27. Urban Rural

UHI in Sao Paulo Observational Studies

• Barros & Lombardo 2016:

comparison between land use (leaf area index) and surface temperature – satellite data 28th September 2011

– Temperature differences up to

8°C

– Substantial spatial variability – Vegetated areas decrease

surface temperature

• Case study

Barros, H. R., & Lombardo, M. A. (2016). A ilha de calor urbana e o uso e cobertura do solo no município de São Paulo-SP. GEOUSP: Espaço e Tempo (Online), 20(1), 160-177. In portuguese.

UHI in Sao Paulo Numerical Studies

• Freitas et al. 2007 (winter)

– UHI accelerates SB

propagation before the urban area and decelerates after

• Ribeiro et al. 2018

– Topography – Synoptic conditions displace

UHI center

– Sea breeze and cold fronts

temporarily mitigate UHI

• Case studies

Ribeiro, F. N., de Oliveira, A. P., Soares, J., de Miranda, R. M., Barlage, M., & Chen, F. (2018). Effect of sea breeze propagation on the urban boundary layer of the metropolitan region of Sao Paulo, Brazil. Atmospheric Research. https://doi.org/10.1016/j.atmosres.2018.07.015

The summer of 2014

• Highest monthly average maximum temperature since 1933 –

31.7 °C

• Highest temperature recorded – 36.1 °C
• Highest monthly average temperature (same as February 2003)

– 24.2 °C

• Second highest value of total hours of sunshine – 244.7 h

(climatological mean is 151.1 h)

• Low values of total precipitation – 199.3 mm (climatological

mean is 231.9 mm)

• These conditions created an UHI intensity significantly higher

than the average of the 10 preceding years

(http://www.meteo.fr/cic/meetings/2015/ICUC9/LongAbstracts/ucp1-6-2241081_a.pdf)

http://www.estacao.iag.usp.br/Mensais/Janeiro2014.pdf

Objectives

• What are the average UHI patterns in Sao

Paulo?

– Numerically characterize the Urban Heat Island in

the Sao Paulo Metropolitan Area

– Investigate the effect of cold fronts and sea breezes

in the Urban Heat Island average pattern in January

– Compare the UHI in January 2014 with the ten year

average UHI for the same month

Methodology

• WRF model
• January – from 2004 to 2014
• 10 year average compared to 2014

(separating sea breeze days and cold front days, based on observations)

• 3 nested domains
• Innermost domain: 107 km E-W and 65

km N-S (grid spacing 1 km)

• 38 vertical levels
• Single layer urban canopy model

SLUCM (Chen et al. 2011)

• YSU boundary layer scheme
• Noah LSM scheme
• ERA-Interim reanalysis for initial and

boundary conditions

• SST updated every 6 hours

Topography Land use

Results – Sea breeze days

• Sea breezes displace UHI

core to the northwest – during the day, when it

• ccurs
• Daily average is highly

influenced by sea breeze

Day Night Daily Average

Results – Cold front days

• Cold fronts displace

UHI core to the northwest

• Both day and nighttime

UHI are similar

Day Night Daily Average

Results – No front days

• Nighttime UHI is more intense
• Daytime UHI reflects more

urbanized areas

• Both day and nighttime UHI

contribute to the daily average Day Night Daily Average

Results – UHI Intensity

Sea breeze Cold front No front Average

Results – Summer of 2014

2014 Average 2004-2013 Sea breeze 2004-2013

• 2014 shows a similar pattern

than the sea breeze days average, but with a more intense UHI in the afternoon, probably related to the higher incoming solar radiation

Conclusions

• UHI is frequently displaced to the north due to sea breeze and

cold front propagation

• Sea breeze days show more diurnal variability in the UHI intensity
• Nocturnal UHI is more consistent, during the day the UHI intensity

varies, in average, from 1°C to 3.5 °C

• Sea breeze and cold fronts tend to cause a decrease in UHI

intensity after their propagation

• 2014 showed an sea breeze day pattern with a more intense UHI

in the early afternoon

• This work is a first step towards a climatology of the UHI in Sao

Paulo

• Future work: investigation of the vertical structure of the UHI for

the different days (sea breeze, cold front, no front)

Acknowledgements

• This work was supported by the Sao Paulo Research

Foundation – FAPESP [grants number 2014/04372-2 and 2018/11217-4] and the National Council for Scientific and Technological Development – CNPq [grant number 204726/2014-0].

• References not cited in slides:

– Chen, F., Kusaka, H., Bornstein, R., Ching, J., Grimmond, C. S. B., Grossman‐Clarke, S., ... & Sailor,

• D. (2011). The integrated WRF/urban modelling system: development, evaluation, and applications

to urban environmental problems. International Journal of Climatology, 31(2), 273-288.

– Freitas, E. D., Rozoff, C. M., Cotton, W. R., & Dias, P. L. S. (2007). Interactions of an urban heat

island and sea-breeze circulations during winter over the metropolitan area of São Paulo, Brazil. Boundary-layer meteorology, 122(1), 43-65.

– Ribeiro Sobral, H. (2005). Heat island in São Paulo, Brazil: effects on health. Critical Public Health,

15(2), 147-156.

Thank you!