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 km 2 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 Urban Rural 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.

UHI in Sao Paulo Observational Studies ● Barros & Lombardo 2016: comparison between land use (leaf area index) and surface temperature – satellite data 28 th 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 Ribeiro, F. N., de Oliveira, A. P., Soares, J., de Miranda, R. M., Barlage, M., & Chen, F. (2018). ● Case studies 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 Topography ● 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 Land use ● 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

Results – Sea breeze days Day Night Daily Average ● Sea breezes displace UHI core to the northwest – during the day, when it occurs ● Daily average is highly influenced by sea breeze

Results – Cold front days Day Night Daily Average ● Cold fronts displace UHI core to the northwest ● Both day and nighttime UHI are similar

Results – No front days Day Night Daily Average ● Nighttime UHI is more intense ● Daytime UHI reflects more urbanized areas ● Both day and nighttime UHI contribute to the daily average

Results – UHI Intensity Sea breeze Cold front Average No front

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]. Thank you! ● 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.