Characterising the nocturnal surface and canopy heat islands in Oklahoma City, USA according to the atmospheric stability

This study aims to evaluate the land surface temperature (LST) and the thermal characteristics of the Urban Canopy Layer (UCL) of the urban canyon in Avenida Rio Branco in the Central Business District (CBD) of Rio de Janeiro during summer. In order to conduct this evaluation, two methods were employed: 1) TIRS Landsat-8 sensor for data selection and processing (latest generation, 2011-2020); ; 2) field survey using nine sampling points — seven along two mobile transects, one fixed point, and one vertical measurement point, which required the use of a RPA (Remotely Piloted Aircraft). Three categories of analysis were established for the field survey based on the prevailing synoptic situations: stability, instability, and post-instability. The CBD is characterized by extensive areas with surface heat islands, in which temperatures were higher than 38.9°C; the areas with milder LSTs were Campo do Santana, Avenida Rio Branco, and one of the Mixed-Use Zones (Praça Mauá). With respect to Rio Branco Avenue, the LST niches of lowest elevation were derived through building shadowing; however, the orbital data diverged from the observation data of the ten field-study days. In situ data revealed that the characteristics urban morphology of Avenida Rio Branco is susceptible to the formation of heat islands, presenting heat islands of very strong magnitude (over 6.1°C) in atmospheric stability, strong magnitude (4.1-6.0°C) in atmospheric instability, and moderate magnitude (2.1°C-4.0°C) in post-atmospheric instability. Despite the synoptic situation, thermal cores were concentrated at 1 pm. The intersection between Avenida Rio Branco, Rua do Ouvidor, and Praça Mauá stored most of the solar energy received during the day due to the greater sky obstruction caused by the verticalization. Finally, vertical analysis demonstrated the formation of a thermal inversion on the night of the highest mean air temperature (29.5°C), probably, due to the roughness and number of buildings in the urban canyon.

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Urban heat islands in Hong Kong: Bonding with atmospheric stability

Atmospheric Science Letters ◽

10.1002/asl.1032 ◽

2021 ◽

Author(s):

Weiwen Wang ◽

Bingyin Chen ◽

Yong Xu ◽

Wen Zhou ◽

Xuemei Wang

Keyword(s):

Hong Kong ◽

Atmospheric Stability ◽

Urban Heat Islands ◽

Heat Islands ◽

Urban Heat

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Urban Canyon in the CBD of Rio de Janeiro (Brazil): Thermal Profile of Avenida Rio Branco during Summer

Atmosphere ◽

10.3390/atmos13010027 ◽

2021 ◽

Vol 13 (1) ◽

pp. 27

Author(s):

Lidiane de Oliveira Lemos ◽

Antonio Carlos Oscar Júnior ◽

Francisco Mendonça

Keyword(s):

Rio De Janeiro ◽

Field Survey ◽

Atmospheric Stability ◽

Urban Morphology ◽

Urban Canyon ◽

Synoptic Situation ◽

Landsat 8 ◽

Observation Data ◽

Heat Islands ◽

Atmospheric Instability

This study aims to evaluate the thermal field of the central business district (CBD) of Rio de Janeiro during summer from land surface temperature (LST) and the thermal characteristics of the urban canopy layer (UCL) of the urban canyon in Avenida Rio Branco. In order to conduct this evaluation, two methods were employed: (1) TIRS Landsat-8 sensor for data selection and processing (latest generation, 2011–2020); (2) a field survey using nine sampling points—seven along two mobile transects, one fixed point, and one vertical measurement point, which required the use of an RPA (remotely piloted aircraft). Three categories of analysis were established for the field survey based on the prevailing synoptic situations: stability, instability, and post-instability. The CBD is characterized by extensive areas with surface heat islands, in which temperatures were higher than 38.9 °C; the areas with milder LSTs were Campo do Santana, Avenida Rio Branco, and one of the mixed-use zones (Praça Mauá). With respect to Rio Branco Avenue, the LST niches of lowest elevation were derived through building shadowing; however, due to the nature of the data, the orbital data diverged from the observation data of the 10 field-study days. In situ data revealed that the characteristics urban morphology of Avenida Rio Branco, by contrast with the LST result, is susceptible to the formation of atmospheric heat islands, presenting heat islands of very strong magnitude (over 6.1 °C) in atmospheric stability, strong magnitude (4.1–6.0 °C) in atmospheric instability, and moderate magnitude (2.1–4.0 °C) in post-atmospheric instability. Despite the synoptic situation, thermal cores were concentrated at 1 p.m. The intersection between Avenida Rio Branco, Rua do Ouvidor, and Praça Mauá stored most of the solar energy received during the day due to the greater sky obstruction caused by the verticalization. Finally, vertical analysis demonstrated the formation of a thermal inversion on the night of the highest mean air temperature (29.5 °C), probably due to the roughness and number of buildings in the urban canyon.

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Impact of Low-Level Jets on the Nocturnal Urban Heat Island Intensity in Oklahoma City

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-12-0256.1 ◽

2013 ◽

Vol 52 (8) ◽

pp. 1779-1802 ◽

Cited By ~ 47

Author(s):

Xiao-Ming Hu ◽

Petra M. Klein ◽

Ming Xue ◽

Julie K. Lundquist ◽

Fuqing Zhang ◽

...

Keyword(s):

Boundary Layer ◽

Critical Role ◽

Vertical Mixing ◽

Atmospheric Stability ◽

Nocturnal Boundary Layer ◽

Oklahoma City ◽

Near Surface ◽

Low Level ◽

Urban Heat ◽

Low Level Jets

AbstractPrevious analysis of Oklahoma City (OKC), Oklahoma, temperature data indicated that urban heat islands (UHIs) frequently formed at night and the observed UHI intensity was variable (1°–4°C). The current study focuses on identifying meteorological phenomena that contributed to the variability of nocturnal UHI intensity in OKC during July 2003. Two episodes, one with a strong UHI signature and one with a weak signature, were studied in detail using observations along with simulations with the Weather Research and Forecasting model. Mechanical mixing associated with low-level jets (LLJs) played a critical role in moderating the nocturnal UHI intensity. During nights with weak LLJs or in the absence of LLJs, vertical mixing weakened at night and strong temperature inversions developed in the rural surface layer as a result of radiative cooling. The shallow stable boundary layer (SBL < 200 m) observed under such conditions was strongly altered inside the city because rougher and warmer surface characteristics caused vertical mixing that eroded the near-surface inversion. Accordingly, temperatures measured within the urban canopy layer at night were consistently higher than at nearby rural sites of comparable height (by ~3°–4°C). During nights with strong LLJs, however, the jets facilitated enhanced turbulent mixing in the nocturnal boundary layer. As a consequence, atmospheric stability was much weaker and urban effects played a much less prominent role in altering the SBL structure; therefore, UHI intensities were smaller (<1°C) during strong LLJs. The finding that rural inversion strength can serve as an indicator for UHI intensity highlights that the structure of the nocturnal boundary layer is important for UHI assessments.

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Urban Canyon in the CBD of Rio de Janeiro (Brazil): Avenida Rio Branco during Summer

10.20944/preprints202107.0272.v1 ◽

2021 ◽

Author(s):

Lidiane de Oliveira Lemos ◽

Antonio Carlos Oscar Júnior ◽

Francisco Mendonça

Keyword(s):

Land Surface ◽

Rio De Janeiro ◽

Field Experiments ◽

Atmospheric Stability ◽

Urban Morphology ◽

Urban Canyon ◽

Synoptic Situation ◽

Canopy Layer ◽

Heat Islands ◽

Atmospheric Instability

This study aims to evaluate the land surface temperature (LST) and the thermal characteristics of the Urban Canopy Layer (UCL) of the urban canyon in Avenida Rio Branco in the Central Business District (CBD) of Rio de Janeiro during summer. In order to conduct this evaluation, two methods were employed: 1) summer LST estimation from the last decade (2011-2020); 2) field survey using nine sampling points — seven along two mobile transects, one fixed point, and one vertical measurement point, which required the use of a RPA (Remotely Piloted Aircraft). Three categories of analysis were established based on the prevailing synoptic situations: stability, instability, and post-instability. The CBD showed extensive areas with surface heat islands, in which temperatures were higher than 38.9°C; the areas with milder LSTs were Campo do Santana, Avenida Rio Branco, and one of the Mixed-Use Zones (Praça Mauá). The shadows of the buildings gave rise to niches of lower LSTs on Avenida Rio Branco; however, the satellite data and the data collected during the ten days of field experiments diverged. In situ data revealed that the urban morphology of Avenida Rio Branco is susceptible to the formation of heat islands, presenting heat islands of very strong magnitude (over 6.1°C) in atmospheric stability, strong magnitude (4.1-6.0°C) in atmospheric instability, and moderate magnitude (2.1°C-4.0°C) in post-atmospheric instability. Despite the synoptic situation, thermal cores were concentrated at 1 pm. The intersection between Avenida Rio Branco, Rua do Ouvidor, and Praça Mauá stored most of the solar energy received during the day. Finally, vertical analysis demonstrated the formation of a thermal inversion on the night of the highest mean air temperature (29.5°C), probably, due to the roughness and number of buildings in the urban canyon.

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