scholarly journals Analysis of Urban Effects in Oklahoma City using a Dense Surface Observing Network

2016 ◽  
Vol 55 (3) ◽  
pp. 723-741 ◽  
Author(s):  
Xiao-Ming Hu ◽  
Ming Xue ◽  
Petra M. Klein ◽  
Bradley G. Illston ◽  
Sheng Chen
Keyword(s):  
Metropolitan Area ◽  
Land Surface ◽  
Critical Role ◽  
Central Business District ◽  
Temperature Inversion ◽  
Oklahoma City ◽  
Near Surface ◽  
Open Questions ◽  
The Stability ◽  
Business District

AbstractMany studies have investigated urban heat island (UHI) intensity for cities around the world, which is normally quantified as the temperature difference between urban location(s) and rural location(s). A few open questions still remain regarding the UHI, such as the spatial distribution of UHI intensity, temporal (including diurnal and seasonal) variation of UHI intensity, and the UHI formation mechanism. A dense network of atmospheric monitoring sites, known as the Oklahoma City (OKC) Micronet (OKCNET), was deployed in 2008 across the OKC metropolitan area. This study analyzes data from OKCNET in 2009 and 2010 to investigate OKC UHI at a subcity spatial scale for the first time. The UHI intensity exhibited large spatial variations over OKC. During both daytime and nighttime, the strongest UHI intensity is mostly confined around the central business district where land surface roughness is the highest in the OKC metropolitan area. These results do not support the roughness warming theory to explain the air temperature UHI in OKC. The UHI intensity of OKC increased prominently around the early evening transition (EET) and stayed at a fairly constant level throughout the night. The physical processes during the EET play a critical role in determining the nocturnal UHI intensity. The near-surface rural temperature inversion strength was a good indicator for nocturnal UHI intensity. As a consequence of the relatively weak near-surface rural inversion, the strongest nocturnal UHI in OKC was less likely to occur in summer. Other meteorological factors (e.g., wind speed and cloud) can affect the stability/depth of the nighttime boundary layer and can thus modulate nocturnal UHI intensity.

scholarly journals Modeling Turbulent Flow in an Urban Central Business District

2007 ◽  
Vol 46 (12) ◽  
pp. 2147-2164 ◽  
Author(s):  
Donald A. Burrows ◽  
Eric A. Hendricks ◽  
Steve R. Diehl ◽  
Robert Keith
Keyword(s):  
Wind Speed ◽  
Central Business District ◽  
Oklahoma City ◽  
Dynamics Model ◽  
Near Surface ◽  
Computational Fluid Dynamics Model ◽  
Sonic Anemometers ◽  
Turbulent Airflow ◽  
Joint Urban 2003 Experiment ◽  
Business District

Abstract The Realistic Urban Spread and Transport of Intrusive Contaminants (RUSTIC) model has been developed as a simplified computational fluid dynamics model with a k–ω turbulence model to be used to provide moderately fast simulations of turbulent airflow in an urban environment. RUSTIC simulations were compared with wind tunnel measurements to refine and “calibrate” the parameters for the k–ω model. RUSTIC simulations were then run and compared with data from five different periods during the Joint Urban 2003 experiment. Predictions from RUSTIC were compared with data from 33 near-surface sonic anemometers as well as 8 sonic anemometers on a 90-m tower and a sodar wind profiler located in the Oklahoma City, Oklahoma, central business district. The data were subdivided into daytime and nighttime datasets and then the daytime data were further subdivided into exposed and sheltered sonic anemometers. While there was little difference between day and night for wind speed and direction comparisons, there was considerable difference for the turbulence kinetic energy (TKE) comparisons. In the nighttime cases, RUSTIC overpredicted the TKE but without any correlation between model and observations. On the other hand, for the daytime cases, RUSTIC underpredicted the TKE values and correlated well with the observations. RUSTIC predicted both winds and TKE much better for the exposed sonic anemometers than for the sheltered ones. For the 90-m tower location downwind of the central business district, RUSTIC predicted the vertical profile of wind speed and direction very closely but underestimated the TKE.

scholarly journals Dome effect of black carbon and its key influencing factors: A one-dimensional modelling study

2017 ◽  
Author(s):  
Zilin Wang ◽  
Xin Huang ◽  
Aijun Ding
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Black Carbon ◽  
Rural Areas ◽  
Land Surface ◽  
Critical Role ◽  
Aerosol Layer ◽  
Near Surface ◽  
Haze Pollution ◽  
The Impact

Abstract. Black carbon (BC) has been identified to play a critical role in aerosol-planet boundary layer (PBL) interaction and further deterioration of near-surface air pollution in megacities, which has been named as its dome effect. However, the impacts of key factors that influence this effect, such as the vertical distribution and aging processes of BC, and also the underlying land surface, have not been quantitatively explored yet. Here, based on available in-situ measurements of meteorology and atmospheric aerosols together with the meteorology-chemistry online coupled model, WRF-Chem, we conduct a set of parallel simulations to quantify the roles of these factors in influencing the BC's dome effect and surface haze pollution, and discuss the main implications of the results to air pollution mitigation in China. We found that the impact of BC on PBL is very sensitive to the altitude of aerosol layer. The upper level BC, especially those near the capping inversion, is more essential in suppressing the PBL height and weakening the turbulence mixing. The dome effect of BC tends to be significantly intensified as BC aerosol mixed with scattering aerosols during winter haze events, resulting in a decrease of PBL height by more than 25 %. In addition, the dome effect is more substantial (up to 15 %) in rural areas than that in the urban areas with the same BC loading, indicating an unexpected regional impact of such kind of effect to air quality in countryside. This study suggests that China's regional air pollution would greatly benefit from BC emission reductions, especially those from the elevated sources from the chimneys and also the domestic combustions in rural areas, through weakening the aerosol-boundary layer interactions that triggered by BC.

scholarly journals Near–surface air temperature and snow skin temperature comparison from CREST-SAFE station data with MODIS land surface temperature data

2015 ◽  
Vol 12 (8) ◽  
pp. 7665-7687 ◽  
Author(s):  
C. L. Pérez Díaz ◽  
T. Lakhankar ◽  
P. Romanov ◽  
J. Muñoz ◽  
R. Khanbilvardi ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Skin Temperature ◽  
Air Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Hydrological Cycle ◽  
Critical Role ◽  
Surface Air Temperature ◽  
Balance Model ◽  
Near Surface

Abstract. Land Surface Temperature (LST) is a key variable (commonly studied to understand the hydrological cycle) that helps drive the energy balance and water exchange between the Earth's surface and its atmosphere. One observable constituent of much importance in the land surface water balance model is snow. Snow cover plays a critical role in the regional to global scale hydrological cycle because rain-on-snow with warm air temperatures accelerates rapid snow-melt, which is responsible for the majority of the spring floods. Accurate information on near-surface air temperature (T-air) and snow skin temperature (T-skin) helps us comprehend the energy and water balances in the Earth's hydrological cycle. T-skin is critical in estimating latent and sensible heat fluxes over snow covered areas because incoming and outgoing radiation fluxes from the snow mass and the air temperature above make it different from the average snowpack temperature. This study investigates the correlation between MODerate resolution Imaging Spectroradiometer (MODIS) LST data and observed T-air and T-skin data from NOAA-CREST-Snow Analysis and Field Experiment (CREST-SAFE) for the winters of 2013 and 2014. LST satellite validation is imperative because high-latitude regions are significantly affected by climate warming and there is a need to aid existing meteorological station networks with the spatially continuous measurements provided by satellites. Results indicate that near-surface air temperature correlates better than snow skin temperature with MODIS LST data. Additional findings show that there is a negative trend demonstrating that the air minus snow skin temperature difference is inversely proportional to cloud cover. To a lesser extent, it will be examined whether the surface properties at the site are representative for the LST properties within the instrument field of view.

An Urban Pattern Dynamics with Capital and Knowledge Accumulation

1993 ◽  
Vol 25 (3) ◽  
pp. 357-370 ◽  
Author(s):  
W-B Zhang
Keyword(s):  
Pattern Formation ◽  
Capital Accumulation ◽  
Research Policy ◽  
Central Business District ◽  
Dynamic Interactions ◽  
Pattern Dynamics ◽  
Urban Patterns ◽  
Urban Pattern ◽  
The Stability ◽  
Business District

In this paper a dynamic model of urban pattern formation with endogenous knowledge and capital accumulation is proposed. The Alonso model is extended to include two of the most important dynamic forces for urban development—capital accumulatin and technological progress. The standard assumption of the existence of the central business district (CBD) is still accepted in this approach. It is assumed that two production sectors (industry and service) and one knowledge production sector (research institutions and university) are located at the CBD. First, a compact framework for analysing dynamic interactions of the three sectors and urban pattern formation is suggested. Then, the existence of stationary urban patterns is guaranteed and the stability conditions provided. Last, the effects of changes in government's research policy and some other parameters upon the system are examined.

scholarly journals Determinants of Apartment Prices within Housing Estates of Nairobi Metropolitan Area

2018 ◽  
Vol 10 (6) ◽  
pp. 104
Author(s):  
James N. Ndegwa
Keyword(s):  
Metropolitan Area ◽  
Significant Influence ◽  
Central Business District ◽  
Swimming Pool ◽  
Primary Data ◽  
Land Value ◽  
Shopping Malls ◽  
Primary Data Analysis ◽  
Business District ◽  
Housing Estates

The objective of this study is to establish the determinants that significantly influence apartment prices that are located within housing estates of Nairobi metropolitan area. The determinants comprise of apartments features including: proximity to shopping malls, proximity to Nairobi’s central business district, proximity to schools, proximity to slums, presence of swimming pool, presence of balcony, size of the apartment, periodic rental income and land value. Both secondary and primary data sources were employed in the research and 30 housing estates where apartment are located were selected for data collection purposes. Multiple regression analysis was employed for the secondary data and the findings indicated that: land value and size of the apartments had a significant influence on apartment pricing. Descriptive statistical analysis findings indicated that proximity to shopping malls, proximity to Nairobi’s central business district, proximity to schools, presence of swimming pool, size of the apartments and land value had significant influence on apartment prices. Triangulation of secondary and primary data analysis results indicated a consistency rate of 50%. The recommendation of the study is that real estate stakeholders especially buyers should focus on size and land value of apartments as these significantly influence apartment pricing in Nairobi metropolitan area.

Examining the Thesis of Central Business District Decline: Evidence from the Montreal Metropolitan Area

1996 ◽  
Vol 28 (10) ◽  
pp. 1795-1814 ◽  
Author(s):  
W J Coffey ◽  
M Polèse ◽  
R Drolet
Keyword(s):  
Metropolitan Area ◽  
Metropolitan Areas ◽  
Central Business District ◽  
High Order ◽  
Economic Base ◽  
Business Services ◽  
Office Employment ◽  
American Research ◽  
Using Data ◽  
Business District

Much recent North American research has focused on the decline of the central business district (CBD) as the economic core of metropolitan areas, and the corresponding rise of suburban employment centres. According to the literature, this trend is particularly evident in the case of high-order service functions: business services, finance, insurance, and real estate services, and head offices. In this paper, we argue that the decentralization of high-order service activities and the corresponding CBD decline may be neither as strong a trend nor as universal a phenomenon as certain authors have indicated. Rather, the growth of suburban office employment may reflect a strong CBD whose economic base is becoming increasingly specialized. Using data from the Montreal metropolitan area, we first examine intrametropolitan decentralization in a shift-share framework, then document the mobility of establishments and employment. Our findings suggest that, in spite of a certain level of intrametropolitan decentralization, the CBD continues to be the primary locus of high-order services.

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

2013 ◽  
Vol 52 (8) ◽  
pp. 1779-1802 ◽  
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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