An Urban Parameterization for a Global Climate Model. Part II: Sensitivity to Input Parameters and the Simulated Urban Heat Island in Offline Simulations
Issue Date
2008Author
Oleson, Keith W.
Bonan, Gordon B.
Feddema, Johannes J.
Vertenstein, M.
Publisher
American Meteorological Society
Type
Article
Article Version
Scholarly/refereed, publisher version
Metadata
Show full item recordAbstract
In a companion paper, the authors presented a formulation and evaluation of an urban parameterization
designed to represent the urban energy balance in the Community Land Model. Here the robustness of the
model is tested through sensitivity studies and the model’s ability to simulate urban heat islands in different
environments is evaluated. Findings show that heat storage and sensible heat flux are most sensitive to
uncertainties in the input parameters within the atmospheric and surface conditions considered here. The
sensitivity studies suggest that attention should be paid not only to characterizing accurately the structure
of the urban area (e.g., height-to-width ratio) but also to ensuring that the input data reflect the thermal
admittance properties of each of the city surfaces. Simulations of the urban heat island show that the urban
model is able to capture typical observed characteristics of urban climates qualitatively. In particular, the
model produces a significant heat island that increases with height-to-width ratio. In urban areas, daily
minimum temperatures increase more than daily maximum temperatures, resulting in a reduced diurnal
temperature range relative to equivalent rural environments. The magnitude and timing of the heat island
vary tremendously depending on the prevailing meteorological conditions and the characteristics of surrounding
rural environments. The model also correctly increases the Bowen ratio and canopy air temperatures
of urban systems as impervious fraction increases. In general, these findings are in agreement with
those observed for real urban ecosystems. Thus, the model appears to be a useful tool for examining the
nature of the urban climate within the framework of global climate models.
Description
© 2008 American Meteorological Society
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Citation
Oleson, K. W., G. B. Bonan, J. Feddema, M. Vertenstein, 2008: An Urban Parameterization for a Global Climate Model. Part II: Sensitivity to Input Parameters and the Simulated Urban Heat Island in Offline Simulations. J. Appl. Meteor. Climatol., 47, 1061–1076. http://dx.doi.org/10.1175/2007JAMC1598.1
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