Extended Abstract (172K)11.7
An Intrigued Analysis to Quantify the Causes for Urban Heat Island by the Revised Architecture - Urban -Soil - Simultaneous Simulation Model, AUSSSM Part.1 Theoretical Background and Model Frame Showing with a Result of Standard Solution
Aya Hagishima, Kyushu University, Kasuga-shi, Japan; and J. Tanimoto and T. Katayama
Recently many studies on computational approach using Meso-scale Model have been carried out in order to clarify the features of Urban Heat Island (UHI). Through these challenges, it has been understood qualitatively that increase of anthropogenic heat and alternation of land covering are regarded as its primary causes. However, quantitative analysis of Factors calling for UHI has not been attained yet sufficiently because of the practical impediment coming from its huge computational load. This will lead following consequences, - Estimation for evaporative heat transfer at the urban surface is so much simplified that it is impossible to analyze quantitative effect on UHI. It might include a crucial problem, particularly if the urban vegetation is regarded as effective on UHI. - Itfs very difficult to carry on a large number of numerical experiments. Therefore he or she canft reach to any general and universal conclusions. Under these circumstances, the authors proposed Architecture-Urban-Soil Simultaneous Simulation Model, AUSSSM as a predicting and estimating methodology for UHI. The revised AUSSSM is composed of several one-dimensional sub-models developed in the authorsf former works. Each sub-model expresses complex phenomenon such as vertical distribution of air temperature, wind velocity and humidity ratio in urban canopy, artificial heat generation from buildings and traffic, evapotranspiration from vegetation, transient evaporation from artificial surfaces shortly after precipitation, dynamic performance of cooling load affected by HVAC system and so forth. They have relatively same level of its accuracy, which leads to practically correct and significant solution.
The features of the each sub-model are followings.
The Urban Atmospheric Model is based on one-dimensional transfer equations for heat, momentum, and vapor, containing the Urban Canopy Model (UCM). Concerning the UCM, the authors performed a series of wind tunnel experiments to identify the Roughness Parameter expressed with the fluid volume ratio, which is one of the most crucial parameters.
The Building Model is principally based on the dynamic calculation theory for a building thermal load. Anthropogenic heat from a building, which is originally derived from the building thermal load and bend by the mechanical performance of HVAC system expressed with COP, is substituted into the Urban Atmospheric Model. In addition to those, to identify evaporative heat transfer at a building surface due to rainfall or sprinkled water, another subordinate sub-model developed by authors is combined with this Building Model. It is a simplified procedure to predict the dynamic Evaporation Ratio based on field experimental data.
Soil Model includes the method to identify dynamic Evaporation Ration being applied to urban natural coverings such as bare soil surfaces and lawn vegetation developed by authors, which is based on a series of experiments and theoretical studies. This method is able to reduce calculation load exceedingly as compared with the conventional procedure by the exact solution, SHTE.
Using the revised AUSSSM, a solution called as gStandard Solutionh that targets typical urban area, possibly Tokyo, was drawn. From these results, the authors clarified the several features of mechanism on air temperature increasing and the heat balance of the urban canopy.
Session 11, Urban canopy layer: models
Thursday, 23 May 2002, 8:00 AM-1:30 PM
Previous paper Next paper