Development of Urban Meteorological Models for Simulation of Heat Island PhenomenonThe following paper was based on his Graduation thesis was published in J. Appl. Meteor. Clim(2010).

  • Ryosaku IKEDA, 2007: Development of Urban Meteorological Models for Simulation of Heat Island PhenomenonThe following paper was based on his Graduation thesis was published in J. Appl. Meteor. Clim(2010). .

Abstract

Numerical studies on urban heat island phenomenon have been actively performed in order to investigate its formation mechanisms. Urban canopy models have been recently proposed to describe an urban canopy structure. Canopy model can simulate the urban thermal environment accurately. In this study, we developed an urban meteorological model, which is the coupled model between an urban canopy model and an atmospheric model. Additionally, we performed numerical experiments to estimate the impact of the urban effect using the developed model.
First, we developed a one-dimensional atmospheric model (Model-1D) and a two-dimensional model (Model-2D). The Model-1D is a column model to simulate development of the atmospheric boundary layer. The Model-2D is based on the non-hydrostatic Boussinesq equations. The vertical turbulent mixing is calculated using the Mellor-Yamada level 2 model. Surface skin temperature is estimated using Force-Restore method. In order to make a verification for our models, we compared them with the models used in the earlier studies under the same conditions. In the verification of the Model-1D, we compared vertical profiles of the potential temperature and the wind speeds from our model with those from the earlier study. And then, we performed verification by comparing the land/sea breeze circulation and the diurnal variations of sensible heat flux between the Model-2D and the model used in the earlier study. As a result, it was confirmed that the performance of our models are comparable to those in the earlier studies.
Second we developed the simple multi-layer urban canopy model. In the simulation, the road skin temperature was cooler than that of the roof during the daytime, but it is warmer during the night. Additionally, the vertical temperature profile in and above canopy layer agreed with that in earlier study.
Third, we incorporated the urban canopy model into the Model-2D, and developed a two-dimensional urban meteorological model. Last, we estimated building effects on the heat island using the two-dimensional urban meteorological model. We performed numerical experiments for two cases; one is no building case (Case 1) and another is building exists case (Case 2). The result of Case 2 showed that the heat island circulation developed less strongly than that of Case 1. This indicates that the drag effect of buildings to the winds make the sensible heat flux decreases in the urban area. Another important result is that the nocturnal heat island in Case 2 is more clearly developed than that of Case 1. This is because the radiation cooling after sunset is reduced by the large heat capacity and small sky view factor. We found that the urban buildings reduce the daytime heat-island circulation and enhance the nocturnal heat island.


The following paper was based on his Graduation thesis was published in J. Appl. Meteor. Clim(2010).
Ikeda, R., Kusaka, H., 2010: Proposing the simplification of the multilayer urban canopy model: Intercomparison study of four models. J. Appl. Meteor. Clim., 49, 902-919. 2010.05.01 (Acknowledgment:S5) .
American Meteorological Society(AMS)

He made the presentation at the 7th International Conference on Urban Climate(ICUC-7)(2007).