Numerical Simulation of the Surface Air Temperature Change Caused by Increases of Urban Area, Anthropogenic Heat, and Building Aspect Ratio in the Kanto-Koshin Area

We investigated a warming trend in the Kanto-Koshin area during a 30-year period (1976–2006). The warming trends at AMeDAS stations were estimated to average a little less than 1.3 C/30 years in both summer and winter. These warming trends were considered to include the trends of large-scale and local-scale warming e¤ects. Because a regional climate model with 20-km resolution without any urban parameterization could not well express the observed warming trends and their daily variations, we investigated whether a mesoscale atmospheric model with an urban canopy scheme could express them. To make the simulations realistic, we used 3 sets of real data: National Land Numerical Information datasets for the estimation of the land use area fractions, anthropogenic heat datasets varying in space and time, and GIS datasets of building shapes in the Tokyo Metropolis for the setting of building aspect ratios. The time integrations over 2 months were executed for both summer and winter. A certain level of correlation was found between the simulated temperature rises and the observed warming trends at the AMeDAS stations. The daily variation of the temperature rises in urban grids was higher at night than in the daytime, and its range was larger in winter than in summer. Such tendencies were consistent with the observational results. From factor analyses, we figured out the classic and some unexpected features of urban warming, as follows: (1) Land use distribution change (mainly caused by the decrease of vegetation cover) had the largest daytime warming e¤ect, and the e¤ect was larger in summer than in winter; (2) anthropogenic heat had a warming e¤ect with 2 small peaks owing to the daily variation of the released heat and the timing of stable atmospheric layer formation; and (3) increased building height was the largest factor contributing to the temperature rises, with a single peak in early morning.

[1]  Yujiro Hirano,et al.  Influence of Air-Conditioning Waste Heat on Air Temperature in Tokyo during Summer: Numerical Experiments Using an Urban Canopy Model Coupled with a Building Energy Model , 2007 .

[2]  T. Aoyagi,et al.  A Square Prism Urban Canopy Scheme for the NHM and Its Evaluation on Summer Conditions in the Tokyo Metropolitan Area, Japan , 2011 .

[3]  F. Fujibe.  Long-Term Falling Trends of Pressure over the Kanto Plain as Evidence of Increasing Heat Content in , 1994 .

[4]  H. Kondo,et al.  A Simple Single-Layer Urban Canopy Model For Atmospheric Models: Comparison With Multi-Layer And Slab Models , 2001 .

[5]  M. Kanda,et al.  ESTIMATION OF ANTHRPOGENIC HEAT AND VAPOR EMISSION, AND THE IMPACT ON LOCAL METEOROLOGY , 2004 .

[6]  Fujio Kimura,et al.  The effects of land-use and anthropogenic heating on the surface temperature in the Tokyo Metropolitan area: A numerical experiment☆ , 1991 .

[7]  Corinne Le Quéré,et al.  Climate Change 2013: The Physical Science Basis , 2013 .

[8]  Valéry Masson,et al.  A Physically-Based Scheme For The Urban Energy Budget In Atmospheric Models , 2000 .

[9]  Keisuke Hanaki,et al.  Impact of anthropogenic heat on urban climate in Tokyo , 1999 .

[10]  Hiroaki Ueda,et al.  Intermodel variability of future changes in the Baiu rainband estimated by the pseudo global warming downscaling method , 2009 .

[11]  F. Kimura,et al.  Urban effects on low‐level clouds around the Tokyo metropolitan area on clear summer days , 2004 .

[12]  Hiroyuki Kusaka,et al.  Thermal Effects of Urban Canyon Structure on the Nocturnal Heat Island: Numerical Experiment Using a Mesoscale Model Coupled with an Urban Canopy Model , 2004 .

[13]  I. Takayabu,et al.  On the Warming Events over Toyama Plain by Using NHRCM , 2009 .

[14]  H. Kusaka,et al.  Reproducibility of Regional Climate in Central Japan Using the 4-km Resolution WRF Model , 2010 .

[15]  S. Kobayashi,et al.  The JRA-25 Reanalysis , 2007 .

[16]  Albert A. M. Holtslag,et al.  Flux Parameterization over Land Surfaces for Atmospheric Models , 1991 .

[17]  Fumiaki Fujibe,et al.  Urban warming in Japanese cities and its relation to climate change monitoring , 2011 .

[18]  Hiromaru Hirakuchi,et al.  The effects of land-use alteration on the sea breeze and daytime heat island in the Tokyo metropolitan area , 2000 .

[19]  T. Segawa,et al.  Nonhydrostatic Atmospheric Models and Operational Development at JMA , 2007 .

[20]  F. Kimura,et al.  Numerical Experiments on Fair-Weather Clouds Forming over the Urban Area in Northern Tokyo , 2007 .

[21]  H. Kondo,et al.  Development of a numerical simulation system toward comprehensive assessments of urban warming countermeasures including their impacts upon the urban buildings' energy-demands , 2003 .

[22]  F. Fujibe.  Long-term Surface Wind Changes in the Tokyo Metropolitan Area in the Afternoon of Sunny Days in the Warm Season , 2003 .

[23]  F. Kimura,et al.  Coupling a Single-Layer Urban Canopy Model with a Simple Atmospheric Model: Impact on Urban Heat Island Simulation for an Idealized Case , 2004 .

[24]  Fumiaki Fujibe,et al.  Detection of urban warming in recent temperature trends in Japan , 2009 .