Journal of Heat Island Institute International Vol. 12-2 (2017) Academic Article Making Climatic Zoning Maps in Yokohama -Comparison among different resolution calculations- Makoto Yokoyama*1 Takahiro Tanaka*1 Toru Sugiyama*2 Satoru Sadohara*3 *1 Graduate School of Engineering, Hiroshima University *2 Center for Earth Information Science and Technology, Japan Agency for Marine-Earth Science Technology *3 Graduate School of Urban Innovation, Yokohama National University Corresponding author: Makoto Yokoyama, [email protected] ABSTRACT Although countermeasures against urban warming and its effects have been studied in recent years, these countermeasures must be introduced into a suitable place for effective urban environmental planning. Therefore, classification of urban areas in zoning maps must be done in terms of climatic environments to find necessary and effective countermeasures for respective zones. Numerical calculations using a meso-scale meteorological model are often used to produce such maps. This study calculated the climatic environment in Yokohama at 500 m resolution and at 100 m resolution, respectively, using a WRF (Weather Research and Forecasting) model and an MSSG (Multi-Scale Simulator for the Geoenvironment) model. These calculation results were then compared with observations. Calculation accuracy of relative magnitude correlation of these calculations were compared to analyze whether high-resolution calculation is effective or not for making climatic zoning maps. Furthermore, climatic zoning maps were produced from these calculation results and cluster analyses. Results show that urban areas in Yokohama are classifiable into five zones in terms of patterns of air temperature change. Additionally, more detailed effects can be incorporated into climatic zoning maps using high-resolution calculations with an MSSG model. Key Words : Climatic zoning map, Air temperature, Numerical calculation, Cluster analysis, Sea breeze 1. Introduction such maps necessitates classification of target areas into some zones in terms of urban climate. Using results of numerical In recent years, the thermal environment in urbanized areas is calculation is apparently effective for such classification. becoming increasingly inhospitable for residents because of Meso-scale meteorological models are often used to elucidate urban heat island effect and global warming. These phenomena spatial characteristics of urban climatic environments (2)(3). are collectively regarded as urban warming. Many Such models are regarded as useful to produce climatic zoning countermeasures against urban warming such as improving wind maps. ventilation and increasing the green ratio in urban areas and its As previous research related to making climatic zoning map effects have been studied. However, these countermeasures based on result of meso-scale meteorological model, Kitao et should be introduced into suitable places for effective urban al.(4) calculated climatic environment of Osaka region with 1km environmental planning. resolution by using Weather Research and Forecalting (WRF) From this background, urban environmental climate maps (1) are model and made regional climate atlas in Osaka region for proposed as effective tools to inform urban planning suggesting the pro-environmental urban plannning. Oba et al.(5) stakeholders such as urban planners, architects, and residents analysed the spatial distribution of heat budget inside Sendai and about the urban environment. As one layer of urban made “heat balance map” with 500m resolution. In addition, environmental climate maps, zoning maps classifying urban climatic zoning to select appropriate countermeasures against areas in terms of urban climate are necessary for presenting and heat island effects based on this map was proposed. Matsuo and considering effective countermeasures for each zone. Making Tanaka(6) analysed the effect of sea breeze on summer diurnal - 107 - temperature in Hiroshima plain for mapping the sea breeze target area. Yokohama, a hilly city, has many small valleys effect for mitigating urban warming. In this study, definite called “yato” throughout the whole city area. Urban areas extend zoning is not defined but spatial distribution of sea breeze effect throughout the whole city area; urban heat island effect has been is calculated with 1km resolution. As shown in these studies, the reported there (7). However, Yokohama faces Tokyo Bay and is spatial resolution of climatic zoning based on numerical located near Sagami Bay. Figure 2 shows wind roses of calculation is rough because of constraints of computation time, AMeDAS Tsujido and the Yokohama Local Meteorological and other restrictions. Observatory (YLMO). Locations of these observation points are Generally, climate zoning with reflecting detailed effects such as presented in Figure 1. As shown in Figure 2, a south wind blows topography and land use. But, these effect is also important for at both points. An east wind blows at YLMO during the daytime. making zoning maps in some citis having complicated Therefore, it is considered that the sea breeze effect mitigates topography. urban warming in this area. However, high-resolution calculations for wider areas can be In addition, fine weather days are classified into three groups (i.e. executed using supercomputers in recent years. A Multi-Scale day without southwest wind, day with southwest wind and Simulator for the Geoenvironment (MSSG) model can be developed for multi-scale calculation in the Earth Simulator. 0 20406080100km This model can execute such high-resolution calculations for a Ü μ wider area. Therefore, more detailed climatic zoning maps can be anticipated using this model. For this study, calculations of two kinds were executed respectively using WRF model and MSSG model. These calculation results are compared with observation results. Then Ü Yokohama calculation accuracy of relative magnitude correlation of these μ city area Elevation [m] calculations were compared to analyze whether high-resolution 3705 Yokohama local calculation is effective or not for making climatic zoning maps. meteorological 0 observatory Additionally, climatic zoning maps are produced from these calculation results. Urban areas in Yokohama are classified into five zones in terms of air temperature change patterns using Tokyo Bay AMeDAS Tsujido cluster analysis. Elevation 2. Research outline - 240 m -0 m 012345km Sagami Bay 2.1 Target area For this study, Yokohama was selected as the target area. Figure Fig. 1 Yokohama location and topography. This area is located 1 portrays locations and topographical characteristics of the near Sagami Bay, facing Tokyo Bay. August 7, 5:00 August 7, 12:00 !( !( !( Ü !( !( !( μ !( !( μ !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( μ !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( Air temperature !( !( !( !( Air temperature !( !( !( [°C] (2m height) !( [°C] (2m height) !( !( !( !( August 7 5:00 !( !( August 7 12:00 !( !( !( !( !( !( !( - 25.5 !( !( !( - 32.0 !( !( !( !( !( 25.5 - 26.0 !( 32.0 - 33.0 !( !( 26.0 - 26.5 !( !( 33.0 - 34.0 !( !( !( !( 26.5 - 27.0 !( !( !( !( 34.0 - 35.0 !( 27.0 - 27.5 !( 35.0 - 36.0 !( 27.5 - 28.0 !( 36.0 - 37.0 012345km !( 012345km !( 37.0 - !( 28.0 - !( Fig. 3 Hourly averaged air temperature distribution of August 7 (left) 5:00 JST, (right) 12:00 JST. Air temperatures in Yokohama are higher around the eastern coastal area at 5:00 JST and higher around the northwestern part at 12:00. - 108 - day with both east and southwest wind) by sea breeze blowing Yokohama local AMeDAS Tsujido patterns among this area(8). Especially, number of days with both meteorological observatory east and southwest wind is largest in these three patterns in N N 30% 25% summer of 2015. Therefore, August 7 in 2015 is selected as a 20% NW 20% NE NW NE target day in this study. This day is a typical sunny day and the 15% 10% 10% end of continuous fine weather days period. East wind blows in 5% the morning and southwest wind blows in the afternoon W 0% E W 0% E according to observatonal data at YLMO. Analysis on other days and other sea breeze blowing patterns are next steps. SW SE SW SE Basic information related to Yokohama is given as shown below. SE SE Area: 437.4 [km2] Daytime（6:00～18：00） Nighttime（19:00～5：00） Population: 3,728,124 [persons] (2015) Fig. 2 Wind roses of AMeDAS Tsujido and YLMO. These 2.2 Meteorological observations figures were made using data of summer, 2011–2015. For this study, 59 air temperature sensors were set in and around Yokohama for the observation period of July 24 through August Case A Case B 31 in 2015. Observations were recorded at 10 min intervals. All Domain1 (4.5 km resolution) Domain1 (100 m resolution) sensors were set in Stevenson screens located at elementary schools throughout Yokohama. Figure 3 shows the air Domain2 (1.5 km resolution) temperature distribution at 5:00 JST and 12:00 JST on August 7. In the daytime, the southern part of the city is cooler; the northern part is hotter. Furthermore, the maximum air temperature in that time reaches to over 37 °C. Therefore, it Domain3 (500 m resolution) seems that the air temperature distribution during the daytime is 0 50 100 150 200 250 km affected by the air temperature reduction effect of the sea breeze, especially from Sagami Bay in this area. In the nighttime, the Fig. 4 Calculation areas of Case A and Case B. Numbers of