ABSTRACT:In the past few decades, the surroundings of the initially urbanised area (the old city) of Jakarta, Indonesia, was rapidly urbanised and the daily mean air temperature increased by approximately 1 K. Accordingly, the effect of the land use change in the area of Jakarta on the local climate was investigated using a mesoscale meteorological model. After model performance was validated against observational data, the model was run to simulate the meteorological field over the city for the dry season. In the simulations, three cases were considered: (1) the land use in the present day, (2) the land use in the 1970s, and (3) land use with no urban areas. The simulations led to the following findings. First, the sea breeze developed at an earlier time of day in the present day than in the 1970s. Second, in the present-day case, a converging flow developed over the old city in association with the low pressure which formed over the same location. Third, the daytime average and maximum air temperature in the old city were higher in the present day than in the 1970s by 0.6 and 0.9 K, respectively, due to the advection of heat from the new urban area. Finally, the amount of heat advected into the old city was estimated to be −0.7 Wm −2 in the 1970s and 77 Wm −2 in the 2000s. The estimated value in the 2000s case was 44% of the magnitude of the sensible heat flux from the ground surface into the atmosphere.

A numerical investigation of the temperature variation in urban and suburban areas due to the presence of buildings was carried out using a one-dimensional canopy model combined with a meso-scale meteorological model. Since temperature increases in an urban area are caused by sensible heat from building surfaces besides anthropogenic heat and reduction of wind speed due to buildings' drag, we estimated each cause separately to determine the contribution by each to the temperature variation. The simulation was performed for Kanda, an urban area, and for Nerima, a suburban area of Tokyo. Comparisons were made with actual temperatures before the estimation. The comparison indicated that the measured temperatures in the Kanda and Nerima areas were nearly reproduced by the model. The sensitivity analysis indicated that, in a comparison with the temperature in no building environment, the contribution of (i) sensible heat flux from building surfaces to temperature rise was 49% in Kanda and 20% in Nerima, (ii) wind reduction due to drag was 41% in Kanda and 59% in Nerima, and (iii) the effect of the interaction between (I) and (II) was þ10% in Kanda and þ20% in Nerima.

Fence for traffic noise control sometimes causes adverse effect on air pollution. Thus in this study, performance of porous fence as a tool for control of both air pollution and noise pollution was evaluated. A two-dimensional numerical model for flow and pollutant concentration and an analytical model for traffic noise were utilized in the analysis of a double-decked road structure with fences only at ground (Case 1) and at both ground and upper deck (Case 2). Porous fences were assumed only at the ground level since the solid fences at the upper deck usually leads to desirable result on air pollution. Effects of the variable porosity on air quality and noise level near road were evaluated. Obtained results showed: (1) flow pattern in leeward of fence was drastically changed at 40-50% porosity in Case 1 and 50% in Case 2. The porosity larger than 40% excluded presence of a circulation behind the fence. (2) Effect of porous fence on air pollution was different in Cases 1 and 2. In Case 1, the porous fence generally resulted in the reduction of air pollution at the ground level; on the other hand, in Case 2, it rather led to increase of the concentration. (3) Traffic noise level was also largely changed by the porosity of the fence; an example of simultaneous evaluation of the effects of porous fence on both air and noise pollution in Case 1 showed that the fence of 60% porosity leads to reduction of air pollution by 20% compared with solid fence case, and reduction of noise pollution by 4-6% in dB compared with no fence case, at 1 m high and 10 m from the road.

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