Residential Intensity
1. x-direction wind
- High residential intensity
- Low residential intensity
Overall, near the surface, the wind blows from the center of the city to the outside. The difference between the two graphs is very small, but the u-direction wind blows stronger when the residential intensity is high at the above the city. In the case of low residential intensity, the wind is blowing in east and west direction even in the most central part of the city, while in the case of high residential intensity, the wind is not blowing in that part. The supposed reason for this is that at the high residential intensity case, z-direction wind is largely developed at the center of the city, so u-wind is relatively weaker than the low residential intensity case. At the beginning, near the surface, the air flow from outside of the city toward the center of the city begins to develop. After that, strong convergence of wind toward the center of the city occurs during August 11th, approximately 09UTC to 13UTC. Then the divergence occurs until about 17UTC, and then opposite convergence wind blows until August 12th 06UTC. At the last convergence wind period, this convergence near the surface is very strong. The higher it goes, convergence and divergence occur alternately, and the wind speed becomes weaker.
2. z-direction wind
- High residential intensity
It seems like there’s no big change at first, but from 12UTC, two graphs are continuously changing and show distinct difference over time. In the afternoon, the rising motion at the outer part of the city gathers toward the center of the city. And after a while, it becomes weaker and even disappears for a short time. Starting from 00UTC, the sun heats the surface and the increased temperature will occur strong rising motion at the center of the city, and this is stronger than the rising motion that occurred before. At this period, we can also detect the rising motion at the outer part of the city.
- Low residential intensity
When residential intensity is low, the width of the rising motion on both outside edges of the city and the center of the city is narrower then the high residential intensity situation.
3. Temperature
- High residential intensity
- Low residential intensity
On both cases, the temperature tendency on the graph shows the increment during August 12th, from 00UTC to 06UTC.
But in this case, the effect of residential intensity on atmospheric variables is significantly less than that of other landuse variables. It is little bit difficult to identify the resulted temperature differences in experiments on a small space-time scale, and the graph did not clearly show the difference between temperature. Therefore, we used a graph of the temperature difference between the high residential intensity case and the low residential intensity case.
- Temperature difference
(High residential intensity - Low residential intensity)
With the temperature difference graph, we’ve found that the temperature difference is about 0.4, which is very small. This temperature difference will appear more clearly if the size of the city is larger. We’ve done this experiment with three city sizes: 20km, 50km, 100km. When the size of the whole city was 20km, the temperature of the low residential intensity case was very slightly higher than the other case. When the size of the whole city was 50km, the temperature between two cases were exactly same so the temperature difference graph wasn’t drawn. And lastly, because the maximum size of the city that can be raised within the range that does not break our existing assumption was 100km, we did not raised the size of the city bigger. But we expected that if the size of the city becomes larger, the temperature between the two cases will be remarkable.
- Temperature at z=2m graph
- High residential intensity
- Low residential intensity
The point at which the slope of the graph changes rapidly is same as the point at which the width of the vertical wind graph narrows and widens. In case of high residential intensity, the graph slope changes more rapidly than the low residential intensity in regardless of the decrease or increase of the temperature. The graph of bottom and 2m above the high residential intensity is more resembled than the graph of low residential intensity. The temperature of bottom is higher than the z=2m level, and changing the residential intensity, we found out that the rate of temperature change is larger when there are lots of residential area in the city.