Let’s learn about weather. | Transport and weather | Welcome to the Web site of TRANSPORT IN JAPAN

| Weather forecasting process | Natural disasters and measures | Learn about weather |

Let’s learn about weather.

Tran will give you information about the weather!

If you know a little bit about weather, weather forecasts will be more fun to watch.

Let’s learn about weather. top

What is the border line between “clear” weather and “cloudy” weather?

It depends on how much clouds are covering up the sky. We add up what percentage of the sky is covered by clouds. Even if the sun is blocked by clouds, we may call it a clear day as long as there are not many clouds in the rest of the sky.
We call the weather “bright and clear” if there are fewer clouds than on a clear day. Here's the scale we use.

Bright and clear: Cloud density 0 - 1
Clear: Cloud density 2 - 8
Cloudy: Cloud density 9 - 10

Let’s learn about weather. top

Why are there white clouds and black clouds?

Clouds are made of small particles of water. If these water particles reflect sunlight, the clouds appear white to us.
The black clouds have thicker layers than the white ones, and the sunlight does not reach the bottom layer, which is why the clouds look very dark to us. Therefore, if we go above these clouds in airplane and look down at them, they will look white to us.

Let’s learn about weather. top

How many types of clouds are there?

Clouds are classified into 10 types. It is the international classification.

1). Cirrus -- These are thin, white clouds shaped like wispy threads.

2). Cirrocumulus -- These are very small, white spotty clouds called “urokogumo,” “madaragumo” “mackerel clouds” and other nicknames in Japan because of their shapes like little spots or fish.
They gather very high up in the sky like rows of little stones.

3). Cirrostratus -- These are high-altitude, thin clouds shaped like sheets, as though cirrus clouds had melted into one another.

(They are usually very high up in the sky, about 5 to 13 kilometers or higher. Their temperature is usually about -25 degrees C or lower.)

4). Altostratus -- These are thin, blue-gray clouds shaped like sheets or layers. Their nickname in Japanese is “oborogumo” or “misty clouds.” They look like thick cirrostratus clouds.

5). Altocumulus -- Nicknamed “sheep clouds” in Japan, the sides of these white and gray clouds are usually rounded, wavy, or fluffy.

6). Nimbostratus -- Nicknamed “snow clouds” in Japan, these dark, gray clouds are usually midway up in the sky, although they often spread higher and lower.

(They are usually 2-7 kilometers up in the sky, and their temperature is usually about 0 to -25 degrees C.)

7). Stratocumulus -- Nicknamed “ridge clouds” in Japan, these clouds look like altocumulus, but they are softer and grayer. The sides of these clouds stick to each other to make the clouds look like waves.

8). Stratocumulus -- Nicknamed “ridge clouds” in Japan, these clouds look like altocumulus, but they are softer and grayer. The sides of these clouds stick to each other to make the clouds look like waves.

9). Cumulus -- These dense, white fluffy flat-based clouds are nicknamed “cotton clouds” in Japan.

10). Cumulonimbus -- These storm clouds are nicknamed “monster clouds” or “thunderclouds” in Japan, these are high, very thick clouds that rise straight up like a tower or big monument. Their top is thin strands like appearance.

(At the top of the clouds, the temperature is as low as - 50 degrees C.)

Let’s learn about weather. top

What is the difference between clouds and fog?

Clouds and fog are the same things.
Fog is just a cloud closer to the surface of the earth. Clouds are in the upper sky.
Clouds are formed when the ascending air current brings the air near the ground to the sky and it is cooled there.
When the temperature near the ground surface drops in the clear night without wind, the air near the ground is cooled and it becomes fog.

Let’s learn about weather. top

Why does it rain sometimes even when the sky is clear?

Rain on a fine day is called “sunny rain” or a “fox’s wedding” in Japan because it is strange to see such rain. Actually, rain will not fall without clouds. Why does it happen even when the sky is clear? There are two different reasons.

Strong wind blows away rain drops from distant clouds.
Strong wind blows rain clouds before it rains and only rains are there.

Let’s learn about weather. top

What is the difference between high-pressure air and low-pressure air?

“Air pressure” refers to the weight of the air high up in the sky. If the air pressure in one area is higher than the other area around it, we say the air pressure is high. If it is lower we say the air pressure is low.

Let’s learn about weather. top

What causes wind?

Actually wind is the movement of air itself rather than something’s blowing air. There is no such wind like staying still. When the air in one area is warmed up, it becomes lighter and goes up. Then, the air in other area begins to move and this movement is the wind.

Let’s learn about weather. top

Is there any year without typhoon’s attack?

In both 1984 and 1986, the same number of typhoons is observed like in other years. But none of them came to Japan. In 2000, the number of typhoon occurrences is fewer than usual and no typhoons came to Japan.

Let’s learn about weather. top

back