Differences in how quickly land and sea warm up produce daily winds (land and sea breezes) and seasonal winds (monsoons).
Basic Knowledge
Land has a small specific heat, so it warms and cools quickly. The sea has a large specific heat, so it warms and cools slowly. This difference produces temperature differences near the surface, which lead to pressure differences and then wind.
① Land and sea breezes (daily scale): During the day, land warms and air rises, making land a low-pressure area; wind blows from sea to land (a sea breeze). At night, the reverse occurs, and wind blows from land to sea (a land breeze).
② Monsoon (annual scale): In summer, the continent warms and becomes a low-pressure area while the sea becomes a high-pressure area, producing a southeasterly monsoon (a hot, humid wind from the Pacific Ocean to Japan). In winter, the continent cools and becomes a high-pressure area while the sea becomes a low-pressure area, producing a northwesterly monsoon (which crosses the Sea of Japan from Siberia and brings snow).
Specific heat（The amount of heat needed to raise the temperature of 1g of a substance by 1℃. Water has a large value of 4.2J/g・℃）
Sea breeze（A wind blowing from sea to land during the day）
Land breeze（A wind blowing from land to sea at night）
Monsoon（A large-scale wind whose direction reverses between summer and winter）
Summer monsoon（A southeasterly wind near Japan. Moist air・hot and humid）
Winter monsoon（A northwesterly wind near Japan. Brings snow to the Sea of Japan side）
Further Study (Background and Significance)
The windless periods when land and sea breezes switch are called calm periods, including morning calm and evening calm. In the Seto Inland Sea region, temperatures tend to rise during evening calm, creating distinctive muggy conditions.
The winter monsoon carries dry air from the Siberian air mass, but it takes in water vapor while crossing the Sea of Japan. When it meets the mountains on the Sea of Japan side, it rises and produces heavy snow. On the Pacific side beyond the mountains, it becomes a dry wind that has lost its moisture and brings clear weather as the “karakkaze” (a type of foehn phenomenon).
In this way, geography (sea, land, and mountains) combines with physics (specific heat, pressure, and adiabatic change) to shape Japan's distinctive climate.
- Water (sea) has a large specific heat; soil (land) has a small specific heat
- Land and sea breezes occur on a daily scale
- Day = sea breeze (sea → land), night = land breeze (land → sea)
- Summer monsoon = southeast (from the Pacific Ocean)
- Winter monsoon = northwest (from Siberia)
- Winter: snow on the Sea of Japan side, clear weather on the Pacific side
- Morning calm and evening calm = periods when wind direction changes
Points to Note (Easily Confused)
① Land and sea breezes and monsoons have different scales (1 day vs. 1 year), but the principle is the same. ② Remember sea breeze as sea to land and land breeze as land to sea: the place of origin + “breeze.” ③ Specific heat is greatest in the order water > sand and soil > metal. ④ Heavy snow on the Sea of Japan side and clear weather on the Pacific side in winter result from the combination of mountains and the monsoon.
Practice
- What is the wind that blows from the sea to the land during the day called?
- State the direction of the summer monsoon near Japan.
- Briefly explain why the Sea of Japan side receives a lot of snow in winter.