海洋信风是一种在热带地区形成的大气环流系统，它在地球表面上的气压差驱动下形成。其中，最著名的是副热带高压和南北两侧的副热带低压。而为什么海洋信风会在30度附近形成，这是一个有趣且复杂的问题。

海洋信风形成的关键因素之一是地球自转。由于地球自转，热带地区的气流会向东方和西方偏转。当气流向东移动时，靠近赤道的水体会被推到30度纬度附近，形成副热带低压带。这个过程称为赤道东风漂移（Equatorial easterly drift）。

另一个影响海洋信风形成的因素是副热带高压。副热带高压是指在30度纬度附近形成的一个高压区域。它是由于高温空气向上升起，形成对流，并且在上升后向外发散而形成的。副热带高压的存在导致了空气的下沉，形成海洋信风。这些下沉的空气在地面上沿着纬度线向赤道移动，并与赤道东风漂移相结合，形成了海洋信风。

此外，海洋温度也对海洋信风的形成起着重要作用。在30度纬度附近，热带地区的海洋温度高，而30度纬度附近的海洋温度比较低。这种温度差异导致了空气的压强差异，从而促使了海洋信风的形成。

总之，海洋信风在30度附近形成是由于多个因素的综合作用。地球自转、副热带高压以及海洋温度差异都起到了重要的作用。这一现象不仅对大气环流系统有着深远影响，也对气候和天气产生了重要的影响。

Ocean trade winds, known as the ocean wind system, are atmospheric circulation systems that form in tropical regions, driven by pressure differences on the Earth's surface. Among them, the most famous are the subtropical high-pressure zone and the subtropical low-pressure zones on the north and south sides. The question of why ocean trade winds form near 30 degrees is an interesting and complex one.

One of the key factors in the formation of ocean trade winds is the rotation of the Earth. Due to the rotation of the Earth, the airflow in tropical regions is deflected eastward and westward. When the airflow moves eastward, the water near the equator is pushed towards the 30-degree latitude, forming the subtropical low-pressure zone. This process is known as the Equatorial easterly drift.

Another factor that influences the formation of ocean trade winds is the subtropical high-pressure zone. The subtropical high-pressure zone refers to a high-pressure area that forms near the 30-degree latitude. It is formed when hot air rises, causing convection and then diverging outward. The presence of the subtropical high-pressure zone leads to the sinking of air, forming the ocean trade winds. These sinking air masses move along the latitudes towards the equator at the surface and combine with the Equatorial easterly drift, forming the ocean trade winds.

In addition, ocean temperature also plays an important role in the formation of ocean trade winds. Near the 30-degree latitude, the ocean temperature is high in tropical regions, while it is relatively lower near the 30-degree latitude. This temperature difference leads to differences in air pressure and promotes the formation of ocean trade winds.

In conclusion, the formation of ocean trade winds near 30 degrees is due to the combined effects of multiple factors. The rotation of the Earth, subtropical high-pressure zones, and ocean temperature differences all play important roles. This phenomenon not only has a profound impact on the atmospheric circulation system but also influences climate and weather.