According to a new paper published in the Bulletin of the American Meteorological Society (BAMS), rainbows are one of the most beautiful optical phenomena in nature, and an astonishing number of rainbows can be seen in Hawaii, citing factors such as sea surface temperature, trade winds and topography. It draws attention by explaining it in detail.
According to a research team at the University of Hawaii at Manoa, the cultural meaning of the rainbow in Hawaii also appears in indigenous languages. Examples include uakoko, meaning to cling to furniture, kāhili meaning rainbow axis, punakea meaning dimly visible, and moonlight rainbow (ānuenue kau pō). In Hawaiian mythology, the rainbow is a symbol of change, and like many cultures around the world, they are thinking of a bridge between the earth and the sky.
The original rainbow starts with light transmitted through water droplets reflecting, refracting, and dispersing to form arcs of various colors. A rainbow is visible when the sun is at an angle of 40 degrees to the horizon. The paper explains that billions of raindrops are distributed at an appropriate angle, leading to a phenomenon that we perceive as a rainbow.
In the morning when the sun reaches the sky, the rainbow’s height is lowered and the highest rainbow is considered to appear before sunset. However, rainbows are not just water drops or sunlight angles. According to the paper, Hawaii’s climate, located in the subtropical Pacific Ocean, is ideal. The Hawaiian Islands are highly sensitive to northeast trade winds 9 out of 10 in summer and 6 out of 10 in winter. There is a lot of rain during this time and it can be sunny in between.
He explains that warm sea surface temperature raises the temperature of the air near the surface of the earth, where radiation in space cools the clouds above, resulting in rain in the morning and rainbows in the morning. At the same time, thanks to the mountains, the trade winds are attracted to the sky, facilitating cloud formation.
In fact, mountains play an important role in Hawaii. While the island receives hundreds of millimeters per year, it receives little rainfall and can be turned into a desert without mountains. The heat generated during the day helps the winds circulate across the island, and when the winds weaken in the afternoon, showers occur on ridges and mountain slopes, making it easier for rainbows to appear before sunset.
He also explains that Hawaii is one of the most distant islands on the planet, and the clean air is one of the factors because it is far from Hawaii. The reason is that the air is clean without air pollution, continental dust, and pollen, there is little scattering of sunlight by aerosols, and the sun contains full-spectrum colors even at a low setting angle. The fact that Hawaii’s natural beauty is not limited to the rainbow, but also the mountains and the sea is scientifically grounded. Related information can be found here.