August 12, 2014 - Clouds off Chile
On August 2, 2014, the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite flew over Chile and captured a true-color image of remarkably beautiful and complex clouds off of the coast of Chile. This image was captured at 1505 UTC (11:05 a.m. Chile Standard Time) on a cool winter morning.
The major cloud type seen in this image is marine stratocumulus – a type of layered, relatively low cloud that forms over oceans. Stratocumulus are the Earth’s most common type of cloud, and cover large areas of the Earth at any given time. About four-fifths of such clouds form over oceans (marine stratocumulus), and they are very highly reflective, bouncing the sun’s energy away from the Earth. Because of this feature, and the potential impact on the Earth’s climate, they are of great interest to many scientists and climatologists.
The waters off of Chile are often covered with marine stratocumulus clouds – they can be found here on about 60% of the days on any given year – and they are most common in winter. Such bands of cloud can drop rain off shore, but the rain seldom makes it onto the arid coastal land due to a complex interaction of features such as the cold Humbolt Current in the offshore waters, the rain shadow east of the Andes mountains, and high pressure over the mountains. The extremely dry Atacama Desert which lies on Chile’s coastline gets extremely little rain, and is known as one of the driest places on Earth.
Although rain is rare, fog on the coastline is a common event, and an important source of moisture. In some areas on the Chilean coast people employ net-like fog collectors to harvest water from the frequent fog. A large bank of fine-textured low cloud (fog) embraces the coastline in this image.
The bright, linear streaks in the southern portion of the image are most likely ship tracks – clouds seeded by particles in the exhaust of ships traveling on the ocean below. The exhaust contains tiny airborne particles (aerosols) which act as nuclei, or seeds, for cloud formation. Also present near the center of the image are cloud streets – lines of cloud which are aligned parallel to each other. Such streets are normally formed in alignment with the prevailing winds – in this case, from east to west.