Buzz
Today’s outlook: a sky full of maps. NASA Earth Observatory has compiled over a decade of data from the Moderate Resolution Imaging Spectroradiometer (MODIS) to produce a comprehensive map showcasing Earth’s average cloud coverage over the past 13 years.
Approximately two-thirds of the planet’s surface is blanketed by clouds at any moment, with a significant concentration over the oceans. Clouds dominate the atmosphere to such an extent that when NASA captures rare cloud-free satellite images of Earth, it becomes headline-worthy.
MODIS cloud data from July 2002 to April 2015 reveals regions of Earth that are consistently sunny. (Dark blue represents areas with fewer clouds on average, while white indicates frequent cloud cover.) Notably, the deserts of northern Africa and Saudi Arabia appear as distinct dark patches against the predominantly cloudy Blue Marble. Mountain ranges can also be identified due to the rain shadow effect: mountains act as barriers to wind, creating lush, cloud-covered areas on one side and arid conditions on the other. This phenomenon explains the dry climate west of the Sierra Nevadas in California’s Death Valley and west of the Andes Mountains in Chile’s Atacama Desert.
Cloud coverage from January 2015 to April 2015. Image Credit: NASA Earth Observatory
In contrast, Europe and the northern regions of South America appear to be consistently shrouded in haze. Cloudy skies are more prevalent near the equator, where tropical weather systems generate frequent thunderstorms. Additionally, the western coasts of continents tend to have more cloud cover due to oceanic circulation patterns driven by Earth’s rotation: surface waters are pushed westward, away from continental edges, allowing cooler, deeper waters to rise and influence cloud formation.
Explore additional cloud maps from MODIS here.
