On January 30, 2012, a large high pressure system lingered over eastern China and North Korea, bringing clear, cold air to the region, and allowing the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite to acquire a clear image of the icy lands and waters of the region on that same day.
In the south of the image, South Korea sits under clear skies. The winter landscape appears primarily dark green, with a covering of snow found only in the highest elevations, especially along the Taebaek Mountains lying parallel to the eastern coast. In contrast, North Korea and, further north, China both appear icy, with the snow covering not only the mountains, but dusting almost all of the land.
The Yalu River, which forms the border between China and North Korea is frozen and appears a brittle white, as does the Taedong River to the east. Both of these rivers flow into Korea Bay, which is covered by a filigreed sheet of ice from the coast as far as 50 miles across the sea.
In the northeast section of the image, over Jilin, China, cloud streets swirl around a clear central oval. High pressure ridges form where air is sinking from high altitudes towards the Earth’s surface. In the northern hemisphere, the descending air flows outward from the center in an expanding clockwise spiral.
Highs normally create dry, clear conditions, which can be seen in the center of the spiral. The relatively low-level cumulus clouds (below 15,000 feet) surrounding the low are likely the product of moisture near ground level being heated by the Sun and convected into the lower atmosphere. The clouds have aligned parallel to the direction of wind flow, in “streets” curving along with the flow of the high-pressure system.