It usually occurs in cloudy days often caused by cold rain and generally lasts for a long time. There is no obvious changes of it during daytime and it can be seen both at day and night.
The rime is the precipitation phenomenon under specific weather backgrounds. Glaze takes place when it is a little bit cold, that is between 0 ~ 3℃. Its appearance is accompanied by rain, strong wind, and big droplet where the cold air and warm air meet when the latter has a stronger force.
In the meantime, the northwest and southwest airflow over the Yangtze-Huaihe river basin are both strong and the ground is intruded by cold air lowering the temperature of the air layer near the ground (just below 0℃). There is also a heat flow above 0℃ going northward 1500-3000 meters above the ground, forming a warm air layer or clouds.
Above another 3000 meters where there is the upper atmosphere, the temperature is below 0℃. The clouds are colder, often below minus 10 ℃, where it is 2000 meters high and the atmospheric temperature is normally is 0 ℃ while it is lower than 0 ℃ below 2000 meters . This means there is a thermal inversion layer close to the ground. The vertical structure of the atmosphere is cold up and down and warm in the middle. And up to down, is is divided into ice layer, warm layer and cold layer.
The falling snowflakes from ice layer melt into rain through the warm layer, then when it get close to the cold air layer close to the ground, it quickly cools down and becomes the over-cooled raindrops, known as "the over-cooled” water drops. Like over-cooled raindrops and droplets, generally speaking, the raindrops and droplets causing glaze are big with high speed of condensation.
Because of the short diameter of these raindrops, though the temperature fells below 0 ℃, the raindrops fell before they can freeze.
When these over-cooled raindrops fall on the ground, branches, wires and other objects which are below 0℃, they gather and cover the surface of these objects and freeze immediately. As ice layer with translucence or ground-glass transparency, the frozen raindrops turn the branches or wires into thick ice sticks, smooth or bulgy as they appear. Sometimes the raindrops drip while freeze, forming long icicles that we call "glaze".
When the glaze is caused by raindrops that are not over-cooled falling on the cold ground or objects or when it is a result of the attachment and freezing of rain with snow, that is to say if the glaze is the mixture of ice layers out of non-crystal and crystal ice, it is usually thin and barely lasts long in general.
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