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
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
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